2012 450 Battery functions

[JCastilla]

This may be a silly question but I have 4 batteries on the boat. My manual only tells me what the replacement model/size I should replace with. It doesn't tell me what each battery is for. I have 2 gauges on the dash indicating the charge level of 2 of the batteries, assume these are for the 2 engines. Are the other 2 for the generator and house use?
Thanks!!!

 

[ranger58sb]

Not familiar with your boat, but you can maybe figure out some details.

Are all four batteries the same size? Are any of the batteries connected to each other? Or is one smaller? And do you have a generator?

If all are the same size, and connected together into two pairs, I'd suspect you have two "banks" and each "bank" starts an engine and services approx. half of your house loads. (In that case, your gauges would be one for each "bank.")

OTOH, if one is smaller and you have a generator, the smaller battery might be your genset start battery.

And in the meantime, probably someone who knows your boat model can trot out the real factoids.

-Chris

 

[JCastilla]

There are 2 banks with 2 batteries the same size in each bank, see below.
We do have an Onan 11.5 generator.
Reason for all the questions is that my port engine would not turn over and I had to hold down the battery parallel switch to start it so I'm thinking that one of the batteries in the bank is low and won't crank enough to start it. But would have thought that my analog gauge would have shown this low voltage?

 

[km1125]

I'm not 100% sure on that boat but with other similar vintage/size boats it is setup as ranger58 says... two banks of two batteries each. You should have a master switch for each bank. One bank typically feeds the port engine and the other the starboard engine, but other loads are distributed between the two banks. There is a diagram in the owners manual which outlines it but it might be a little difficult to read.

You should be able to read the voltages separately for the two banks.

You also need to check your charger and the breakers that connect the charger to the battery banks (there should be two separate breakers). You may not be charging the one bank.

 

[ranger58sb]

There are 2 banks with 2 batteries the same size in each bank, see below.
We do have an Onan 11.5 generator.
Reason for all the questions is that my port engine would not turn over and I had to hold down the battery parallel switch to start it so I'm thinking that one of the batteries in the bank is low and won't crank enough to start it. But would have thought that my analog gauge would have shown this low voltage?

Then my guess -- 2 banks, each servicing one engine and half the house -- sounds correct (as @km1125 also suggests).

Voltage isn't a perfect measure of battery bank capacity, and if the charger was on when you read that voltage it would have been "charger voltage" anyway -- or engine on, "alternator voltage" -- not necessarily actually battery voltage.

Still, you can do another test or two. Turn the charger off for about 6 hours or more, or even 24 hours. THEN check voltage for each bank. Even more thorough, disconnect each battery from the other in its bank, do the wait thing, and then test each battery individually. You may find one battery ins a bank is deader than the other... although it's usually best to replace a whole bank at once, not just an individual battery within the bank. Assumes they've been in service for a good while...

While you're testing stuff, you'll find it useful to pin down what battery (bank) starts your generator. And if you anchor out a lot, you might even want to consider adding a separate genset start battery to the boat, anyway.

You haven't mentioned battery age, size, brand, type (flooded? AGM? gel?), if flooded when last watered, etc.... and some of that can matter, too.

-Chris