Have tested battery an it reads fully charged but when I put a battery charger on it it still takes a charge . What could be wrong

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Apr 3, 2019 at 18:44
  • Older batteries increase in leakage current at full CV and also your CV may be set too high. This is a common sign of battery aging Actual charge rate and battery specs can be more specific Commented Apr 3, 2019 at 19:04

1 Answer 1


Nothing is wrong. You can always pass a current "backwards" through a battery if you connect a higher voltage across the terminals.

If the battery is fully charged and you force a high current "backwards" through it, you will heat it up, produce potentially explosive gas, and evaporate some of the liquid inside it, but a battery charger won't cause that sort of damage unless the charger itself is faulty.

  • 2
    I'd have to caution you on what you're saying here. A "non-smart" charger (which there are plenty of them out there), can and will boil a battery. Even if you have it on a 2A setting, it can still cause issues. It's not good to leave a battery charger on a battery for an extended period of time after the battery is fully charged. It can cause issues. There are such things as battery maintainers which will do the job without issue, but I would never trust a charger past when the battery is to the full mark. Commented Apr 3, 2019 at 18:47

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .