question

albert-vd-westhuizen avatar image
albert-vd-westhuizen asked

PylonTech SOC/voltage cycling with 'Keep batteries charged'

3kVA Multi; Venus GX; 3 x 2.4kWh PylonTech's and 3.96kW PV in ESS mode with feed-in allowed and 'Keep batteries charged'. DVCC on as should be, 2.31 Venus firmware and all other firmware no later than 3 months. Battery voltage rapidly drops to below 50V and SOC progressively during night from 99% to 94% in early morning just before sunrise. Is this normal? If not, how do I correct?

PylontechSOCvoltage
soc.jpg (37.9 KiB)
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

1 Answer
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Albert vd Westhuizen,

The battery voltage drop from 52V to 50V once removed from charge is normal and expected.

I will set the ESS with Pylontech in my shed to Keep Batteries Charged tonight and see if I notice similar SOC cycling behaviour over the next couple of days.

My initial theory:

You are seeing a self-consumption discharge internal to the batteries. So the Multi/ESS sees 0W going in or out and thinks that it is "keeping the battery charged".

The solar doesn't make a conscious charging decision, it just raises the voltage, which recharges the battery.

If I am right, it might be possible to "correct" it by setting the sustain voltage in the ESS assistant quite high, such as 50.5V. But I don't think this extremely shallow daily cycling is an issue, and I would suggest leaving the settings as they are.

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

@Guy Stewart (Victron Community Manager) Thanks Guy for response! Looks like the Multi does see watts flowing out - see below amps from battery - very little but with occasional spike...? I don't see this SOC fluctuation on any of my other installations? Could it be a faulty battery? Have you run some tests of your own yet? I can share site on VRM if you'd like to look at data/settings?

0 Likes 0 ·
1565758047233.png (44.9 KiB)