Hello,

I'm looking for experience and advices from users having Pylontech running in parallel with other 15S batteries.

Currently I have 4xUS5000 and I'd like to add a diy bank 15kwh. Pylontechs are connected by CAN to Deye inverter.

Thus appreciate any advice, any settings/configuration, warnings, best practices, etc on this.

Thanks!

Just use any 15S LiFePO4 cells, then connect the new battery in parellel with Pylontech and it will work okay.

Before connecting in parallel for the first time it's better to get all the batteries to the same voltage in order to avoid sparks and disbalance. For example:

• Charge Pylontech to 100% SOC, then disconnect.

• Connect DYI battery, charge to 100% SOC.

• Then connect both batteries in parallel.

Do not forget to set the same CC and CV target voltage for charging DYI like you have set for Pylontech.

The only issue is, that the BMS of DIY battery will not be able to daisy-chain with Pylontech BMS. If you want to daisy-chain comms, then you will need to use salvaged Pylontech BMS board for the DYI battery, plus use the cells with the capacity equal or slightly larger than what that BMS board is set to (50Ah, 74Ah, 100Ah).

Edited September 20, 2025Sep 20 by Youda

13 hours ago, maxmaia said:

I'm looking for experience and advices from users having Pylontech running in parallel with other 15S batteries.

Just for information purposes not Pylontech with other 15s but rather FW e- tower paied with Svolt rack mount at the identical capacity and same bms Pace. As a pilot project i pushed the anvelope to see if i could successfully pair the FW etower with Svolt. To my amazement it actually turned out quite successful.

The setup: Victron Multiplus-II Gx paired with FW 51.2v 16cell( Master) and Svolt 51.2v 16, cell( slave) both incorporating Pace bms. Capacity combined 200ah.

I updated the Svolt pace bms with the same firmware version using Pbms tools via Rs 232 serial communication.

The outcome a perfect hand shake between the bms's via can communication and daisy chained between FW and SVolt.

It goes to show you would not know the outcome until you experiment.

Thanks for your ideas. The way how is now in my side Deye set is by Pylon protocol, rather by voltage control. I just set a automation in Home Assistant to reduce charging amps to 2A once voltage on Pylontech reaches 52.7V. This way I have info about battery charging percentage.

The diy will have a JK bms. Can I leave Pylon protocol as it is now and set JK to work with voltages?

1 hour ago, maxmaia said:

The diy will have a JK bms. Can I leave Pylon protocol as it is now and set JK to work with voltages?

Yes no problem. Should JK detect some error, like overvoltage/undervoltage etc. it will disconnect DYI battery. Very same like when you have JK with an inverter that does not support BMS comm.

If possible, I would leave Pylon CAN connected to the Deye and connect JK to the Home Assistant in order to be able to monitor it comfortably.

1 hour ago, maxmaia said:

Deye set is by Pylon protocol, rather by voltage control.

Just check the Pylon voltage at 100% SOC and then charge DYI to the 100% SOC and that same voltage before connecting these two set of batteries together.

All right, thanks for valuable points. I'll go this juorney in a month, let's see how it goes. :)

18 hours ago, maxmaia said:

Pylontech reaches 52.7V.

Just ensure your Bulk Absorption is not above the 52.7v safe range between 52.5v~52.7v. It is important to pre- charge both batteries separately to 100% Soc then let them rest for 2 hours then check each pack voltage if they are within 50mv of each other then connect them in parallel. Then charge both pack so the charger goes to float. You can do this a few times for the batteries to spend time in the balancing region.

Edited September 21, 2025Sep 21 by TaliaB

The goal is to get the cell delta between the pack cells as close as possible <50mv.

Below delta between the 2 packs 3mv

Edited September 21, 2025Sep 21 by TaliaB

Thanks, will keep an eye on cell differences. Currently when at 100% charge, Pylontechs stays below 40mV difference.

Both lifep04 batteries at rest with a delta of 13mv 100%soc charged at 0.2C, charge voltage 55.8v (as stipulated by FW) DVCC(Dynamic Voltage Current Control) setup on Victron Multiplus II The "forced on" means both batteries are controlled by the bms's.

Edited September 21, 2025Sep 21 by TaliaB

Just a small update on this:

the setup is in place since 12days and it works very well, cell are pretty ballanced, stays under 0.004V normally and when at 100% charge it raise to around 0.02V. The total voltage between batteries is a bit different by 0.1V. Probably due to wiring/internal battery resistance/bms measuring accuracy.

Set the inverter to voltage control, using following settings (winter settings):

Battery float charge voltage 51 V

Battery absorption charge voltage 52.5 V

Battery equalization charge voltage 52.5