question

@johnparVIC

What I have noticed is in an ESS system SOC (in case of grid faliure) to 100% is very different from keep batteries charged.

Which one do you have it set to? Switch to keep batteries charged if you have not already.

Happy New Year to all!

I've been monitoring this over the last couple of weeks and it is still the same problem, Quattro is not fully charging the battery from the grid because it is skipping the Absorption phase

Any ideas?

Kind regards

John

Hi all

I've been reading and Googling but clearly there is a significant gap in my knowledge.

In this ESS system, with Cerbo GX, Quattro, MPPT, SmartShunt, and Batteries, surely the Cerbo should be in charge of charging, telling the Quattro what to do. That seems to be the case when charging from the PV via the MPPTs - they are clearly in "External Control" mode and using the SmartShunt measurements.

When I set the ESS to "Keep Batteries Charged", the Cerbo should tell the Quattro what to do and use the measurements from the Smartshunt.

But clearly the Quattro is using its own measurements because it is terminating the bulk when the Quattro sees 55.2V (at which point the Smartshunt is only at 55.0V). It then skips the Absorption phase and goes straight to float for some reason.

Is there any way to see diagnostics from the Quattro directly? Or details of the communication between the Quattro and Cerbo on VE.Bus?

@Guy Stewart (Victron Community Manager) would you be able to assist?

Many thanks

Kind regards

John

Huge thanks to Mike Davidson at Midsummer Energy for helping me find the culprit, and discovering something weird about the way the Quattro/Cerbo/ESS combo works!

It turns out that despite having DVCC turned off, the Seplos BMS is still controlling the charge current from the Quattro.

At the point where the charge voltage drops, actually just after the Absorption phase starts, the BMS is telling the system that the max charge current is only 10A so the Quattro dutifully drops the charge voltage until the charge current is under 10A.

I've not found the reason why the BMS is doing that yet, but from what I've read it is likely to be that one of the cells has hit one of the limits set in the BMS.

The fact that DVCC is turned OFF but the Quattro is still respecting the current limit sent by the BMS is very odd. (DVCC was off because the Seplos logic is a bit wrong).

I've also just updated the Cerbo to v3.13 and the behavior is the same.

So, I'm now looking at what is happening on the batteries to see what is triggering the behavior and will update here when I have some answers.

Kind regards

John

So, after extensive investigation and experimentation, I can confirm that the strange behaviour regarding the Quattro not fully charging, was due to the CAN connected Seplos BMS throttling the charging even though DVCC was turned off and the Seplos BMS was not selected in DVCC or System Setup.

However, the Seplos BMS was actually doing the right thing so I decided to try turning on DVCC.
That opened a whole new can of works (pun intended) so I'll start a thew topic for that!

So, beware! If you have a CAN connected BMS connected but not configured as Battery Monitor, it can still affect the operation of the system.

(VenusOS v3.13 on Cerbo GX)

Kind regards

John

@johnparvic, are you using the newer Seplos version 3 BMS?

To follow up on my question above; I experienced a similar issue with my "CAN connected" Seplos v2 BMS... Current dropping to half every 2 or 3 minutes (only on one of my Split Phase Legs) when the Seplos is connected, usually starting about 4-5 hours into my nightly battery charge from the Grid... the logs show this clearly. Something I think Victron should be looking at, yes?