Problem With 2 A/C Inverters/Batteries - How to Prevent Cross-Charging

Hi All,
I'm hoping someone can help me resolve this problem.

I had 2 a/c inverters with 9.5Kwh batteries installed 2 months ago. Initially they operated without a problem charging at night using the Octopus Go cheap rate and then discharging during the day. The 2 inverters were required to meet the high loads of an air source heat pump (up to 6 Kwh).
However, for the last week, during the afternoon, and for no reason that I can see, the inverters start to take energy from one battery and pass it to the second until the first battery hits its minimum charge level of 4/5%.

I just want the batteries to discharge in a balanced way. Can anyone help?

This is a known issue and is why my installer is refusing to install a second AC3 for me. GivEnergy are releasing a new extra box they are calling an EMS which will manage dual inverters correctly. ETA for this device is Q2 this year, thought it was due November / December last year.

I would go back to your installer and ask if they are know about this issue. I am happy to link the list of issues with dual AC3's if you need it. Hopefully they will come back saying they are aware and will add the ems once available.

Alipo If they start playing "push me, pull you", apparently, an inverter restart on each should calm them down for a bit.

As tim says, this is what I do for the issue currently whilst I await the ems. I knew about it going in and there would be a period of this, but needed the discharge rate. An alternative if you are software/technical inclined is to use HA and GiVTCP to run scripts that some members have developed to control their inverters in this scenario

Many, many thanks for the advice. I wasn't expecting this problem.
Just to clarify, does an inverter reset also imply a battery reset with the pain of a discharge/recharge cycle?
I would also be interested in a link to other dual A/C Inverter issues.
Thanks again

Alipo i think it just resets the inverter.

Alipo For the sake of clarity.....

To stop cross-charging, all you need to do is 'restart' one or both inverters (i.e. restart the inverter software).
No hardware needs to be physically turned off, and no calibration will take place.
All you need to do is use the Portal, select My Inverters, and then click the power symbol on the right hand side. After a minute or so, the inverter is usually back up and running, and on-line. I don't believe you can do this in the App (but I would be happy if someone can show otherwise).

This is not to be confused with a 'reset' (to defaults), which is something different.

After a month or so, today I noticed batteries cross charging (with 2x AC coupled inverters). I tried the app quick setting (Hamburger button, settings, preferences, show quick settings button) to ‘pause’ then after 10 secs ‘play’ and seemed to do the trick and stop the cross charging.

KWcomm Many thanks. Good to know it can be stopped with the App.

Many thanks for your help. I'll give the solution using the app a try next time the cross-charging occures.

The official list from GE on dual AC3 issues

"The current issues surrounding the AC Coupled inverters in a plant setup are balancing issues between the two inverters, cross charging between the batteries/inverters and data anomalies in the system readings on the app and portal. I hope this helps."

KWcomm
I'm sure others have said this before, but I just tested what 'Pause' actually does, in the App. By looking at the settings on the Portal, it seems to reduce both 'Battery Charge Power' and 'Battery Discharge Power' to zero, whilst keeping everything else as is.

Every day is a leaning day.....

ToothyChris whenever I’ve paused it in the app, I still see a few watts flowing. It should be zero. I’ve reported it to GE only be told “
the battery is showing that it is discharging minimal wattage, but from looking at the inverter data it is in fact paused”. Not really sure I agree with this. If it’s paused, then everything should pause.. no energy flow?

I am about to push my installer to install a second AC3 for me based on the instructions above but I have some questions. I know (in theory) the EMS box is only 2 - 6 months away but with the sunnier weather I am already generating more than I can capture.

1, how often does cross charge happen for people?

2, how are you spotting it? Are you checking daily?

Many thanks

Reply to THALL
Hi,
To answer your questions:

1. After two months with no problems of cross-charging, cross-charging is now occurring almost daily, and yesterday I also noticed that the batteries had stopped feeding energy into the house for no obvious reason.
2. I only notice a problem by checking at various times during the day. The problem is resolved by either using the online inverter restart, or using the app pause/continue routine. It's all a bit stressful and I would hope that it is resolved soon.
   I do wonder whether an extra EMS box is the way to go when a change to the programming might be expected to resolve the issue.

Alipo Daily? Right ok that means I will wait! Trying to avoid monitoring all this daily as it has become an obsession the last year or so.

The EMS box will take over the EMS built into the current system. I beleive they already have something like that on the commerical side to manage all the inverters/batteries from 1 point.

Earlier in the year we were getting cross-charging about twice a week. We are now getting it once or twice a day (due to the different weather, and hence different use pattern, perhaps?).

It is easy to spot, as you see both charging and discharging in the graphs at the same time (usually it is either above the line or below it, but not both).

It is not the end of the world (you lose some of your stored energy as heat), and occasionally you end up with a reduced charging/discharging power (if one battery reaches 0%, or 100%), Yes it is annoying, but for us the benefits of double power capability outweighs the occasional inconvenience. We use the same methods as Alipo, to stop it in its tracks.

How do you prevent cross-charging using HA?
The reason for asking is that EMS is delayed until next year and could possibly be pulled i.e. not released. So is HA an alternative? Even if the do release EMS a HA solution will be cheaper - much cheaper.

Slartibartfast why do you say they might pull it? I rewatched the presentation where they discuss it and the only comment really where that can be inferred is the blog saying “So, we are now just waiting for a firmware update and further testing before we make the decision to roll out the EMS.”

And if they are already planning a v2, then why not launch v1??

If the batteries are charged only overnight from the grid (no solar), could you set max charging power to 0 on both during the day?

'before we make the decision to roll out the EMS'. That could be 'roll out' or not. The thing about HA is it offers a lot of flexibility. The question is can it block cross charging?
The EMS has been on the cards for 18 months. Will they wait for V2?

Slartibartfast the short answer is yes, HA can mitigate cross-charging. See other posts here and on FB for details.

Slartibartfast I doubt it. AC are what mostly shows cross charging and requires the fix. Besides from the presentation data shown it does work in its current v1 config. I would imagine it’s mostly to minimise any software issues (they have enough elsewhere from what people post).

HA can certainly help with things, considering myself. Trouble is not sure I would have the time to devote to setting it all up and learning it as I’m not from an IT background (where people seem to be able to sort it in about 5mins😂).

Sure I’ve had cross charging but it’s been manageable on the whole. Besides with the EMS all the rest of the data supplied/recorded should make sense again in app/portal.

DD this is what I do with my battery only system.