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Re: [OM] E-M5 Mk2 battery replacement options

Subject: Re: [OM] E-M5 Mk2 battery replacement options
From: Wayne Shumaker <om3ti@xxxxxxxx>
Date: Sun, 22 Feb 2026 09:32:34 -0700
At 2/12/2026 01:39 PM, Moose wrote:
>...
>
>OTOH, we spent 66 days away from home last fall, New England, Old England, 
>Scotland, Orkneys, Morocco, with a pair of OM-1 II bodies. I never once used 
>my back-up batteries. I never once used my external charger. With a PD 3.0 
>100W USB C Charger, more powerful than the one that comes with the OM-1 
>external charger, I simply charged the batteries overnight in-camera, 
>switching bodies on the charge wire when I got up to pee in the middle of the 
>night.

Coming late to the conversation, and haven't read all the posts... My Sony 
Xperia phone has a charge control that I have set to 90%. Two things kill 
batteries, dropping below some level, like 10% and over charging the battery. 
My point is the charger may not stop at the right point. Only charging the 
batteries to 90% can greatly extend the life of the battery.

I'm sure most of us just put the battery in the charger, perhaps over night, 
until the thing says 100%. If the charger does not stop at the right point, it 
will progressively destroy the battery. This is especially true the older the 
battery gets, where the 100% point is no longer accurately detected. A charger 
that stops short at 98% will extend the life versus one that thinks 102% is 
full charge and will progressively destroy the battery. The error could be in 
the battery circuitry or in the charger, and I know the tolerance on this can 
vary a lot.

Note that Moose used the in-camera charge controller, which probably does a 
better job of detecting the charge level and preserve the battery. So not just 
the battery quality, but equally important is the battery charger. Perhaps the 
safest method is using the in-camera charger. Some chargers go into trickle 
charge mode toward the end rather than shutting off, so always a good idea to 
remove the batteries as soon as possible. I suspect the in-camera charger shuts 
off on full charge.

WayneS - in electrical engineering mode

PS I spent quite a bit of time as an EE designing with battery charge circuits, 
coulomb counters, etc. There are a lot of ways to detect full charge, and all 
of them have tradeoffs. My last major project was a battery powered radio that 
was supposed to last 2-4 years on a 3V battery. I used a coulomb counter to 
track the life of the battery. The other method was to measure the internal 
battery resistance, which would increase as the battery discharged. The coulomb 
counter required knowing the initial condition of the battery. Kinda glade I'm 
retired now. 
-- 
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