Solis Hybrid Night rate headache

peatoire · 23-08-2022 6:09pm #1

Hi Folks, I've got my system ordered 6kw array, 5 kw Solis hybrid and 3 x 4.5kw batteries. I'm really interested in optimising the use by tailoring when and how much to charge the batteries on a cheap night time tariff and so have been looking at many discussions on the subject. Here are my questions:

During the winter months, if I set the batteries to charge at the start of the cheap rate, say 11.30 - 2am and they are fully charged, once it stops charging the batteries from the grid, can I keep those batteries fully charged until the peak rate kicks in? Basically, I don't want them being depleted over night after the charge period.

(I suppose I could set it to charge at the end of the cheap rate, say 3am - 5.30am but I'd still like to know)

This is the awkward one, during those months in spring and autumn where I still need to charge the batteries but not to 100% can I set a limit on how much they charge to? I understand that I can estimate how long it will take charge up to a certain limit but the problem is I might not be starting from the same baseline every night, let's say I have the oven on late one evening and it empties the batteries, this will need a longer charge to get to say 80% than if I had not.

I don't want to be setting the charge time on the inverter every night, it will be a right faff.

I've seen many posts on people using raspberry pi with Home Assistant, I'm fairly technically competent but this blew my mind and cannot see myself being able to do it.

Any help greatly appreciated because if this system spec cannot do what I want I'm considering cancelling it and looking at a different system instead where you can set schedules

silver_sky · 23-08-2022 6:40pm

Welcome! It's possible to do what you say regarding charging and not using (more on that later) until the next day.

For example, say you had a day night meter so in winter time it's cheaper between 11pm and 8am. You could set this as the charging time. The battery would charge during this time and as it's set to charge it wouldn't discharge*. If you had such a long period at a cheap rate you could even set the battery to charge at lower amps over the full period which would be better for it also. The house would run from the grid while the battery is charging.

*the newer solis firmware has a "feature" where it will slowly discharge a battery to stop it sitting at 100% for long periods or being charged repeatedly for the last few percent which wouldn't do well for its health. For my own it's discharging at about 40W so not a huge amount.

For the limit to charge I'm not sure if this is an option but I haven't looked for that. Perhaps someone else will know.

You mention homeassistant and automation, this is a possibility but you don't NEED to do it. Some of us just like playing with these things and trying to get the most out of it.

yankinlk · 23-08-2022 7:24pm

^^^^ agree with this post.

We are entering the autumn - before the clocks go back and before the light really starts to drop. I stopped charging my battery around the start of Summer Time. I intend to go fully back to schedule charging when the clocks end SummerTIme. BUT I only have a 5KW battery.

Its tricky if you have a larger battery - as like today for example - i never really fully filled my battery... i got very close to 100% but it didnt fill. If i had 13.5KW of battery like you are planning - then my strategy might be to at least half-fill the battery around this time of year - and then fully fill it in Nov/Dec/Jan/FEb months.

I would recommend DrPhil (not tagging him here) but he might offer good advice. He regularly posts in the "Daily PV Production" thread. And sometimes he posts the bad times when he charges up AND over produces and gives back to grid. There is no full-proof solution even with predictive automation.

peatoire · 23-08-2022 7:55pm

Hi guys,

Thanks for the replies, good info. I suppose it will be best to suck it and see after summer, get an idea of how much to charge the battery. If I export too much then charge for less time/ lower amps I know it will never be an exact science and the last thing I want to do is get obsessed (that WILL happen)

It's a shame if they don't give an option to limit charging capacity on the batteries. It would make things much easier to manage.

Best,

Andy

Edit: I notice that solaredge enable different profile schedules for seasons on their inverters which seem very detailed and comprehensive, not sure how good they are though.

silver_sky · 23-08-2022 10:12pm

Whats you're reasoning for the upper limit on the battery state of charge? Is it so that you have some space left for charging from generation?

bullit_dodger · 23-08-2022 10:57pm

The GivEnergy one is excellent. All available via a web interface, or if you want via a REST API (which I use to set the charge levels automatically every night)

bullit_dodger · 23-08-2022 11:00pm

Its worth noting however (and I did the math on it)......for the 4-6 weeks that you are in the transition between fully charging at night rate for winter verses summer time......you might save yourself a fiver by optimising the battery to have the correct charge rate over doing somehting cheep and cheerful like setting it to 35%, then two weeks later setting it to 60%, then 2 weeks later setting to 80%, etc

That's not why I did it. I did it as a fun project, but if you wanted to know the expected savings....about a fiver

peatoire · 24-08-2022 8:32am

https://www.boards.ie/discussion/comment/119513113#Comment_119513113

Yes, that's right. I want to ensure I don't end up paying for energy I could have generated from PV. I know it's not an exact science either way due to weather etc. but by leaving a certain amount free in the battery at least I'm starting from the same point every day.

peatoire · 24-08-2022 8:34am

https://www.boards.ie/discussion/comment/119513299#Comment_119513299

Yes, this is why I want to do it. Thanks for the cost savings info, it does put it in to perspective somewhat, the tendency (for me especially) is to get obsessed with the detail!

peatoire · 24-08-2022 8:35am

https://www.boards.ie/discussion/comment/119513289#Comment_119513289

This looks excellent, thank you. I did give these guys a call but it just rang off and it put me off. Maybe I'll give them another go.

AndyBoBandy · 24-08-2022 8:53am

On my Solis Hybrid inverter, in winter I set the battery to start charging at midnight, and have it timed to stop charging at 8am when the night period ends..... now if it charges at the full rate, it will be finished charging at 2am..... but as the end timer isn't until 8am, it won't allow discharge until after that time......

But,

As a backup, and to protect the overall life of the battery, I have adjusted the charge rate down to a low amperage (5-7 amps) meaning it continues charging all night albeit at a much slower rate, and by doing this it's usually finished charging by about 7:30am... (why charge the battery fast over 2 hours when you can charge it slow over 8-9 hours...? and save it a whole load of heat stress).

Then for your 2nd issue, What I found was by simply slowing the rate (amps) of charge further, and not adjusting the timed periods when the battery is set to charge, I could manipulate roughly where the battery ended up at before it stopped charging to within about plus/minus 10%.... So for instance in late Feb & March, I needed some juice in the battery for the morning period after 8am as the solar production wasn't enough at that stage, so I adjusted the charging amps on the battery so that by 8am when it was timed to stop charging, it ended up around 60%. A few mornings that value was higher as the battery hadn't fully depleted the previous night, so it might have ended up on 66%-70%, but I can live with that.

The last time I adjusted the settings was beginning of April and I'll probably be going up again in a few weeks to start partially charging it again up to ~50%-60%, before going up a few weeks later again to set it to charge fully for throughout the winter.....

My inverter is in the attic in a press (attic is converted), and although it's not too awkward to get in and make the adjustments, I still have to climb into one of the presses and tinker with it for a bit, so its not something I would be doing on a daily basis looking for fine adjustments as the days get shorter........ I know some folk will go and make adjustments based on the weather forecast for tomorrow, and that's absolutely fine, but I'd say the vast majority aren't looking to delve down to that level of constant adjustments

I'd say overall, 4 adjustments should see me through a full year;

September - Set battery to charge to 50%-60% on night rate
October - Set battery to charge to 100% on night rate
March - Set battery to charge to 50%-60% on night rate
April - Set battery to not charge from grid at all

peatoire · 24-08-2022 9:10am

https://www.boards.ie/discussion/comment/119514021#Comment_119514021

This is really useful info. Thank you, I suppose it's about finding a sweet spot between macro adjustments where it takes over your life vs unnecessarily wasting free solar. I like the idea of reducing the charge rate to control the capacity. I think I will try what you have suggested.

I know for me, having too much control might be a curse! Those four adjustments will be a great start point for me.

Best,

Andy

yankinlk · 24-08-2022 11:15am

https://www.boards.ie/discussion/comment/119514021#Comment_119514021

Excellent Post. I think we might add this or at least link to it from the FAQ! @DrPhilG - can you do the needful? link to that post here: https://www.boards.ie/discussion/comment/119514021/#Comment_119514021

Jonathan · 24-08-2022 5:35pm

https://www.boards.ie/discussion/comment/119514662#Comment_119514662

@DrPhilG stepped down as a mod last month (Thanks again for all the work Phil).

I'll update the FAQ when I am on the desktop later.

Solis Hybrid Night rate headache

Comments