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myozone avatar image
myozone asked

Solar shed + batteries + micro inverters

I'm thinking of putting solar panels on the roof of my shed, the panels would have micro inverters rather than optimisers - the roof has shading. I intend to use Enphase IQ8H microinverters when they come available in Europe.

I would also have a ~10kw battery, I intend to power a small ~100W continuous load and small intermittent loads. The battery would be charged via a Victron MultiPlus and when the batteries are too low (no solar) via the grid at night.

Can the charge rate of the MultiPlus be adapted to the varying power input from the panels and microinverters (240V) ?

I prefer Microinverters over optimisers because data from Tigo inverters isn't free (API+fee)

MultiPlus Quattro Inverter ChargerLithium Batterysolar
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8 Answers
Mike Dorsett avatar image
Mike Dorsett answered ·

your battery seems to be large compared with the load ( 5 days autonomy). Partial shading problems would not be an issue for MPPT trackers, so it would be possible to arrange one MPPT rather than micro-inverters for such a small load. You can the down size the inverter to cope with the load rather than sizing it to cope with the charging power (typ 5 times the load ?). This will result in a lower cost system, and all the data will be freely available. If you add a Venus device (CCGX, Pi) then you can get this on VRM too.

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myozone avatar image
myozone answered ·

I would like run smaller loads as well as the 100 watts or so of my PI servers etc hence the sizing of the battery. Good point on the MPPT trackers though, I just wondered if the Multiplus would adapt it's charging current to match the solar output. I thinking longer term as well to have reserve power available. On the PV I think I have space for 6x ~350 watt panels but shading is a issue from neighbours house. The house baseload is about 75 watts but that may change to around the 100 watts mentioned.

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kevgermany avatar image
kevgermany answered ·

To add tIso previous comments.

Is your load AC or DC or mixed?

Guessing that under normal use you only want solar with AC backup for extended low light, but not normally overnight? Hence big battery.

If DC, no need for inverters.

There's a max charge current on the multiplus, but I don't think there's an adaptive one. Can play with voltage settings, might get you there. But messy.

Just throwing ideas in:

Trigger AC charging from battery state of charge.

Drive Pi servers from DC, possibly through a DC to DC converter to prevent over voltage from charging.

Not clear why you want the added complication of micro inveryrrs and not a normal MPPT as previously suggested.


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lussilas avatar image
lussilas answered ·

Is your load AC or DC or mixed?!

happy wheels

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myozone avatar image
myozone answered ·

Sorry all AC, I have a separate circuit for the PIs (ex-storage heating), router etc plugged into.

That's basically it, use most the power from the battery ~65% of capacity at most for a long battery life. And have solar recharge when available, or if the battery is say down to 25% full use the grid.

The idea of micro inverters is to maximise the available solar from a shady site. The shade comes most in the winter from a two houses plus chimney. I thought treating each panel separately would help, I could connect the them in parallel but then the current is around 60 amps. Also I like the idea of having a load of stats about each panel.

For the record I'm thinking of using four PylonTech 2.4Kw batteries.

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shaneyake avatar image
shaneyake answered ·

Yes, you can do this using micro inverters.
With the shading you are talking about I would use microinverters.

You have to AC couple them, if you aren't allowed to feedback to the grid this becomes more difficult.
https://www.victronenergy.com/live/ac_coupling:start

When AC coupled or if you use a grid meter the multiplus will charge using any excess PV. So will track the output of the micro inverters.



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myozone avatar image
myozone answered ·

No, feedback not allowed, I don't have a feed in tariff and I think if the meter detects a backfeed it sets a tamper flag. I've never come across that page before I've was looking the MultiPlus II GX pdf in particular this part with a combination of the two, the left example with the right solar input - only using multi inverter not a single string inverter as shown. The current sensor detects and backfeed and stops the inverter.

2021-11-18-14-09-23-datasheet-multiplus-ii-gx-inve.png


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So just keep in mind that a Multiplus is a hybrid inverter and this means that when grid is present then the inverter will run as. Grid-Tie inverter and you will get small amounts of power pushed back to the grid. This can be avoid if you run it in ignore AC mode but then the system is off grid till low SOC and then reconnects.

The only PV inverter that supports Zero feed-in is fronius as it has a 2 way comms with the GX.
The multiplus can stop PV inverter from exporting till the battery is full and then it can't, while grid connected.
If your meter doesn't care about feedback then everything will work fine even without tariff.
If your meter is sensitive about feedback then you have run disconnected from grid and only connect when SOC is low.

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myozone avatar image
myozone answered ·

Anyone know if Enphase inverters will play nicely with Victron MultiPlus II because I guess the inverter needs to know the solar output to vary it's charge current and power available for the inverter. I've read the ESS design guide but not much detail on comms between the inverter and solar inverter(s).

Anyone know of any good information on how exactly ESS works with respect to communication between the Multiplus II and the solar inverter(s) Most of the information I've come across is a bit lacking or assumes one knows how it all works already.

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Currently No comms between Enphase and Victron. I would put the blame on Enphase as they are very closed about their systems.


You can put a Victron Meter on the Enphase system and that will at least allow the Victron system to know how much power is being made but the Victron system has no control over the Enphase systems output unless it goes off grid and then can use Frequency derating.

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Thanks, I'll look into frequency derating. I thought the Envoy S gateway box had some sort of output that can be logged etc - I'm thinking node-red. It seems daft to have systems that are closed or use preparatory protocols.

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