LiFePo4 and FLA negative

[Hillbillybuddha]

When using a FLA battery for your starter battery and LiFePo4 for your house bank do I keep the negative wires separated? I'm guessing, you'd use the engine at the Neg for your starter battery and a bus bar for your LiFePo4 batteries? And not use a "off/starter/house" switch in the system? The only connection being an Isolated DC to DC charger.. >alternator > starter battery > DC/DC > House batter?

Would the only way to change the starter battery be the alternator?

 

[grizzzman]

You can separate if you want but it won't hurt anything if the grounds are togeather.

 

[Hillbillybuddha]

You can separate if you want but it won't hurt anything if the grounds are togeather.

I was looking at Victron DC to DC chargers and the difference was, if I'm understanding it correctly, is the isolated charger has starter battery pos and neg IN and house battery pos and neg OUT. While the non isolated charger has a starter battery pos IN, a house pos OUT and a common neg. If I can connect my LiFePo4 neg and my FLA neg, it's there any reason to get an isolated charger?

 

[Short_Shot]

Not really necessary as I understand it.

 

[grizzzman]

My trailer system is FLA and LFP and all the system including the 120 power is on a common ground.

 

[Tecnodave]

I was looking at Victron DC to DC chargers and the difference was, if I'm understanding it correctly, is the isolated charger has starter battery pos and neg IN and house battery pos and neg OUT. While the non isolated charger has a starter battery pos IN, a house pos OUT and a common neg. If I can connect my LiFePo4 neg and my FLA neg, it's there any reason to get an isolated charger?

There are two reasons for isolated chargers

1: if the systems are not at the same ground such as a positive ground vehicle and a negative ground solar system

2: radio noise, isolated ground is especially used for ham radio , other communications, and medical use as the isolation keeps the EMI/RFI generated in one system isolated from each affecting the other system

For most users the non isolated variety will work for your needs.

with most dc to dc chargers it is not possible to charge the source battery from the target battery.......most...not all...are one way only.

There are two way DC to DC chargers but those are very much a very special item. The Junsi iCharger is one example of a two way DC to DC charger, though it is for a very special purpose, the charging of model airplane lithium batteries then discharging them back into the source battery.

 

[DerpsyDoodler]

You can separate if you want but it won't hurt anything if the grounds are togeather.

As long as the dc-dc charger is isolated. If not isolated, then the battery banks should have a common ground.