Adding a new EG4 LifePower4 V2 to an existing bank

[ColtB45]

I have an existing bank of 4 x EG4 LifePower4 (V1) batteries. I'm considering adding a 5th. I'm concerned with keeping everything balanced so all batteries dis/charge at the same rate and to the same depth. I was very meticulous to make sure all batteries were "even" in regards to electrical wiring. All leads from the batteries are the same length, the left bar (+) is connected to the inverter from the top while the right (-) is from the bottom.

On the surface, V2's seem to be nothing but Pros over the V1's (better warranty, better cells, better BMS, shorter cabling internally) but I wonder if those differences lead to bank balancing issues when mixed with V1 batteries?

With all that in mind, should I get a V2 or a V1, and why?

 

[wpns]

May not matter, if internal resistance is lower on the new ones it'll take more of the load, but they'll all function OK.

Are you using closed-loop comms? How old are your 'old' batteries?

 

[ColtB45]

closed-loop comms: Yes
how old are the batteries: Very (for EG4 LP4). I bought the first few in 22, and another in 23.

One looks like this (v0.9)?:



The rest look like this (v1.0?):

 

[ColtB45]

May not matter, if internal resistance is lower on the new ones it'll take more of the load, but they'll all function OK.

That's at the core of my concern. I start some fairly large loads, a 4 ton AC without soft-start for example (120A AC inrush).
I don't want a situation where the new battery gets a disproportionate amount of that load and trips.

 

[wpns]

That's at the core of my concern. I start some fairly large loads, a 4 ton AC without soft-start for example (120A AC inrush).
I don't want a situation where the new battery gets a disproportionate amount of that load and trips.

It won't trip out, if all the wire lengths and fuses, etc are identical between batteries, it'll just take some small (10?) percent more power, and hopefully you aren't that close to the edge.

 

[ColtB45]

Would the BMS & closed loop comms help any here? Somehow leveling the discharge/charge amongst the batteries (adding resistance on the least resistant to "match" it to the others maybe)?

 

[DougfromdaUP]

Somehow leveling the discharge/charge amongst the batteries (adding resistance on the least resistant to "match" it to the others maybe)

This is already taken care of. The overpotential voltage goes up as current draw does, automatically working to equalize current draw from the batteries. That's why banks of LiFePO4 are so easy to use and maintenance free.
RCinFla has tons of great information about this in his posts.

 

[wpns]

Would the BMS & closed loop comms help any here? Somehow leveling the discharge/charge amongst the batteries (adding resistance on the least resistant to "match" it to the others maybe)?

The BMS will not 'throttle' the batteries to match the currents, you need to make sure the interconnecting wires are close enough in resistance to balance the currents without any external help, but that's not hard, just use similar wire gauge and lengths and you're fine.

And don't get all wound up about 'but their SOC doesn't match perfectly during charge/discharge cycles'. You'll use all the batteries, and by the time you get to 0% (please don't), you'll have used all the storage capacity of all the batteries.

 

[ColtB45]

So the consensus is, the V2's wont "match" the V1's but that OK so long as wirelength, and other practical things are matched?