Detector Batteries Make a Difference

[Bryannagirl]

Ok,
I hope you do not mind a girl chiming in here but there seems to be some misinformation going on about regulators batteries and power supplies. To keep things simple coils are current driven devices more current equals more field strength.

Next most modern power supplies are designed with both voltage regulation and current protection in mind. The also are designed to have minimal noise impact on the production which it is being used. Note I said current protection not current regulation. Current regulation in my applications is not necessary or desired only protection from over current conditions.

Voltage regulators do not ad voltage only regulate a higher voltage to a desired level. For the majority of designs if voltage falss below the regulated set point the voltage output from the regulator will be less the the set point.

Batteries under load can and do have voltage drop. The higher the current out the higher the voltage drop. Better batteries have less voltage drop in general the less expensive batteries. So it is very possible under high current demand for the out voltage of a battery to drop below the level at which the regulator can regulate I.e. Under high current loads voltage can drop below the designers desired operating voltage.

These are all facts. In general circuit designers design there circuits with margins the keep voltages and currents in ideal operating area. But battery powered devices do often suffer from performance degragration whe battery power drops.

I do not know any specifics about any of the detectors circuits but I do believe that it is very possible for a better battery to help a machine perform better but it does depend a lot on the circuit being used

 

[tab-nabit]

For my detectors and other devices that use the "AA" cells, I'll stick to using my NiMH rechargeable. If anything, as many that gets used around the home, I got tired of the bulk packs of alkaline I was going through.
I keep a few chargers around too, from 2 cell chargers to a couple 8 cell chargers. A couple years ago, 2 of the chargers I trashed because for some reason they didn't charge up as well as others I had. Took me awhile to figure it out but I noticed when using them, I didn't get the run time compared to if I used a different charger. I don't know if they were faulty, all I know is they didn't juice up the battery like my other chargers so I trashed them.


Bryannagirl mentioned "Batteries under load can and do have voltage drop. The higher the current out the higher the voltage drop. Better batteries have less voltage drop in general the less expensive batteries. So it is very possible under high current demand for the out voltage of a battery to drop below the level at which the regulator can regulate I.e. Under high current loads voltage can drop below the designers desired operating voltage."

Bryannagirl - Oh yeah, I had to convince a few coworkers on this one. They couldn't figure out why one of our module testers was shutting down after a brief start.
Although we always been using a well known brand, once in awhile a bad one gets in the batch. Came to find out that one of the batteries voltage was fine @ no load. But apply just a slight load and that cell voltage dropped below operating threshold and the other cell (2-cell device) couldn't sustain operation. Remove load and the voltage worked up till it read like the others, but dropped unlike the others when reapplying some load.
Took me a bit to convince them it's not always only voltage. Maybe they just figure I was retarded and went along rather than debate, I think they were getting to that point when I got to NiCAD w/memory, but had it later when it came to like 4 & 5 stage chargers for AGM using pulse maintainer/tenders for the plates - Ah...never mind I finally told them

 

[Critterhunter]

Rather than re-hash all this I just posted an update at the end of a low thread we have covering chargers and batteries. This last page is kind of a summary of the proper feeding and care of various battery types along will destroying a few myths people have about rechargeable batteries as well as detector power...

http://www.findmall.com/read.php?21,1178409,page=7

I haven't read the above response yet as I have to go for a few minutes, but I will say that a voltage regulator not only drops the voltage to a given desired level (it CAN NOT raise it, only drop it) but there is a limit as to the amps or current that the regulator can handle the device wants to draw. Increasing the amp delivering ability of the battery does not alter what the product consumes. However, if you were to use a battery that can not handle the current draw the product wants to power it's self then bad things can happen, mainly to the battery. Same deal with voltage regulators. They have a limit as to the amount of current they can supply to a device. If the device wants to draw more current than the regulator can handle it's either going to blow or if you're lucky shut down on thermal overload.

Trying to force feed a detector more voltage than it can handle is not going to improve it's performance, and as said your typical AA battery is well within it's capability to handle the low amp draws of modern detectors, so the amp delivering ability of the battery isn't really a concern. That said, there are instances when a dropping voltage can increase the amp draw of a device and cause bad things to happen. For instance, in a condenser compressor for your house AC if the voltage it needs drops too far below specs then the compressor motor will start to draw too many amps to try to do the same job. Amps go up and if you are lucky fuses blow before something worse does.

 

[Critterhunter]

Ok,
I hope you do not mind a girl chiming in here but there seems to be some misinformation going on about regulators batteries and power supplies. To keep things simple coils are current driven devices more current equals more field strength.

Next most modern power supplies are designed with both voltage regulation and current protection in mind. The also are designed to have minimal noise impact on the production which it is being used. Note I said current protection not current regulation. Current regulation in my applications is not necessary or desired only protection from over current conditions.

Voltage regulators do not ad voltage only regulate a higher voltage to a desired level. For the majority of designs if voltage false below the regulated set point the voltage output from the regulator will be less the the set point.

Batteries under load can and do have voltage drop. The higher the current out the higher the voltage drop. Better batteries have less voltage drop in general the less expensive batteries. So it is very possible under high current demand for the out voltage of a battery to drop below the level at which the regulator can regulate I.e. Under high current loads voltage can drop below the designers desired operating voltage.

These are all facts. In general circuit designers design there circuits with margins the keep voltages and currents in ideal operating area. But battery powered devices do often suffer from performance degragration whe battery power drops.

I do not know any specifics about any of the detectors circuits but I do believe that it is very possible for a better battery to help a machine perform better but it does depend a lot on the circuit being used

True that detectors like any thing else have a certain amount of required current draw that the battery needs to be able to deliver, but the amount that it draws does not change with an increase in battery capacity. Not only due regulators have a desired source voltage range but they also have limits in terms of how much current they can handle being drawn by a device. Most detectors have very low amp draw and that's why most batteries aren't really going to be an issue for them. Most double A or 9V cells can easily sustain the amp draw a detector requires, regardless of how cheap they are.

What the other guy below this response talks about it was is referred to as "surface voltage", in that when the battery is put under a load any surface voltage quickly drops to something much lower. Even a good battery will sag under heavy amp draws, but the amp draw of most detectors is so small that that's not really a concern or issue. Another variable in voltage sag is the capacity of the pack. A higher capacity pack will sag less in voltage than a smaller capacity pack under higher amp draws. That's one of the reasons why regular non-rechargeable batteries don't always provide a higher voltage to a device than a good high capacity nimh or nicad. Many non-rechargeables have LESS capacity than today's high MA nimhs or nicads, resulting in more voltage sag under higher loads and less run time. I don't think in detectors amp draw is much of a concern. Even a lowly 9V battery could be able to hold up to the current draw of a modern detector without much in the way of voltage sag to become any kind of issue. If the pack has a bad cell then yes, it will show up as severe voltage sag and could become an issue.

Regulators require certain input voltages ranges above the desired output voltage in order to operate properly. So long as the voltage is within specs and the device doesn't try to draw too much current then the regulator is for the most part happy. Once the voltage drops below a certain point the regulator can no longer provide the correct output voltage to the device and that's usually when the low battery alarm starts kicking in to warn you that that's about to happen.

 

[Critterhunter]

Just wanted to make it clear- Yes, voltage sag under load can put a weak battery at it's limits in terms of the voltage or amps it can deliver to the regulator. If the battery is borderline in this respect it can push things right to the edge in terms of how well the regulator is able to function and provide the proper power to the detector. That being said, that's something very rare to happen and you'd have to be "right there" on that line for a long time without going over it (thus sounding the low battery alarm). Bottom line is most cells can easily handle the amp draw of a detector, regardless of how cheap they are. A good quality cell with high capacity will ONLY increase the run time of the detector, not it's performance....Unless like I said it's riding right at that edge of component function, but within minutes you are more than likely to hear the low battery alarm as the battery continues to degrade. Being "lucky" enough to hit just that right spot at the fringe edge of performance parameters of the regulator without going over that edge is about as rare as hitting the lottery, and as said it should quickly "announce" that to you in the form of a low battery alarm.

 

[grumpyolman]

Critterhunter is spot on about the batteries. You get no more oomph because you are using alkalines. And not all Nimh are the same. Nicads...get rid of em. Old technology that will create issues later on in the life of the battery, or earlier if you always keep them topped off. Nimh DO NOT have a so called memory effect. However, Nimhs tend to air bleed over time and the batteries you charged to capacity last month, may not perform as long as you think they should. That's just the nature of the beast. However, Sanyo Eneloop Nimhs, and a bunch of other brands I just don't have the names of, are 'supposed' to retain 80% of their capacity sitting on a shelf for a year. I haven't tested that personally, but lots of folks I trust have experimented with them and say that's pretty accurate.
In my final analysis, I will use the old Nicads I have till they die. I have already started replacing them with both kinds of Nimhs. Alkalines are what you carry in the car in case you regular battery dies and the backup filled with Nicads/Nimhs has also puked on you. Grab the alkalines and keep hunting.
One other thing. You really should get a GOOD charger for any of your rechargeables. There are lots of features in a well designed charger that will eliminate a lot of problems and will prolong the real time life of your batteries.
jim

 

[Critterhunter]

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.

 

[grumpyolman]

Appreciate the technical discussion about the battery thing. Get the NiCad or the NiMh but, as others have advised, get the one with the greatest Mah capacity. The E-Trac comes with a rechargeable that is labeled 1800 mah. (Maybe it's only 1600 but I am not going out to check) Lets just say that Mahs is the number of gallons of gasoline needed to power your detector. If you are heading out for a long detecting trip do you want a 1600-1800 gallon tank or do you want a 2600 gallon tank. Some of the Nimhs I use have a 2700 Mah (Gallons) of storage. I can't detect that long in one shot but it seriously runs longer than the measly thing ML provided.

A good charger is the accucel 6. I just paid $22.95 for one...on line. jim

 

[DiggBird]

I'm a little confused. I see a lot of people saying they use rechargeable batteries. I don't know what machine everybody is using, but I use a BH QD II and the manual say's to use Alkaline Batteries only. Is this just for their protection or is it just for this particular machine?

 

[Critterhunter]

Trying to run rechargeables in it shouldn't hurt anything. Never heard of a device being damaged by trying to use them in it. It's either going to work or not. A lot of devices that say that will still work with rechargeables. I have yet to run into anything that wouldn't work with them myself.

 

[wasp]

DiggBird, I think the reason they say to use only alkalines is so you won't put cheap "heavy duty" batteries in your detector which can and will eventually leak, possibly ruining your detector. Get a good set of rechargeables for your Qd II and you won't be sorry. I use Powerex true 9.6V in my BH detectors and they work great. Just be sure to use a good charger like the Powerex MH-C490F Stealth charger. All rechargeables are not created equal and some cannot be safely charged in a rapid charger.

Good luck!

 

[UK Brian]

Someone contacted Bounty Hunter a few years back about this and it was just to avoid leakage.

Doesn't mean there's still not detectors that can't handle rechargables because they don't provide enough power and there's insufficient internal room to take the extra cells required. The old Minelab Sovereigns (8 AA alkalines recommended) were not happy with 8 x 1.2 AA rechargables so Minelabs own rechargable pack had 10 1.2 AAA's. The Mk 1 Whites Surfmaster P.I. had an eight cell AA holder for alkalines and a ten cell AA holder for rechargable use. The next version only had the alkaline holder as the box design didn't allow the ten cell holder to be fitted so it was better to stick with alkalines rather than keep opening the waterproof box and increasing the risk of leakage.

 

[Critterhunter]

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.