Batteries discharging

[HamsterMike]

Earlier this season after two or three days off grid my engine barely had enough power to start. Short term solution turn off the starter battery switch while at anchor. During my current trip after two days off grid battery bank two, as per the DC panel meter, was very low. I ran the generator for an hour and couldn't get it to charge above normal per the inverter panel. During the night battery bank two discharged again. The next morning during a 2-1/2 hour run the inverter panel read full charge. Later that evening battery bank two was discharged again. Rather than run the generator I ran the engine for a half hour and rhe inverter panel read full charge. This time I turned off all battery switches except the house switch. During the night alarms went off and battery bank three was discharged. Any ideas out there??

 

[Rode Trip]

I would need a lot more information to help. Outboard or inboard? Solar and if yes how much? You need to know which bank is which, not just 'bank 1' or 'bank 2'. Refer to them as house, engine start, or thruster. Only your house bank should be discharging overnight. How old are your batteries and what chemistry? The engine start battery should be isolated and not run down even with the switch on, so there's at least a possibility that the start battery is going bad.

 

[Submariner]

Without even knowing what boat it is, makes it tough to provide assistance. I know that the early models (2018-2019) R27-OB's came from the factory with the 24x7 fuse block wired off the engine battery. 2020 and newer models have the 24x7 fuse block wired to the house bank. This could potentially be your issue?

It also could be time to replace your engine battery depending on how old it is.

 

[NorthernFocus]

Earlier this season after two or three days off grid my engine barely had enough power to start. Short term solution turn off the starter battery switch while at anchor....

That's not just a short term solution. Engine starting bank should always be isolated. The whole point of having separate banks is to protect the starting bank for the one and only job of starting the engines. That's a start. There's not nearly enough information to speak to the rest of it. What type batteries, what loads are you running all night, etc.