I have a charger. I have batteries. Now what?

[williaty]

We bought two AA-hungry flashlights (Romisen RC-N3 II R4 and Fenix LD20+). After chewing up a bulk pack of AAs in a couple of rides, we decided we had to get rechargables. We've now got 8 Eneloop AAs and a Maha MH-C9000 WizardOne charger.

So now what?

Do I just toss the Eneloops in the flashlight and recharge them ones the lights go out? Do I need to do something fancy to them with the C9000 before I use them the first time? Should I recharge them every time we use them or wait for them to go dead?

In other words, school a noob.


Thanks!

 

[Mr Happy]

Congratulations, you have made some good purchase decisions! Mostly you can just charge your Eneloops using the default charge rate on the C9000 and use them. Although the Eneloops arrive pre-charged, it won't hurt to top them up in this way before first use.

One word of caution, though: when running 2xAA lights such as you have, it is best not to let the batteries run too low before you swap them out. If you run the batteries right down until the light goes out you run the risk of harming the weaker of the pair by reverse charging. So the best thing is to keep an eye on the light output and as soon as the light shows any sign of dimming then swap them out immediately. Alternatively, you can just recharge the batteries after every use so you know they are starting out fully charged every time.

 

[sappyg]

LOL.... when i read the title i just had to read the post.

slap them eneloops in and go have some fun. like Mr. Happy says it would'nt hurt to put them on the charger for a bit if you can. there is no telling how long they were sitting around waiting for you to come along.

 

[williaty]

OK, so I tossed the batteries in the charger to top them off and it added 270-300mAh. It showed a final voltage on all of them of 1.4V, which sounded weird to me. I got out the DMM, and sure enough the cells are all at about 1.44V. I thought AA's were nominally 1.5V and usually started in the 1.6-1.7V range. Is 1.44V normal for Eneloops, or does it indicate a problem?

 

[mdocod]

Hi williaty,

"AA" is just a cell size. Has nothing to do with what voltage it could or should be. AA size cells can range in voltage from ~1.2V to 3.7V depending on chemistry.

NIMH chemistry (eneloops) is rated at a nominal 1.2V. In operation under a load they will generally deliver somewhere around 1.2V. Eneloops have lower resistance than most consumer oriented NIMH cells and will often hold slightly better voltages when loaded than alternative cells. Final charge voltage can vary between 1.4V and 1.5V depending on the charge rate used.

Alkaline chemistry cells do start off around 1.6V open circuit fresh from the package, but they will quickly sag under a load to something lower, between 1.2 and 1.5V initially is not uncommon. To use all of the available stored energy in an alkaline cell the device has to be able to continue operating as the cell drops down to well below 1V. NIMH cells will deliver 90% of their stored energy above 1.1V in most cases. While NIMH starts off lower, it holds more ideal voltages longer under most circumstances.

Eric