I put the "house" battery back in my boat (which is on blocks) last weekend. It had what I thought was a good charge - it had been on a trickle charger in the garage. When I put it in my volt-meter showed it with 12.98 volts. Nothing, that I know of was on in my boat. When I went back to my boat today ( 7 days later ), the CO monitor was wailing (low voltage alarm) - [yes obviously it was on] and the battery was down to 6 volts.

I guess there is a short somewhere, or else something is on. Anybody have any ideas as to how I would track this down?

My house battery is a group 27 deep cycle marine battery.
On the 29th of Jan all of the cells were right around 1.275 specific gravity. Since then I have been periodically hooking it up to my trickler. I have not tested them since.

Rich S.

One trick you can do it to take the negative lead off your battery and put your test light, one end on the negative wire, and the other on the battery negative. if the light lights up you have a draw. If not you are ok. You can tell the size of the draw by how bright the light is.

Jon

The test that Jon suggested is really the bottom line for checking battery drain. Just in case it is a really small amount of current (not enough to light the bulb), you can put a voltmeter across the light. It sholud read 0. But if it's that small it should not kill your battery in a week anyhow.

Jon I did what you suggested. It is such a simple and effective test that I am suprised that somebody has not designed a negative end battery cable attachement with a bulb built into it! Anyway, I have re-installed the house battery after charging it back up again and disconnected the CO monitor. The CO monitor alarm came on again immediately after I re-connected the battery and it stayed on. I know there is no CO. So I pulled the fuse on the CO monitor and detected no drain at all. I did play around with some of the lights in the boat just so that I could see the 12volt light bulb I put on, at the negative end, come on.

At this point I think that the CO monitor is defective. Could 7 days of the CO monitor's alarm running have been enough to discharge my house battery from 12.97v down to 6v?


I did play around with some of the lights in the boat just so that I could see the 12volt light bulb I put on, at the negative end, come on.

Anyway I will go back next week and see what state the battery is in.

Thanks again for this really simple and very effective testing method.

Rich S.

Glad it worked. As MBam stated guys like he and I would use other methods but this is a kind of poor mans way to do it that works and does not confuse you with numbers on a volt meter that if you do not know what they mean can have you chase your tail around. If your light is out or very dimm then your battery will not go dead from a draw for a long time if ever. So if you saw no light then you found your problem.

If your CO alarm is going off it is not going to take long to discharge battery. I would recharge batterry & then wait at least 12 hr before checking the voltage. Voltage should be 12.7 v for a full charge battery. If you check a battery after pulling it off charger you will not get a good reading showing the battery condition, I believe they call it surface charge. I would then recheck battery voltage a day or 2 latter & see what voltage is. Make sure you did not connect it up. If still about 12.7 battery is proably still good. If voltage is going down then battery may have a shorted cell. I have used dfferent volts meter & have found that they all do not read the same voltage one would say 12.5, another say 12.7 so put on another battery to get a good refrence.