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I have two separate 2000mAh LiPo batteries (not RC type the standard 2 wire DIY component type https://coolcomponents.co.uk/products/lithium-polymer-battery-2000mah) Which I want to wire in parallel to achieve a combined 4000mAh. The specs say max charge current for one battery is 0.5C or 1A. If my charger charges at 2A is that shared between each battery so they are ok with 1A max or do both get 2A?

Many thanks in advance.

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  • \$\begingroup\$ It won't be shared equally. You can't rely on that happening. \$\endgroup\$
    – Andy aka
    Commented Aug 21, 2020 at 14:00
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    \$\begingroup\$ It is common to hard parallel LiPo batteries - but the charge and discharge currents may not be identical. If the batteries are identical in type, age, past use and state of charge then they MAY load share 'well enough'. If you charged at say 1A or even 1.5A then it would probably allow both to be charged at less than 1A. One possibility (though not commonly done) is to add a small series resistor so that say about 0.05V to maybe 0.1V is dropped at full charge. As long as max discharge is about the same this will assist balancing at the cost of some capacity. \$\endgroup\$
    – Russell McMahon ♦
    Commented Aug 22, 2020 at 0:05

2 Answers 2

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The specs say max charge current for one battery is 0.5C or 1A. If my charger charges at 2A is that shared between each battery so they are ok with 1A max or do both get 2A?

The charge current will be shared approximately equally between the two cells, depending on the resistance of each battery. If both cells are the same type, age and capacity then their resistances should be close to the same, and the current should split nearly equally (ie. ~1 A per cell). A small charging current imbalance shouldn't cause damage, because while the cell with lowest resistance will get more current it probably will be able to handle more current.

However if one cell becomes disconnected or its connector develops a high resistance the other cell will get much more current than it is rated for. Therefore you should either hard-wire the cells together into a single connector, or limit total charge current to 1A.

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  • \$\begingroup\$ Thanks, I really appreciate your reply, clear and very useful. They are same cell model, type, capacity and manufacturer. I accept manufacturing and cell age might mean they aren’t literally identical and therefore the current won’t be literally identical. Maybe I should have been more descriptive when I said “equally”. Thanks for the safety note, I’m looking to see if my charger supports 1A. It’s for an imbedded device to power a raspberry pi which will most likely be plugged in to the AC and charging, I’m not after a fast charge so happy with lower current if I can. Thanks again. \$\endgroup\$
    – SteveUK
    Commented Aug 22, 2020 at 18:51
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No problem , but for much longer life energy cycle goal Ah keep SOC between 25~75% or 3.5 to 4V CV charge . So your capacity is reduced to 50% but 5 x charge cycles.

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