battery drain question

[gonesail]

I have a 12v system and usually leave it on trickle charge while boat is at the dock. Last week I disconnected the shore power cable but left both batteries switched on. all 12v breakers were off. several days later I noticed the battery voltage was at 12.5 volts and this seemed a little low. I turned batteries off at switch and the next day saw they had gone back up to 12.6 volts. since I have a xantrex monitor I did a test and found there is a very small amperage drain when I have the batteries switched to both. but no drain when either 1 or 2 is selected. anybody seen this before? bad battery switch?


alan

[ssullivan]

Alan, is this definitely repeatable? Did you see this happen more than once?

[AnchorageGuy]

Alan, 12.56 is about normal for a battery of some age sitting for a week and should not be of much concern. As for the voltage issue, that is a bit more difficult to track down. it could be something in your battery monitoring system or an LED light or a slight short. The only way I know of to check is to open up your electrical panel with the shore power disconnected. Put the battery switch on both. Look for a connection that might be attached to the post for the switch. Then start disconnecting the wire from each piece of equipment on the panel to see if the voltage goes away. If it does you have found your issue. Also disconnect the battery charger from the batteries to see if that is the problem. Also look for things like bilge pumps that are connected directly to the battery and not to the panel. Finally check with the shore power cord unplugged from the boat.

[senormechanico]

If it's electronic rather than just an analog gauge, the battery monitor also takes a small amount of current all of the time.

Steve B.

[Pura Vida]

Alan,

With my battery switch in the off position there was a small amperage drain as measured between the cable end and the terminal on the switch. I replaced the switch and the problem stopped. I will admit to not being much of an electrician having learned on British cars and motorcycles, but I'm of the opinion that a switch in the off position that is leaking electricity to one of the other poles needs to be replaced.

pv

"If Lucas made guns wars wouldn't start." Anon

Anyone with and MGC for sale let me know.

[AnchorageGuy]

Sounds like you figured it out without a lot of fuss.