I would like to double the battery capacity of my system from 3x5kWh (Voltsmile V10) to 6x5kWh.
In general the connection and right setting of the battery IDs is clear, but I think I should not connect batteries with different charging state.
Is there a good way to do this? I was thinking about connecting them with a resistor/load to limit the current, measure the voltage difference and when it is 0V directly connect them. But I am open for better suggestions.
Using a bench power supply, perform a top balance (charge to 100%) first on each cell individually, then connect them in parallel and perform a collective top balance.
Thanks a lot. That’s an ideal solution.
Unfortunately I don’t have a battery charger with sufficient power. Thats why I was looking for an alternative.
I first measure the voltage of the new batteries and set Max charge voltage in DVCC to the measured voltage of the new batteries. Once the old ones are at the same voltage, connect them together and let them all charge up to 100% at their leisure.
The displayed 50% SOC could actually be 30% or 70%, so high equalisation currents may flow.
It’s better to have both batteries either fully charged or fully discharged.
You can also connect them to the Victron system one at a time to fully charge them both.
Don’t use SOC use voltage. Soc can be incorrect
Add the battery to the bank (not live) when the battery bank is basically within 0.1v of the battery you purchase.
Thanks, for all the support.
Here what worked for me.
I charged my old batteries up to approx 90% (as I was doing this “live” I missed 100% due to some consumption). Then switched to the new batteries (disconnecting first the CAN bus to force disable discharge while keep everything running). Charging the new batteries to roughly the same SoC. Then comparing the Voltage and slightly discharging to the same voltage (a EV-Charger is a good big load 
). Again disconnecting the CAN switching all batteries off, changing IDs, connecting all batteries and switching them on again.
For each (dis/re)connect step I disconnected the CAN-Bus, waited till in VRM the batteries showed no load, switched the batteries off/on and checked that there was no current in/out-of the batterie with a current clamp.
For the voltsmile batteries this worked like a charm, and now everything looks good.
With an ESS system, I use the “Keep batteries charged” function so the new and old batteries can balance each other out. This can sometimes take quite a while / run overnight.
You always have the +/- connection cables connected to one battery.
I’d recommend connecting the cables diagonally, so the positive cable goes to battery 1 and the negative cable to battery 2.
And shouldn’t the CAN cable be connected to the top battery?
I didn’t want to go all the way up to the maximum voltage/SoC, because the voltage curve gets very steep around 100%.
Why should I connect them “crosswise”? To keep the resistance the same all the time?
Because of all the swapping around, the order of the IDs doesn’t match the order of the batteries in the rack. I also wanted to use a new battery as the “master”. From top to bottom, the IDs are 4, 1, 5, 2, 3, 6, so the CAN connection is at ID 1. The batteries are connected to each other via a simple bus, so the connection order doesn’t matter.
Only thing to change there would be to take the negative off one battery in each pair and the positive off the other in the pair. (Diagonally connected)
There will be uneven current sharing there.
And yeah Comms maser is number 2 in the stack? Not incorrect if it works I guess.
Are all modules showing correctly on the GX?
Thanks for the tip about the connections; I’ll change that as well.
The Master module (ID 1) is exactly the second one from the top.
The cables are rated for up to 120 A, but yes, if batteries fail, that could cause problems. I should find a better solution for that, or add fuses to the Lynx Power In.
