1/BOTH/2/OFF Switches Thoughts & Musings

Dec 3, 2020
2
Beneteau OC37 Greenwich Bay, RI
Great post and I learned a lot.
I plan to upgrade my Beneteau OC37 electrical in the spring so doing research now. I'll upgrade the dumb Hatachi alternator with Balmar Alt+MaxCharge Reg, remove the diode based isolator and install ACR. I hope to add solar after this upgrade is done also but not part of this project. My OC37 comes with 3 switches so I plan to use the 3 three switch design outlined by MaineSail as his favorite in his post.
My question is; When cruising and my house batts discharged quite a bit to say 60% for example, they need much longer charge time than the start batt requires. With the ARC relay enabled charging both banks all the time, will this burn out my start batt? Should I disconnect the start bank during long charges? I'd like to have a set it and forget it and remove the human factor as much as possible.
Any feedback appreciated.
 
May 17, 2004
5,028
Beneteau Oceanis 37 Havre de Grace
My question is; When cruising and my house batts discharged quite a bit to say 60% for example, they need much longer charge time than the start batt requires. With the ARC relay enabled charging both banks all the time, will this burn out my start batt? Should I disconnect the start bank during long charges? I'd like to have a set it and forget it and remove the human factor as much as possible.
Maine Sail talks about this at Making Sense of Automatic Charging Relays - Marine How To. See Myth & Lore #3, about 60% down. The TLDR version is that an ACR for this purpose is no worse than a regular smart charger. You can put a switch on the negative lead of the ACR to disable it if you really want. Given the numbers of boats and electrical failures Maine probably sees, if he hasn’t seen a start battery burnt by an ACR yet I think it’s safe to say it’s a non-issue.

By the way, you have traditionally voltage dropping diode isolators on your OC 37? Ours came with a voltage-drop free isolator. It’s not a Blue Seas ACR, but as far as I can tell it provides equivalent capabilities.