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.
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 )
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.
UPS Off
The result in terms of SOC change over 90 minutes were excellent - about a 25% increase which would indicate the Multi is charging at it’s rated capacity, which is great
The numbers showing on the Cerbo interface still vary greatly, especially the DC System value, which flicks anywhere between -1300W and +500, when is reality there is a <-100W DC load on the system during this test. The value for DC current output from the Multi in it’s detail screen also varies widely, from around 30A to almost 80A.
The generator beat is very even - it doesn’t sound like the load it’s seeing is varying a lot.
I have uploaded a couple of very short videos of the Cerbo screen and the Generator screen here to show what I’m trying to describe.
As it seems the generator is happy with it’s output, and the Pylontech’s are happy with the charge they are getting, I’m wondering if it’s an instrumentation/display problem rather than an actual one?
Yeh, I think what you show there is fairly typical of what many genset users see. They’re not like grid power in that their own power quality is affected by loads, then distorted sinewaves, etc result. And measurement gets tougher.
Bear in mind too that the DCPower tile is a calculated figure. And it’s components aren’t all sampled at exactly the same time. So it will show exaggerated results from measurement ‘anomalies’.
Your gen seems stable, though you could try testing it with an Input Current Limit just slightly under where you’re running now, just to see if it makes a difference.
Hi LX,
Yes, it’s calculated at the moment, but I have purchased a SmartShunt so I can measure it instead.
I’d have to re-create the test to check the CCL exactly, but usually it’s 320A if the Pylons aren’t aproaching full.
Hi John, and everyone who has chipped in.
Thanks so much for your input!
Knowledge like the methods behind the production of the calculated DCPower figure are just what I’ve needed to understand why the system behaves as it does.
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