I am familiar with 3.6V/4.1V and 3.7V/4.2V LiPo cells. I have a bunch of cells rated at 3.6V/4.2V. What's up with the odd rating? Can these be safely charged with a 4.2V charger IC such as the MCP73831?

This is all the info I have on the cells:

Models: Sony NP-FD1, NP-FT1, or NP-BD1
Nominal voltage: 3.6V
Maximum charge voltage: DC 4.2 V
Maximum charge current: 1.24 A
Typical capacity: 2.4Wh (680mAh)

(All three models have the same form factor and power specs but different keying; thanks Sony)

Image of the three batteries


The battery voltage reads as 4.20V after being fully charged using the original charger. I opened up the charger and the charge control is being done by an M34501E4FP microcontroller so no clues there.

  • \$\begingroup\$ 4.2v is a normal lithium ion cell. The nominal voltage can be defined different ways, so being 100mV different is not meaningful. \$\endgroup\$ Apr 21, 2020 at 4:00
  • \$\begingroup\$ @user1850479 That's what I'm thinking. I reckon that as long as I keep the charge current under 1.24A all should be good (the chargers I want to use max out at 500mA). The oldest of these batteries (and the charger I mentioned) date from 2001 so perhaps the 3.6V rating is a result of the nomenclature not yet being standardized or the chemistry of the time plateauing at a slightly lower voltage. Given that these are Sony batteries though I wouldn't be surprised if they were doing something odd. \$\endgroup\$ Apr 21, 2020 at 4:23


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