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xpatrik avatar image
xpatrik asked

Ess weird behavior (charging and discharging battery)

So i just installed my system yesterday and this is my first solar production day.

I have the system set to "Optimized without BatteryLife"
Soc limit is set to 40%
Inverter power limit set to 1000W (Don't want to discharge the battery super quickly because its a smaller one)

So i'm having a problem when the solar recharges the battery to around 43% then the inverter discharges it back to 40% and the cycle repeats.
I would like to somehow prevent this and just use the 600W thats coming from solar directly to power the inverter and just keep the battery charged at 40% no more no less.
Do i have something set up wrong?

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ESSess discharging
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2 Answers
nickdb avatar image
nickdb answered ·

Your system is a bit mismatched, with that little solar it isn't going to work well.

At 40% ESS will dedicate PV to charge the batteries, at 43% it will allow battery discharge so if your loads are greater than the 600W (less overheads) of PV, it will just discharge down to 40% again and repeat.

You need to either up your solar, significantly lower the inverter limit beneath the PV limits, or set the system to keep batteries charged. With this it will fully charge batteries, then use all remaining solar for loads, never discharging batteries unless grid fails.

If you enable batterylife it will raise your minimums to something the system will cope with, but ESS is not designed (in that mode) to do what you want. You would need to integrate with the more complex other modes to try force that behaviour.

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xpatrik avatar image xpatrik commented ·

If i set it to keep batteries charged it would fix my issue but that also isn't ideal to keep the battery at full voltage all the time. Do you think that its fine to just leave it as is and just wait until i upgrade my system with more solar. Am i missing on some soalr production if i keep it like its now?

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xpatrik answered ·

Until i upgrade my system with more solar i fixed it by coding a small app that comunicates with venus device via modbus and sets the max inverter power to pv-power * 0.92 (i claculated the conversion efficiency is around 92%) and that keeps the battery at around 0w all the time

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nickdb avatar image nickdb ♦♦ commented ·
As long as it works for you. You could also use node red with the venus large image, which gives you a lot of control to automate.
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xpatrik avatar image xpatrik nickdb ♦♦ commented ·

I made this and tweaked it in around 30minutes and works perfectly

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Related Resources

What is ESS training video

ESS Quick Installation Guide

ESS design and installation manual

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