Arm battery low voltage

[Normf943]

I unplugged my shorepower including ground to avoid eroding the anodes but just for two days. However I forgot to turn the main battery off. When I got the the boat the main was at 10.3 volts and the engine would not crank. The engine battery appeared to be fully charged. I hooked up to shore power and after an hour the battery was at 11.8 volts but the engine still would not crank. Questions have I ruined my main agm batteries and why would not the engine crank.

Any thoughts?

2019 c28 with Volvo Penta 260 hp.

 

[Normf943]

Should be agm batteries

 

[JeffreyAC77]

Did you put the batteries on parallel?

 

[Normf943]

The batteries are as installed Cutwater.

 

[Ralf H]

Hi Norm,

You will need to charge the house batteries for a longer term to get them back up to full charge. They should charge to around 12.6 volts. If they do not reach that voltage, they may have suffered damage. For the engine batteries, if they are fully charged, as you had mentioned, they should start the engine just fine. Make sure the key fob is close by to ensure that this is not the issue instead of a problem with the batteries. You may try turning the crossover battery switch on and see if this allows the engine to crank. If your issue was truly with the house batteries, then you should have no problems starting the engine. If that is the case, there may be something else at play here.

Cheers,

Ralf