Battery Drain Conundrum

[flag400]

I'm hoping forum members may be able to shed some light on this problem I'm having. The marina mechanic was unable to solve. He installed two brand new batteries on my 2000 326 aft cabin. He advised not to leave the battery charger on while it's docked on shore power for days at a time. When I leave the boat I shut off shore power two switch, and leave one on, with only the three bilge pumps and refrigerator left on. All the other switches in the off position.
Returning several days later my batteries are drained. The mechanic took a reading, one battery was very weak, the second completely drained. He replaced the dead battery and we were off and running. For only about a week or so. I discovered this past Sunday my batteries are dead again. This time I turned on the charger for a couple of days, but no luck, they are still dead. What am I doing wrong?

[bud37]

Check your fridge, maybe just feeding off 12v instead of the 110 when on shore power......shut it off ( make sure it is off....unplug and turn off at panel and inside fridge) there should be no indicator light and take a volt reading at batteries then leave boat and see what happens....its a shot but start somewhere...

[tomschauer]

If you have a good charger, there should be no issue with leaving it on. The purpose of the charger is to keep your batteries topped off when you aren't running the boat.
As Bud says above, start with the fridge. It will make batteries dead pretty quickly. If you want to leave it on, shut off the 12 volt breaker to it, then even if you loose shore power it wont drain your batteries. I don't keep perishable items in the fridge when we are away from the boat. I don't want to come back to bearded cheese and such.

[g36]

Where's the charger connected too? Do you have a battery selector switch?is it connected to the batteries or the switch? Maybe your charger isn't working. A volt meter with a clip on amp probe is a great tool to have on a boat easily troubleshoot this.

[flag400]

Thanks folks. I'm heading over there in a little while and will shut off the fridge, and try charging the batteries again. I've been meaning to pick up a volt meter too, good advice,
Thanks . .

[bud37]

Actually , if you are turning off all other switches are you turning off the 110 circuits ( wall outlets)....because if your panel is like ours then you are turning off the 110 to the fridge where it is plugged in, forcing it to use 12v side only...quite possible.....can check by watching indicator light in fridge and operating the 12v and 110 switches to see what happens.......

[Viper]

Source of the post....The marina mechanic.....advised not to leave the battery charger on while it's docked on shore power for days at a time......

I would understand this logic if it is an older ferroresonant charger as they are notorious for boiling batteries, however the recommendation should not be to shut it off while you're away, it should be to have it replaced with a new tech smart charger so it won't boil the batteries. Leaving it off in your absence means nothing is keeping them charged up if something goes wrong such as springing a leak, and the only thing preventing you from sinking are bilge pumps that are relying on a charger to maintain power until someone notices there's something wrong.

This shouldn't be that hard for a tech to figure out!

[flag400]

OK, Took a reading on the batteries. Battery "A" was 9.2 volts, battery "B" 2.4 volts.
I used a portable starter and was able to get the port side engine running. When I tried to crank the starboard, the port engine shut down.

So, the fridge is off, everything on the panel is shut down, except for Shore One, the three bilge pumps and the battery charger. I will give it a day or so to charge before going back to check on it . .

[tomschauer]

Flag, if these batteries went that low, especially battery 2, I would put a load test on them both before I would trust them to start me up out on the water, even if they come back up to 14V. These "new" batteries may have sat around a couple years before you bought them.

[flag400]

That's a good point . . If they don't charge up properly on the boat, I'll pull them out to get a deep cycle charge.