At what voltage should an AA eneloop be recharged?

[Ray1968]

We use a handful of AA eneloops here in the office for various electronics, my cordless mouse being one of them. I'll get a 'low battery' warning from the mouse when I shut down the computer, but I just continue to use it until it stops working and replace the eneloops, putting the 'dead' ones on the charger.

I've never checked the voltage on an eneloop that was pulled from the mouse to be recharged, but this morning I had a DMM on my desk and for kicks checked the voltage on the two batteries. They were 1.13 and 1.14. Is this normal? I was expecting them to be lower.

 

[matrixshaman]

Re: At what voltage is an AA eneloop be recharged?

I believe Silverfox who is a very knowledgeable battery person here said one time in a similar question I posed that charging them at around 1.2 or 1.25 volts would be good. I think if you run Eneloops down too far they tend to lose their low self discharge function. So your reading is not that low for an open circuit voltage. That is they usually charge to around 1.45 volts on a Maha 9000 and I find most are fairly depleted by the time they hit around 1.2 volts. Your mouse is very probably a real low current device so they may work until the voltage is lower but it may be best to pull them a bit sooner. I'm not battery expert but that's my understanding and hopefully that will help until the real experts chime in.

 

[Mr Happy]

Re: At what voltage is an AA eneloop be recharged?

If the resting voltage of an eneloop is 1.20 V it is for practical purposes completely discharged and ready for recharging. Although that voltage seems quite high, if you put any load on the cell the voltage will quickly drop lower indicating that there is no significant charge left to be delivered.

It is not totally harmful to discharge a cell to lower voltages than that, but in some circumstances it can be a bad thing so it is best to recharge sooner rather than later.

 

[Ray1968]

Re: At what voltage is an AA eneloop be recharged?

/nod

Thanks guys.