chiusdea-sabin avatar image
chiusdea-sabin asked

cerbo gx - battery and inverter programing

i want to program the inverters and battery like this (the schematic of how the solar installer installed is in the pdf file):

- all day whenever the house draw more then 9kw from the grid the inverters should discharge the batteries (or take power form the solar pannels if there is sun) so that the power drawn from the grid does not exceed 9kw (this is the most important thing)

- in the morning (after the sun rises) the battery will charge from solar

- after the bateries are full from solar, the excess will be fed to the grid at a maximum of 10kw (now there is less then 10kw solar pannels but in the future will add 5 or 10kw more pannels)

- at night (from 2am) the batteries discharge until 35% is left

- all the time the batteries should have at least 35% battery left so that the critical loads are always maintained for minimum 30 minutes even if the power is out


the solar installer said this can not be done, i asked him to program so that at no time the house will draw more then 9kw during the day or night and if it draws more for the batteries to help with that, he did not even do that.

the non critical loads are usually 3-5kw, but they could be up to 12kw for short periods of time (30-40 minutes)

the critical load is usually 2-3.5kw but it could be up to 6kw for extended period

grid contract limits the enery i put on the grid or take at 10kw.

in the future there will be another wictron 5000 in paralel , so there will be 3 in total

one last question, is normal for the wires to get hot to the touch (if you keep your hand on those wire you get burned), the solar installer said it is normal for those wires to get hot, that is why he put the wires outside of the conduit. (that is why i also wrote in the pdf the wire thickness)


cerbo gxsmart solar set-up helpsmart solar charging behaviouress dischargingscheduled charge
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3 Answers
Alexandra avatar image
Alexandra answered ·

@Chiusdea Sabin

Your battery bank is 10kWh, 9kwh if you follow the 90% DOD that Pylon recommends.

So the installer is right that battery cycling is not a good idea, 35% battery is not enough reserve if you need your critical loads supported for 40.minutes with no solar no grid power.

Right now you don't have enough. But maybe if you keep to your upgrades on the future you could.

You can peak shave with your batteries if you set your Input current limit to just under the 9kw limit and set the peak shave in ESS.

I don't like hot wires and usually move to larger gauges for that reason. But in a parallel system on the AC having them bigger can cause issues in balancing the loads.

It sounds like you have less than the minimum system for the loads you want to run. Your inverters are too small for the job you are asking. Wait for your upgrade before asking for more circuits to be added.

Just FYI one big inverter is better than a bunch of small ones for efficiency and power management.

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chiusdea-sabin avatar image
chiusdea-sabin answered ·

i just want for peak shaving to accur if the max input power is reached, the batteries to charge ONLY from the sun and discharge ONLY at this not possible ?????

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nickdb avatar image
nickdb answered ·

Some general observations, you have 4kW max per inverter at 25C, run them hotter or fully loaded for extended periods, they will derate. So you are undersized there.

Your 2 x US5000 are also under spec. The 5000C has better specs, you will get max 160A off both, which is way beneath the > 200A needed as a minimum to cover the inverters full spec, not considering any transients above this.

Pylon "allow" 95% DOD, that does not mean that they will maintain their voltage under load, especially larger ones at that state of charge.

Hot wires like you are describing does not sound normal nor safe.

Much of what you want to do can be done out the box. ESS is a self-consumption model for running off battery and PV, with controls that allow scheduled charging/discharging.

It allows for feed-in.

Some will require more advanced customisation via node red etc.

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