rechargeable AA batteries ?

[babulin2002]

Hi all,
I was wondering whether the rechargeable AA are good enough to use in my GT. I bought the machine with only a battery holder for 8 AA batteries. These are 1,5 V, as opposed to 1,2 V for the rechargeable AA . I tried the rechargeable and they last half or even less of the time i get with normal 1,5 V AA. I am wondering if i get lower performance due to lower voltage, for example less depth etc. On one hand if the detector does not complain (no low-battery beep) i guess it should be fine, but then again 2,4 V difference is a lot. There's also a question of the mAh of the batteries, but this is just the capacity as i understand, higher mAh results in longer operation, right ? So, has anyone used the 1,2 V rechargeable in this way, and what is the theory to that, can i use them and not suffer decreased performance of the machine ? I did search the forums to try to find some answers but didn't get anything decisive. Nay info greatly appreciated !
Thanks, cheers !

 

[Critterhunter]

Read this thread and the other it's linked to. Already answerd all your questions there. Rechargables should work but they need to have good high capacity (shoot for 2500ma or higher, but 2000ma may work) and be peaked off the day or so before you hunt. All the info is in those threads and explains why it's a myth for most devices that rechargables won't work. I will say this, though, I have yet to run 8AA nimhs or nicads in my GT to be sure of that, but based on what I hear it's voltage regulator requires for input voltage I don't see any problem with just using 8 instead of the 10 inside the rechargable pack. That pack is only 1000ma and so the voltage on thus should sag real quick, which is why I bet they put 10 in. Very old school. Sub As like those found in that pack in the 1000ma range are about the cheapest/oldest you can lay your hands on these days. I think they go as high as 3000ma or at least close to it, but it's been a while since I played with those Sub As in RC. I think at the time I was using them 1600ma was big, replacing 1000ma, but can't remember for sure. If they follow what I've seen done with Sub Cs and such I bet they are at least over 2000ma. Why Minelab would put such a low capacity yet huge heavy cell in those packs is beyond me. Well, we know why, but they could have thrown something both higher in capacity and much lighter in there. That's probably stock from the early 1990's some battery maker has been selling off cheap for years to companies who don't care.

http://www.findmall.com/read.php?21,1162011

 

[Rick(ND)]

I myself wouldnt use them in the Sovereign, but will in the Explorers and the E-Trac as that is what they use. On the Sovereign Minelab uses 10 AAA cells to get them to fit in the pack from what I understand as it needs the 12 volts, not the 8 cells 9.6 the rechargeables have. Some say they have no problem, but as you see they dont last very long either as the Sovereigns will go into low battery alert around 9.2 volts, so it dont have very far to go to get below the 9.6 volts needed.
Back in the late 90s we used to see a lot of post where people were having problems with low battery alert with the Sovereign only to find out they were using rechargeables in the alkaline packs, some didnt run more than 30 minnutes while others could go a good 4 hours because some had used 2000 Mha or larger.
I do feel I have better performance with the factory rechargeable pack fully charged and seem to lose some performance a while before the low battery alert. When I go out detecting I want my GT to be at max performance so my battery is fully charged and the coil cover is clean and use a good set of headphones to hear those deep coins others have left for me.

 

[babulin2002]

thanks a lot guys !

 

[Critterhunter]

If they don't work and give long run times in a Sovereign that will be a first for me on any device that wouldn't run with 8AA nimhs or nicads. Providing that they are high enough capacity (like 2000 to 2500ma or more) and are peaked within a few days of use I don't see that there would be a problem. I've got a computerized TX that draws more current than a Sovereign (I think) and when I charge up 8AA 2500ma Energizers I can fly all day on that pack and probably well into two or three more days before hitting LVC (low voltage cutoff). This TX also has an onscreen voltage level and a fully charged pack often starts out around over 14 volts and stays well above 11V for hours. It's LVC point is I believe 8.9V, at which time it will sound an alarm to land your plane or risk loss of control.

Everything else I've used rechargables in has also worked fine for me, from digital cameras to remote controls and endless other devices. Still, there is only one way to put this to rest. I'll make it a point to charge up my 2500ma 8 AAs and see just how long the Sovereign goes on my next all day hunt. If what I hear about it's very low amp draw is true then I'll guess it should run a very long time before hitting the LVC battery alarm.

So far as less performance goes, I don't see how it would be possible to get less performance from a machine when it's running a voltage regulator. Actually, although I didn't look close it looks to me that it's running several linear regulators in one corner of the board. If it is and they are putting out a constant voltage to the board then it doesn't matter what the pack voltage is, so long as it's higher than what the regulator requires to still function. Others have more experience with playing with Sovereign boards than me so somebody chime in and correct me if I'm wrong here.

 

[kered]

I always used them in the Elite with no problems, lasted longer than the stock battery too to a point the stock battery was only used as a spare instead of the other way arround, tried them in a borrowed GT too but never got to drain them properly flat while i was testing, they also work in the excalibur alkaline pod but i don't know for how long as i put in all subC refill packs within a few days of getting the pod, the 8xAA holder that was in the alkaline pod has come in handy for charging 8 together with the Acucel 6, saved me buying one

 

[Critterhunter]

That's what I figured Kered, but there is only one way to tell for sure and put this to rest. I'm going to charge up my 2500ma nimh Energizers (Walmart) and stick them in my GT. I'll only charge them once, right before going out. After that they'll sit in the GT without a freshening quick charge so there will be no doubt about just how long they last in the field. If I was to charge them say two weeks prior to the first hunt that might drasticly cut down on run time, though I hear some of the very latest nimhs really do hold a charge on the shelf very well. As good as nicads or better. I once owned some 2500ma Energizers about five or six years ago that would only hold a charge for a few days. Once I used them they were near dead. However, the newer 2200ma or 2500ma Energizers I've bought in the last year or two will hold their charge much better on the shelf.

This will be a fun experiment to finally put this thing to rest as it always seems to pop up in the Sovereign forum, even more so than other forums. The only thing that gives me cause for concern is why would Minelab run 10 cells in the rechargable pack when everybody else probably only puts 8 in other rechargable packs. The only answer I can come up with is they used such a low capacity/old technology Sub A cell that it sags under voltage real quick. As I said, I bet 8 AA nimhs or nicads will hold their voltage higher than those 10 through most of the discharge.

 

[Critterhunter]

Also, another bonus to using nimhs is that I think they are a good bit lighter than normal store shelf batteries but I haven't weighed them to be sure. At least they feel much lighter to me. Besides that, if you are going to use regular store shelf batteries then I'd look into the lithium (NOT lipo rechargables....two different beasts) Energizers at Walmart and such. They are MUCH lighter than a regular battery and will give you probably 2 to 3 times the run time or more so it will more than make up for any extra price involved. These are not rechargables so don't try that with them. I keep those in my regular holder as my backup to the stock GT rechargable pack, which I plan to ditch soon for a lipo to drop a bunch of weight.