dead battery charging question - 2a or? it's been charging 17 hrs....how long can i leave it charging

Charles wrote: ↑ hi. so battery was dead. it was new about 15 months ago. long story but car wasn't driven for 7 mos. life happens.

anyways i boosted the battery and ran the car for 30 mins before charging. Then i removed the battery and plugged it into the charger (said 60% charged) and it's now been running 16 hrs at 2amp (it's on auto) - and now it's only 70%. Should I up the amperage from 2a to 6 or 8? Also should I leave it on for more then 24 hrs? thx

ps..im using a motomaster smart charger

Charles wrote: ↑ it's weird = i have a "smart" charger and i switched it to 10a and it refused to charge above 2.1a. It won't let me charge at the higher rate...still only 80% full

edit...voltage shows 14.4v (that's max i think) and now charging at 1.5a and still just 80% full. I think my battery is whacko.

craftsman wrote: ↑ You ran into a common misconception when it comes to chargers and the current output. The battery will ONLY accept a charge at a certain current regardless of what you set the charger for. The setting on the charger only controls the MAX current to be used for charging and nothing more. As the battery state of charge gets closer to 100%, the current the battery requires drops like a rock. You might only be able to charge a battery at 10A when the state of charge is close to zero and once you get to 30%, that might drop to 5A and at 80^ drop to 1.5A. This is NORMAL and why I tell people that paying lots of money on a higher current charger doesn't make sense for most people as the charger will typically not run at that level for very long.

You could have left the charge current at 2A and got to the same spot you are now as the battery is getting full.

Charles wrote: ↑ thank you. so it may not ever show 100% since the voltage is 14.4 and the charging has dropped to 1.3?

Charles wrote: ↑ thank you. so it may not ever show 100% since the voltage is 14.4 and the charging has dropped to 1.3?

craftsman wrote: ↑ No. You are making the wrong conclusions about what is happening. As the battery gets closer to FULL, the charging current will drop which is NORMAL. Once the battery charger detects that the charging current basically hits zero or close enough to it, the charger will declare the battery to be FULL which NORMAL. Everything you are seeing is NORMAL.