Excal Charger.

[Critterhunter]

Good info Kered.

Jbow, you are right about the numbers and it looks like you are starting to learn all the mysterious things about batteries and capacity. Still yet I've thought of a few more tidbits to add...

Many people confuse capacity with how many amps are being delivered to the load (such as a detector). They often believe that if they are using a higher capacity battery it will try to deliver more amps to the machine than the machine is supposed to use and burn it up. Nope, any "load" (light bulb, detector, whatever) only draws the amps it needs to power it's self. It doesn't matter if the battery is the size of a pack of smokes or the size of a house, the load will only draw what it wants and the battery capacity will do nothing to alter that. The only thing you need to be concerned about is voltage. If you tried to hitch up a battery that is putting out too many volts than the load wants to see then you could very well burn it out.

Also, you need to be concerned with if the battery can supply the amount of amps the load needs. For example, your car wants about 12V to start. An 8AA in series pack can deliver that voltage, but it can not handle the high amp draw the car's starter is going to try to draw. That's what the "C" rating on a battery (most lipos have this listed) is meant to tell you. A 10C 2200ma lipo can handle about 22 amps of draw. A 20C rating would make it 44 amps.

Some lipos will also have a "burst" C rating, meaning that they can handle a certain higher amount of amps for X amount of time. It's never a good idea to go by that number, and also a safe rule of thumb for a long healthy life is to never draw more than 80% of the continuous C rating the pack is meant to handle. Meaning, to be easy on the pack don't draw more than 80% of it's C spec of continuous amp draw (not the burst rating). Another area where a lipo C rating might be used in it's charge ability. Most say do not go above 1C in amps charging it.

Capacity does have an effect on amp delivering ability. For example, a 1000ma lipo rated at 10C can deliver 10 amps. A 2000ma lipo rated at 10C can deliver 20 amps. See, this is all pretty easy stuff once you understand a few basic rules. By putting two packs in parallel not only are you increasing the ability to deliver whatever amps the load will need, but you are also increasing the capacity (or run time). Two 1000ma 10C lipos placed in parallel with each other now doubles the capacity to 2000ma. Double the run time and also double the amp delivering ability (10Cx2000ma=20 amps.

While I'm thinking of it, another thing I'd like to mention is a bit more about using the discharge function on a charger. Let's say you want to drain a nicad pack dead and use .5 amps with a target voltage of .1 volts. Usually the charger will drop the discharge in amps down as the pack gets near dead. It does this to maintain a "true" voltage reading of the pack by not putting it under too high of an amp draw. Trying to keep the discharge at .5 amps when the pack is near dead would cause the voltage to sag under the load and give a false reading, so the charger would then shut off but the voltage would then bounce back higher once the discharge is stopped. However, a charger doesn't always handle this properly it what it senses to be the limit it should keep the amp draw at to keep the voltage right. For that reason after the charger terminates it's discharge I would then drop the discharge to .1 (Meaning 0.1) amps and re-start the discharge. What this will do is insure that it wasn't sagging under the load and will drain the last bit of voltage out of it. Even doing that still is not draining the pack deader than it would if you let it sit on a light bulb after it goes out for another few hours.

 

[kered]

I charged the etrac battery at 0.8amps till it read full and it put in 1684ma, it took 135 minutes, i then let it sit for half an hour and topped it off at 0.4amps and got another 158ma in 25 minutes, thats a total of 1842ma in a 1600mah battery and it wasn't flat, only down to cutoff on the etrac.
This shows that with an efficient charger you can get more in, also if i watch these totals over a period i can tell when the battery capacity is getting down and needs cycling.

If it wasn't for the thermister in the original pack i could charge it in half the time as i do with the 2800mah rechargables in the alkaline pod(I charge it the same way in my protatype holder)

sorry for the photo quality of my cellphone, all this charge power and my camera battery is always flat when i need it

 

[Dom of NJ]

Kered and Critterhunter,
If I understand this correctly, the Excalibur ll wallwart is nothing but a 12v power source. The actual charging unit is located somewhere in the SEALED battery pack. Inside the pack resides the thermister which regulates maximum input amps. Ok, now I have a question. If we are inserting another charging unit (the Accucel) between the wallwart and the internal charging unit, what is happening? I have a feeling that I will have to break the seal and remove the batteries and charge it/them with the Accucel. Is this correct? Or does the Accucel actually somehow charge through the ML internal charger? I AM SO CONFUSED!
PS: I just ordered one of these things.
Dom

 

[kered]

In simple form
Battery chargers all work in the same fashion, they put out more voltage than thats in the battery so the current flows to the battery, how they detect and control this is where the difference comes in.
Your car has a 12v battery but the alternator puts out between 13.8-14.1v so the battery charges. The amount of amps in output determins the time it takes

The thermister is only a thermal switch, if you try to charge too fast the batteries heat up and the thermister detects the change in temperature and opens stopping the charge. Inside the Excalibur battery there is no circuit, only the thermister, in the etrac i don't know as i haven't opened it but i presume its the same, the XS battery has a small circuit and thermister but i think its only for reverse polarity protection.
I think minelabs idea is to protect the batteries in its cheepest form as when they are getting full they start to get warm, the charger keeps pushing charge in at the same rate and doesn't cut off and relies on the thermister opening, i think its a crude method to stop overheating and damaging the batteries. Rechargables don't like getting hot and it will reduce thier life.

The excalibur wall charger is just a power source higher than the battery and puts out 14.3v not 12, the etrac 15v, these being higher that the voltage in the packs will charge them(continuosly) although at a very slow rate(small amperage)

These wallchargers won't power the Accucell-6 as thier output amps is too low, even though the voltage is within range, you need something with more amperage(5amps minimum)

http://en.wikipedia.org/wiki/Battery_charger

 

[jbow]

I'd just keep using the wooden holder.

Thanks for helping me with this.

J

 

[Dom of NJ]

All great info Kered, but the question remains: Do I have to pull out the sealed battery pack to charge it, or does the Accucel charge through the internal charger via the Excalibur's ikelite connector?
Thanks,
Dom

 

[jbow]

Thanks, i'll read over all this again as I get the charger and holders. Question... can you completely discharge a battery like you would a capacitor in a tube amp, you do that by either using a wire with two alligator clips and tying pin one of the first preamp tube to the chassis or the + side of the first filter cap to the chassis, but that is dealing with residual, but deadly, voltages. ??

I get it that a high capacity battery will just last longer.. which is what I want. Plus, now that I am aware... I don't want to ruin my good battery packs by under or over charging or not using proper care and occasionally taking them from flat to full. I know I have never completely discharged any of my detector battery packs but i've never used "loose" rechargables, just the rechargeable packs that came with certain detectors... Minelab. I am pretty sure the Whites charger wont over charge, at least it has a red light that comes on when it is fully charged, I assume that stops the charge but I don't know and I have never discharged that pack.

I bought two 9v rechargables yesterday. I think they are 150mah.

J

 

[jbow]

I am guesing that if Iwere to build a pack from 2900mah NiMH batteries and assuming I use the Accucel 6 and know what I am doing... leaving the thermistor out would be a good idea.... as long as I use the Accucel and set it or watch it.

J

 

[kered]

All great info Kered, but the question remains: Do I have to pull out the sealed battery pack to charge it, or does the Accucel charge through the internal charger via the Excalibur's ikelite connector?
Thanks,
Dom

As luck would have it the accucel comes with the same size plug thats on the stock charger and plugs directly into the ikalite no problems, the only thing is if you try to charge too fast the thermister will cut out and stop you damaging the battery, you can still charge it under an hour from flat though, the other cables i made up are for other batteries, including the wooden etrac block:blush: i even charge my drill batteries with the supplied aligator clips

Jbow, to discharge the battery completely just put a12v car bulb with alligator clips across the 2 terminals, leave it over night(till the bulb just goes out is not enough)
I have 2800 and 2500 rechargables in the explorer/etrac alkaline pod and i charge them in the wood block too, i do have an 8 cell holder though that came inside the excalibur alkaline pod(now filled with a 1400mah pack) i also had these 2500 in the elite/GT pack that lasted longer than the stock battery
The wihites charger once charged goes into a trickle charge (at least my mxt one did) to maintain the battery full, just over the self discharge rate

 

[jbow]

n/t

 

[Dom of NJ]

Ah! You've brought a smile to me face me hearty :cheekkiss
Thanks Kered!
Dom

 

[Critterhunter]

Printed out to read later. Looks like Kered has posting a bunch of great info.

 

[Critterhunter]

Good job and info, Kered. One thing I would point out though is that if a pack is peaked and then stuck back on a charger but shuts off in say less than 20 minutes then you can assume it didn't take any more charge. The charger will try to put about 40 or 50ma into the pack before it figures out the pack can't hold anymore charge and is full. For that reason I'd discount any further capacity put back into it if it's say less than 60ma before the charger once again says the pack is peaked.

But, what you did by charging the pack at a higher amp rate until it terminates and then dropping to a low amp rate often will put even more capacity into the pack. Slow charging a pack will fill in the little last bits of capacity that the higher amp rate doesn't do a good job of taking care of.

Also, one more thing about discharging a pack on the charger. Let's say you set it at .5 amps and find that as the pack is say 2/3rds drained the charger is only showing 0.0 amps being drawn out of it. Some times this is due to the pack being so low or is just a small pack that it can't handle higher amp draws, causing the charger to over react. Try stopping it and using a .2 amp rate. Often you'll find the pack can sustain that and as a result the charger will drain it faster than if it was set to .5 amps because it's not going to cover compensate and drop down to 0.0 amps to avoid the voltage sagging. As I also said, once it's done I'd reset it to 0.1 amps and do another discharge. This will drain a bit more out of the pack, but it's still better to use a light bulb to get even more out of it and insure all the cells are drained equally.

 

[kered]

Just looked at the Accucel-6 charger to see if they were in stock again to get another one, i noticed the lead connections are now changed so if you get one of the newer ones you might have to do a bit of soldering to get the exact connections you need(or buy readymade for a couple of bucks

 

[Dom of NJ]

I got the accucel and charged my spare nicd battery pack using the .7 amps that kered recommends. It was charged within 2 hours. This is reasonable to me because the pack was not dead, and was probably about 3/4 charged.

If I understand kered and critterhunter correctly, it isn't good to fast charge these packs constantly. You should charge for 10-12 hours. If this is the case, for a 1000mAh battery, I should charge at 0.1 amps. (1000mAh = 1.0A, therefore 1.0A/10hrs = 0.1A).

I wonder if someone could confirm this thinking and calculation?

Thanks
Dom

 

[kered]

Charging for 2 hours at 0.7amp charge rate would put in 1400mah(700mah per hour), the nicad is only 700mah so something is amis, probably it didn't pick up the initial voltage drop properly, you might have to adjust the mv slightly. At 0.7 amp it should charge from flat to full in 1 hour being 700mah.(did you notice the final reading, bottom line right hand side? xxxxmah)

Yes your calculation is correct. the 0.1amp is known as a form charge on a 1000mah battery and should be used the first time you charge the battery from new(probably better 12-15hours as the manual suggests) if you have done it with the wall charger supplied till now you shouldn't need to do it again unless the battery duration shortens and just charge at the 0.7-8amp rate. Doing a cycle charge at low amps every 3-4 months or so will keep them in peak condition.

Your 1000mah nimh should charge at 1.0amp when in a hurry but the thermister may cut in and gives a connection break alarm so i do mine at 0.7 or 0.8amp and all is ok, only takes just over an hour from flat and the battery stays cool at this charge rate.

I have charged my 1400mah at 1.4 amps and they only get slightly above room temperature when they are nearly full.

If batteries get hot while charging your giving them too much candy and the heat will shorten thier lifespan. drop the charge rate and start again when they cool.

Now you have the charger a handy thing to have is a cigarette lighter plug(easy to make one), that way you can top the batteries off on your way to the beach, especially usefull if you don't get out much as nicad/nimh self discharge over a short time and it saves you putting them on charge the night before, also if you go away for a few days you always have means to recharge in the middle of nowhere.

 

[Dom of NJ]

Thanks kered.
When you say adjust the m/v, I take it to mean to bump it up?
I like your idea of adding a cigarette lighter plug. Great idea. I'll do it!
Dom

 

[kered]

Thanks kered.
When you say adjust the m/v, I take it to mean to bump it up?
I like your idea of adding a cigarette lighter plug. Great idea. I'll do it!
Dom

No, mv is the voltage drop in millivolts the charger needs to detect in order to switch off, if the charger is not detecting it and not cutting off when full you need to lower it, if it false peaks(stops charging before full) you need to raise it so that it takes a slightly bigger voltage drop to cut off, there is a difference in setting between nicad and nimh settings even though it reads Default (NiCd default:12mV, NiMH default:7mV) both are adjustable between 5 and 20mv in the settings menu

 

[Critterhunter]

Reading the rest of this later as I've been on here too long, but I'll say this...A one hour charge rate on a nimh or nicad is harder on the pack then a slower charge. A 3 hour or 5 hour charge is easier on it. A 10 hour is probably best for a long life. But, I wouldn't say a 1 hour charge time on a dead pack is bad. Just be aware that many feel you are shortening their life. It's like not stopping your car until you get real close to a stop sign. Is that a bad thing? Well, if that's the way you drive then I wouldn't call it bad. Is it hard on the car? Yea, a little. You'll probably have to replace the breaks sooner and gas milage will suffer some. But, you have to decide which is more important to you- Replacing breaks a little more often or sacrificing a little drive time by slowing down sooner. The capacity of the pack may start to suffer over time (like say a year or two down the road) and not give you as much run time, but truth be known you probably won't notice that so long as you cycle the pack dead 3 or 4 times say twice a year to keep it in better shape. I also feel a fast charge doesn't put as much back into the pack for the hunt. Charging slower will give you more run time for that charge.

Bottom line is charge it as slow as you can whenever you can. If you are going hunting tomorrow charge it at a rate that will take say 10 hours if the pack was dead. If you plan to hunt in 6 hours then charge it at a rate that will take say 5 hours, which will of course take less time than that at that rate unless the pack is completely dead. If you plan to hunt in an hour then do a 1C charge, or as high as your pack will allow you to go without throwing a thermal overload switch. Another deciding factor is if you are around. I keep mine in the garage in the middle of the cement floor when charging but I still don't like to leave the house while charging or discharging packs. So long as I can go out in the garage every hour or so to check on it I feel safe. If you can't be home to watch things here and there then charge it at a faster rate that will be done before you leave.

Just use common sense. Go as slow as you can (up to 10 hours on a dead pack charge rate, no need to go longer than that...it won't make it any easier on the pack) whenever you can, or adjust faster up to a 1C charge when you just have to. Also, a fast/hard charge rate is a good thing on a pack here and there say 4 or 5 times a year because it breaks down resistance crystals. On a bad pack I may go 3C for at least five or ten minutes just to wack it good and blast out any crystals to try to recover the pack, but then will go back to 1C to complete the charge. Later I go easier on it to try to bring it back to life in say a 5 or 10 hour low charge rate. Just like driving a car fast and hard here and there can help to blow out carbon in the motor when it hasn't been driving on the highway much, fast charging can do the same in a sense for a pack.

 

[Critterhunter]

I'm finding that on a slow 1/10th C charge rate I like to drop the m/v a few digits, like say from 7m/v down to 5m/v for a nimh, and say from 14 m/v on a nicad down to 12 or even 10m/v. If charging at say 1C then I'll keep it at like 5 to 7 for nimhs and 12 or 14 for nicads. Reason being that with a very low amp rate the m/v drop won't be as pronounced as it will be at a higher amp charge rate. So long as you keep it somewhere in the 5 to 7 m/v for nimhs and like 10 to 14 or so for nicads you are right in the ballpark for those types of cells. Just adjust slightly according to what charge rate you are going at.

Another handy thing to do is after cycling a pack 4 or 5 times (keep going if the capacity put back in shows no improvement after say the 4th or 5th cycle because it's still improving) is to then write right on the pack via a magic market just what the highest capacity is that is has taken. That way a year or so down the road when you do another dead/charge cycle several times you can monitor if the pack is holding it's capacity or is going down hill. It's a good way to indicate when the pack isn't long for this world, once capacity has dropped a lot over what it originally was holding. Also keep in mind that amp charge rate can alter that number, so mark on it what amp rate and m/v setting it was set at when doing that, so you can replicate the same charge settings when comparing. A high charge rate (1C) often will show less capacity than a slower one. Write the m/v settings for the various amp charge rates on the pack as well once you find what seems to work best for that pack.

If you are real unsure that the m/v setting is correct and that it might be too high then note what voltage the display is showing for the pack. Come back 15 minutes later and see if it's climbed. Check it again another half hour or so later and so on. The voltage should be steadily climbing. If it's dropped or is staying right around where it was an hour ago then the pack might have peaked but the m/v is too high and so the charger didn't shut off. Wait another half hour and check again. Packs will hit dead spots where they drop some or stay at the same voltage for quite a while and that's why m/v needs to be set high enough to not false terminate, and also why if you aren't seeing the voltage climbing just come back later a few times and look again. Also, if charging at a high amp rate put your hand on the pack and see if it's real hot. If it's anything more than luke warm the pack is either being overcharged or you have the amp rate too high for proper charging. Heat kills cells.

The way to tell if the m/v is too low and has caused the charger to false terminate is to throw the pack back on the charger. Wait about ten minutes so the pack settles, because if you throw it right back on the pack is already low in voltage if it indeed has peaked and the charger might not see any further voltage drop to shut it off. The pack will spring back up in voltage a bit once it's peaked and sat a while. Anyway, when you do throw the pack back on raise the m/v setting by two digits and then watch the pack voltage over the next hour. If the pack terminates it's charge within say 20 minutes to a half hour then you can bet the pack was indeed peaked. It will often take about that long for the pack to start dropping in voltage again and terminate. High charge rates will tend to shut it off sooner (less than 10 minutes), while low amp rates might take a good half hour before it triggers it to shut off. Normally the MA "put in" to the pack will be something south of 100ma, like around 50 or 60ma. That's also a good indicator that the pack was peaked, and you can ignore adding that 50 or 60ma to the total capacity put into it since it didn't really "take" that extra capacity. On the other hand, you might still have the m/v set too low and it's still false triggering a shutoff. If you are approaching say 8m/v for a nimh or say 14m/v for a nicad then I would suspect the pack isn't false terminating. Rather than raise the m/v higher just wait ten minutes and then stick the pack back on. If it once again terminates in under 30 minutes then it's for sure peaked. Often though, even with the proper m/v setting, a pack can false terminate 2 or 3 times through a charge. Either raise the m/v a digit or two or just throw it back on. I'd rather have it false terminate than have the m/v too high and the thing never shuts off. Some guys go as high as 8 or 9 m/v for nimhs and 17 or so m/v for nicads, particularly when charging at 1C or more. I never go that high even at 1C. About 7 max for nimhs and 12 or 14 for nicads. You'll have to find these things out for yourself, though.