question

Hi @Bigbadbob76

You seem to know your way around, so I won't bother too much with deep stuff.

To give the mppt priority it needs to see a higher V target than the Multi does. You've tried that (& presumably DVCC and temp-comp settings make it for real), but in a UPS situation 0.1V will just allow the mppt to rest the Multi charger while the sun's up. But the charge states can't be synchronized, and the Multi entering Absorb while the mppt is in Float will reverse the priority. You could set the Multi to a lower flat Storage V and let the mppt give the batts a daily stir-up.

But if you want more from the pv then you'll need to leave some space in the batts. You've explored this too, but the easiest way is just to Ignore ACIN. Think about doing this using V, not SOC (could be fun). So it will neither charge at all nor passthrough to loads. You mightn't like the batt discharge, but they'll likely enjoy the exercise. :)

Questions.. Re the 'generator relay', what's that for, auto-start? No second relay in your model Multi?

And the 'input current limit control', for the genset? Really necessary with such small loads relevant to batt capacity?

Enough for now.

Thanks for your suggestions JohnC, I understand what you're saying about using battery voltage to trigger ignore AC input. that should work. :-) and about lowering the Multi charge voltage to a flat storage voltage, both these should give some room for the MPPT charger to have something to do.

Haha, I'll take my batteries for a run round the block to give them exercise, understood, they'll like to be used just not too deeply. Once we get some summer sun I'll probably be able to leave the multi in inverter only mode most of the time. it's in winter that I can't do that but still want to use my solar as much as possible on the few sunny days we do get.

Solar in Scotland is a bit hit and miss compared to countries with predictable sunshine.

I've seen this request over and over again. There are some things you can do to get partially there like ignore AC input but it's not a clean solution.

The functionality within ESS does what you want but ESS can't always be used. I suggested before that ESS functionality be broken out so that pieces of it can be used (like solar energy priority in this case) without all the other baggage ESS brings to a system.

What‘s your reason for not using the ESS functionality? ESS will offer the functions, your are describing

a) giving grid-failure protection by keeping the battery charged

b) (if available) using DC-PV via MPPT for powering devices on AC-out on the multiplus

c) no feed-in (!) There is an option to disable export to the grid.

From my point of view you should have a look into the ESS guide:

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/ess-introduction---features.html

Having failed to get Venus to switch the multiplus mode depending on pv output, I'm now looking at this from a different angle. I understand hardware better than software so...

I have a 12v 1.5W pv panel that is supposed to keep a car battery topped up when not in use for extended periods, frankly it's useless for that as it only supplies 100mA max.

I'm thinking I could use it as an irradiance sensor to switch a relay which I would connect to the aux or temp inputs of the multiplus and set up an assistant to ignore ac input if the relay is closed for a few minutes, and not ignore ac input if relay is open for a few minutes.

I'll have to play with the load resistance across the panel to get it switching at an irradiance level that will supply sufficient power from my main panels to keep up with demand from the loads on the inverter.

The relay coil might be enough load on the panel to do this but Ideally it should be adjustable.

I could also have an over-ride switch in series with the relay for when I'm running the generator.

Another thought on prioritising solar. Thanks for the hint bathnm. :-)

My MPPT 100/50 has the "streetlight" function which is designed to Automatically switch streetlights off during the day. It learns when sunrise and sunset are and corrects for changing seasons.

The panel voltages used to detect sunrise/sunset are configurable. :-)

This seems like it could be very usable for prioritising solar use and switching "ignore ac input" assistant. unfortunately it uses the same i/o port as the ve-direct port so I would lose the data I'm currently sending to my Venus device.

I now have my system prioritising solar. :-)

But it's not very elegant. I use a separate time switch on the ac input which at the moment switches the grid supply off at midnight and back on at 4:30 pm. with current solar availability my batteries are discharged to 97-98% SOC by the time the sun comes up and then PV charges the battery and keeps up with load demand during the day while i'm at work but not in the evening, so I allow grid use in the evening. This will improve as we come into summer and I can extend the grid off time.

This keeps my UPS batteries well charged to prolong their life and provide plenty of capacity in the event of grid failure while maximising solar use.

Having the ability to schedule "ignore ac input" via venus would be nice, then I could adjust the times remotely without having to re-program my time switch manually. I might have a go at programming that in venus but if anyone else fancies the challenge I'd be very interested.

Scheduled charging is an option in ESS but It would be nice to have some of the options from ESS available separately as Kevin says.

I think I've cracked it.... Another way to prioritise solar.