Lead acid with LiIP

[pterrien]

Looking for someone who is successfully using a Lithium house battery with a Lead Acid cranking battery. I intend to do the same but not entirely sure how to do it. I am thinking of using a DC to DC for the alternator and two different chargers for shore power. Make sense?

[sailorboy1]

I have that (lots here have that). Everything charges directly to the house LFP. The house and start are separated by a FET isolator connect such that it allows current to go from the house to the start, but not the other direction. So the house can feed the start circuit and that made a big difference to the windlass on that circuit. It also allows the start battery to be a dump load if somehow the 4 LFP ever disconnected at same time.

[pterrien]

Thanks. Is a FET isolator the same as a DC to DC. I already have an isolator, diode I believe.

[pterrien]

Other question. You can charge LFP with alternator without anything in between or does the FET also regulate the voltage?

[sailorboy1]

All an FET is is a fancy 1 way current flow devise (like a diode).

A DC-DC is basically a battery charger from 1 DC source to another.

An isolator is normally something that physically separates systems and gets energized to connect them

[team karst]

A FET is a 3 wire device. Several ways much not like a diode. More like a low R switch. Off or on, when the gate is fully driven.

[sailorboy1]

sure confuse the guy with techno stuff

[team karst]

Sorry. Seemed like an important point. [emoji848]

FET’s are an important component in switch mode power supplies. Isolating or not. The FET is actually the switch.

[Nauticatarcher]

We have LA start with two 15 amp DC DC chargers feeding Lipo house battery, also have seperate alternator dedicated to house battery that is temp regulated.

[hjohnson]

Originally Posted by pterrien

Looking for someone who is successfully using a Lithium house battery with a Lead Acid cranking battery. I intend to do the same but not entirely sure how to do it. I am thinking of using a DC to DC for the alternator and two different chargers for shore power. Make sense?

I have all my charging sources (solar, alternator, and inverter/charger) directly charging my LFP house battery, and then an 18A DC to DC battery charger maintaining my starter battery. That said, I’m running an advanced regulator on the alternator in order to control the load on my poor little 1GM10, and not melt the alternator when charging LFP).

Maintaining your cranking battery doesn’t take much, so if I was you I’d compare the price of a dc or ac charger for your cranking battery.