Low starter battery voltage

[PapaBruce]

I searched threads and will apologize up front if this is repetitive, but here goes...

I have 2 house batteries and 1 starter battery. Both house batteries (8G8D) show 13.3 volts with everything disconnected. The house (8G4D) shows 2.4 v. The engine starts right up every time ( now I've probably jinxed it!) so I'm confused as to why the voltage is so low. We're hooked up to shore power when not sailing. Any thoughts? Thanks so much!!

[djmarchand]

My guess is that you are actually starting on your house batts. Disconnect the ground terminal of your starting battery. If it starts, then the house is connected and the start is not and is probably dead at this point.

Replace your start battery and figure out your wiring.

David

[PapaBruce]

Thanks! Can I use a less expensive battery than the 8G4D?

[Sailmonkey]

Originally Posted by PapaBruce

Thanks! Can I use a less expensive battery than the 8G4D?

What size engine are you starting?

[PapaBruce]

It's a 62 hp. I took David's advice and found that the house batts were starting the engine. I also discovered that one house battery and the starter battery are on one battery switch and the other house battery is on its own switch. Both switches were set to #1 position which does not include the third battery. So it looks like the starter battery was not getting charged plus it has the stereo and the air horn wired to it so was being drawn down. I have a charger on it now and will see if I can recharge it

[Cheechako]

I assume you mean the starting battery is 12.4v? If not you are not starting with that battery and have a dead short likely. if it is 12.4 volts... that's pretty much resting voltage on a wet cell battery. (I have two that are a month old and they sit at about 12.45 volts) You could use a combiner to charge both whenver you charge..

[PapaBruce]

Nope. It measured 2.4 volts. My first clue was that my stereo stopped working and I checked voltage to I--2.4 vdc. The starter batt shows 2.4 vdc. I really think that the battery switch settings actually isolated it and the stereo has continued to draw on it til it got too low to even drive that. Thoughts?

[Cheechako]

I had that happen recently (vhf left on, boat unused for 2 weeks) Never could get the battery's to recover. (thus the two new batteries!) I ended up rewiring with a hous On Off switch and used the selector switch to determine which bank to send to the starter. (usually the starter battery) Then used a combiner so I dont have to think about the switching all the time.... charges the start battery if it's low.

[PapaBruce]

What type of batteries did u have. And thanks to all for the input

[Sailmonkey]

If you're only starting an engine with it, all you really need is a group 27 start battery.

[Cheechako]

Originally Posted by PapaBruce

What type of batteries did u have. And thanks to all for the input

Interstate group 27 wet cells.

[PapaBruce]

Then can I use my xantrex charger to keep it charged?

[Sailmonkey]

Originally Posted by PapaBruce

Then can I use my xantrex charger to keep it charged?

You can do anything you want so long as the boat is wired to do it. Really the start battery should also be charged when running the engine.

I think you need to spend some time figuring out how your boat is wired.

[PapaBruce]

I think you're right.

[Captain Bill]

Originally Posted by PapaBruce

Then can I use my xantrex charger to keep it charged?

This depends on the specific charger and the way the boat is wired. Some chargers have auxillary charging ports so that they can charge two banks at once. The only limitation is that they usually require both banks to use the same charging program so they should be of the same chemistry and type. In your case LA wet cells. If your charger cannot do two banks then you might want to use an automatic charging relay. You set these up so that they charge your house bank first then when the voltage is high enough it connects the start battery so that both banks are charging.