question

Hi, I have the following system:

1 x Multiplus ii 48/3000/35-32

1 x Smart solar MPPT 150/70

1 x pylontech US2000

Running ESS feeding excess to the grid.

Unfortunately I sit with exactly the same problem and my grid feedback is capped early morning from 2800W down to 2100W. Having analyzed each and every trend available my only conclusion is that for some reason there is a sudden spike (not a gradual increase) in the MPPT battery voltage where at the same time the MPPT current is reduced drastically. I was told the pylontech is in charge of the charge voltages but after disconnection of the can bus on the pylontech and setting the multiplus II as the BMS I still got the same result. On another Easy solar 5KVA system with also only 1 pylontech US2000 and a 150/100 bluesolar mppt where the can bus is disconnected the capping problem does not ever happen. This is what I tried to simulate as a last resort hoping to prove it was or was not the pylontech battery causing the problem but with no luck.

I have spoken to 2 suppliers/installers already and it seems there is no answer for this problem. Just wasted a lot of money on extra panels etc.

Hope someone comes to the party with a solution quickly as I lost my faith in Victron, seems to complicated to solve real problems.

PS. Also did the fan thing that did not work either.

Hi yes I can confirm all the firmware are the latest

Multiplus II on V2628476

Venus GX V2.60

Smart Solar V1.5

Pylontech Firmware version -- ( not shown in remote console device info and not sure where to get it)

In response to your comment w.r.t. the small battery I can confirm the following:

1. A easysolar 5KV system with also only 1 pylontech US2000 bty running under the VE bus BMS does not have this capping problem of the MPPT feedback to the grid. My question would in any case be why the issue is a capping on the backfeed to the grid and also only after some time of running at 2800W.

2. I have seen a similar post somewhere on the portal where a multiplus II with 2 pylontech US2000 batteries has the same problem.

3. While I am trying to feed back into the grid, there is actually no requirement to discharge from the Battery, it is all PV panel input to the MPPT rated at 4000W before it will cap the input. The max I can reach is about 2800W only so that should not be a problem.

I think my biggest challenge at the moment is to find out what is actually in control of the process that causes the capping of the feedback to the grid problem. Is it the Pylontech, the Multiplus charger, the multiplus inverter or the MPPT.

Only received a reply notification yesterday. It seem that I have managed to find the answer to my own question. Not sure if/when the documentation was updated within the last few years, but I cant seem to remember this, as it would have been obvious.

It seem that the multiplus is downrating the power it's is able to invert, in my case to 2x1700w. It is thus safe to assume that the inverter is actually only rated for 1700w continuous use as even at 18-20 degrees air temperature, it's still operating at the lowest possible output. Forced air cooling fans did not assist in any meaningful way either. I have never seen power production more than 3800w and that was shortly after a power failure when the batteries was charging, thus extra power was used in dc rather than being inverted.

The only solution is to "generate" dc loads during capped peak production hours by scheduled battery charging or a dc geyser/hot water element as the bottleneck/throttling lies at the inverting stage.

@Karel how is this one resolved? Can you share?