This forum post is an attempt to bring this issue to Voltronic's attention.

As @Coulomb has mentioned many times, and now myself and many others have observed, our Voltronic inverters will cut off all PV power once the battery is full, and then start charging again once the SOC drops lower. This prematurely shortens the life of the battery, because it ends up performing more charge/discharge cycles than necessary.

This only seems to happen when a BMS cable is plugged in.

Here is a graph demonstrating this in action:

 

As you can see, once the Battery SOC reaches 100% just after 12:00, PV power (green line) cuts out, and does not power loads (orange line). PV power idles at around 100W, which looks like the inverter's internal power usage. When the battery SOC drops briefly to 99%, at 13:25, then PV power once again kicks in, but then the battery hits 100%, and PV cuts out again.

To be clear, the problem is this: PV should not cut out. It should continue to power loads.

My equipment:

1. Kodak MKS4 5.6 kW
2. 1 x Pylontech UP5000 battery with RS485 cable attached
3. 8 x 350W PV panels

I'm going to refer to this forum post when trying to contact Voltronic support.

If other people are able to graph their metrics which show the same problem, then please share your data here.

Unfortunately I suspect you won't get a fix that does not also void the warranty on the Pylontech. (Because I suspect the inverter design will let the Pylontech go overvoltage if you keep on generating PV when it is full).

But wait.. there's more!

I just figured out a big culprit in my setup:

My "Back to Grid" voltage was 47, and this morning while it was cloudy and load was high, this was triggered.
My "Back to Battery" voltage was the default setting of 54, and my Pylontech battery will never go that high. So the moment we hit 47 V, we get stuck in "grid" mode, and never come out of it.

It still seems wrong that the inverter won't mix PV power into the load when in grid mode, or keep the battery at a floating voltage, but at least I can work around this particular issue.

4 hours ago, P1000 said:

Unfortunately I suspect you won't get a fix that does not also void the warranty on the Pylontech. (Because I suspect the inverter design will let the Pylontech go overvoltage if you keep on generating PV when it is full).

Will this inverter keep on charging to cause this over Voltage. I would have thought it should sense being at 100% and cover the load instead.

@Ben Harper

When you say under high load it went down to 47V is it not because you had say only 1.2kw or so PV and load say over 3kw?

Does this model blend power with SUB or set to SBU?

I notice your PV already started dropping when battery was @ 98% @ about 11h42.

Edited May 31, 20224 yr by Scorp007

20 hours ago, Ben Harper said:

My "Back to Grid" voltage was 47, and this morning while it was cloudy and load was high, this was triggered.
My "Back to Battery" voltage was the default setting of 54, and my Pylontech battery will never go that high. So the moment we hit 47 V, we get stuck in "grid" mode, and never come out of it.

First of all - what model are you using?

I experience a similar problem with my MKS5K with no BMS communication. Coulomb explained it with the fact that 72 cell in 3S setup PV panels OCV exceed the max operating voltage of 115V of the inverters MPPT. When battery is full at the bulk and floating voltage it reduces charging current and causes the PV to increase output voltage. With 60 cell PVs this will not happen and floating works fine. Alternatively 72 cell panels could be connected 2S to comply with MPPT specs.

In any case 54V for "back to battery" is way too high as floating should be at 52.5V, bulk at 53V (my settings for 15 cell LFP battery). My settings for "back to battery" are 49V or 50V and 47V or 48V for "back to utility".

Edited June 1, 20224 yr by Beat