Lithium Batteries? School Me , marine/boat applications!

For starting battery, lithium isn't recommended. I think there are only one or two different manufacturers that have a factory lithium starting battery.

Here's my understanding (feel free to correct me): all Lithium batteries include a battery management system (BMS) that controls charging and protects the battery - because an unhappy lithium battery can cause a runaway reaction leading to a serious fire. When you start a large engine, a lot of things happen very quickly - large amount of current out, and then a quick change as the alternator takes over and begins to charge. This can cause a lithium battery BMS to trip to protect the battery. If the battery trips - the alternator on your engine has nowhere to dump the excess current - poof, you just fried the electrical system on your outboard.

Lead acid batteries don't have a BMS - they use the basic chemistry of their construction to act as a big shock absorber on your electrical system, If they get excess charge for a few seconds - water turns to a bit of hydrogen - no harm done (hopefully).

For an engine battery - flooded lead acid, or AGM. For house load - lithium can store vastly more energy, lasts longer, can be run down further with no damage, etc. First, talk to a marine electrician and check out the youtube marine electrical series by jeff? in Vancouver? Don't listen to internet cowboys like me especially when it comes to electrical!

Dakota and a few others make Starting Lithium batteries but do your research, one on ebay by another brand did not even have a cold cranking amp much less marine cranking amps. The dakota's and others lithium lipe04 starting batteries I have seen are very expensive.

House batteries are cheaper, but you'll require a DC-to-DC charger to use your alternator to charge them, or solar array. Your existing shorepower charger may not charge them fully. New Victron and noco charge them other ones...? Look at the owners manual or sales page for your onboard charger.

Try to get one with low temp charging protection as well.

I think I can get discounts for Eco-Worthy products, which are the most affordable ones, but based on my research, I'd look at Litime for marine house batteries.