For a long time, I used 2 deep cycle marine batteries to run my house system and for starting the engine (I have a Yanmar 2GM20F. ). Each battery went to a separate post on the 1-2-both- off switch. I think Benes use a different switch arrangement, but it can work the same. I would use battery A one day, and Battery B on the next day. Worked Ok. No reason you can’t have a separate starting battery, but not really required.
Then I switched to 2) 6-volt golf cart batteries. these were wired in series to give me a 12-volt battery. I did not have any start battery…just used this 215ah 12-volt bank to do everything.
Last year, I added a 12-volt “starting” battery to my system. It was just connected to battery 2 on my switch, and I could just switch to battery 2 if the house bank was weak…. All of this was charged by an old Guest battery charger that had 2 outputs (10 amp &5 amp). I see no reason your current battery charger can’t be used to charge 2 batteries, both being Lead Acid (AGM is still lead/ acid chemistry).
This year, I decided to wire the start battery directly to the starter (with a cutoff switch), and separate it from the house bank. This was in anticipation of going to Lifepo4 batteries. My 2 golf cart batteries are 5 years old and on their last legs. I could probably day sail on them the rest of this year, but I am planning g a few weekend sails on the hook, and don’t think they will keep the fridge and lights on over a weekend. So I just bit the bullet and ordered 2) 100AH LIFEPO4 Batteries. I will wire these in parallel to give me a single 200 ah house bank.
With the addition of the LFP house bank, I did purchase a new battery charger just for the LFP battery bank. My old charger was not designed for the Lithium Chemistry, and I did not want to take a change of ruining my new battery bank. But this really driven by the addition of the LFP battery bank.
Greg
