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.

[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.

[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