M10M Weird Battery Readings

[Alexander108]

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I bought a preowned M10M that came with two batteries. I went for a walk with the camera to take a few pictures. Battery level was 75% which should be sufficient for a few hours. But I ended up with a dead battery rather soon. It depleted in no time.

First thing I identified was that this very battery was built in 2016. I would expect it would not perform well. What I don't understand is the behavior. I did a test: left the camera on, power savings off. Nothing on the screen, no EVF mounted no live view and let it sit.

Every 15m I pressed the middle button to see the info screen that shows the battery level. I then took a picture in LV. Even after more than one hour it was still at 100%. I took out the battery after 1h and measured 7.7V (max is around 8.15V). This is clearly not 100%. I did the same test with the other battery from 2021. This one dropped pretty steadily 5% every 15min (checked every 15m). Very predictable and as I would expect. 

The battery seems to be OK. It took 4h until the battery was depleted but the readings were weird. It shows 100% for 2m switched on and a picture taken every 15m. The other battery is at 60% after 2h with the same procedure. Bot batteries depleted in roughly 4h. The newer one lasted a bit longer. Given that one battery has proper readings while the other doesn't, I assume the camera is not the culprit.

My questions are:

• Are others experiencing the same behavior with some batteries?
• Is there a cure?

It is not too important. More my curiosity.

[pgh]

My 2016/2017 batteries behave the same, more or less, as my 2020 and 2025. 

[Alexander108]

I did another test: interval every 1min until the battery was depleted. I lasted 260 pictures. For the first 2h the camera showed 100% battery level. Then it dropped 10% every 15min.

So, the battery has a reasonable life for the age (9y old) but the readings don't fit. I'll use it as a 3rd backup in the future. I still don't understand how this is even possible. Where does the battery level come from? It seems not the simple approach of the camera just measuring the voltage (which dropped to 7.7V after an hour). 

[TomB_tx]

I've had aftermarket batteries that showed similar or worse in-camera life readings, but haven't seen it on OEM.