Two LifePo4 battery packs I need to switch between, suggestions?

[BritManToo]

So I have 2x 48V packs that don't seem to work well connected in parallel, but work fine seperately.

Would like to switch between them, so only 1 connected to inverter at a time.

 

DC switch than can handle 100A, just switch the positive wires, and not expensive.

Any suggestions for a product on Lazada/Shoppee?

[Crossy]

Are you intending charge and discharge via this switch?

 

Manual changeover or auto?

 

Will it need to switch whilst under load?

 

 

 

[sometimewoodworker]

Also a switch that can handle 48v 100A through it is a very different beast to one that will switch that load. So if you can stop the load and switch you will have an easier time.

[Crossy]

Also, do you have a separate charge controller and inverter or an "all in one" inverter and charge controller?

[Crossy]

Daft thought.

 

Do your BMS's have an on-off switch you can use to isolate one or other pack?

[BritManToo]

1 hour ago, Crossy said:

Are you intending charge and discharge via this switch?

 

Manual changeover or auto?

 

Will it need to switch whilst under load?

 

 

 

Yes, Manual, maybe.

[BritManToo]

1 hour ago, Crossy said:

Daft thought.

 

Do your BMS's have an on-off switch you can use to isolate one or other pack?

The BMS have a mind of their own and will switch on when they feel like it.

I don't trust their software switches.

Edited August 12, 2023 by BritManToo

[BritManToo]

1 hour ago, sometimewoodworker said:

Also a switch that can handle 48v 100A through it is a very different beast to one that will switch that load. So if you can stop the load and switch you will have an easier time.

I do have a breaker between inverter and battery packs, so I can remove the load while switching batteries ........ and my normal DC load is 5-10A.

Edited August 12, 2023 by BritManToo

[Muhendis]

Batteries, Charge controllers, solar panels and inverter all separate and non-intelligent.

Good for the simple life.

Nothing with a mind of it's own except my wife which does occasionally give trouble.

[BritManToo]

I think this might work ...... 250bht

https://www.lazada.co.th/products/3-32a-63a-100a-220v-knife-switch-2p-32a-63a-100a-i4267348771-s16911919450.html

[Crossy]

Great minds and all that carp ???? 

 

It's not rated to actually switch DC, but if the load is small when you switch, I reckon it will be the cheapest way to go.

 

 

[BritManToo]

7 minutes ago, Crossy said:

Great minds and all that carp ???? 

 

It's not rated to actually switch DC, but if the load is small when you switch, I reckon it will be the cheapest way to go.

 

 

I think I only need to connect the positive, the 2 batteries can share the negative 24/7.

[Crossy]

1 minute ago, BritManToo said:

I think I only need to connect the positive, the 2 batteries can share the negative 24/7.

 

Yeah, no issues doing that. You could also run the two poles in parallel for extra safety margin.

 

[Crossy]

General wisdom is that an AC rated switch can handle about a tenth of the AC voltage rating on DC.

 

These knife switches have a large contact clearance so are probably capable of a much larger AC voltage than they're rated for (insulation notwithstanding).

 

Move it briskly when swapping and give it a try.

[sometimewoodworker]

2 hours ago, BritManToo said:

I do have a breaker between inverter and battery packs,

Is that breaker rated for DC? If so then almost any sufficiently beefy switch will do, like the knife switches above 

Edited August 12, 2023 by sometimewoodworker