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I've bought some rechargeable batteries for my Canon EOS 30, but I've noticed that their voltage when fully charged is 4.2 V, rather than the 3.5-3.7 V of a regular CR123A battery. Does anyone know if this might damage the camera?

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    \$\begingroup\$ Rather unlikely... The worst I would expect would be the exposure meter to be a bit inaccurate, but I assume that the Canon engineers did a good job to prevent this. \$\endgroup\$
    – xenoid
    May 9, 2022 at 10:14
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    \$\begingroup\$ Presumably you're not measuring this under load. Putting a regular multimeter on a battery to test voltage really doesn't give you any kind of accurate figure, as it cannot simulate the load. Some meters can… but you don't know what the load should be. \$\endgroup\$
    – Tetsujin
    May 9, 2022 at 10:14
  • \$\begingroup\$ @xenoid Based on the information in Mike Sowsun's answer, I'd say the camera has built-in over voltage protection that's almost certainly capable of protecting it from 4.2V DC. However, if that voltage protection is triggered, the exposure meter nor any other part of the camera will function at all. \$\endgroup\$
    – Michael C
    May 10, 2022 at 5:59

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I use rechargeable RCR123 batteries in my EOS 30V/ELAN 7NE film camera. I tried using one brand (Olight RCR123A) that had high voltage, and the camera would shut down and show an error code. Another brand I use (Soshine RCR123) also has high voltage, but the voltage is slightly lower, and the camera behaves normally.

I believe the camera is able to detect an over voltage and shuts down to protect itself.

I think you would be safe to try your rechargeable CR123A batteries in your EOS 30 based on my experience.

I have read that some rechargeable battery manufacturers use a diode inside the battery to slightly reduce the voltage, and that could be why some will work in my Canon film camera, while others don’t.

enter image description here

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  • \$\begingroup\$ Thanks for adding your own firsthand experience here. Might I suggest that you more explicitly point out in the answer that the camera does seem to include built-in over voltage protection? \$\endgroup\$
    – Michael C
    May 10, 2022 at 5:50

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