Solar setup advice please

[blokefromstoke]

Dont think it supports export stuff, but utilita do an economy 7 tariff of 5p kw/h overnight. Expensive during the day, but NO standing charge. I dont export and never use peak electricity due to battery storage, so is far better than octopus go if you never use peak leccy and dont export.

Hi @Ucatchmydrift - your setup sounds spot on - would you mind me asking what components you've utilised? I've been considering solar vs simple battery storage - and have been looking at an 8Kw sunsynk inverter- with 8k solar & then an array of pylontech / sunsynk batteries - a big outlay - but inflation proofed (free solar) - and also hoping to pair up with air to air heat pump for free air con (+ cheaper heating overnight in winter) in the summer... That Utilita tariff sounds exciting if you can get zero grid use in the day. How fast do inverters react to load - and do you pull absolute zero from the grid - I thought I read somehwere that inverters pull from the grid? Fantastic if you've managed to get down to zero during the day though...

Split from hi-jacked post

 

[Ucatchmydrift]

Hi @Ucatchmydrift - your setup sounds spot on - would you mind me asking what components you've utilised? I've been considering solar vs simple battery storage - and have been looking at an 8Kw sunsynk inverter- with 8k solar & then an array of pylontech / sunsynk batteries - a big outlay - but inflation proofed (free solar) - and also hoping to pair up with air to air heat pump for free air con (+ cheaper heating overnight in winter) in the summer... That Utilita tariff sounds exciting if you can get zero grid use in the day. How fast do inverters react to load - and do you pull absolute zero from the grid - I thought I read somehwere that inverters pull from the grid? Fantastic if you've managed to get down to zero during the day though...

Hi, sorry, bit late, didnt realise you had posted this.. My setup is unique as i did the lot myself (diy), which is very unusual. Atm its producing about 3/4 of my daily usage, and the rest i pull from the grid at cheap rate and store in my battery banks to use in the day, so never have to use peak rate leccy.. Its been alot of work, but also a great project and am still enjoying tweaking it, for example, i am now using a raspberry pi and home assistant to pull all the inverter data/bms/shut into one place to view over wifi etc.
I was also looking at all the expensive inverter/pylontech battery stuff once, but it just seemed far too expensive for what it is etc and thought i could do better and learn more if i did it all myself (for example just over £4k for my entire setup 3kw panels 3kw inverter 14.4kw batteries - but i do live on my own in a bungalow!).
See below for my build thread over at diysolarforum.com (ive not updated the thread for a while, and there is more added now!)
https://diysolarforum.com/threads/first-build-3kw-panels-3kw-inv-14-4kw-storage.52783/#post-672398

 

[blokefromstoke]

Hi, sorry, bit late, didnt realise you had posted this.. My setup is unique as i did the lot myself (diy), which is very unusual. Atm its producing about 3/4 of my daily usage, and the rest i pull from the grid at cheap rate and store in my battery banks to use in the day, so never have to use peak rate leccy.. Its been alot of work, but also a great project and am still enjoying tweaking it, for example, i am now using a raspberry pi and home assistant to pull all the inverter data/bms/shut into one place to view over wifi etc.
I was also looking at all the expensive inverter/pylontech battery stuff once, but it just seemed far too expensive for what it is etc and thought i could do better and learn more if i did it all myself (for example just over £4k for my entire setup 3kw panels 3kw inverter 14.4kw batteries - but i do live on my own in a bungalow!).
See below for my build thread over at diysolarforum.com (ive not updated the thread for a while, and there is more added now!)
https://diysolarforum.com/threads/first-build-3kw-panels-3kw-inv-14-4kw-storage.52783/#post-672398

Thanks for getting back to me. So you manage to pull 3Kw no problem I expect from your array of batteries?

Interested to hear what users on here can get from their battery / inverter combos. It seems different inverters have different charge / discharge capabilities - but then this is also influenced by the number of actual battery units.

I'm ideally looking for something that can do 5-6kw charge and discharge - but I believe this would need circa 2/3 actual batteries.

Was also told the absolute amount you can put back to the grid is 3.6kw on a single phase supply - is this true?

 

[Ucatchmydrift]

Thanks for getting back to me. So you manage to pull 3Kw no problem I expect from your array of batteries?

Interested to hear what users on here can get from their battery / inverter combos. It seems different inverters have different charge / discharge capabilities - but then this is also influenced by the number of actual battery units.

I'm ideally looking for something that can do 5-6kw charge and discharge - but I believe this would need circa 2/3 actual batteries.

Was also told the absolute amount you can put back to the grid is 3.6kw on a single phase supply - is this true?

3kw from 14.4kw of lifepo4 storage is not straining the batteries in the slightest, i could pull 14.4kw+ and drain them down in an hour no probs. - (edit, nearly forgot about the bms's - which would limit the power being drawn to 9.6kw continuous, but the batteries themselves are more than capable of 14.4kw continuous)
The inverter is usually the limiting factor.. My inverter is just 3kw, so can supply a continuous 3kw to the house, but its best to limit the length of time you max out your inverter, i try to keep it to 2.5kw or less for any length of time.. The inverter also has a max charge rate of 100amps at 24v (its a 24v inverter), so 2.4kw max, which for a 3kw inverter is not bad. Dont forget you will be running a load also when charging the batteries, so need to take that into consideration so as not to overload the inverter and have it shut down..
If you want to charge at 6kw, you would need a pretty powerful inverter, im sure others on here could suggest one, or run two in parallel, but how often would your solar panels actually be producing that much power?
Mine is a semi off grid setup and i dont supply back to the grid, just not worth it in my case, so best to ask others about grid supplied inverters..

 

[Mrjmegson]

Hi BFS,

I run two parallel systems to give me more power.

Both roofs have 6.5kw of panels on them, each roof split into two strings, which go down to their own 6kw hybrid inverter.

The rear roof, which is SE facing, has 25kwh of batteries attached to it, and the front roof, which is NW facing, has 15kwh of batteries (when I installed them, I didn't realise I could get both inverters to work together and share their power, which is why the banks are different sizes, but I didn't need to do that at all).

So as you've guessed the inverters are commed together, but otherwise are completely independent, each with its own panels, batteries and feed into the consumer unit.

These 6kw inverters can pull 6kw from the grid, and also output 6kw back to the house, so 12kw total combined if running off enough solar

My battery banks are limited to only 4.8kw output, so 9.6kw combined if running off batteries.

I'm not as clever as UCMD, so I bought all my gear, and they are:

Afore 6kw Hybrid inverter x 2
Afore 5kwh 48v life-po4 battery x 8
Then all the isolators and switches, which I can tell you about if you want to know, and two generation meters.

Hope this helps.

 

[Mrjmegson]

Just posted these on the wrong thread, so you may have already seen them.

These are my batteries, 5 at the rear are the 25kwh for the rear array, and the 3 at the front are the 15kwh for the front array.

 

[Mrjmegson]

Those batteries feed into the two smaller isolators, centre and right. Then these feed into the there own inverter.

The large switch on the left is the rear PV isolator.

 

[Mrjmegson]

This is the rear Hybrid inverter. The front is just to the right of this on a perpendicular wall. Both identical in every way.

 

[Mrjmegson]

The inverter AC feed both go through a generation meter, you can just see bottom right in the inverter pic, and then through this AC isolator, switch on the left (the large one on the right is the front PV isolator), which then feeds into the consumer unit.

Hope these help. I wanted to upload a video, but can't get the file small enough.

 

[blokefromstoke]

Thanks for all the images MrJMegson - that's some setup you have there!

I think I may be able to get up to 8kw on the roof - then a 6kw Hybrid inverter - with the hope of being able to charge and discharge batteries at the rate of the inverter. What are peoples thoughts on ratio of on roof to inverter size? I shall be having a W/E split - so doubt I'll get max output with that split anyway?

Does anybody have experience of a system that offers these kind of numbers? Looking at perhaps a Fox hybrid - would that work?

Also reckon on three smaller batteries (2.5 kwh ish x 3) - to then charge twice per day - overnight on car tarriff, then top up from solar during day...

 

[Mrjmegson]

Does anybody have experience of a system that offers these kind of numbers? Looking at perhaps a Fox hybrid - would that work

Not exactly sure what your asking? My system is similar to what you propose, E/W roofs, each has 6.5kw panels on, so 13kw it total.

I know they say you can undersize your inverter by 50%, as you're very unlikely to push it to the limit very often, so it's a waste of money, but I think you should go as big as you can. 6.5kw of panels and a 6kw inverter. The specs on mine say they will take 9kw of solar input. No idea why as it can only output 6kw.

I'm going to say something totally useless now, but I looked at the FOXESS range, but LOADS of stuff out me off them, of which I can only remember one thing, the startup value was really high. Sorry, I really can't remember any of the other reasons. Useless

 

[Mrjmegson]

You realise each charge is a cycle, so buying smaller batteries that need charging more often will reduce their life. You need to be careful with that, as batteries ain't cheap.

 

[binky]

You realise each charge is a cycle,

Each full charge is a cycle, so if you only charge up 50% that's half a cycle, and undesizing inverters by 20% was the norm.

 

[Mrjmegson]

Each full charge is a cycle, so if you only charge up 50% that's half a cycle, and undesizing inverters by 20% was the norm.

But a partial charge still degrades the battery though, just not as much, right?

 

[blokefromstoke]

I'm hoping to get the most from the system - agree that batteries are expensive - so the more I can utilise them the better. They do seem very expensive right now - and I'm hoping that as tech develops - they will drop in price by the time I exhaust the ones I install on day one.

I wonder how many years I'll get out of the inverter - at costs around £1500 - that can be a major consideration if we need a new one of those every 7/10 years... 25 years plus for the panels seems a good stretch - so hear your point about maxing out the roof.

I'm planning to install the batteries and inverter in a bedroom wardrobe (only 400mm deep) - so the Fox stackable range seemed ideal - as they actually fit !

I see lots of comments about people having issues with batteries in the winter not charging / discharging properly - so keeping them at room temp seems a good idea.

 

[bladerunnerpv]

"I'm planning to install the batteries and inverter in a bedroom wardrobe"

In a bedroom ?

 

[binky]

But a partial charge still degrades the battery though, just not as much, right?

correct, not sure how that really works to be honest, but I asked the question any years ago, and that was the response from one of the battery suppliers.

 

[blokefromstoke]

It's actually a room we use as a study - and there is then a bathroom and an ensuite separating the rooms we use to sleep in (family of 4).

Is there an issue with noise / heat / fire risk?

I had an alternate location downstairs - and that would place the batteries under my sons bedroom - and at the bottom of the stairs - which although a minimal fire risk - I felt the preferred option would be to have them in the corner of the house upstairs.

From what I've read - LifePo4 batteries have a minimal risk of self ignition - but if set on fire by another source - they will burn - but not explode.

We also have choice of house loft - or a well insulated outbuilding - or a poorly insulated garage. The loft is super hot in summer and super cold in winter - so that didn't seem ideal - for fire risk or battery performance. The latter two choices would involve excavation and voltage drop - but happy to be corrected in my current tack

 

[Mrjmegson]

correct, not sure how that really works to be honest, but I asked the question any years ago, and that was the response from one of the battery suppliers.

Yeh that's the way I understand it.

A full 0 to 100% charge/discharge hammers them, let's say it takes away 1% of its life.

But then a lesser volume cycle will reduce the life by less, so giving effectively more cycles, let's say 50 to 100% reduces battery life by 0.5%, then 80 to 100% reduces the life by 0.2%, etc.

 

[Mrjmegson]

It's actually a room we use as a study - and there is then a bathroom and an ensuite separating the rooms we use to sleep in (family of 4).

Is there an issue with noise / heat / fire risk?

I had an alternate location downstairs - and that would place the batteries under my sons bedroom - and at the bottom of the stairs - which although a minimal fire risk - I felt the preferred option would be to have them in the corner of the house upstairs.

From what I've read - LifePo4 batteries have a minimal risk of self ignition - but if set on fire by another source - they will burn - but not explode.

We also have choice of house loft - or a well insulated outbuilding - or a poorly insulated garage. The loft is super hot in summer and super cold in winter - so that didn't seem ideal - for fire risk or battery performance. The latter two choices would involve excavation and voltage drop - but happy to be corrected in my current tack

For mainly the reason of high and low temps, I avoided the loft, and put my system under my stairs, which also happens to be where the CU is anyway, so super convenient.

The stairs are in the centre of the house, so the under stair cupboard always stays at a very stable temp, which is great for all the equipment.

Despite reading that life-po4 batteries don't self combust, and also don't really stay lit if you can get them going, with two inverters and all that wiring, I completely fire boarded the room out, every inch, all butt joints have heat resistant silicone in them, and I have a smoke detector in there with them.

No point taking any chances, especially when boarding it out only cost a few hundred, and made mounting everything much easier than mounting to my awful walls.