what rate to charge 12v 7.2ah

Discussion in 'The Projects Forum' started by mdemetri2, Mar 30, 2013.

  1. mdemetri2

    Thread Starter New Member

    Mar 30, 2013
    I have a Fiamm lead acid battery, 12v 7.2ah. At what rate should I be charging this battery i.e. the amp and voltage and for how long?

    Last edited: Mar 30, 2013
  2. wmodavis

    Well-Known Member

    Oct 23, 2010
    First place to start is to get a copy of the manufacturers full data sheet of that battery. Usually it will have some information re the correct charging.

    A good second step would be to read up on lead acid batteries in general so that you will understand some of the overall guiding principals. A good source is The Battery University .com.

    Another fact is that for a fully discharged battery you need to charge it with it's required amp-hour rating plus some for process losses, i.e. 7.2 AH in your case + some to make up for losses. So that means 7.2 A for 1 hour or 3.6 A for 2 hours or 1.8 A for 4 hours (+ some more for losses). But there are many more factors to take into account to not reduce the battery life.
  3. k7elp60

    Active Member

    Nov 4, 2008
    Another factor is wether the battery is being used as standby or cyclic mode plus the ambient temperature should be taken into consideration also.
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    SLA charging efficiency is about 70%, so to charge 7.2Ah needs about 7.2 / 0.70 = 10.3Ah.

    With SLA batteries there is often a printed max charge current on the battery. It's usually about 30% to 40% of the Ah current, and for best reliability 15-30% is a good goal. So you could charge at about 1.5A and it would take maybe 7 or 8 hours for the bulk charge.