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Will a Multiplus in charge-only mode play nice with 3 x parallel Phoenix Inv, Pylontech battery?

I am building a system that will have 4 x MPPT 250/85, 3 x Phoenix 48/5000 inverters in parallel and a Pylontech 48V battery bank. I will not be using a backup generator source but I do have a RV parked in my driveway with a 12V 6.6 kWh battery and an Easysolar 12/1600/70 installed. This is wasted capacity when we are not using the RV, so I may as well put it to good use.

Obviously, the 12V battery in the RV and the 48V Pylontech battery in the house need to have some method of interfacing. 12VDC to 48VDC conversion is not the answer, so I looked into using the 240V output of the Easysolar to run a 48V charger for the Pylontech batteries. Naturally, I want this to be controllable to ensure that my very expensive batteries don't overcharge. I can already ensure that the RV batteries don't over-discharge as that system is fully integrated into Home Assistant and customisable via automations.

I looked into Skylla 48V chargers but they are essentially dumb units and don't appear to be controllable by the Pylontech battey BMS and Cerbo GX. Next option is to use a Multiplus in charge-only mode. The Multiplus 48/1600/20 matches well with the output of the Easysolar in the RV and has a VE Bus connection but I cannot definitively find out whether its output would be controlled by the Pylontech BMS in the same manner that the MPPTs are.

Any help would be much appreciated.

charge controller compatibility
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Mike Dorsett avatar image
Mike Dorsett answered ·

As a thought, you could configure a relay output from the Cerbo to close at say 80% soc on the pylontech. this could be wired to the remote input of the Skyla to shut down the charging. - if the Cerbo has a spare relay output !!

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away avatar image away commented ·

Thanks Mike. I do a similar thing now, with the Easysolar in the RV. Most of the time it charges the batteries using only solar but, at present, it is acting as a giant UPS and runs some of the mission critical stuff in the house. So, on those days when we don't get enough sunshine, I use the SOC of the RV battery to trigger a relay that applies mains AC power to the Easysolar, just to peak the batteries.

This will change when the off-grid installation is finished. There will be no need for the Easysolar to be the UPS, but the principle remains - yes, I could use a Skylla and do relay switching based on SOC of the Pylontech. I was hoping to keep my intervention levels low, but it would definitely be a fallback plan.

Edit: To perform this function I use Home Assistant, which uses Modbus the gather data from the Color Control GX in the RV. I will be doing the same with the Cerbo in the house. A Home Assistant automation switches a wifi relay that makes or breaks mains power to the Easysolar at present. These relays are as cheap as chips and very reliable (so far). So, I won't necessarily have to have an available relay in the Cerbo.

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