Can you totally discharge Eneloops AA's?

[ELDRAW]

hi,
Just brought a Quark Mini AA and need some rechargable AA's. I want to get some Eneloops becuase ive read they are brighter and last longer than Alkalines, but can i totally drain Eneloops and recharge them or do they have a protection on like my AW 186500 that im not supposed to drain completley and have to keep recharging?

hope that make sense, thanks

 

[CaseyS]

They don't have or need a protection circuit and they don't become unstable if you over-discharge them, but they'll last longer if you avoid deep discharges.

http://www.batteryuniversity.com/partone-14A.htm

 

[Anders]

Hello ELDRAW.

It is important to know that if you use a light with more than one NiMh cell, you cant drain them to much.
They have very little energy left under 1.0 Volt under load and if you have several cells that is not matched the strong ones would destroy the ones with lowest capacity.

As soon you see less intense from the light its better to charge them again.

Anders

 

[ELDRAW]

Hello ELDRAW.

It is important to know that if you use a light with more than one NiMh cell, you cant drain them to much.
They have very little energy left under 1.0 Volt under load and if you have several cells that is not matched the strong ones would destroy the ones with lowest capacity.

As soon you see less intense from the light its better to charge them again.

Anders

Ok thanks, but the Mini AA only uses one AA battery.

 

[EngrPaul]

My wife has done so by putting them into incandescent window candle lights.

They recovered OK. However, they were at such a low voltage the charger would not recognize a cell was installed. I had to jumper another cell to it to give it a non-zero voltage.

I do not believe an LED flashlight will take your cell the whole way down to zero. It will probably stop around 0.8V or 0.9V, which is the minimum operating voltage for the driver.

 

[ELDRAW]

My wife has done so by putting them into incandescent window candle lights.

They recovered OK. However, they were at such a low voltage the charger would not recognize a cell was installed. I had to jumper another cell to it to give it a non-zero voltage.

I do not believe an LED flashlight will take your cell the whole way down to zero. It will probably stop around 0.8V or 0.9V, which is the minimum operating voltage for the driver.

So your saying because the light wont deplete the battery completely its OK to use it until it stops?

 

[Anders]

It is not ok.

Anders

 

[Mark620]

I put a NimH (powerex AA 2300mAh) in a solar light...did not take too long for it to have problems...the battery quit taking a charge...lasted less than 2 weeks. Seems id did not like being drained like that every day...

The lights come with 600mAh AA Ni-Cd.

 

[EngrPaul]

So your saying because the light wont deplete the battery completely its OK to use it until it stops?

Maybe. I'm not sure somebody has tested this case.

It's not the best way to use rechargeable cells. However, I would expect you still get more value out of an abused NiMH than the cost of the equivalent amount of Alkalines and the risk of leaks.

 

[EngrPaul]

I put a NimH (powerex AA 2300mAh) in a solar light...did not take too long for it to have problems...the battery quit taking a charge...lasted less than 2 weeks. Seems id did not like being drained like that every day...

The lights come with 600mAh AA Ni-Cd.

NiCads are usually constantly charged, a reason they are still widely used in cheap consumer devices. A NiMH needs a terminated charge.

 

[Mark620]

So your saying because the light wont deplete the battery completely its OK to use it until it stops?

NO, that will destroy the battery if done repeatedly.
you might get lucky and drain it once (few times) and it still function somewhat normally.

 

[Mark620]

NiCads are usually constantly charged, a reason they are still widely used in cheap consumer devices. A NiMH needs a terminated charge.

Solar lights would NEVER fully charge the batteries...only drain them to death.

 

[EngrPaul]

NO, that will destroy the battery if done repeatedly.
you might get lucky and drain it once (few times) and it still function somewhat normally.

How do you know it will deplete the cell to a damaging voltage?

I think the correct answer is we do not know the definitive answer.

 

[EngrPaul]

I did some more testing (vs. the original post), if you leave a voltage source on the Mini input, and decrease the voltage, it will continue drawing current way down toward zero volts. So yes, a MiNi can fully discharge your cell.

It's only when you disconnect and reconnect the voltage that the current is a few microamps (below 0.79V).

Sorry for the confusion! It was hard to do a continuous test with only two hands.

 

[The Dane]

Yes!
All batteries can be discharged to 0.00V, BUT they dont survive it!

Depending on chemestry there is a minimum voltage that is to be sustained or else chemical break down will take place, and capacity will suffer!
I know that for LA first time to 0V depletes about 1/3'rd of the capacity end the following @25% for each time.
NiMh's dont like less than 0.9V.
NiCd's are a bit more recilient but tend to crystalize the Cadminium and internally short (capacity loss), when deep cycled to heavily.
Li-xx dont go much below 2.8V/cell under discharge before damage, the lower the worse!
Li-Fe can go to 0V but suffers capacity loss under 2.0V.

 

[chas0039]

Just to confirm what I think is true, could someone address the difference between a discharge in a device and the discharge cycle in a good charger like the MAHA 9000? I am assuming that the MAHA cuts off before the voltage drops too low but I need reassurance from someone who truly knows.

Thanks

 

[SilverFox]

Hello Chas0039,

Welcome to CPF.

The Maha stops the discharge when the cell reaches 0.9 volts.

Tom

 

[DigitalZen]

I use Eneloops exclusively in high-powered strobe and all my AAA and AA lights. The trick is simply to charge them when you've used them for a while. If you have to kill them, you have to. Otherwise it's like voting in Chicago: charge early and often. Mine are two years old now, and still hold a good charge.

As the man above said, most cells are murdered, they don't just die. Modern NiMH's, especially hybrids, don't develop memory and can be charged sooner than the early ones. Just keep 'em juiced and they should give you good service for a long time.

And yes, they do hold the charge in storage. I've shot two to three hundred times off a set that was in the camera bag for six months, and it's a BIG flash.

 

[ICUDoc]

I believe very deep discharge is bad for most battery chemistries but I am no expert. Anecdotally, I have a pair of eneloops that were left on in a toy car (direct drive to the motor) for several days and measured 0.03 volts. I cycled them on the Maha and they perform as strongly as ever, now. BUT, I won't do it again....