Battery charging...how long?

[chris in va]

I have an automatic 10 amp charger. How long does it typically take to charge a battery that is around 11 volts? Overnight?

 

[andrewkafp]

Re: Battery charging...how long?

I think it depends how flat it is.<br />But @ 10amps from dead flat, overnight would do. Then if it's automatic, it should just turn off.<br />Make sure there is water over the cells and take the caps off cause she will get hot.

 

[roscoe]

Re: Battery charging...how long?

Depends on the size of the battery. Number of amps battery, divided by 10 amp charger, equals approx number of hours.<br /><br />127 amp battery divided by 10 amp, equals 12.7 hours.<br /><br />200 amp battery, 20 hours<br /><br />There is probably a more precise way to figure it, but this is close.

 

[SeaHorse]

Re: Battery charging...how long?

I assume we are talking about a conventional lead/acid battery here. At only 11 volts, the battery is VERY discharged. At 12.1 volts it would be 50% discharged. Since your charger is rated in input amps, it will probably only charge at about 7 amps into the battery. Only about half of those electrons go to charge the battery the other half are lost, so your effective charge rate is only about 3.5 amps. If your battery is a 140 amp, divide 140 by 3.5 amps giving 40 hours charge time. Try to keep the battery at 12 volts or more all the time.

 

[chris in va]

Re: Battery charging...how long?

Ok thanks guys. This is on an 'EverStart Marine starting battery' for the motor. I borrowed the boat from the guy I sold it to and he didn't charge the batteries for oh...7 months.

 

[ndemge]

Re: Battery charging...how long?

If the batteries have been dead for that long, don't be surprised if it takes longer to charge... if they will come back at all.<br /><br />Charge it all the way up, let it sit for a day and check voltage, if it's under 12.7 ... it's a weak battery. The plates may be sulfated from sitting so long.<br /><br />If it does take a charge, you may want to do a load test. Some batteries will show good voltage, but if you put a load on them, they die very quickly... not a good thing to find out when out on the water.