Hi. I need to mount a new Pylontech US3000C module in replacement of a old defective module. Is a best practice to charge all the module at the same voltage before to chain them? I have Cerbo, Multiplus II and some smart solar chargers.
Just plug it on the system and the master battery and Kirchhoff’s laws will take care of the rest… 
New battery should now be master!
Well, depends on the stock… Could be an old stock.
Pylontech says that the firmware version number is the safest thing to consider and the newest firmware should be the master.
But as the firmware version is more complicated to read than a serial number label, also the serial number of the battery could be considered an indicator, as the newest ones have a great probability to carry a newest firmware.
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Treu!
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Thanks. The old modules were made in 2022. In the next few days, I’ll check the firmware versions.
I usually charge up the new individual by itself and balance it. It is good practice. then add it to a full bank. Same voltage is close sexond. But circumstances will dictate how you handle it in the end.
You will find posts on this forum about people being stressed about balancing after the new is added. But they supposedly do sort themselves out in a stack.
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With the Pylon, it’s recommended to have a “console” connection cable to be able to more precisely control their configuration and status per cell. @lxonline is right, you should set the new one to the same voltage as all the others; this will facilitate overall balancing; this is also a manufacturer recommendation.
Furthermore, with the “console” cable, you’ll know the exact firmware and therefore where to position your US3000 because, as @alex says, the serial number isn’t always a reliable value in such cases.
All of us are right…
For the passionate user who has the time to watch carefully his new “toy”, indeed, charge it separately, watch the end of charging, see how it’s balanced, observe the voltages and temperatures and so on…
For the more pragmatic installer who doesn’t have the time for each customer to do all the above, connect it with the pack and as I’ve said, the master will do the SOC average and send it over to the charger. The charger will keep supplying current, that will be redirected according with the Kirchhoff’s laws to the least charged and, at the end, the pack will have SOC 100% which means that also the new battery will be at 100% and balanced.
I’ve started with 3 batteries and now I have 8.
First ones… I was curious and charged them separately to see what’s happening.
Towards the last ones… Just stuck them there and forget.
So best practice?
Whatever it suits you according with your desires, but within the limits of the manufacturer specifications.
The rest will be taken care of by the firmware and the physics laws. 
Yes you are right, everyone does as they want but the title of this post is “Best practice to change a Pylontech US3000C module” hence our responses from concerned users
Thanks to everyone. I received this reply from Pylontech customer service:
“You can try force charge mode on the inverter and set SOC to 100% for 5–8 hours.
Or you can use a DC charger following the steps below. Please disconnect the modules and charge each individually with a DC charger at 53.2 V, 2 A for 5–8 hours to balance the cell voltages. And please make sure all batteries have the same voltage when you install them; otherwise an imbalance may occur in future battery operation.”
Could someone suggest which battery charger and suitable cables I should buy to try charging the modules individually?
a CC-CV switching power supply up to 60V-5A will do the job very well and will cost you less than a specific 48V battery charger.
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I’m a bit confused about the charging voltage: the customer service write 53.2V for the external charger but, when I asked about the Multiplus II charger, they write me to set 52.4V (from Pylontech: “For Victron, it normally need reduce the voltage to 52.4V.”). I’m not sure how to properly set the absorption voltage in VE Configure. At this time I set 52,4V in this tab.
52V absorption voltage in VE Configure and 51V Float
Thank you. I use Ignore AC Input to save energy from grid: i’m looking for the best condition to ignore AC for full battery and balance the cells at same time. Udc higher than 52V for 30 min is it a good solution?
I am not competent enough to answer you. Sorry 
@cpalfius
Are allowed to remain grid connected?
If you are use ESS.
Uodate all your components firmware.
I can’t feed the grid, at this time.
We have the same here and still use the ess assistant.
You can set your grid set point to a few watts positive to prevent feedback when there is solar production.
From ess you can control where power to your house comes from (solar or battery) and control depth of discharge and rate of charge - also when it charges.
Otherwise the easiest way to ignore grid but still have some interaction (nad ease of swt up) is using the generator start stop option on the gx with it wired to the aux relay/temperature sensor (that is programmed to drive the primary relay for grid connection). There are quite a few posts here about it and youtube videos.
I connected my four 15kWh batteries from a different brand while having SOC in range 40-80%.
In that range the voltage curve is nearly flat. With small difference in voltage there will be small current to balance among battery blocks. I saw around 20A on the 280Ah batteries rated 140-200A load.
After having all connected, I connected the stack to my MP2/MPPT and charged via solar to 100% SoC let the balancers doing top balancing the cells some hours.