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I have some 3.7v (when fully charged) lion batteries that I would like to repurpose. All I have to charge these is a few chargers for some 4.2v lipo (when fully charged) batteries. The specific charger is here. It puts out 100 mA. Would this difference in voltage result in the harming of either my charger or the battery, or would it be safe?

Thanks for your help.

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1 Answer 1

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3.7V is the nominal voltage of the cell. As long as the maximum voltage for the cell is 4.2V or higher and the charge current is equal to or less than the amount recommended in the datasheet (usually 0.8C or less is safe) then you can charge the cell with the charger.

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  • \$\begingroup\$ Not actually sure this is accurate. 3.7V and 4.2V lithium batteries use different internal chemistry. The 4.2V charger would run a CV charging cycle near the end of the charge which could potentially over charge the battery. I haven't tested this though. \$\endgroup\$
    – Hari
    Commented Dec 7, 2015 at 2:18
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    \$\begingroup\$ @HariGanti: There is no "4.2V lithium battery". They are marked with their nominal voltage, which for a battery with a maximum of 4.2V is only 3.7V. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Dec 7, 2015 at 2:36
  • \$\begingroup\$ Ah yes, you are correct. I just check the voltages for different chemistries, and none are 4.2V. I get that nominal vs open-circuit voltage will be different, but I had thought a 4.2V nominal chemistry existed. \$\endgroup\$
    – Hari
    Commented Dec 7, 2015 at 6:38

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