Excal Charger.

[Critterhunter]

What changes when you wire batteries in series as opposed to parralel .....Will the voltage double or will it be cut in 1/2 ? ....Jim

In series the voltage is added to. Each new cell in series adds say 1.2V for a nimh or nicad or 4.2 volts for a lipo. The capacity stays the same, though. If the cells are 1000ma then 3 wired in series will still be 1000ma, so no longer run times. Typical detector batteries are 8AAs wired in series to total 12V. If you too two 8AA series (12V) packs and wired those two packs in parallel now you've got a 12V battery source (so same voltage), but your capacity has now doubled to 2000ma.

 

[synthnut]

GREAT REPORT AS USUAL !!!! .....Jim


Thanks so much for explaining Series and Parralel effects on batteries ...... This really helps me for wiring my boat batteries too ....Ya learn something new every day ........

My lesson for the day .......Take you pack of cigarettes and open carefully .....Take each cigarette in a series , and crumble one with your left hand .....Repeat this process with your right hand .....Each time each cigarette is crumpled , dispose of in the trash .....Do this until all 20 cigarettes are in the trash .....This proceedure will not only give your system more power, but it will also increase run time !!!......... .........Jim

 

[Critterhunter]

I noticed where I used the wrong word here or there that might prove confusing. If something seems contrary or wrong feel free to point it out and I'll correct it. By the time I read over these messages I noticed a few places where I used the wrong word and it looked like I was saying the reverse. Unfortunately this web site has a time limit how long long after posting a message that you can go back and edit it.

For example, I said...

"While little switching regulators like this are very expensive, they are still more pricey than linears, and you would also have to add a fair amount of noise cancelling electronics to the detector to keep the noise from doing things like locking up IC chips."

Meant to say little switching regulators aren't all that expensive, but they are still more pricey than linears.

Also...

"If you too two 8AA series (12V) packs and wired those two packs in parallel now you've got a 12V battery source (so same voltage), but your capacity has now doubled to 2000ma."

Meant to say if you were too take two 8AA series 12V packs and wired those in parallel you've still only got a 12V battery, but the capacity has now doubled to 2000ma and thus longer run times.

And this one...

"The other the milliamps the more run time you will get on the detector, NOT the more power the detector will have as so many commonly confuse things. It just means longer run times."

Meant to say the higher the milliamps the more run time you will get on the detector, and that this will not change the amount of power the detector wants to draw. Increased capacity only increases run time and to some extent the maximum amp delivering ability of the pack.

There was one other huge mistake I made somewhere in the phone book of a posting above that I wanted to correct but I can't remember what it was or find it to correct. For that reason if you see something that seems odd (other than the entire message ) point it out to me. If I remember right it was another point about batteries in parallel or something but I can't find what it was. I just remember it being entirely the reverse of what I meant to say.

One other detail I'll add is that this charger is slow in it's discharge ability. On the discharge function besides setting the amp discharge rate you also are able to set the lowest voltage the pack will go to before stopping the discharge. Some nimh and nicad guys believe you should never drain them completely dead when cycling the pack. Others like me believe that's the best way to recover full capacity of the pack. The lowest this charger will allow you to set the cut off voltage to is .1 volts (that's point 1 volts). That's pretty much dead in any body's book but I prefer throwing a pack on a light bulb for a car tail light. After the light goes out I'll let it sit for about two or three hours to insure every cell in that pack has made it to the after life. Once done I'll then re-charge it.

The other good reason for doing this is because it's faster than the charger can drain it. As the charger gets near that .1 volts it will decrease the amp draw to avoid going over .1 volts. In other words, if I set the charger to drain the pack at .4 amps it will do that for most of the discharge but once the pack voltage gets down to like .30 volts or so the charger will drop the amp draw to something lower than .1 amps. It will even say 0.0 amps as it goes to this tiny amp draw. Result is that even if the pack was draining fast before now it's crawling long and might take a good hour just to finish things up. A quick way to get around this with the charger is to stop it when it's doing this and cut the amp rate in half and press discharge again. With the lower amp draw the voltage of the battery won't sag as much and so it will keep drawing at that lower rate (which is higher than what it wants to do have you set the amp draw higher when the pack is almost dead like this). So say I'm drawing the pack down at .4 amps and I come back and see that it's less than a volt now in total voltage and the amp draw is 0.0 amps. Stop the charger. Change the amp draw to .2 amps and re-start it. After a few minutes you'll once again see the charger saying 0.0 amps. Stop it again and change it to .1 amps. Doing this will drain the pack dead faster than whatever the charger fancy's the amp draw should be when near dead.

The quicker/faster/easier way to drain the pack is with a car light bulb. There is no polarity on those things so hitch the pack up to the two leads on the bulb any way you like. The bulb will get hot so stick it on a cement floor. You should always do that anyway when charging or discharging any type of batteries regardless of chemistry. Some even lay a clay flower pot over the battery on the floor in the middle of their garage when charging or discharging it.

The only concern with using a car light bulb is that I think it's amp draw is something like 1.5 amps. That's pretty aggressive so I'd be careful with using that on say AAA rechargeables. Those types of cells aren't really meant to handle that much current draw, or at least some aren't. Even some AA cells (ones with low capacity of say less than 1500ma) might get a bit fussy (hot) with that kind of amp draw. Most AA nimhs or nicads with at least 2000ma or higher can handle that with no problem. If you aren't sure then don't do it, or at least use the charger and drain them at something real easy that will take say 2 or 3 hours to drain the battery. It's easier on them that way anyway.

One FOR SURE final tid bit on C ratings...Some batteries (usually lipos) will also have a C rating for their charge rate. Most lipos say never to charge them above 1C, meaning 1 amp for a 1000ma battery which will in turn take 1 hour to charge it. There are now some lipos that can handle 2C and higher amp rates. However, there are some who believe even 1C is being rough on a lipo and prefer something much lower. I fall into the camp that says (unlike for nimhs or nicads) that a 1 hour charge rate (1C) on a lipo is perfectly fine and healthy for it. That being said, make sure you know the maximum charge rate of your battery. Some lipos can catch fire or explode if charged at anything higher than 1C. I don't care if it says it's able to do 2C, I'll never go to that high of a charge rate myself, if not for the risk of fire then at least to be easier on them. I mean, who can't wait 1 hour for a battery to charge?

As said before...much of the above info ONLY pertains to nimhs or nicads. Lipos should never be drained lower than 3V per cell or charged higher than 4.2V per cell. They require a special charger and should never be punctured, dented, shorted, or eaten for that matter.

As always...Use at your own risk of house fires, lost limbs, or blowing up your house cat. If you don't know what you are doing then don't do it! I make no claims to being right and there is still great debate among the rechargeable battery crowd as to how and why on the feeding and care of your batteries. My experience has put me in certain camps as to who I believe and don't. Do your own research and don't just rely on my opinion so you can make up your own mind on things like how to condition batteries, proper charge or drain rates, and such.

 

[Critterhunter]

(Sigh...Another Quick Question & Answer from PMs

(QUOTE)
I just the other day RE charged my Eneloop batteries and put them in a case .....I charged them at 500 ma .....I just now took them out ( only a couple of days later ) and I'm now RE charging them again at 200 ma and they are charging and have been for the last 15 minutes !!....Hmmmm !!!.... Did they drop in power in THAT short a period of time ????
(END QUOTE)

Any fully charged battery that's thrown right back onto a charger within an hour or two after charging will charge again for a while. It takes time for the charger to notice the voltage drop that happens when the battery has peaked. That being said, some nimhs or nicads will drain faster than others when sitting on the shelf. Even at little as a few weeks later they can be pretty much dead if they aren't good cells. Nicads tend to hold their voltage on the shelf for longer periods of time than nimhs, though I hear nimhs are just as good these days in retaining a charge for months these days. Lipos will not lose voltage as they sit. One year later they are for the most part still fully charged, but it's not a good idea to store a lipo fully charged for long periods of time like that. This charger features what's called a "Sleep Charge" for lipos that will stick them at a certain voltage level for long term storage. Stick then in a metal box and stick that in your refrigerator when not in use for long periods of time. I even throw my fully charged lipos in there when not in use, but if I plan on not using them for more than 2 or 3 weeks then I'll often stick them on the charger and use the Sleep Charge function to put them to bed.

I've had some bad nimhs that would be about 80% dead roughly 2 to 3 days after fully charging them. These were a bad batch of Energizer 2600ma cells made about 5 to 7 years ago. The newer ones I use seem to hold their charge for long periods of time just like certain Nicads I own. I don't think there is much difference in storage performance between a good nicad or nimh these days. To store them for long periods of time (nimhs/nicads) most say they should have some form of charge to them and that it's not good to store them completely drained. Others, on the other hand, believe that storing a fully charged nimh or nicad for long periods of time also isn't good on the cells, so take your choice! I fall into the camp of storing them when say they are roughly have drained or so as a compromise. However, truth be known I don't really pay that much attention to my nimhs or nicads in how I store them. So long as I exercise them 2 or 3 times a year as described above they have held up very well. Just don't store them somewhere hot or where they might freeze for that matter. Same deal with lipos.

Nimhs or Nicads can be used in things like TV remote controls. Although they might go months before seeing your charger the amp draw of something like a remote is so low that even if the cells have drained as they sat some they'll still provide long use before needing another re-charge. Then there's a lot of power tools using nicads. I can charge those things up and a year later they can still run my cordless power tools without needing to be re-charged first.

 

[Critterhunter]

GREAT REPORT AS USUAL !!!! .....Jim


Thanks so much for explaining Series and Parallel effects on batteries ...... This really helps me for wiring my boat batteries too ....Ya learn something new every day ........

My lesson for the day .......Take you pack of cigarettes and open carefully .....Take each cigarette in a series , and crumble one with your left hand .....Repeat this process with your right hand .....Each time each cigarette is crumpled , dispose of in the trash .....Do this until all 20 cigarettes are in the trash .....This procedure will not only give your system more power, but it will also increase run time !!!......... .........Jim

That's TOO FUNNY! Good one.

Almost forgot...Wiring batteries in series means negative of this cell goes to positive of that cell, negative of that next cell then goes to positive of next, and so on. With a car battery wiring the negative of one car battery to the positive of the other would create a 24V battery. You'd then hitch your device to power to the unconnected (free) negative of the one battery (the battery that has it's positive going to the negative of the other battery) and the unconnected (free) positive of the other (the other battery that has it's negative going to the other battery) to the device to power. Again, make sure whatever you are powering is meant to handle 24V, and the capacity of the cells does not increase so the run time will not increase for the device.

In parallel (same voltage but double the capacity or run time), you would take both positives of those batteries and hitch them directly to each other, and then take both negatives of those two batteries and do the same. Now hitch your device (like a trolling motor) to the positive and negative and you've got a 12V battery that can run your trolling motor for twice as long.

Here's what NEVER to do. NEVER take say two car batteries and hitch the negative of one to the positive of the other, and then the other negative and positive together. What you've done there is make a direct short between two batteries. You might be scratching your head and thinking "isn't that a battery wired in series?" Nope, remember that in a normal series circuit while the negative of one is connected to the positive of the other, the other negative and positive of those two batteries is then routed to your "load" (trolling motor, outdoor beer cooler, whatever...). In order for current to flow from one battery to the other and complete the circuit it must go through the resistance caused by that device you are powering. If you were to directly hook that free positive lead from one battery to the negative free lead of the other there is no load or resistance between the two. Results are you are about to take a nice led acid bath and probably lose your eye site. NEVER short the negative and positive of a battery together, or in the way I just described above for two batteries. There should always be a "free" positive from one battery and a "free negative" from the other that go to the device you are going to power.

In parallel hitching the two positive posts of two batteries together and the two negatives together nothing bad will (should) happen. That's a normal parallel circuit. There is no "potential difference" between the two positive posts and the two negatives. Potential difference is another word for voltage. In order for voltage to flow it must 1) have a complete pathway from it's positive to it's ground, 2) have a load between them to pose resistance and thus do work in one form or the other. If the pathway from the positive goes directly to the negative then what you have there is a runaway short and I'd run for cover or at least push your friend on top of the battery so as to avoid it taking both of you out. I prefer to kick them in the groin as that makes it easier to them push into position to provide me cover.

Once again the disclaimer- By now I'm suffering from nicotine withdrawal and since I've been typing faster than I can think for the last few hours I'm sure I probably said something wrong. Re-think what I just said above and make sure I didn't switch a word or make a mistake. My mind is jelly right now...

 

[Critterhunter]

Finally uncovered that huge mistake I was talking about...

"One more thing about capacity to sum things up. You might have realized by the above examples of "C" ratings that besides it's amp draw rating the battery's ability to deliver amps is directly impacted by the capacity. As an example, a 10C battery at 1000ma can deliver 10 amps. Conversely, a 1000ma battery rated at 20C can deliver 20 amps. But, as said, that does not increase the performance of a device so long as it's needed amp draw is lower than the 10 amps of the first battery. If it drew 9 amps then I would say you are pushing it with a 10C 1000ma battery and being hard on it. Either buy another 1000ma battery rated at a higher C rating or buy another 10C battery to increase it's amp delivering ability that way. For example, a 10C 1500ma battery can deliver 15 amps and so would probably be a more wise option for that device which wants to draw 9 amps. The golden rule in RC is 80% of the continuous C rating, so if the battery can deliver 10 amps in total continuously I would use it to run anything that will draw more than 8 amps."

That last sentence is the exact reverse of what's true. I meant to say I WOULD NOT use it to run anything that will draw more than 8 amps. 80% of the battery's amp delivering ability is about max you should go in order to keep it easy on the battery. Using a battery to power something that draws near the continuous C or constant amp delivering ability of a pack is being rather hard on it and I wouldn't expect a very long battery life.

Some batteries (usually lipos) have a C rating for the amp delivering ability as I already explained. Other batteries (again, usually lipos) have a C rating for how fast they can be charged. Most lipos are 1C. 1C meaning 1 X Capacity, so a 750ma lipo should never be charged higher than .750 amps, which will take about 1 hour on a fully dead pack. My new solar light nicads are 700ma. While they don't have a listed C charge rating I tend to never go higher than 1C on a nimh or nicad, but if I wanted to then I'd be charging those cells at .7 amps and from completely dead they would take about 1 hour to charge.

As I said before try to charge your nimhs or nicads lower than 1C whenever possible. Anything beyond 10 hours is pointless, and that would be 1/10th C or 1/10th of 700ma when it comes to these Nicads. Since that's going to take 10 hours to charge and I did them multiple times I don't want to go that slow, so I charged them at .3 amps a few times and .4 amps for the rest. .4 amps would roughly take less than two hours to charge since 2 X .4 equals 800ma, a bit higher than the listed capacity of the cells. That's not being overly hard on the cells but something in the 4 or 5 hour range of a C rating would not only be easier on the cells but also tends to "fill them up" more evenly with capacity. If you think of pouring water into a buck fast versus slow doing it fast will often trap air bubbles in the bucket. In the same respect the faster you charge a battery the less it's really completely full. Charging it slower is not only easier on the batteries but you will also get higher capacity for that charge and thus more run time. I've got the numbers listed below for the conditioning of the new cells listed and you will see this illustrated among other things...

Accucel 6 charger set to Nicad mode. M/V (threshold) setting of 14mv. I made a mistake before about this when I said most use 12m/v regardless of how fast or slow they charge a nicad. I mostly use 14mv but will drop it down to 12mv if doing something like a very slow 10 hour charge rate. For nimhs I tend to keep the m/v setting at 7, but I may drop it down to 5 if doing a very slow like 10 hour charge rate. Mostly you don't have to change those numbers. 14m/v for nicads and 7m/v will work will most nimh and nicad packs regardless of how fast or slow they are charged.

The reason for these differences between the nimhs or nicads along with what this function does is this...When a nimh or nicad reaches it's fully charged state it will start to drop in voltage rather than rise. This voltage drop is less pronounced in a nimh than it is a nicad. That's why it's never a good idea to charge a nimh in a nicad charger. The charger may never shut off and could over charge the nimhs. The m/v setting is what they call a "per cell" setting in that the charger would expect each cell in the pack to drop 14m/v for a nicad set at that X the number of cells in the pack. You don't have to worry or do the math for the number of cells as the charger does that for you, so just set it at 14m/v and the charger will then multiple that number by the number of cells and arrive at a number in voltage drop it expects to see when the pack is fully charged.

If you have the m/v setting too low the pack will false terminate. During the normal charge process the voltage may raise and fall a bit. If you have the m/v setting too low the charger will notice one of these voltage dips and think it means the pack is done charging, causing early termination of the charge. On the reverse side, if you set the m/v setting too high then the charger may never notice this peaked voltage drop and over charge the battery. If you suspect it has missed this peak then put your hand on the pack. If you are charging at roughly 1/2C or higher you should notice the cells getting very warm due to the overcharging. At a lower charge rate than that the current flow is so low that the batteries may never get real hot, but just the same you are overcharging the cells.

Back to the charger settings...For discharge I also matched the amp rate to the charge rate, .3 amps when doing .3 amp charging and .4 amps discharging when doing .4 amp charging. These two don't have to match. You can charge the pack at say .4 amps and then drain it at an amp if you wanted for instance. I just was trying to be easy on these new cells to condition them as gently as possible.

For the discharge cutoff voltage I set that to .1 volts. What that means is that the discharge will terminate when the pack voltage drops to below that. Those are all the settings you really need to charge/discharge nicads or nimhs. There are a few other features on this charger involving safety mainly (like time or capacity limits) but I keep those turned off. Otherwise if the pack holds 1000ma yet I've got the capacity limit set to 700ma then the charger will stop when it hits that. Same deal with the timer. If the charge isn't done within whatever X amount of time you've set that to then the charger will stop. I don't use those features but I would if I knew I wouldn't be able to come back to the pack for a few days. In that case if it's a 1000ma pack I might set the capacity cut off to something like 1500ma. That way if the charger misses the m/v peak it will shut it's self off when it hits the 1500ma mark. Always use a slightly higher capacity than the pack is labeled to hold. If it's a good pack I've seen 1000ma cells hold 1300 or 1400ma, so I wouldn't set the capacity cut off right at 1000ma. Figuring out the time limit if you use that feature is obvious. If the pack is dead then the math is simple. Length Of Time To Charge= Pack Capacity / Charge Rate. If I'm charging a 1000ma pack at 250ma then it's going to roughly take 4 hours to charge it. For the same reasons for capacity shut off settings I would raise the time limit to maybe 6 hours or so in that case. I don't really use either one of these features but they are good to know if you do want to.

There are two other features on this charger related to something called "Waste Time" and something else that I can't think of at the moment. I think one of those is set to 1 minute for me and 10 minutes for the other. What I think they amount to (can't remember) is Wait Time will wait a certain amount of time after discharging the battery before starting to charge it again. This is handy when a pack is say getting hot due to your amp rates. It gives it time to rest and cool down. The other feature I think involves doing lipo batteries. Set at like 10 minutes it will check the lipo voltage to see if it's roughly correct for the number of cells you are charging to avoid user setting errors, such as trying to charge a 2 cell lipo in the 3 cell mode. I don't remember all the above exactly and I might have a few things reversed, so check the manual or a forum like on RCGroups to brush up on those settings. Once they are set you'll never change them again. With Lipos you select the number of cells you are charging. With nimhs or nicads the machine automatically figures that out so you don't have to tell it that info.

So finally here's my numbers on conditioning those cells...To make this quick when I put a "C" beside the capacity that means what Charging put into the pack, and with a "D" it means what discharge took out of the pack...

First cycle .3 amps charge rate and .3 amps discharge. C 737, D 677

I then went to .4 amps for the next5 cycles for the charge/discharge...

Cycle #2. C 760, D 697. #3 C 782, D 706. #4 C793, D709. #5 C783, D703. #6 C785, D710.

For the 7th and final charge so they are ready to throw into the solar lights I went back to a .3 amp charge rate and that put 831 milliamps back into the dead cells.

As you can see above, as the cells were exercised they showed improvement from cycle #1 through cycle #4 or so and then we kind of hit the wall in terms of showing improved charged or discharged capacity after that. #6 was starting to show more improvement again but really about 3 to 5 cycles is all you really need to do to exercise a new pack or an old one for the most part.

As you can also see, when I went went for one final 7th charge for the packs I dropped the amp rate down to .3 amps and then the capacity for the pack showed the greatest number yet. Why would it do that if I think the pack can no longer show improvement with exercise? Because I lowered the amp charge rate to .3 amps. Remember the water in a bucket analogy above? The slower you charge a pack the more fully it will be "filled" with the charge and so you'll see higher capacity and thus longer run times. It's not just about being easier on a pack. A charge amp rate that will take you roughly 3 to 4 hours to charge a pack is much easier on it and will fully charge it more than a 1C or 1 hour charge rate on a dead pack. Charging a pack very slow like something that would take 10 hours or 1/10th C also can help recover the capacity of a bad pack that you've drained dead. It gives all the cells enough time to catch up to each other during the charge and so they will be equally fully charged at the end of that 10 hours.

Conversely, a hard and fast (1C or more) charge rate here and there as said is good for breaking down the crystals in nimhs and nicads that can build up and so recover capacity or lost voltage that the pack has lost. Some people regularly charge there packs at 1C. I don't normally do that, other than for a quick top off before going into the field. If the pack was say 25% drained and I topped it off with a 1C charge rate (For the stock 1000ma GT pack 1C would be 1 amp), since the pack still has roughly 75% of it's charge it's only going to take about 15 minutes to top it off. But as a rule, charge as slow as you can when you can, but a 1C charge rate shouldn't hurt things and is actually healthy for it here and there a few times a year. Many believe constantly charging a pack at 1C all the time will shorten it's life or at the very least lower it's capacity more quickly over time than using a slower more gentle rate.

There you go...As I've said before more than you probably ever wanted to know about batteries and chargers. I'm sure we both hope I'd done for a while.

 

[Critterhunter]

Here's a link to a thread in the general detecting forum that goes a bit more into regulators and the amp draw of detectors. Mainly I'm trying to squash the re-occuring myth that better batteries produce better detector performance either based on voltage output or current delivering ability of those cells...

http://www.findmall.com/read.php?18,1245520,page=2

 

[Critterhunter]

Concerning rechargables in the Sovereign or Excal...

The voltage of rechargeables is often above 1.2V when freshly topped off so long as they are good high capacity cells like 2500ma or higher. Minelab does put 10 in the GT's rechargeable pack but they are ancient sub A monster cells that are only 1000ma. What gets me about using Sub A's is not only are they heavy but they are designed for high amp draw applications, which the Sovereign doesn't require with it's very low amp draw. Needless weight. I bet they got those cells cheap because they are technology from over 20 years ago.

A more sensible solution would have been to use normal AA rechargeables in that holder. I'm willing to bet that if they are above 2500ma and freshly charged they should last a long time, even if you are only using 8 instead of 10. I've used my 2500ma Energizers in my GT's regular holder here and there without issue, though I did not see just how long they would run before hitting the low battery alarm.

If you are re-building the old rechargeable holder on a GT and want to use 10 cells I'm not sure if 10AAs will fit. They are less fat than Sub As but about twice the height. In that case I seem to remember somebody a while back putting 10 AAA cells into the holder to re-build it. I'm not sure exactly how high of capacity you can get an AAA in but I would assume 1000ma to at least match the old capacity wouldn't be a problem. Just remember to use the same (nimh or nicads) cells and the same amount (10) if you plan to use the stock "charger". Higher capacity or a different cell (AAA versus AA) doesn't matter, so long as the number and type match when using the stock "charger". Otherwise you could use nimhs or nicads if you are charging them with the right aftermarket charger, and you could use 8 or 10 cells (if 8 will run the detector).

I believe the GT's voltage regulator requires at least 10.5 volts to operate. If you are using a good high quality/high capacity nimh or nicad 8 only in the regular holder should be able to power it so long as they are freshly charged, but I haven't fully tested that. I just know that typical voltage for my 8 pack AA 2500ma cells in things like my RC plane transmitters show a voltage of around 14.5 volts when fully charged, and will hold well above 11 volts all day long.

 

[Critterhunter]

Another little blurb I posted elsewhere that might be of interest...

Nicads aren't so bad these days. Some say any memory problems they had is no longer an issue, but it never really was an issue anyway so long as you exercised the cells by draining/charging them like 3 to 5 times in a row or so. Do that two or three times a year and they'll never risk memory, or erase it if they did develop a problem. Even still, nimhs can in a sense suffer from "memory" in that like Nicads they will often greatly increase their capacity so long as you give them that exercise a few times a year. When new it's also a good idea to cycle the packs like above 3 to 6 times or so to work them into shape.

Nimhs used to be fairly bad at keeping their charge on the shelf. I had some nimhs years ago that would be more than half dead if they sat for less than a week. Nicads tended to be better at retaining their charge on the shelf, but I feel there probably is no difference between the two these days in storage performance. They've both gotten better at it with tweaks in chemistry and construction.

Mainly Nimhs tend to be a little lighter while holding larger capacity than a Nicad of the same cell type, but again the difference between the two has sort of blurred over the last several years. You can often find Nicads with just as much capacity as a nimh in certain cell types. It also used to be that Nicads could withstand higher charge rates (like less than an hour) and higher amp draw applications than nimhs, but once again this line has become less distinct over the last five or so years.

I'd say either cell type is a good choice but I'd still lean towards the nimhs. Mainly buy the highest capacity cell you can find in either, and if price is an issue often the nicads will be slightly less in price. The most important thing is that if a device charges the battery on it's own (like say a cordless home phone) then make sure you replace the cells with the same type, either nimh or nicad. The capacity of the cells can be higher and it will offer longer run times, but changing battery type (nimh to nicad or vise versa) can cause problems with a device's internal charger. Namely nimhs drop less in voltage when fully charged and so the charger might miss that and over charge them. Truth be known either cell type should work fine in a device that says you can use only nimhs or only nicads, but ONLY in a device that doesn't charge those cells. Sticking nimhs in a flashlight that plugs into your wall to recharge is not a good idea, but if that flash light can't charge the cells on it's own then either type should work fine in it.

For example, I've got a radio transmitter for my RC planes that says "NICADS ONLY" on the back. Well, that's because the cheap junk charger they gave you with the radio is for Nicads only. I run higher capacity nimhs in that radio now, but I charge those cells using a nimh charger.

 

[kered]

Just a small remark to your great posts
RE Eneloop
Eneloop are supposed to be new generation rechargables that hold 80% capacity for a year
in the case of your PM re the eneloop, what might have happenned is the mv cutoff was set too low and a false peak was detected and the charger thinking they were full cut off early, thus after putting on the charger after a few days they took more charge.
I have noticed that the higher the charge rate the faster the charger detects a peak(and hence a slightly larger mv works better, within reason) and puts less ma into the battery, at a slower charge they will fill up more to capacity and its better for the batteries when possible.
I'm still experimenting using your basics and have found that each set of batteries have thier own little quirks as to charge rates, mv cutoff etc. and take a little trial and error to get the best results for each individual pack.

(PS not much posting from me lately been very busy, the lipos holding fine(28hr+) and i'm sure i can get one of the 1450mah into the SovGT rechargable pack (when i get time)

 

[synthnut]

Kered,
I"ve been able to use Eneloops in my E Trac and was surprised to find that they did not work in my Sovereign .....HOWEVER !!!.....I put them back into my charger, and charged them at a slower rate (200 ma the lowest m charger will go ) and I was pretty surprised that they charged for as long as they did ....I had just charged them at 500 ma not 5 days earlier !!!.....I think that I will cycle these batteries for better performance ......The Eneloops are only 2100's and not the 2500's of other batteries ...I ran these batteries after the 200 ma charge for 3 hrs and the detector is still running WITHOUT the low voltage cuttout kicking in !!... I sent to H.K . for some 750 Rhino Lipo's and also sent for the Turnigy charger ....After speaking with Critter , I think it will be the hot setup .... Which Lipo 1450 did you find that will fit the GT's pack ? .....That sure sounds good to me !!.....Thanks, Jim

 

[kered]

Not having used the eneloop as yet i don't know the final voltage but as you say they work in the Etrac, this is probably because the etrac is 9.6v cutoff or thereabouts and the Sovereign is slightly more
this is the mod i did on the XS with the 1450mah lipo http://www.findmall.com/read.php?22,1230451 i'm sure it will fit the GT too although i may have to file down the bits that hold the AA's in place if i use the AA holder

 

[Critterhunter]

Kered, good job on that "How To" thread. Been wondering where you've been. I just posted a message in that link with a rebuttal to somebody who said he wouldn't risk using that charger or lipos for that matter. This charger is very reliable and accurate as has been proven by the RC crowd, and lipos offer no more risk in use than any other battery type provided you follow a few of the same basic rules which for the most part apply to any rechargeable type.

Not sure if those 1450ma 3 cell lipo packs will fit into a GT's battery holder. My 750ma 3 cell Rhinos just fit and I had to grind down those little raised plastic lips that help guide the AA batteries into place. I went through every pack on Hobby City's site and anything above 750ma in a 3 cell was too fat to fit. I think the pack you are using is thin enough but too long if I remember right. One or the other.

If anybody does get rid of those little plastic guides or lips at the bottom of the holder make sure there is nothing sharp left behind that might puncture the lipo. Normal AAs will still work in the holder without those little raised plastic tabs. The way I modded my holder was to add a JST plug spliced into the two wires in that little empty chamber on the side of the holder where the normal charge circuit would go for the stock rechargeable pack. I can then move the plug into that little empty chamber when not in use and run regular AAs in there, not that I'd ever want to do that again.

Yes, some packs might require a slight adjustment of the m/v setting on a charger depending on amp charge rate. Typical slow charge rate (like 10 hours) for a nimh for me would be around 5 m/v, 12 m/v for a nicad. Faster charge rates of 3 hours or less might cause me to raise them to 7 m/v for nimhs and 14 m/v for nicads. Really I probably use those last two numbers all the time, regardless of how slow or fast I charge a pack. Often a 5 or 12 m/v setting will cause false peaks regardless of how slow you are charging the pack.

It's always better to start out on the low side. Set the m/v to 5 (nimhs) or 12 (nicads) and charge a completely dead pack. If you find the charger turned off too soon (didn't put nearly the listed capacity back into the pack) then raise it by two. Also remember that a good pack will often hold more capacity then what it says on the label. That's why I don't set the time or capacity safety limits on the charger.

If you think the charger has missed the peak just watch the voltage. Note what it is and check 20 minutes later. If it's still going up then note that number and check again in a half hour or so. So long as the voltage is higher it's still charging. It's only when the voltage stays the same or has dropped in 30 minutes that the battery might have peaked already. Check it one more time in another 20 minutes. Often a pack will drop some in voltage while charging here and there, so the lower voltage might only be temporary.

Also, notice that the amp charge rate goes to zero off and on. That's normal and the voltage will of course drop while it does that. The voltage will rise when the charge current kicks back on. Once it stops at it's highest point and hasn't changed for about ten or fifteen seconds write that number down. That's the number you want to go by when you check it later.

So long as you are charging about 1/2C or faster (two hour charge rate or faster) you should notice the pack getting very warm or even hot if the m/v setting was too high and the charger has missed it's peak. A 1 hour (1C) charge rate probably will cause the pack to get a little warm but it should never be very warm or hot. If the pack was drained dead then you should have a good idea just how much capacity it's going to take. If it's a 1000ma pack for instance and it only takes 700ma (on a completely drained pack) then chances are the m/v was too low. Either that or the pack has gone down hill in capacity over time. On the other hand, that 1000ma pack might hold 1300 or 1400ma, so don't assume you missed the peak if it's still charging.

It's rather simple and basic to set the m/v. Like I said, 7m/v for nimhs and 14 m/v for nicads will probably work regardless of how fast or slow you are charging it. If you simple can't get back to the pack when it should be nearing it's peak then I'd lean towards 5 and 12 m/v to be safe. Only problem with that is often it will false peak, usually within the first hour of charging. If that happens you can either raise the m/v a digit or two or just throw the pack back on the charger with the same m/v setting. Often it will already be past that "dead spot" in battery chemistry and won't false peak again.

If you are doing real small cells like below 800 or so in capacity with a nimh or nicad then you might lean towards the lower m/v settings of 5 (nimh) or 12 (nicad). The bigger the pack often the higher the m/v setting, and as said the faster the charge rate often a slightly higher m/v setting works better. 7 (nimh) or 14 (nicad) should work for most cells regardless of size or how slow or fast they are charged, though. For instance, for charging these 700ma AA cells I used in my solar lights I kept the m/v at 14. I was charging at about 1/3rd to 1/2 C (.4 amps a few times and .3 amps the others). The cells never false peaked or missed their peak, always stopping when they were over the capacity on the label by close to 100ma. I was confident then that I had the m/v set right. Being new, anything less than 700 and I would have been suspicious of too low of a m/v setting, though in general I almost never go higher than 7 or 14. Sometimes lower down to 5 and 12, but almost never higher. The only time you might do that is with a particularly difficult pack that you know is in good enough shape to hold more than it is but it keeps tripping the charger to terminate. Raise it by two and try again.

Synthnut, even if you just charged a pack and threw it right back on the charger often it will take a charger some time to see the voltage drop of a peaked pack. For that reason if the pack say takes another 50 to 80ma or so more "capacity" before the charger peaks I would suspect the pack already had peaked the first time and ignore that extra capacity as being added to the pack. It's never a good idea to throw a pack right back on the charger right after it's done, though. The pack's voltage has "hit the wall" and might not show any more drop to indicate it's peaked and shut the charger off. If you let the pack sit for 30 minutes or so and then throw it back on the charger the voltage has had time to settle and so should indicate to the charger that it's peaked when thrown back on again. Just the same, it's still probably going to try to put about 50 to 80 more MA of capacity back into the pack before it sees the voltage drop. Now if the pack takes say 150ma or more capacity before terminating then chances are it wasn't peaked before and I would count that as added capacity.

 

[synthnut]

Critter,
The batteries that I RE Charged were a few days old ....I didn't put them right back in to charge after already charged ........ Do you know if that XS battery pack is deeper than the GT's battery pack ? ....Is it the same pack ? .....That battery that Kered is using is only 2 mm thicker than the 750 ma battery that you and I have ......I will order the 1450s if they fit next time ..... I have 3 - 750's coming now ....I did not order that power supply , so I ordered another battery pack ... Heck , I charge everything up that I have and I may NEVER come home !!!....LOL !!.....Jim

 

[Critterhunter]

I've never seen the XS battery pack but I think Kered mentioned they were Sub C cells. That would be surprising because Sub Cs are even fatter than Sub As that the GT uses. if that's the case then obviously those cells are thicker and so his pack would fit. I think when I looked at that pack it might have been too long to fit the GT's case and not too thick, but I don't remember. Remember that lipos are much smaller than any other conventional battery, rechargeable or not. They have a much higher power to weight density, meaning smaller and roughly 1/5th the weight with roughly double the capacity of a nimh or nicad. In other words, a 1000ma nimh or nicad pack will weigh much more and take up more space than a 1000ma lipo. In fact, a 2250ma 3 cell lipo pack is probably still half the weight of a 2250ma nimh or nicad pack.

Regardless, what I'm saying is that the problem of fitting a 3 cell lipo into the GT holder is mainly it's thickness. These 750ma Rhinos only take up around half of the battery space in the holder, but anything higher than 750ma was too thick to fit. Put it this way, I could easily stick two 500ma 3 cell lipo packs side by side in the holder and run them in parallel for 1000ma. Another option would be to say take a 1500ma 2 cell pack and wire it in series with a single cell 1500ma pack that sits next to it in the holder. You could probably go as big as over 2000ma doing it this way and still get them to fit the holder. It's just that the holder is an odd shape on the GT in relation to how the batteries fit versus more of an in-line holder used in most other things like RC Transmitters. It just so happens that the way they configure the batteries in the GT makes it an odd match to using a standard lipo pack, where as they fit well in other configurations of 8AA cells like in the RC transmitter.

Just the same, even one of these 750ma packs is giving me at least two good hunts before I hit LVC (low battery cutoff or alarm) on the GT. I'm finding these packs when drained down to 9V (never go below 9V on a 3 cell series pack or 3V per cell on lipos) will take over 900ma of capacity when re-charged. That tells me they are very close to the stock rechargeable in terms of capacity and so should offer about equal run time. Also, since a lipo holds it's voltage very high to the end of it's discharge I suspect a smaller capacity lipo pack will run longer than the stock 1000ma rechargeable pack. Mainly because any conventional battery and nimhs/nicads have a more constant voltage drop as they discharge compared to a lipo.

 

[kered]

Here you go, Sov XS 2apro battery pack

should have put something in the pic to give an idea of size, like an AA

Just did the same mod on the GT as i did on the XS, the 1450mah lipo fits perfectly into the alkaline pack will upload photos in the mod section - XS battery mod

 

[synthnut]

Kered,
I went over to the mod forum to check out your work .....NICE JOB !!!... .......That battery should run a good 30 hrs or so ..... I will use the 750 ma batteries that I have on order, but will surely remember these for the next go around .....Thanks for sharing ....Jim

 

[Critterhunter]

Yea, those sure look like Sub C cells. WOW, and I thought the Sub As the GT uses were heavy! Both these cell types are really meant for high amp draw situations. That's touched on in the following re-post below. So that 1450ma 3 cell TX pack fits? I could have swore I found the dimensions of that pack to be too much in one respect for the GT's holder. I thought it was too long but perhaps it was slightly thicker than your typical AA cell diameter. That wouldn't matter anyway because the holder's cover will flex out a bit to accomodate a slightly thicker pack.

Now I wish I would have got the 1450ma pack. As I said I went through all the packs on their site and 750ma in standard 3 cell configuration was the thickest I could go. You could put higher capacity packs in there by putting a 2 cell and a 1 cell side by side in series with each other but why hassle with it. And I know my 3 cell 500ma packs don't even take half the space in the holder, so I could run two of those packs in parallel for a 1000ma pack.

No matter, these 750ma Rhinos are holding over 900ma in capacity. That combined with the voltage being held higher over the discharge than a nimh/nicad probably equals roughly the same run time of the stock 1000ma pack. Right now I believe I'm getting about two long 6 to 7 hour hunts (or roughly at least 15 hours or more) before I hit the low battery alarm. That's using the 15x12 which might be a little more power hungry than smaller coils.

Re-Post...

My Sovereign GT uses 8 regular AA batteries and has 10 Sub A cells in the factory rechargeable pack (I took it apart). These cells are monsters, mainly meant for high amp draw applications like Sub Cs are, and are yesterday's technology of about twenty years ago. No wonder why that pack is so heavy. The GT's low battery alarm starts kicking in when source voltage reaches about 10.5V. On the older XS model I believe I heard it kicks in at around 9.6 volts or so. I have used 8AA nimh 2500ma Energizers in the regular holder and the machine ran fine, although I didn't test just how long it would run before it hits LVC.

A good high capacity nimh or nicad pack charged properly on a good charger will often have a total pack voltage much higher than 1.2v per cell. Some of my 8 cell AA rechargeable cells that I run in my plane transmitters start out at over 12V and hold a source voltage well above 11 volts (they constantly display this on the screen) all day long while flying planes. I would figure similar performance from my GT as it's amp draw is very low.

I believe the 1.2V per cell is an averaged industry standard for the nimhs/nicads. Just like a 3 cell series lipo is listed as I think 11.1V where as in reality it charges to 12.6V total. 11.1V is the averaged voltage under high amp loads I believe, or is at least averaged down to provide a more universal idea of power available when doing things like figuring out say the wattage of a specific motor. You don't take the highest peaked voltage of a battery nor it's lowest at 80% discharged and use those numbers for computations. That's why I believe they list lipos this way as well as nimhs or nicads. There's only a few low capacity/cheap cells I'ved used over the years that seemed to be right around 1.2V per cell even when just fully charged.

Today's nimhs or nicads in a quality high capacity cell will often provide 2 to 3 times the run time compared to regular store shelf batteries. Their high capacity also means that they tend to hold their voltage higher over the entire drain cycle than a non-rechargeable. Even if the regular store battery has a higher starting voltage it will soon be much further below that of a nimh or nicad provided they are high capacity. In an AA cell 2500ma or higher will give outstanding run time. These cells run my digital camcorder at roughly 2 to 3 times the length of time of any brand name non-rechargeable that I've used.

I *THINK* the reason why Minelab is using 10 Sub A cells is because they are relatively low in capacity at 1000ma and also pretty low quality cells, and as a result 10 is needed so the voltage doesn't drop too fast. I just keep thinking there is some guy in a warehouse somewhere selling a pile of twenty year old 1000ma cells off at dirt cheap prices when they should have been recycled. A 1000ma Sub A is pretty darn low and represents typical capacity of *at least* 10 years ago or more.

As I've said, my better nimh or nicad cells often have a source voltage much higher than 1.2V per cell, and yes this was checking pack voltage hours later when the cells had time to settle after a charge. Checking pack voltage right after a charge will of course show higher total voltage then what the pack is going to settle to. Provided you are using a good quality/high capacity cell and have peaked it in say the last few days I wouldn't see any problem with them working fine in a Sovereign. I've used mine here and there but not long enough to provide actual run time numbers spanning more than a single hunt.

I've said it before and I'll say it again...I have yet to run into any device that would not operate fine and for long or even longer periods of time using rechargeables nimh or nicad cells. Much of the bad reputation they have was created years ago when cell capacity was so low that you would get roughly 1/5th the run time using them compared to a non-rechargeable. Things are much different these days. Chemistry has been tweaked, cells are constructed better, and capacity has increased drastically...All of which equate to these cells working well in just about anything and in the process providing longer run times.

Since 8AA's in a non-rechargeable is roughly 12V total series voltage, a 3 cell series lipo at 12.6V is the ideal replacement to power many devices. It's much lighter even with double the capacity, takes up less space, and a healthy 1 hour charge time is not being hard on it. The lipo also will hold it's voltage higher for more of the discharge span even under heavy amp loads and as a result can provide more power to devices which need it. They also don't discharge over time on the shelf. Come back a year later and it's still going to be fully charged. Mainly the weight factor is why I use lipos in my planes and also why I use a 3 cell pack in my Sovereign GT. I dropped over a pound in weight off my machine by building a custom shaft and doing a few other things. A lipo was an obvious weight saving measure as well for it.

Lipos are finding their way into things like cordless hand tools that's performance is directly related to the available voltage and requires high amp draws. Up until now a Sub C nimh or nicad was pretty much the standard in hand tools. You're slowly starting to see those be replaced by variations in lipo chemistry because of the greater power they can provide.

That's what cracks me up about Minelab using Sub As. Those were pretty much the standard in RC because they could handle the high amp draw of plane motors. The Sovereign doesn't need such high amp draw ability in a cell. A triple A cell would surfice just like a double A. Even if they still wanted to use 10 of them that would still be much lighter of a cell size.

 

[kered]

Tipical of Minelab, everything is realy beefed up

 

[synthnut]

Now if the battery charger they sent would match the quality of the rest of the package .... Jim