Charging batteries

wchevron · #1 (**permalink**) 02-24-2008

with a portable auto-style battery charger, what is the difference between a 2amp charge cycle or a 10-amp charge cycle. i'm assuming the 10 amp charges the batteries quicker but would you get a better charge with the 2 amp setting? my batteries are out of the boat and need to be charged so i'm just wondering which way would be the way to go.

PBzeer · #2 (**permalink**) 02-24-2008

Automotive batteries or deep-cycle ones?

camaraderie · #3 (**permalink**) 02-24-2008

Take water caps off and fill if necessary. With caps off...charge at 10 amps and watch to insure the water does not ACTIVELY boil. With a deeply depleted automotive size battery you may need to charge as long as 8 hours at 10 amps...but keep an eye on it for boil off. If it does...then switch to 2 amp charge over about 8 hours to finish charging.
Wait for 5-6 hours after charging and measure voltage. Should be 12.6 or slightly higher.
The above is GENERALIZED info since you did not provide any detail about your size and type battery.

wchevron · #4 (**permalink**) 02-24-2008

sorry. i believe they are marine batteries but i'm not sure. manufacturer: DBMC. they say 24DCM? purchased by PO in '02. there are 2 large caps on each battery. when i popped one off, there were 3 holes under each cap.

camaraderie · #5 (**permalink**) 02-24-2008

OK...these are 12V wet cell deep cycle batteries of group 24 size meaning about 75 amp hour capacity each. If they are currently pretty discharged you should be able to charge them at 10 amps for about 6 hours each then at 2 amps overnight to get a full charge.
Fill properly with DISTILLED water only if the levels are low in each of the 6 holes on the battery before charging.
Put a voltmeter on them no sooner than 6 hours AFTER charging is complete to get a voltage reading OR purchase a hydrometer at the local NAPA type store to see the condition of the cells BEFORE you charge OR add new water. With a voltmeter you should see 12.6V if they are in good condition by a hydrometer is even a beter way to analyze the shape they are in.

sailingdog · #6 (**permalink**) 02-24-2008

IMHO, you'd probably be better off with a three-stage smart battery charger.

artbyjody · #7 (**permalink**) 02-24-2008

Quote:

Originally Posted by wchevron

with a portable auto-style battery charger, what is the difference between a 2amp charge cycle or a 10-amp charge cycle. i'm assuming the 10 amp charges the batteries quicker but would you get a better charge with the 2 amp setting? my batteries are out of the boat and need to be charged so i'm just wondering which way would be the way to go.

The issue over marine versus auto style charges is the "smart sense" capability... You'll be better off with a smart marine charger even if those batteries are auto as they rapid charge to 80% and then trickle charge - which keeps the number one issue of battery charging - electrical heat - to a minimum...resulting in a more accurate and less damaging charge cycle... auto chargers work full on and rarely have any trickle logic in them...resulting in subpar charging cycle, if relying on the charger alone (ie not using the vehicle to charge after you get it started)...

wchevron · #8 (**permalink**) 02-29-2008

finally got around to charing the batteries tonight. both batteries were low on water so i filled each one with distilled water. the p.o. had a hydrometer that i found but when i filled it with the battery water, it wouldn't move. i assumed it was broken. one battery was reading 9.6a with the voltmeter. i tried to charge it but no luck. i think it's gone. the second battery starts off at 11A when i first put the voltmeter on it. for the next 10-15 sec the meter fluctuates up and down from 2A to 11A and finally settles on 11A. i put this one on the charger at the 2A charging setting and left it for 3 hours. i just went to check on it. after removing the charger, the voltmeter was reading 13.1A on the battery. i also noticed there was water which looked to have leaked out the caps. maybe the boil off camaraderie had mentioned earlier? does that mean this battery is gone also? both batteries were from 2002.

camaraderie · #9 (**permalink**) 02-29-2008

The first battery is definitely toast. Wait overnight on the second battery with it disconnected from the charger...then measure the voltage. If it is 12.6 or better in the AM...you are in luck.

sailingdog · #10 (**permalink**) 02-29-2008

Hmmm... If the batteries were that low on water, the plates are probably completely shot, since they're probably sulfated, which is what happens when wet cell batteries are operated with low electrolyte levels.

Are you confusing Amps with Volts???

A fully charged 12 VDC battery will register about 12.6 Volts. A fully discharged one will register about 11.6 Volts. It sounds like every time you're saying Amps... you mean Volts.

BTW, generally, batteries that are six years old and have been badly maintained aren't worth even trying to look at.

Quote:

Originally Posted by wchevron

finally got around to charing the batteries tonight. both batteries were low on water so i filled each one with distilled water. the p.o. had a hydrometer that i found but when i filled it with the battery water, it wouldn't move. i assumed it was broken. one battery was reading 9.6a with the voltmeter. i tried to charge it but no luck. i think it's gone. the second battery starts off at 11A when i first put the voltmeter on it. for the next 10-15 sec the meter fluctuates up and down from 2A to 11A and finally settles on 11A. i put this one on the charger at the 2A charging setting and left it for 3 hours. i just went to check on it. after removing the charger, the voltmeter was reading 13.1A on the battery. i also noticed there was water which looked to have leaked out the caps. maybe the boil off camaraderie had mentioned earlier? does that mean this battery is gone also? both batteries were from 2002.