50amp deep cycle approx full voltage

Submitted: Monday, Feb 12, 2007 at 17:57

ThreadID: 42230 Views:2229 Replies:5 FollowUps:4

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pixiemops

Just wondering approximately what voltage would be full for one of these batteries. I was thinking 12.7. I know SG meter is the way to go for better accuracy.

cheers.

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Reply By: Alloy c/t - Monday, Feb 12, 2007 at 18:07

Monday, Feb 12, 2007 at 18:07

A wealth of knowledge ,,,,, www.uuhome.de/william.darden/carfaq.htm

AnswerID: 221268

Reply By: Member - Olcoolone (SA) - Monday, Feb 12, 2007 at 18:52

Monday, Feb 12, 2007 at 18:52

A fully charged battery will be 12.6 volts, when checking after the vehicle has been running always put a load across the battery for about 15 seconds to remove the float charge, by doing this you will get a accurite reading, if you don't you will have a reading of 12.8 to 13 volts.

Regards Richard

AnswerID: 221274

Follow Up By: pixiemops - Monday, Feb 12, 2007 at 19:20

Monday, Feb 12, 2007 at 19:20

Thanks Olcoolone thats exactly what Ive been getting . Was told that a battery in the boot connected to the starting battery may not get fully charged. I would have been happy if it wasnt 100% charged but looks like the commodore alternator has enough grunt to do it .

thanks

FollowupID: 482009

Follow Up By: Member - Phil G (SA) - Monday, Feb 12, 2007 at 20:58

Monday, Feb 12, 2007 at 20:58

Pretty hard to be sure about how much its charged from the voltage, but a voltage of 12.8 after you've brushed off the surface charge and left it sitting for 12 hours is an indication that its getting up there. No wet cell deep cycle gets fully charged by a vehicle alternator, no matter what the voltage says. But theres nothing you can do about that, without getting anal and putting it regularly on a 240volt charger.

Practically speaking, I check voltage each morning after running the fridge overnight and get and idea of whats been used. If its 12.6 volts, its not used much, If its 12.3 it might be 50% discharged, if its 12.0 its probably 80% discharged. They are just the ball park figures I use.

FollowupID: 482042

Follow Up By: Mainey (WA) - Tuesday, Feb 13, 2007 at 01:29

Tuesday, Feb 13, 2007 at 01:29

A really good reason to use an AGM Deep Cycle battery & solar power.

When I check my Aux battery system voltage first thing in the morning, before the sun starts to shine on the solar panels, the AGM battery system is still showing 12.7v to 12.8v and that's after the fridge has been running at some time during the night.

The Stecca solar reg charges the AGM battery system at 13.8v during the day, unless on 'boost'

When the fridge is 'running' during the day the battery is still showing well in excess of 12.66v, which is the fully charged voltage of a 12v battery, because about 4 amps still going into the AGM battery system even with the fridge running and 8 amps from the solar panels powering the fridge direct.

FollowupID: 482106

Reply By: Member - Brenton H (SA) - Monday, Feb 12, 2007 at 20:54

Monday, Feb 12, 2007 at 20:54

I'm no expert but I retreived this some time ago from a well respected battery site.
"These voltages are for batteries that have been at rest for 3 hours or more. Batteries that are being charged will be higher - the voltages while under charge will not tell you anything, you have to let the battery sit for a while. ..... It is important to realize that voltage measurements are only approximate. The best determination is to measure the specific gravity, but in many batteries this is difficult or impossible. "

State of Charge 12 Volt battery
100% 12.7
90% 12.5
80% 12.42
70% 12.32
60% 12.20
50% 12.06
40% 11.9
30% 11.75
20% 11.58
10% 11.31

However...
If the battery is an AGM or Gel cell the full charge voltage is approx 12.8-12.9

AnswerID: 221296

Reply By: MEMBER - Darian (SA) - Monday, Feb 12, 2007 at 21:08

Monday, Feb 12, 2007 at 21:08

I have a 50 amp-hour Delco battery in my camper trailer - glass mat far as I know -(can hardly see it and have not had it out yet - but have seen the label with specs on it). When fully charged by the inbuilt 3.5A charger, the meter reads 13.8 volts (did get to 14 once) - once the charger is off and and the first minor current is taken (a light etc.), it settles back to the high twelves.

AnswerID: 221300