Lithium House battery?

[bigskymudflaps]

I have a two battery setup all lead acid for now, they're isolated house/starting. I'd like to drop in a 12v 100ah lithium house battery so I have to worry less about running the stereo while the boat isn't on. I believe that I have a 120amp alternator. I'm thinking I'll smoke the alternator if I drop in a Lithium? Decent stereo and a bunch ballast pumps run off the house battery (I usually increase rpm and turn off the stereo when running all the pumps to keep the voltage up). I was thinking of wiring a 40amp dc to dc charger into the house side? I've heard of putting a temperature sensor on the alternator? Has anyone had luck with lithium, failures, or tips? Thanks all.

[chpthril]

I'm thinking I'll smoke the alternator if I drop in a Lithium? Decent stereo and a bunch ballast pumps run off the house battery (I usually increase rpm and turn off the stereo when running all the pumps to keep the voltage up). I was thinking of wiring a 40amp dc to dc charger into the house side?

You do realize that the alternator you are worried about smoking, is the supply side of that DC to DC, right? So you are still in the same boat, pun intended, even with the added DC to DC.

With that said, ive looked into doing AGM/LAWC to Lith swaps, and it seems a DC to DC is needed, as the typical alternator is not going to work. Basically, the DC to DC is a 12V DC powered Lithium battery charger. Then theres the AC to DC lithium charger for when the boat is back at the dock.

[bigskymudflaps]

I was hoping to see a comment from Mike, he's the wizard of all when it comes to these issues -- and a great resource if you need ballast or stereo parts / design. Fabulous customer service. Nonetheless, back to the issue at hand. From what I gather, a DC to DC charger is likely the way to go -- this is because a drained lithium battery will draw as much amperage as the alternator will give it (very low internal resistance). Great for charge time, but the alternators on our boats aren't designed to push maximum power for an extended time. It's like driving car motor at redline...it will explode. So, assuming I'll go with a DC to DC charger to slow down the power demand on the alternator, how much power can it safely and continuously produce? I have a 120amp alternator, can it continuously make 60amps? I'm thinking of a Renogy 40amp DC charger. The next question is whether I will have issues running power the other way, i.e. when I'm drawing a bunch using the 5 x 11.5amp ballast puppies (and sometimes the stereo). Without the DC charger, I think the alternator kicks in when there's a lot of draw on the battery. At least I can say that when the pumps are on, the voltage drops and increasing motor RPM will bring it back up to 13v+. I'm afraid that the limit on electricity coming in will "retard" the ability of the alternator to make up for demand for power. It may be a non issue, it may not. What's crazy about this issue, is that I can't find a dealer that's done a lithium house battery. And none of them are even aware of the issues related to a retrofit. In the RV world, it's commonplace.....

[CodyRyan]

What solution did you ultimately end up using?