12v vs 24v

[OldJimbo]

Just bought two 12v 100ah Lossigy batteries for $315 each on Amazon, and the description unequivocally states that will not accept charging below 0 degrees Celsius. Now I have to return the 24v 100ah battery which is still boxed and the Victron SmartSolar 100/20 so that I can order a Victron 100/30. That will let me add one more 12v solar panel in parallel if I need it. Got to admit that this all shows how much I need to learn about electricity.

 

[12VoltInstalls]

Should I just get a manual shut off switch for the solar positive and stop worrying?

That’s one way. You could actually do it automatically with a pizza’s worth of parts.

They make 7W? battery heating pads too

So combining the two would be a couple or three pizzas.

running Victron Connect against a demo 100/20 shows the option for cold temp shut off for LiFePO4 batteries.

And that could be the best method

 

[OldJimbo]

Bought the 100/30 Victron SmartSolar w the Long Range temp sensor. Combined with the Lossigy lifepo4 batteries I will have redundancy on freezing protection. Also got the AiLi shunt to get a good SOC on the batteries. Now all I need is a break from this cold & wet weather to get some things mounted.
Question about the negative bus bar: Do I have to ground it to the chassis? Will that mess up the shunt since the chassis will now ground both the engine starting system and the house/solar system? Also, I’d like to get extra charging from the alternator after the starting battery is recharged - so should I be thinking about a lifepo4 starting battery when I need a new one?

 

[12VoltInstalls]

Question about the negative bus bar: Do I have to ground it to the chassis?

Yes

Will that mess up the shunt since the chassis will now ground both the engine starting system and the house/solar system?

No. It shouldn’t be a circuit

Also, I’d like to get extra charging from the alternator after the starting battery is recharged - so should I be thinking about a lifepo4 starting battery when I need a new one?

I’m a proponent of lead acid batteries for starting batteries still at this point in time. And for several reasons. Including the starting amps could 350A or 600A or whatever the draw is: it’s big.

 

[Rednecktek]

so should I be thinking about a lifepo4 starting battery when I need a new one?

Nope. LiFe's are great at a lot of things but pumping out the high amps to turn over an engine isn't really one of them. Most LiFe batteries have a 100 or 200 (for the big boys) amp discharge rate and car batteries usually run in the 600-900a range. You COULD do it but you'd need to strap 6-9 batteries in parallel to get that kind of amperage and that would be ridiculous.