What can I expect from deep cycle batteries? I think I killed them

Hi Cabindoc,

I think you must have had something else drawing a lot of power from the batteries, or a problem with the batteries. Those lights probably couldn't have pulled 10 amp hours in that short time period.

Damage? Try recharging them. Also, might take them to an auto parts store for testing.

Cabindoc said:

Hi folks, I have 2 newer deep cycle batteries in parallel. They are average size. I performed a little test overnight and I think I may have killed them. With shore power disconected, I left on some cabin lights, about 21 LED's and 3 small halogen and running lights, not LED for 11 hours. When I went in, voltage had dropped to 7v. Is this normal? Picture was taken shortly after shore power disconnected.

Click to expand...

I would agree with Dan that there is no way the batteries should be down this low. If the meter reading is showing the max draw then over 11 hours that would only total a little more than 30 amp hours. With two batteries in parallel there would enough charge in the batteries to show a full charge. the batteries might have a couple of bad cells in them. They will need to be tested to know for sure.

Thanx guys. I'll have them tested. I thought they should have lasted longer.

Those Halogen bulbs will draw quite a bit of power. 3 50 watt bulbs will draw 12.5 amps, if they are 25 watt, your looking at 6.25 amps. Just on the halogens.

Cabindoc said:

Hi folks, I have 2 newer deep cycle batteries in parallel. They are average size. I performed a little test overnight and I think I may have killed them. With shore power disconected, I left on some cabin lights, about 21 LED's and 3 small halogen and running lights, not LED for 11 hours. When I went in, voltage had dropped to 7v. Is this normal? Picture was taken shortly after shore power disconnected.

Click to expand...

Looks like you have a good monitor panel. What was the amp draw when you first turned on the 21 LED's and the 3 other light. Multiply the number by 11 and you will get the amp hours used. Check that number against 1/2 the amp hour rating of the batteries(each) times 2. Note: Batteries in parallel increase amps, batteries in series increase voltage. So two 12V 110 amp hour batteries equal 220 amp hour 12v battery bank.

This spread sheet I created can be set to any battery bank capacity. If you want a copy send me a PM with an email address.

Drawing batteries down to 7V is not good for their over all health. Chris


Dan, if I send you the spread sheet above can it be place somewhere that people can down load it?

11.9v = fully discharged for a 12v (12.7v) battery. 10v is dead.

What you see on the panel is with everything on. I think the halogens are 25 watt, but not sure. Going to load test batteries this weekend.