Solar PV battery options

DrPhilG

First month since install of battery.

Slightly less generation than last August, but a 64% drop in import and 57% drop in export.

SD_DRACULA

Cmon CATL get those Salt Ion batteries out there 😂

bullit_dodger

I gotta admit - fair play to you for having the stones to do that PhilG. Technically, it's probably not beyond me, but I'd be planking it.... that I

a) would electrocute myself

b) create a fire hazzard

So tell me are you finding now with the extra capacity that you can "ride through" a bad day's charging. i.e. say on Tuesday you get the battery charged and if Weds was a dull day that you can get through that and night time and back charging on Thurs? i.e. you have enough to do a full 36 hrs?

DrPhilG

Pretty much yeah. Today was a scorcher. I filled a fair but into the car even before the battery filled so it didn't quite hit 100%, but it's discharging at the minute and sitting at 75%.

It'll be down to around 50% by the time the sun kicks in tomorrow so even if tomorrow isn't a great day, chances are that even a pretty crap day will still be topped up enough by the charge leftover from today, to get through to midnight tomorrow.

championc

https://www.boards.ie/discussion/comment/117833109#Comment_117833109

It's really not hard to do, nor dangerous, once you take your time. Once you also have disconnects in place to isolate the batteries from the inverter, you can safely work on the batteries without too much worry, since you're only working with 48v and zero current.

It's all about having a good digital multimeter. The most time consuming would be wiring up the BMS.

We will happily guide you or anyone else through the whole install.

bullit_dodger

You can kill yourself with ~30-40 mA :-) , although 48v it lacks the punch to really do damage, but yeah, I'd be very appreciative of some guidance if/when I go down that DIY battery road.

I've a Givenergy inverter and battery (8.2Kwhr) enroute. Should have it installed in Sept I hope. My provisional thinking is to run that for 6-12 months. See what kind of utilization I get, but from doing some thought experiments....I'm keen on having about 15-20 KwHr storage. I use about 20Units/day and it'd be great to be able to run the house off battery for 24-36 hrs, a bit like PhilG can do now. Being able to get a 10Kw DIY battery from Aliexpress for €1800-2000, that's a punt I like to take.

Before anyone says it, I know the math. The 2nd battery, if I go there, isn't a financially sound investment. That's not my thinking. Like many of us here, I've a keen interest in this stuff, and even at a (fiscal) loss, a lot of the "value" that I get out of these things is the enjoyment and satisfaction that you get from learning stuff and then for years being able to look at it, and say "I did that - and I didn't kill myself!" :-) That's why seeing the great pictures and work that's gone on in this thread is so interesting to me.

slave1

I've yet to do the math on a DIY AE battery setup but the way electricity prices are going the financials are only getting stronger.

RE AE price increases, there was a container of batteries en route from China to Europe that exploded earlier this year, as a result the transport costs have increased dramatically which is driving the purchase price for us, I can't remember where I read/heard that

bullit_dodger

I was writing a little executable for myself to compute the various payback periods for a single battery (along with some forecasting logic - but not really started that)

Happy to share it once I finalize it.

Note: This wouldn't really work out the payback on a 2nd battery. With a 2nd battery, you have to use all of the charge therein everyday to generate savings, if you tap only into it every now and then, you can't say that you'd be generating (much) savings. So in general I'd say you'd never make back money on a 2nd battery. Still though, there's more to life than simple money. Great to incentivize something, or know that you'll get your money back..... but being able to work on a project and get it to work has it's own rewards.

insular1

I think it's been discussed in the thread already but I can seem to find it. What size shelves would you need for a 10kwhr pack installation?

bullit_dodger

https://www.boards.ie/discussion/comment/117837809#Comment_117837809

While not exactly an answer to your question, you can get a good sense of scale from this.....

youtube.com/watch?v=atYZ4RtUJhU&t=7s

All those batteries was for 16Kw.

DrPhilG

https://www.boards.ie/discussion/comment/117837809#Comment_117837809

I bought a shelving unit on Amazon that was supposedly rated for the weight, it wasn't...

The shelf started to dip a little so I've since had to split and rebuild the pack on the attic floor (with reinforcement).

insular1

@DrPhilG Thats 20kwhr isn't it? Roughly what length is the pack? I'm DIYing the shelves from a bunch of left over 2x4s so should be able to make it as strong as needed.

DrPhilG

Each cell is about 280x183x72mm

So 72mm per cell, 16 in the row, allow for minor gaps, I'd allow 1.2m for a 10kWh/16 cell pack.

slave1

When you say reinforced, did you lay timber rafter to rafter and then a board on top of that?

Also, attic, how do you think weather extremes will impact the batteries?

Also, no strapping?

Thanks again Phil, with RTW this will be a nice project to work on over Winter (once AE battery prices come down hopefully....

unkel

Looks like horizontal and vertical timbers to me, should be fine on top of the rafters. A cell is what, about 5kg roughly? So 160kg in total. Not all that much. No need for strapping on these cells. And as for weather extremes, I presume it will not go below 0C in that attic. If it does, you need to program your BMS to NOT charge then. Otherwise the cells will be a gonner 😂

graememk

https://www.boards.ie/discussion/comment/117837793#Comment_117837793

Totally agree, its a great project to work on.

But the one you have coming, is exactly the same as the Calb cells. Going on the stats of the battery, its marketed as 100% discharge, and 8kwh, but its exactly the same as a 20-100% 10kwh battery.

But if your keen on it in the future, you should be able to sell on the battery you are getting, and replace it with a bigger one.

DrPhilG

Yeah the attic is floored already, and I've added 2 layers of solid oak flooring, at 90 degrees, then the boards from the shelving and the batteries on top.

The attic can drop below 0° at times in winter, so I'll be adding a temperature stat to the BMS and also building an insulated surround for them.

bullit_dodger

https://www.boards.ie/discussion/comment/117839758#Comment_117839758

LOL! I've not even got the thing installed and I'm already thinking about an upgrade. Ha! Although this would be "normal" in this forum I bet :-)

To be honest, I'd probably leave this system all alone and setup a smaller 1-2Kw system in a shed I have out the back. Basically do a complete self-install with it's own inverter, a DIY battery but ....I gotta "walk" before I can "run". Might even be able to get a few vertically mounted panels as the wall of the shed is exactly due south .

I assume that's possible folks, right? i.e. that you can (safely!) have two separate solar systems feeding your house, assuming you have isolator switches etc. No desire to murder some poor chappie down the road who might be fixing a line after a storm.

Got the panels installed today. Sadly not a 50-50 split, but 4 panels East and 10 panels on the West facing roof. Damm velux windows! I'm sure I could have "squeezed" 5 or 6 panels on the East one, but it probably wouldn't have been in regulation. The lads who were doing it seemed like they knew their arse from their elbow, so bowed to their knowledge. Reckon early next week should be up and running!

Has anyone done anything with the Givenergy API?

graememk

https://www.boards.ie/discussion/comment/117839968#Comment_117839968

Extra solar is easy, just another inverter and grid tie it, and your off to go.

2 separate battery systems (that are on-grid) is more complicated. The hybrid inverters/Storage inverters monitor the import/export of the grid coming into the house and try and keep balance.

If there is 2, and there is no outside overall control, they tend to end up fighting each other, one could end up discharging and the other charging.

I have heard of some people doing manual control, only enabling the second inverter when the demand is greater than one of the inverters.

(huh, just realised with the DIY battery, with the right bms and wiring, you could hook 2 storage inverters up to one battery...)

bullit_dodger

I'll probably shelve that for a bit. I'd say there's a solution, but I know enough..... to know that I don't know enough. Will need guidance and to educate myself to do it safely. It's also a little more complicated as the professional fitted jobbie is going in next week is going into one of the eves of my attic and if I was doing a self install out in the shed, it's a little messy connecting a battery 50 meters away to that inverter, or the panels DC output as I already have 2x strings. So it's a project for the "must look into that at some stage" book !

Still I've got a lot of fun stuff up ahead in the next week. It's was like Christmas seeing the new toy being installed on the roof earlier!

championc

If they installed the panels yesterday, why do you reckon it will only be early next week until it's up and running ? I'd be very surprised if you weren't operational by lunchtime today.

You'll now get to see to how bl00dy easy the whole install is. The hardest part is the fitting of the roof brackets tbh

unkel

https://www.boards.ie/discussion/comment/117840609#Comment_117840609

Indeed. Unless you have a steel roof, then even the roof brackets are supereasy like the rest. Place bracket, place special screw with waterproof rubber grommet. Drill in. Done. 😂

The only hard part for me was to lift up the oversize very heavy panels up a ladder and onto my roof. On my own. I installed a 12 panel array, with zero help from anyone else, including cabling going back to the inverter, in about 3 hours.

insular1

https://www.boards.ie/discussion/comment/117839836#Comment_117839836

Thanks for the reply. Is it easy to add a temp stat to the BMS? I plan to install mine in an insulated garage with minimal heating so think mine could drop below zero at times too. Will need to check this out this winter.

graememk

https://www.boards.ie/discussion/comment/117840698#Comment_117840698

Depends on the BMS really, If it has a temperature input. (most do)

If its in a insulated garage, a small green house heater (or mining rig :P) would work perfectly to keep the chill out of the air!

reklamos

https://www.boards.ie/discussion/comment/117838266#Comment_117838266

I thought that they supposed to be compressed and not left loose?

bullit_dodger

I agree I don't think it's a hard job, doing the wiring etc compared to the panel installs, but I think it'll be next week.

I asked the panel installers what the story was with the spark(s) to tie everything together and he mentioned that he's was a bit ill lately (hopefully not covid!) and running a few days behind the panel installs catching back up. So sadly next week is probably likely.

MAULBROOK

20210903_092954.jpg

20210903_112648.jpg

My lazy way in upgrading to 10.5kw.

unkel

Do those BYD batteries have built in heating like a Tesla Powerwall? If not be very careful the BMS does what it is supposed to do when temps go below zero or those batteries will be toast.

MAULBROOK

https://www.boards.ie/discussion/comment/117841461#Comment_117841461

Has never gone below zero in the garage. the best thing is the BYD can output just over 3kw, very handy in a power outage.

unkel

Yes same 3kW with the Sofar that several regulars of this forum have (myself included). I need to buy a decent 48V charger so I can charge my 10kWh home battery from my car to keep things going. I should be well prepared for (long) power outtages this winter if we will get any.