MultiPlus-II 48/5000/70-48 charging Pylontech bank off grid not reaching rated 70A charge current

Q&A and troubleshooting
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1

Hi All,

I have a MultiPlus-II 48/5000/70-48 charging a bank of 4 * US5000 Pylontech batteries via 7KVA generator on its AC Input. With SOC around 60% the charge current into the battery bank is about 48A - well below the 70A rating on the Multi. This is in dense cloud with less than 200W from the solar panels. There are no loads taking significant current, and the output wattage reported by the generator matches that going into the Pylontechs. Room temp is mild (23deg).
The system has about 5KW of panels spread across two SmartSolar MPPT 150/70 controllers, and when the sun is good I have watched the Pylontech bank charge current go over 90A, so I know the Pylontech BMS will allow larger charge current, at least from the solar controllers. System is managed by a Cerbo GX.

Settings on the Multi:
AC1 Input Current Limit = 32A (7500W)
Grid Code is None (It’s an Off Grid System)
UPS mode is on
BatterySafe is on
Power Assist is on
Boost Factor is 2
Weak AC Input is on
Max Charge Current when viewed via VictronConnect over MK3-USB is 70A, but I believe this setting is irrelevant as the BMS will overrule.

Ideas?

Shalom

Bill

2

Hi Bill.
You have a reason for enabling Weak AC? This will be limiting charge. Disable it if you can.

3

I had Weak AC disabled initially, and the values for watts for generator in and DC Power on the Cerbo were very unstable. Jumping about up & down. So was the watts output reported by the generator itself. Average was certainly much higher than currently, but after an hour the increase in SOC on the Pylontechs was much lower than what I was expecting. Changing to Weak AC stabilised the figures - no more wild jumps - and the SOC now increases much more as I would expect for the charging rate.
The generator is a single cylinder diesel, 7KVA.
Should I test again with Weak AC off? I was concerned I might damage something.
(I’ll post a screenshot of it right now. It may be irrelevant, but hey :slight_smile: )

4

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image1784×1408 208 KB

5

While you’re changing Weak AC, try also enabling Dynamic Current Limiter. That will help stabilize the gen, it’s like a soft-start for smoothing sharp load increases on the gen.

6

OK, thanks. Will test with Weak AC Off and Dynamic Current Limiter On.