Two scenarios: Alternator to LFP House Bank or Alternator to Starter battery?

[Keep Calm]

You'd better ask that question in the solar panel topic, etc. Here is the topic: Two scenarios: Alternator to LFP House Bank or Alternator to Starter battery?

[col50]

Originally Posted by alctel

When I installed my lifepo4 pack on my old boat I ditched the start battery entirely, a lifepo4 pack will start a motor even when almost completely dead (and it should never get to that point, because you have a BMS, right?) and I wanted to free up the space/weight.

There is a really good way to integrate a lead acid start battery into a lifepo4 in a way that it also acts as a buffer and protects the lifepo4 pack, it's well described here:

https://nordkyndesign.com/electrical...-battery-bank/

Worth taking a look at if you want to keep a lead acid battery on the boat

Very good links. Thank you.

[hjohnson]

Originally Posted by dreuge

Hi,

I would never use option 1 as it could end up killing your alternator when the BMS disconnects the battery during charging unless you have an alternator protector.

Your other option is to have your BMS signal your system to shut down charging before it gets to the point of "pulling the pin" as it were. The system I'm designing for my boat has this ability. As the LiFePO4 battery approaches 100% SOC, the BMS will signal to the alternator (and other charging sources) that it no longer wants power. These will back off their charging capabilities until the whole thing goes steady state.

That said, I'm using a REC BMS, Wakespeed regulator, and everything else is Victron. It will all integrate nicely over CAN bus.

[CaptainRivet]

Originally Posted by hjohnson

That said, I'm using a REC BMS, Wakespeed regulator, and everything else is Victron. It will all integrate nicely over CAN bus.

That's the luxury and expensive way to do it right.
With the wakespeed regulator you wouldn't even have to have a BMS, you can just program it to stop charging at a certain SOC or voltage level.
Also this a tip for
A) people that use basic BMS eg Dali that just cut of everything so before BMS pulls the trigger the wakespeed shuts down charging earlier
B) the luxury version above to have this as last borderline in case BMS fails, in this case at eg 14.5V as your BMS should cut off earlier.

[AllenRbrts]

Originally Posted by CaptainRivet

That's the luxury and expensive way to do it right.
With the wakespeed regulator you wouldn't even have to have a BMS, you can just program it to stop charging at a certain SOC or voltage level.
Also this a tip for
A) people that use basic BMS eg Dali that just cut of everything so before BMS pulls the trigger the wakespeed shuts down charging earlier
B) the luxury version above to have this as last borderline in case BMS fails, in this case at eg 14.5V as your BMS should cut off earlier.

Not sure protecting expensive alternators or batteries is a luxury. At least in my case, I have other devices that charge the batteries beside the regulator (solar, inverter/charger, hydrogenerator) and the BMS makes sure that everybody plays nice to the batteries. Replacing the alternator because the BMS disconnected under load is at least as expensive as buying (and properly connecting) the regulator in the first place. Not having a BMS might damage a very expensive set of cells (or worse). For me, I frequently cruise a long long ways from repair facilities, so having the system be bullet proof is very important to me.