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Rechargeables for Goldquest

Hi Kev,
No, I have not modified my low voltage indicator. The reason is, I have modified my detector so I can charge the batteries in place and do so each night after a long day's use of nugget hunting. As such, I really don't worry about having them die on me in the field.
I do this because I may be a mile or more from my vehicle at any point during my hunting periods and really do not want to carry my spare set of batteries with me while I am out in the field. Even a set of extra batteries can get tiring lugging them up and down hills all day.
I just use a simple modified wall charger that charges the batteries with a current less than the .1C rating. I started out with 1300 mah batteries and picked a charger that would charge the batteries at less than 130 ma (.1C) when the batteries were near full charge. This has worked quite well and is about as simple as one can get. After a long day's hunt, I just don't feel like pulling the batteries and placing them in special chargers. Instead, I just plug in the charger and let them charge.
This has worked quite well for me on my GQ clone. It is the detector I use when nugget hunting and that only happens a few times a year. I will use it from early in the morning to late in the evening during those periods.
I do play with the detector during other times and I am constantly trying different things to improve it. As such, it is on a lot but much of the time I am at or near home. To be honest, when at home, I deliberately do not charge the detector as regular to get a feel of the overall time I can safely use it before having to worry about changing them. I don't actually time it, but just make a general mental note. I have gone more than a week without charging them, but that has occured when the testing is reduced to just short periods each day.
This also allows me get a better feel of just what might happen when the batteries begin to fail. Normally, the detector gets erratic.
However, my first premature battery failure was quite strange. The detector seemed to work fine but would just beep every couple of seconds or so for no apparent reason, which might be what the low battery indicator is supposed to do. It really didn't make much sense at the time, and I was about a half mile from my vehicle. Since batteries are the logical thing to fail, I hunted my way back to the vehicle and replaced the set, and went about my hunting again. Later I checked each battery and found one was bad. BTW, it was just a short time after changing the battery pack that I found my 3/8 oz nugget.
I never had any battery problems or failures at all prio to the ones that failed from one particular batch and that bunch had several fail prematurely. Up until then, they seemed to be indestructible no matter what I did to them or what brand I used.
Since batteries are constantly improving, I also have a tendency to just replace my detector batteries with higher current rated ones when the price is right. This usually happens about once a year. The old batteries are then used in my flashlights, etc.
It is hard for me to justify trying to maximize the life cycle of a NiMh when they only cost me about $1.25 USD apiece to upgrade. Recently I was lucky enough to get 2250 mah for the price of 2000 mah batteries. Unfortunately, I just ordered another set of them and did get 2000 mah this last order instead of the 2250 mah I received on the previous order. Now, I need to find time to see just how much of a difference there really is between the 2000 mah and the 2250 mah batteries.
Since my GQ clone is really not hard on batteries, current wise, I haven't really worried too much about batteries. In fact, the actual current draw is much less than the .1C of most AA NiMh's sold today.
Reg
 
Hi Reg,
Thanks for that information. I too had some problems with a batch of NiMH cells (Nexcell) I was using a set of 8 in my Minelab Explorer, all went well for a number of charges then one cell would reach end point voltage well before the others, lowering the capacity as a whole to around 1Ah instead of 1.8
I thought I had just one bad cell, but after changing it, I found the same thing would happen, but a completely different cell would let the bunch down. This happened a few times.
I think it might have something to do with my charging setup. I split apart the battery holder and put a 317 voltage regulator configured as a current source in the housing, just like the production packs. This enabled me to recharge them as a gang.
I know that the connections between loose cells in an arrangement like this, isn't very good. Occasionally the pack only needs a good smack to get it up to capacity again.
I will need to get some cells with tabs to overcome this problem
I think manufacturers of packs must combine cells of equal properties to ensure all cells have the same discharge/recharge parameters.
It appears Reg, that the claim of no memory with NiMH cells maybe correct in your case.
Cheers Kev.
 
Hi Kev,
I am not sure your problem was a problem of charging. It could be you got a bad batch also. What mah rating Nexcell's did you have problems with?
At first, I thought I might have been overcharging my batteries that failed, but found out later that Nexcell had a problem with some of their batteries. This info was posted on the site that compared NiMh batteries, but I also found a couple of other postiings where people had problems just like me. The 1800 mah seemed to be the worse of the lot, but there may have been failures with some of their 2000 mah batteries also. So far, I haven't heard of any negative comments about Nexcell's 2100's.
Actually, I have been using the same technique for charging on several different brands and have only had problems with the particular batch of Nexcells. One thing that made it easy to tell a failure is the battery will charge to a higher value than normal but will just not work.
So far I have used NiMh's made by Nexcell, GP, Powerex, Powerizer, Digital, Sampsonite, and some green ones with no name on them and all have performed very similar, except for the batch of bad Nexcells. All have been used in my detectors, cameras, and flashlights. None of them have really stood out as being the best. Obviously, the Nexcell 1800 mah have been the worse, but my Nexcell 1300's performed quite well.
I guess I really should be monitoring the batteries more closely. Some of the weird glitches I have experienced just might have been the result of battery problems.
As for charging techniques, one could build a fancy pulse charger that, in theory should do a better job of charging, but I am not sure it is worth it.
As for a memory effect, I haven't experienced any problems with the NiMh's, but I really haven't been looking that closely for it either. I would just make a quick check of the battery voltage and if it is in the range I think it should be, and the equipment is working fine, I was happy. Now, I will watch the voltage more closely, especially when testing.
Reg
 
Hi Reg,
My batteries are Nexcell 1800 mAh. I'm pleased to hear that there are others experiencing problems with them, since it vindicates my charging circuit. However it
 
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