NiMh batteries and my Fenix...

I use NiMH batteries in my Fenix L1p and L2p. I can't help myself,
but everytime I notice a perceptable drop in brightness, I pop in
a fresh battery.

My battery tester indicates the batteries I've removed to be about
1.1 volts, which is hardly worn down.

My question: When I recharge the (nearly fresh) batteries, does
the charger drain them first, then totally recharges them, or does
it just top up the power, or does it get confused and potentially
shortens the life of the AA?

I'm using an Energiser which charges them for 15 hours.

One more brief question: can I mix a 2500 mAH battery with a
2300 mAH battery into the charger at the same time?

1.1v for a nimh is pretty pooped. it's definitely time to charge.

Chargers with independent channels let you mix cell types. Chargers without independent channels don't let you mix. Energizer makes both types. Any 15 hour charger is likely not independent, but it's such a slow charge rate that it probably still won't hurt the cells.

1.1 volts on a NiMH battery without a load is in the range to be recharged. The voltage probably drops below 1.0V when your flashlight is on. Your charger will not discharge the battery then recharge it unless it has a mode that will perform that function. Almost all chargers will just start to charge when you drop the battery in the bay.

If you post what model of Energizer charger you use, someone could answer if it is safe to mix capacities of cells. Usually, if it is required to place two cells in the charger to start charging... it is not advised to mix cell capacities. "Smart chargers" tend to be able to charge single cells at a time so mixing cell sizes and capacities is OK.

Thanks for the replies so far.... what happens if you
put a totally flat battery in a charger with a near new battery?

After 15 hours the flat one is fully recharged, but what has happened
to the previously fresh one? Does it just sit there not gettting charged
at all after the first 6 hours that it took to recharge?

Can you "overcharge" a battery???

If the charger is multiple channels, it will sense when a particular battery is full and just "maintain" that battery at full charge until it is removed. If your charger has indicators for different channels (my energizer I bought to charge my D cell NIMH has 4 independant channels, each with own LED display) then you should be fine.

Also, my energizer charger manual states that you can achieve extra capacity (quote - 100-200 mah more than the battery capacity) if you leave the batteries in the charger after the indicator says full charge.

dragoman

The real danger for "overcharge" is in the faster rate chargers - 2 to 3 hours or less. They will start to heat up the battery to a damaging level if peak is not detected on the battery and charging continues. But chargers that charge this fast always have a peak detection built in for just that reason. After peak detection, they will generally "top off" at a slow rate. The overnight chargers, like your 15 hour rate, will either go until you stop them or cut out at a fixed time, which is always enough to have charged a fully depleted battery. Partial batteries could be stopped much sooner. The extra charge time on this type of charger is of no real harm to the battery, but if left on a non-timer charger for days or weeks will start to have a measurable effect on the life of the battery. I like to stop my slow charge, when I know I don't need a full cycle, by plugging my charger into a light timer. Then I just set a "stop" pin for how many hours out I want it to stop and forget it.


I found a cheap, 2-cell AA or AAA Digital brand overnight charger at Wallmart that charges 1 or 2 cells - it has no timer cut off. That takes care of the odd number of cells problem in paired chargers, as you can just charge the one low cell by itself. You would probably enjoy a good independent channel "smart" charger, though. For under $20 I bought the Titanium TG700 from Ammondotech, and it works great. All AA or AAA cells charge in under 3 hours, then top off at a slow rate. 1,2,3 or 4 cells, mix charge levels and even AA with AAA. I try to avoid the REAL fast chargers like 30 or 15 minutes, as the cells get real hot during the charge, but they seem to work fine. I just figure slowing it down a bit will extend battery life. Hope that helps, I'll shut up now.

The model number of my Energiser is CHM4AA... and thanks for the replies
(what are multiple chanels?)

My charger has two red leds which both light up when charging 4 AA's.
Would this be multi-channel?

Hello Fenixfan

So far I have read about your charger, the series was born in 1998. It should have a 15hour timer and was delivered with 1800mAh nimh cells.

When you will charge modern high capacity cells (about 2500mAh or more) with this charger, the charging rate (mA) will be too low imo.
I have a modern charger with different charging rates and set it to 700mA. 200mA with my charger can be problematical with high capacity cells.

My advice: use your charger for older cells (until 1800mAh) and buy a modern charger for the modern cells. I would use the new charger for the older cells too, after setting on refresh function.

Best regards

_____
Tom

fenix_fan said:

(what are multiple chanels?)

Click to expand...

The newer smart chargers have dedicated channels in that all the channels are independent of each other. Each channel will shut off when the charging is complete and different cells can be charged at different times. The old chargers charged slowly using a timer to shut off the charge cycle. It is best to use a smart charger for all batteries, very important for the large capacity NiMH available these days.

Right, think of "multiple channels" as each cell bay being a seperate 1 cell charger. It charges and checks the status of each cell individually, and stops fast charging each one when appropriate - they will all finish at different times. A red/green LED for each bay is the norm for these. The two red LED's on your charger probably indicate two pair of batteries charging. I am guessing you can charge 2 or 4, and when only charging 2, only one of the lights comes on.