How much lithium?

[CapnCrunch]

I'm seriously considering switching to lithium for my house bank and have several questions. My boat is a demasted motor sailer so, technically she is now a power boat, but I'm posting here because IMHO sailors know more about these systems.

Our current system is 1000 amps of 9 12v (+ an isolated "oh s**t" starter battery) FLA batteries charged by 1000w of solar panels controlled by 3 Victron 100/30s plus a 400w turbine with its own controller. We also sometimes use a honda 2200 to charge the bank via a 3000w inverter/charger. The boat has 2 engines with factory internally regulated alternators.

Our current regular power usage is @ 320 amps/day plus intermittent usage like water pump, shower drain, propane solenoid, coffee maker.

1. How many amps of lithium do I need to replace the house bank?

2. I understand that I will need to keep 2 FLAs to start the engines so should I run the windlass off the FLAs or the house bank?

3. Can/should I charge both the start batteries and the bank with the alternators when cruising?

All info will be greately appreciated.

[sailorboy1]

It comes down to money. Some will say you need half the amp-hr capacity you have now. But I say get what you can install. So if you have 9 lead acid batteries now that sound they are G31 I would say get 9 drop-in 100ah G31 batteries.

But there is a problem because last I looked the manufacturers say you could only parallel 4. So in that case get 4 of the 200ah batteries and see if they fit. Or ask the manufacturers if putting 9 is really an issue (I bet it isn't except for a balancing issue that is mostly meaningless)

[Pandor]

Why are you asking others? How have the 1000 Ahs of batteries worked so far and how low do you run them before recharging? If you really only need 320+/- Ahs per day than the 1000 Ahs (or 500 usable Ahrs) was probably great, right? Assuming you will cycle your new LFP at 80%, start will 500/.8 or 600 Ah. That is probably the most you’ll get from your solar panel on a good day as well. If you want to reduce risk more in cloudy or wintery days, you should go up from there.

But consider a smaller number of larger batteries. I’d say 2 300 Ah batteries or 2 460 Ah if you want overkill. Too many smaller batteries is just a pain to keep balanced. And two separate house batteries gives all the redundancy you’ll need.