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ross-skyenergy asked

MPPT only charging battery and not supplying loads

Hi everyone

My setup is a grid-connected Multiplus 2 with a SmartSolar MPPT 250/100 and 19.2kwh of Pylontech batteries. I also have an ET340 meter connected

I only want the batteries to kick in during a blackout so "keep batteries charged".

The issue is the MPPT will only come on when it needs to charge the batteries and doesn't supply any PV to the loads during normal daytime operation, as seen below, the PV is only charging the battery when there are tons of loads that need solar. This stays like this all day, never going over 150w unless the batteries dip down and it cranks up to it's 5kw so I know the PV is working.

I have DC feed-in enabled as well.

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Does anyone know why the solar won't feed the loads?

Thanks

Multiplus-IIMPPT Controllers
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2 Answers
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ross-skyenergy answered ·

1 bank of batteries for the 3 phases, but phase compensation is setup to discharge enough to take care of all 3 phases on a net meter.

I have gone in actually changed the ess setting from Optimized (without battery life) to "Keep batteries charged" and it now seems to be working, I do believe there is something within the ESS code which is prevententing the MPPT from supplying the load if anything but "keep batteries charged" is selected.

It seems to be working for now, but this solution won't work if the customer decides they would like anything less than min 100% soc in the future.

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Rob Duthie avatar image Rob Duthie commented ·

If you keep batteries charged set it will charge from the grid as well at night time etc.

I the whole idea is to charge from the PV only as it is free power.

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ross-skyenergy avatar image ross-skyenergy Rob Duthie commented ·

Agreed, but this customer wants the system purely to prevent blackouts and is not too concerned about the financial savings from the solar/battery, that being said, I still would like to know why I can't choose other ess settings to keep the batteries at a min SOC.

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Rob Duthie avatar image Rob Duthie ross-skyenergy commented ·

Hi

So have you wired the Multiplus2 in series with the clients load? so all the power from the grid flows though the inverters for each phase.

Also you have 1x MPPT charger for the batteries, I did a system but had the smart shunt take care of the charging currrent so when AC load came on the shunt would see a load change and aply more current to the batteries.

Also from what i have heard from other installers for 3 phases systems is to have separate battery banks for each phase to make it work correctly.

In ESS mode you can set the min SOC to suit the loads etc. so you always have spare or reserve in case of black outs etc.


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ross-skyenergy avatar image ross-skyenergy Rob Duthie commented ·

The MP is in series with the critical loads, so not the entire house is running through the MP, but it has a decent load running through it.

The Multi has a built in battery monitor so a shunt is not always required especially when working with managed batteries that report accurate SOC and charge/discharge limits to the GX.

I have installed many 3 phase systems (mostly SMA) and I would disagree with using 3 banks, you should always have all 3 inverters connected to one battery bank, this gives you the increased charge/discharge rate of having 3 inverters all in parallel on the same bank assuming the batteries can handle it. Having 3 seperate is also an issue if one bank runs out first and then you have 2 banks doing nothing because they can't access the inverter on other phases.

This is my understanding of how it works from experience, but I open to feedback on that.

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Rob Duthie answered ·

Hi

I think you need a smart shunt to give data so the multiplus knows what to do with the MPPT data

I have done a similar design but off grid and on grid.

So when the loads pull more power the MPPT will deliver the extra current as required from information from the smart shunt.

Have you setup the ESS with VE configure up yet? which has effect on how the system pushes and pulls power between loads and grid etc.

Regards

Rob D

NZ

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ross-skyenergy avatar image ross-skyenergy commented ·

Hi Rob

Thanks for your response, yea I have setup the ESS with VEConfigure.

The weird thing is I have set up a few grid-connected systems in a similar config to this one and I've never used a shunt and they all seem to work fine, the only difference being this one is my first three-phase with a meter, it is also the only system I have done that uses the option of keeping the batteries charged, so I'm not sure if this is paying a part in the problem.

It might help to know as well, that if I drop the battery min SOC to a lower level, the solar and battery both unleash full power until it reaches the min SOC and then they both basically turn off together so I feel like the ESS is doing something weird..

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