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Battery Question

A

Anonymous

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I just got home from the store with an 8 pack of Energizer 2300 MaH rechargable batteries. With a quick charger, this seems like the way to go. I ahve a question though. The battery pack is supposed to be 12 volts. The alkaline batteries are 1.5 volts each. 8 of them is 12 volts. The rechargables are only 1.2 volts each. That's only 9.6 volts total. Is the amperage that these put out making up for the lower volatge or are we losing performance by using these rechargables?
Thanks,
Todd
 
Thanks C.C. I didn't get a rechargable with mine (I bought it used). I guess that explains it. In theory, the 2300 MaH rechargables *should* last almost 50% longer than the 1600 that Minelab supplies.
 
because I had to double check the Nimh pack voltage. I also have 2300s (Powerex) and have been having a little trouble. I'm getting the low battery sound with the pack still showing 1/3 full. That on 2300s I figure should still be several hours. I have also noticed several times a couple batteries seem to linger behind the others when charging. I have been using two sets and haven't really tried to isolate a potential problem. On top of that my detector has shut it self off and even at times which the batteries were not sounding off. I'm not sure if these two problems are related, but at this point it doesn't affect me much. I would hate to see my detector not turn back on some day. Could be dirty contacts I guess. Will look into that.
 
In therory yes but in reality you can expect them to run about the same time .. maybe a tad bit longer after a few charges <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=":)"> I've measured the voltage after a few recharge cycles and they hit 11.8 volts but drop off after an hour or so to 10.2 and stay there for quite awhile.
I've been running them as back up's on weekend hunts when I'm out of town. Especially like the quick recharge time that I get even with the cigarette lighter adapter. Nothing better than knowing you can have a full charge in under 30 minutes and you're back to swinging again.
Good Hunting
Mike
 
I was told that I should match my batteries.
I have 16 of them and the way I was told is to do a full charge then let them sit for 3 or so hours then check voltage on each one, some will drop more than others match up the best ones and mark them as a set.
I have one that drops faster than the others and it will shut my machine off at times and the bar says it has a 1/2 full pack in it.
Charlie
 
1) "then let them sit for 3 or so" ... You mean run them down for three hours in the detector?
2) Did matching up the batteries prevent this problem, or do you still have it? These things cost enough I wouldn't expect to have to deal with something like this.
Doesn't really make sense why the Minelab pack works well but my freakin high end recharables are crap.
 
You need to buy a decent charger with peak detection (i.e. maha intelligent charger) when using commercially available nimh cells. The wall type chargers (non-automatic no peak detect)available at wally world and those made by energizers do not stop charging until you pull the cells from the tray.
Without peak detection circuitry, nimh batteries will loose capacity due to overcharging. This happens faster with fast chargers that use high rates for charging which literally cook the cells after they become full.
I have a set of 1800 mah energizers that have been with me for 2 years and they are still going strong. I use them on my detector and digital camera. They get used at least twice a week.
A set of alkalines have nominally 1800 mah of capacity in them. If alkalines last much longer than a pack of nimhs, then you are doing something wrong.
Note though that nimh have a self discharge rate. They will lose capacity on the shelf. To get the rated capacity, use them 1 to 2 days after charging. Otherwise, weekly you lose about 5%. The self discharge rate is higher for older cells.
The NIMH pack for the EXII is 9.6 volts so it is fine to just load up a nimhs into them if you are willing to invest in a decent charger.
The sovereign elite has a 12 volt 10 cell pack. I do not recommend stuffing nimhs into an alkaline pack for that one.
bing
 
It is not necessary to match batteries for our purpose. You can do a format charge. This is done by charging at a maximum rate 1/10th of capacity to uniformly bring up the charge on all cells in a rechargeable pack.
For example, 180mah charge rate for 1800 mah cells, 230 mah for 2300 mah cells. Run them down in the detector and repeat. Doing this twice in a row will be enough to bring all cells to a uniform level of being charged. Formatting twice a year is enough to maintain your nimh cells. Note though that NIMH cells will lose capacity when you bring them to a zero volt state. This is as bad as over charging. The lowest voltage an nimh cell should reach before deterioration of capacity is 0.9 volt per cell or 7.2 volts for an explorer pack.
bing
 
I dont own a minelab explorer rechargeable pack but I do own a Sovereign elite nimh pack. It has a charger circuit built into it. I suspect the explorer nimh pack may be the same.
Charging retail nimhs on wall chargers only cooks them, which causes progressive loss of capacity, unless you are willing to time a charge taking into account the pack's state of discharge, which is next to impossible.
bing
 
Over time do you know if the batteries will level out? It's not really a big deal but I would rather not deal with it forever.
Thanks
 
If you dont maintain your nimh batteries, they will destroy each other. Cells with a higher state of charge will overcharge when charging and cells in a lower state of charge will over-discharge when in use. The difference between cells gets worse over time.
The full proof and least hassle way to use nimh batteries is to use a flexible and decently featured charger like the HITEC CG340 ($ 39.99). Using this sort of charger, charge mostly using a rate 1/10th of rated capacity. 160 mah for 1600 mah cells and so on, hence formatting them all the time. This will keep them in tip top shape. When pressed for time, ramp up the charge rate at a maximum of 1C or 1.6 amps for 1600 mah cells. But do this sparingly. No maintenance needed since you are formatting 90% of the time.
bing
 
I have done discharge tests on alkaline batteries. They dont hold 12 volts very long. Over the entire discharge, a set of 8 nimh cells will hold a higher average voltage than a set of 8 alkalines.
I am a battery geek. I fly electric RC airplanes and I needed to know these things way back when. If one didnt know what he was doing then, he'd eat up batteries like peanuts. Hurts the wallet. These days, we use lithium ion and lithium poly batteries. My PI detector is Lithium powered.
bing
 
Only options are a 1 hour quick charge or the regular 5 hour. They certainly aren't the cheapest around.
4x2300 AA Digital Camera Value Pack
Maha PowerEx C401FS Charger; Four 2300 mAh NiMH AA PowerEx batteries; standard 120V AC adapter; 12V car adapter;
 
It is a good charger.
Something you should know, it says it has a 50 mah trickle charger. A trickle charge is when a low rate is still given to the cells after the main charge has ended. Dont leave the batteries in there after the LED turns green. 50 mah is enough to cook nimhs, although very slowly. A couple of days on green and your batteries are toast. A few minutes won't hurt.
Second, avoid the 100 minute charge setting as much as possible. This increase the possibility of the 8 cells you use going into imbalance. The 5 hour setting is just right for most charging.
Thirdly, I have no experience with POWEREX cells. I do recommend Sanyo's (Energizers are rebranded Sanyos) and GP cells.
Lastly, take a digital volt meter to your cells and measure each one of them. They should measure within 0.05 to 0.08 volts of each other. Otherwise they are not balanced. Formatting may help unles they are already damaged.
Rgds, bing
 
Excellent! Thanks for the reply.
I don't quick charge unless I have too (which will be never now) and always keep an eye for when they go green. Once the winter hits I'll look into testing them out.
C.C.
 
I have tried several differnt brands with some good and some bad, but always like ot keep the same brand and rating in my packs. I Have one of the SunRays super chargers so I charge and discharge each set twice before I use them. Now if I have a problem as not lasting as long or after the second or third time I charge them I will run them low, take them out and check each cell on a battery tester and see if I have a weak one or a bad one. If they all read about the same I will put them back in a recharge the pack. Now if I have one reading quite a bit lower I will replace it as it is a bad one. I have notice more bad cell with the batterys with a Mha rateing over 2000. That one brand that is 2200 I have had 5 out of 16 that have gone bad by the second or 3rd charge. I will wind up testing my batteries 2 or 3 time a years if they are working correctly to keep them matched up and those I think have a problem I will check when they are low as you can see which battery is giving you the problem.
Rick
 
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