Charging options from Alternator

[Brian Cope]

I'm upgrading my house bank to lithium. I currently have a balmar high output alternator and a bep combiner beween my LA starter and LA house.

I am trying to determine the best way to set up the alternator.
1. to charge starter batt from alternator then run a dc-dc charger to house
2. charge house with alternator (the balmar should be able to program for Lithium charging) and run a small charger to maintain starter batt
3. rely on a small solar I plan to add (about 400w) and inverter/charger to charge house and keep alternator for starter battery only.

[barnakiel]

If you are going to have



a\ the alt
b\ the solar


and



2 battery banks


Then I would make the alt charge BOTH banks (does not have to be at the same time, a switch will do as the most basic solution).


And I would make the solar charge BOTH banks (again, does not have to be automated or concurrent, but to do have this capacity, a basic switch, again, will do).


Given $ or $$ you can automate the process and add some monitoring too.


However, if you sail mostly close to docks, you may just wire one thing to one bank and then upcharge while at the dock - for from my experience shore based chargers are cheaper than alternator and solar regulators for mixed and advance batt banks.


BTW I would keep the battery banks SAME chemistry. If your home bank is Lith, make the starter bank Lith too. Or simply start the engine from the house bank. Then you can either forego the 2nd bank or else have a smaller bank as a "reserve". Still, I would not mix the chemisties - have one kind again simplifies the gear attached to charge everything.


ymmv


b.

[pnw2022]

A few of my neighbors have made the switchover to LifePO4. One of them actually had a marine electrician come up with his design, then the others looked it somewhat as well.

All three went with alternator to an AGM starter battery, then DC=>DC charger from AGM to the LifePO4 house battery. Solar and shoreside all to the house battery.

There are advantages on installation with this too. Keeping an AGM starter battery simplifies the install if you have a simple/stupid alternator setup and also not worrying about the BMS disconnect when charging off the alternator.

I am definitely not an electrician, just parroting what I have seen others doing that seemed sensible to me.

[CaptainRivet]

Originally Posted by Brian Cope

I'm upgrading my house bank to lithium. I currently have a balmar high output alternator and a bep combiner beween my LA starter and LA house.

I am trying to determine the best way to set up the alternator.
1. to charge starter batt from alternator then run a dc-dc charger to house
2. charge house with alternator (the balmar should be able to program for Lithium charging) and run a small charger to maintain starter batt
3. rely on a small solar I plan to add (about 400w) and inverter/charger to charge house and keep alternator for starter battery only.

We discussed that million times here that with an external regulated alternator then option 2 is the right way.

[Brian Cope]

how do you determine what size dc to dc charger you need.

I have 150 amp balmar alternator and I plan to use 2 large 12v lithium house batteries (hopefully about 400 ah each battery)

[CaptainRivet]

Originally Posted by Brian Cope

how do you determine what size dc to dc charger you need.

I have 150 amp balmar alternator and I plan to use 2 large 12v lithium house batteries (hopefully about 400 ah each battery)

Don't determine at all.
That just hurts....having an externally regulated alternator and want to have DC2DC. The only one you need is a 10A one to charge your dreaded lead starter from Lifepo4

[pnw2022]

Yeah,
If you have a beefy Balmar alternator and regulator, you probably want to take advantage of that and go to the house bank, then a small DC=>DC to the starter battery.

My neighbors that kept their AGM start battery and left that charged by the alternator primarily did it because they did not have a lithium-ready solution on the alternator side. At least one (and my boat also, with all AGMs) was wired that way already so it saved them a little money and labor as well.

[CaptainRivet]

The best solution is replacing the lead starter with an LFP starter or a bigger backup/starter and charging both via an argofet 200A in parallel.
No lead anymore and an LiFePO starter doesn't need to be floated.