Advice wanted: windlass & LiFePo4s

[svANON]

I’m designing an upgrade from Lead Acid to LiFePo4 batteries. I currently have a 400 Ah capacity Lead Acid house bank, and a separate 200 Ah Lead Acid engine start bank. These 2 banks are joined during charging by a BlueSeas ACR.

I have purchased 4x 100 Ah LiFeTime mini batteries and all 3 of my charging sources include LiFePo4 profiles:
- Solar: 4x 450 watt solar panels (Axitec brand, German made) plus 4x 40 Amp MPPT charge controllers (EPEver brand)
- Alternator: Balmar 6 Series w/ MC-618 external controller
- Shore Power: Xantrex Freedom 3000 charger/inverter

I have read that I should not rely on LiFePo4 batteries for engine start, as the instantaneous draw exceeds their capacities. For this reason, should I remove the ACR and choose a different charging solution for the Lead Acid batteries (either a dedicated solar, an additional alternator, or a DC to DC Charger)?

And what about my anchor windlass? I see amp draws of 65-90 Amps when raising the anchor. Is this load also too excessive for LiFePo4s? Currently, my windlass is drawing from my house bank, and they are therefore isolated from the engine start bank when charge voltage is not present.

What would be best practice in this situation? Create 3 separate banks, one for house (LiFePo4 - charged by Solar/Balmar/Shore Power), and two Lead Acid banks (one for engine start and another for the windlass - joined by the ACR - and charged by a 2nd solution)? Or would you suggest 3 totally separate banks wherein the 2 Lead Acid banks each have their own charge solution? Or yet another option that I’m not yet seeing?

[JustMurph]

The LiFePO4 batteries are perfect for your windlass. Large current is what they do well. Your batteries are rated at 100A continuous discharge each, so a few of these in parallel will handle the windlass easily. No need to run the engine when using it.

[fxykty]

Originally Posted by JustMurph

The LiFePO4 batteries are perfect for your windlass. Large current is what they do well. Your batteries are rated at 100A continuous discharge each, so a few of these in parallel will handle the windlass easily. No need to run the engine when using it.

Exactly this.

Even if your windlass is wired such that it requires the engine, you can just turn on the ignition switch only and run the windlass. The alarm buzzer is annoying though, so if you have this setup, rewire it so the windlass is independent of your engine. LFP’s will easily handle the windlass load.

[fxykty]

Leave it as separate house and engine start. Your only decision is whether to have your alternator charge either your house bank or engine battery - lots of discussions on CF about that. Charge the other bank using a DC-DC charger.

[JustMurph]

Given you have a good regulator, I'd personally charge the house bank with the alternator and back feed the start batteries with the DC-DC. Have a switch to parallel the two systems if that's ever needed.

[Bennyhill]

My solution on a Beneteau Oceanis 40.1 with bow thruster was to Siamese the windlass and bow thruster to the two forward 50Ah AGM batteries; retain the 100Ah AGM engine battery for starter and winch; retain a left-over 100Ah AGM as an auxiliary battery; have these three AGM battery sets inter-switchable for redundancy and extra power when necessary; and charge them from a Victron Phoenix 120v charger that runs off the Victron MultiPlus inverter, which draws from the 1,000Ah Victron lithium House bank (no DC-DC charger, in other words). This way, the lithium House bank is only responsible for autopilot, fridge, lights, and electronics when on an extended cruise, holding up for three days without starting the engine and no solar, or nine days with solar.

[CaptainRivet]

Originally Posted by JustMurph

Given you have a good regulator, I'd personally charge the house bank with the alternator and back feed the start batteries with the DC-DC. Have a switch to parallel the two systems if that's ever needed.

2nd vote on that. Your 65-90A tells me you are having a 1000 till 1200W windlass means your surge is around 250A in worst case if eg anchor stuck. That’s ok for 4x100AH but it would have been better if you would have gotten 2x200A with 200A cells and 200A BMS as one of these can handle starter and windlass while a single 100AH cannot, better it’s BMS cannot. 2 gives you enough redundancy. In the rare event that 3 of the 4 li-time shut off and you use the windlass you risk that one shorts out and dies.
Just makes me wonder why sailors buy stuff first and only afterwards ask serious questions…