Sanyo XX, Powerex, Eneloop, something else?

Started May 20, 2013 | Discussions thread
Per Baekgaard Senior Member • Posts: 1,268

Michael Skvarenina wrote:

I have the Powerex MH-C808M

Maybe the problem is that I usually leave the Eneloops in the charger until I need them.  I assumed the charger would stop charging them once full and not keep current flowing into the battery?  Maybe this has conditioned them poorly?

I'm not familiar with the MH-C808M (I use the MH-C9000), but many chargers keep a trickle charge running after it shuts off the "normal" charging cycle (even the MH-C9000 does that).

I believe that especially for the Low Self-Discharge types, it might not be a good idea to keep them constantly in a charger. They maintain their charge quite well without. So all you benerfit is a little extra heat build-up. It almost certainly does not do the Eneloops any good to be sitting with a small charge running through them constanly.

The MH-C808M apparently runs 7 mA in trickle charge mode, so this is probably one of the best chargers for keeping batteries in constant charging mode, if you insist. The MH-C9000 that I use runs around 10mA in trickle mode, so they are very close. But I am not personally leaving batteries charging for extended periods.

The 3rd gen Eneloops loose 10% charge in a year (according to spec). This is around 200 mAh, and would be equivalent to a discharge current of roughly 0.02 mA. Thus, the trickle charging is maybe >300x more than what is needed to keep up with the loss... and through a year, you actually try to add >60.000 mAh that will hopefully mainly be dissipated as heat

Further on the Eneloops: You don't say it specifically, but it looks like you're using yours for the SB-800? I also use Eneloops in my D800 grip, and they work reasonably well there (keep their charge well and run for a long time). However, the battery indicator bar drops faster than what I was used to in my D300 using at that time Uniross Hybrio batteries -- not sure whether it is due to the D800 or the batteries or a combination of the two.

Basically, in my D800, they start to indicate the battery is nearing completion already when 30-40% of the charge has been used, and with still 2/3rds left. I can keep on using them, and they will deplete almost down to the "real" empty level before they crap out, so I just have to live with the battery sign showing low charge a little too early.

It is not due to a high internal resistance, by the way. The Eneloops have probably the LOWEST internal resistance of all the batteries I've seen in use here -- my current set are ~50 mOhms even when fully discharged! Some of the higher capacity ones can actually grow up to 200 mOhms internal resistance after real-world use... (see also e.g. for one comparison)

So instead of having your batteries charging constantly, just use them and accept they may only be at 90% capacity if you've really stored them for a year -- or top them up the day before you need them. Or keep a spare set

 Per Baekgaard's gear list:Per Baekgaard's gear list
Nikon D800 Nikon D500 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S Nikkor 14-24mm f/2.8G ED Nikon AF-S Nikkor 24-70mm f/2.8G ED +17 more
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