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# What happens when you charge 2 1.2V batteries with 5 volts?? Answered

The 2 1.2V bateries are in series.
Will they explode?
Will they glow?
Will they recreate the big bang?

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## 3 Replies

If they're 1.2V they're likely to NiMH rechargeables. If you actually want to charge the batteries, look at the capacity for the type of battery you have, e.g. 1500mAH.  You can safely charge them indefinitely at that value divided by 10, e.g. 150mA, although in practice you'd disconnect after 15 hours or so when they're fully charged.

You'd need a series resistor to limit the current.  The value of that would be the power supply voltage (5V) minus the battery voltage (2 x 1.2 batteries in series give you 2.4V) all divided by the charging current (e.g. 150mA = 0.15).

In my example it would be (5 - 2.4) / 0.15 = 17.333 ohms.
(Call it 18 ohms.)

Vyger (author)2011-07-03

Also depends on how long you apply the voltage for. If you overcharge a lot of batteries it will kill them, it depends on the type. Lithium ones can explode, They have more power but Lithium is a volatile metal.. You don't want to get pieces of burning Lithium stuck to you. It would be very uncomfortable.

silverwindro (author)2011-07-03

Depend on what current has that 5V source :P.