I have a 3000mah 7.2 v battery and a charger that outputs 7.2 v at .3 amps. Would it take 10 hours to charge the battery?

  • \$\begingroup\$ No, battery charging is a lot more complicated than that and depends on battery chemistry, which you mentioned nothing about. \$\endgroup\$ – Matt Young Feb 25 '13 at 17:29
  • \$\begingroup\$ The battery is a six cell nimh battery \$\endgroup\$ – Micah king Feb 25 '13 at 17:48
  • \$\begingroup\$ I am not a battery expert, but the manufacturer most likely has charging curves available. The process isn't as simple as just applying a voltage to the terminals and waiting. en.wikipedia.org/wiki/… \$\endgroup\$ – Matt Young Feb 25 '13 at 17:52

Assuming your batter has zero capacity right now and your charger has a constant current output of exactly 300mA (no trickle chagrining), an ideal NiMH 3000mAHr battery with no heat losses will take exactly 10 hours to charge. However, taking into consideration that you have losses, the time can go up by 20% or more.

The reality of it is, is that quality chargers don't charge NiMH batteries based on time (only cheap chargers do that blindly at very low charge rates). There are at least two criterion quality chargers look at:

  1. The rate of which temperature is increasing (if the battery gets too hot too fast, this tells that the battery is near full capacity)
  2. The voltage peak and roll-off (depending on the NiMH battery chemistry, the voltage will peak and hold OR start roiling down after hitting a local maxima)

Then there is the issue of trickle charging... so its not as simple as you might think. Its really depends on the chemistry of the battery as well as how complex is your charger.

  • \$\begingroup\$ @Micah king IF your question is answered, then click on the tick mark next to the answer. \$\endgroup\$ – AndrejaKo Feb 25 '13 at 22:26

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