Conversion sailboat from FLA to lifepo4 (12V setup 200AH)

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feeling asked Jun 4, '23

Conversion sailboat from FLA to lifepo4 (12V setup 200AH)

Hello,

I plan to convert my battery setup from the original FLA batteries on my 35ft sailboat ( 1 engine 70AH and 2 service 70AH ) with lifepo4 batteries (200AH setup)

I don't need a lot of energy, nor AC power inside the boat, but I need security and reliability.

Needs are basically (maximum values) :

- Laptop : 3A

- Electronics : 2A

- Fridge : 3A

- Navigation lights : 1A (led)

- Cabin lights : 2A (led)

- Autopilot (? average 3A ?)

- rarely : anchor winch ( ~100A ? ) -> He will stay on the engine FLA battery.

I'm rarely more than 3 days at sea.

The original setup is the following. (I dont know why there is a GND swtich on the original setup, any Idea ? installed factory by Beneteau).

I plan to convert to something like this.

Any advises/recommandations about this setup ? (missing breakers ? fuses ? ...)

Best regards.

Lithium Battery orion dc-dc

electricity-schematic-as-is.png (195.3 KiB)

electricity-schematic-ideal.png (248.7 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2023-06-04T23:01:16Z

ingo21 answered · Jun 04 at 11:01 PM

the main thing is see is you took off the diode between the alternator and the lifepo batteries , assuming to stop over charging for the lifepo and you replaced it with a 30 B2B charger. this means your lifepo won't get the possible 80amp from the alternator. not quite sure how the alternator is regulated at this setup??

if you do not use your engine often too charge your battery that should not be an issue , if you mostly rely on charging your battery with the engine it makes a difference between 30 and maybe 70 amps.

i do not see a BMS in this system. do the batteries have internal BMS.

(I dont know why there is a GND swtich on the original setup, any Idea ? installed factory by Beneteau)

maybe the idea is to disconnect the battery completely from the

engine (and usually some ground to the keel and metal thru hulls)

if you leave your boat stored in salty water.... so electrolysis and the potential damage of a lighting strike maybe being reduced by not having the electric system connected to the water thru the engine /shaft/saildrive....

i which case your diagram or setup is not right.....
one house battery is going thru the GND beaker the other one not?

the startermotor is going thru the GND breaker the alternator not?

and in your second diagramm the alternator is permanently connected to your starter battery that can't be right??

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feeling commented · Jun 05 at 06:44 AM

Thanks for your feedback ingo21,

Correct, I will only feed the leisure batteries with maximum 30 AMP from the alternator. I don't use often my engine to charge the batteries, and ... I've read that an alternator can be cooked if used to hard ... so I prefer to use the alternator at ~50% load maximum.

BMS, Yes !!! there is of course an internal BMS with temperature/load protection. (I plan to use 2 batteries in parallel, so if a BSM is defect, I hope the second will be ok).

Thanks for your analysis about the GND breaker, so I will keep it. (between the battery GND and the GND busbar).

Not right :

- Both batteries should go trough the GND breaker, maybe the schema is not clear.

- Actually, the alternator is wired directly to the batteries (not trough the breakers), this is the same in the 2 schematics ... Is this a bad practice ? I can modify easily and put them after the breakers. This is maybe because an alternator can be cooked very quickly if the breaker is accidentally turned OFF while motoring (Indeed, the starter go trough the breakers)

Thanks for your feedback !!!

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Answer 2 · 2023-06-05T04:13:21Z

kevgermany answered · Jun 05 at 04:13 AM

Assuming you're adding a battery monitor, suggest you use the BMV712 and monitor starter battery voltage as well. Common negative must remain connected for this to work.

@Ingo21 commented on the B2B. It's not clear whether you're charging starter or leisure with it. One can infer, but... If you want bi-directional, you'll need two.

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feeling commented · Jun 05 at 06:34 AM

I plan to use the B2B to charge the service (leisure) batteries from the starter battery (the B2B will be only active when the engine is ON, ... this is the reason of the signal wire between the engine panel and the B2B charger, pin H I think).

Regards.

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