Charging Battery from Solar - Sometimes Exports Instead of Charging?

[StealthChesnut]

Today I've had an instance of a problem that I've seen a couple of times recently. The batteries will be charging from solar generation, but the Home Assistant plot for the hour shows export instead of charging:



When I look at the system behaviour I can see things are charging (dark blue), but they stop charging at 15:43 and start exporting (orange) despite the battery being only 53/54% full.



Any ideas what's going on here?

[Will]

Which integration are you using the cloud version or modbus?

[StealthChesnut]

Modbus of course, Will. (see signature!)

[Will]

have you had a repeat of the issue again recently?

[StealthChesnut]

It's not happened since then, but apart from one day there's not been enough solar generation to charge up much!

[Will]

no worries, keen to hear if this is still happening and we can help to debug.

[mbbphoenix]

I'm having the same problem today.
Panels generating 5kW with an H1-5.0-E; house load 480w, battery 1.75kW, exporting 2.74kW even though the battery is only 67% charged.
I'm also running homeassistant with modbus so can provide more data if required.

(Can't work out how to attach screenshots to the post)

[Will]

Hello,

You're being limited by your batteries sadly. Only having 2 batteries will restrict your charge/discharge rate.

Only having two means you're going to be stressing the batteries the most vs an installation with 4 or more.
In perfect conditions you will be unable to charge for long above 3.7kW, as the cells heat up you'll have thermal throttling.

You'll notice a serious improvement adding one battery and even more performance adding 2 additional giving you a total of 4 which is a 208v system.

[mbbphoenix]

Hi Will,

Thanks for the reply; I did wonder if that was the case, but StealthChesnut had a virtually identical system, ie 18 panels 5kW inverter + 2 HV2600 batteries, and you appeared to think there was a problem somewhere.
So if I understand correctly, there is a limit to the peak power used to charge the batteries, meaning that even if the inverter can handle the load (ie 5kW) there is still excess power fed back to the grid. (I'm pleased now that I've got something to use the excess power to heat the water, in preference to returning to the grid )

If I have more batteries, does that mean (in my scenario) that I could charge 3 batteries in the same time as I currently charge 2 (assuming sufficient solar power generation)?

How easy is it to add more batteries as a DIY install?
I have V2 batteries, so no issues with the BMS, etc.

Thanks

[Will]

Correct, the inverter is limited to 35amp DC which is limited under the capabilities of the inverter until you go over 3 or more batteries so you will notice a charge and discharge kW performance improvement.
Installing extra HV2600 is easy, hardest part is lifting the battery into place as they're 35-40kg but connecting the push fit cables and updating the dip switch to the additional battery is maybe a 90 second job tops.