Solar PV battery options

Big Lar

@unkel I would find it very hard to tell the SOC from that graph, sun is shining one minute then not the next, kettle on - kettle off.

SOC is the job and it doesn't have to be very accurate, for my automations @80% SOC when there is over 1800w from the solar, then the immersion or the car charger comes on depending if the car is plugged in our not.

@graememk I am sure that I have read someplace about someone damaging an inverter by wiring can incorrectly so I am a a bit nervous about that, then as above I have everything that I need for the moment so if it aint broke kind of a thing, I may take the plunge going forward thou as I am considering collecting Realtime data from the inverter for the next project https://github.com/Jumpy07/Solis---SolisCloud-and-Home-Assistant

fael

https://www.boards.ie/discussion/comment/120593998#Comment_120593998

I run a Batrium BMS with a shunt (I think sometimes referred to as coulomb counter) and it literally just measures the energy going in and out of the battery. It's SOC is bang on. Depending on age, temperature etc the capacity of your batteries might vary a little bit so you can enable the feature to reset to 100% if it were to reach for example 101%.

Since the Seplos has a maximum Amp rating, I'm assuming all the power is routed through the BMS and therefore should be able to do the same thing?

unkel

https://www.boards.ie/discussion/comment/120595292#Comment_120595292

Batrium is a very good BMS. And not cheap. My point has always been about cheap BMS not giving accurate SOC readings. But yes of course if the BMS has a shunt and works properly and has done a full cycle from empty to full or the other way around, it should theoretically know the full capacity of the battery and thus the correct SOC at any point based on the sum of incomings and outgoings since empty or full

Any link to where you bought your Batrium and what you paid for it?

fael

https://www.boards.ie/discussion/comment/120595757#Comment_120595757

Fair enough, cheap BMS would be different alright.

I bought from Batrium direct (don't think they have a retailer in Europe). They are expensive, paid €620 for the BMS + shunt etc. On top of that duty/import cost was €165, ouch. I don't regret paying that though. It's not just to make financial sense, it's a bit of a hobby project as well so I enjoyed the whole learning process. And sometimes it's nice to work with well engineered stuff. If I were to put another battery bank in parallel it won't be that same price, you just buy a cheaper expansion set. Or just parallel more cells obviously.

I mostly regret buying cells from PWOD and getting scammed with 125 Ah cells instead of 200 Ah. Still contemplating to buy cells from NKON or elsewhere and replace the whole shebang. But that won't be cost effective, mainly because I won't sell the low capacity PWOD cells for a good price. Despite the lower capacity I still have a well performing 13 kWh battery for just over 3 grand. Should have been closer to 20 kWh though...

HotSwap

https://www.boards.ie/discussion/comment/120597127#Comment_120597127

Looking on NKON.nl? I assume that’s the site your referring to?

what’s the difference between A / B grade? Which of the batteries listed on there now would you buy?

Ginger83

https://www.boards.ie/discussion/comment/120597215#Comment_120597215

Any luck with the battery prices? I got a price off the installer.

HotSwap

https://www.boards.ie/discussion/comment/120597233#Comment_120597233

What were you looking for? I sent some prices to someone in DM; must of been someone else.

Ginger83

https://www.boards.ie/discussion/comment/120597271#Comment_120597271

5.1kWh dyness and recommendations if possible

HotSwap

https://www.boards.ie/discussion/comment/120597283#Comment_120597283

2152 including vat. What was the quote?

Ginger83

https://www.boards.ie/discussion/comment/120597306#Comment_120597306

€2500 or €4600 for 2×5.1kWh. Are they vat exempt?

Would you have any other options?

HotSwap

https://www.boards.ie/discussion/comment/120597317#Comment_120597317

did they put VAT on the quote? they are only costing the installer 1750 as they can claim back the vat on supplies.

Technically I would say they are not exempt as they are not being installed in the same invoice as PV panels. Read here: https://www.revenue.ie/en/tax-professionals/tdm/value-added-tax/part03-taxable-transactions-goods-ica-services/Services/solar-panels.pdf

Ginger83

https://www.boards.ie/discussion/comment/120597343#Comment_120597343

Thanks. That's not exactly clear.

I just emailed the installer and received an email back. It wasn't a quote on headed paper but I assume the figures are for supply and fit.

Would Dyness be a good battery?

fael

https://www.boards.ie/discussion/comment/120597215#Comment_120597215

I don't know, haven't done any proper research into them. Still in a dispute with PWOD on AliExpress, so how that plays out first.

Solarwicklow

They are not compatible,I asked Dyness last year,I might be selling two of my 2.4kwh Dyness in couple of weeks if you are interested

graememk

No active balancer but this looks like another alternative to the seplos, it has can output

https://youtu.be/ONn6tLXKHQY

redmagic68

https://www.boards.ie/discussion/comment/120600690#Comment_120600690

I may be interested if you decide to sell. Let us know.

munsterfan2

https://www.boards.ie/discussion/comment/120598393#Comment_120598393

They have a note on their site about B grade batteries

"B-grade cells are cells usually did not qualify as A-grade by the manufacturer. This may be due to optical imperfections, higher self-discharge, lower capacity and/or higher internal resistance. Unfortunately manufacturers don't tell which aspects or aspects are the reason to mark a a specific cell as B-grade. We have sold several and get seldom negative feedback. We tested several eve B-grade and one had about 2% lower capacity, the other ones we did not find a difference with A-grade cells. We don't advise B-grade for high performance electric vehicles but for home energy storage they will work fine. In case you get one which performs significant less than the others like lower capacity, high self-discharge or fast wear we will replace it. Take care that we don’t put a lot of trust in a simple test of a single cell, if you buy 16 cells and you test them and they are all 6% lower than expected then your test gives to low results. If you buy and test 16 and 15 cells give you 100% and one cells gives 5% lower results then we will replace one. When we buy cells the cells are tested for voltage and internal resistance. Also a couple of every batch are tested for capacity, and if one gives less than 100% capacity we test the whole batch and discard the bad ones or don't buy the batch at all. Lot of seller in china buy B-grade cells, test them, even swap qr-codes and sell the good looking and performing as A-grade cells. We believe our B-grade cells are the same as lot of A-grade cells from China, including the well known resellers there with good reputation. We give regular warranty on these cells (at least 2 year)."

I purchased the 300ah B grade cells, working perfectly.

unkel

@munsterfan2 - if you look at the tests from off grid garage, all EVE type cells get at least full rated capacity or damn near to it. Be they automotive grade cells, A grade, B grade, rebadged and some rather dodgy ones.

It seems it's the CALBs that can often get nowhere near full rated capacity, as you and others found out yourself! It's the main reason I now plan to rebuild my battery as 15S because I will be able to get one more cell in parallel, meaning different capacity cells will even out even better.

casey80

What's the view on installing lithium iron phosphate batteries (e.g. Huawei, givenergy, puredrive) in the cold attics? I heard that these batteries may have issues with charging properly once temperature drops below 10 degrees?

I'd prefer to install mine in the attic, but may find other place if charging issues would be expected...

Thanks in advance

unkel

https://www.boards.ie/discussion/comment/120610173#Comment_120610173

It depends on the battery and what the BMS in it is programmed to do. LiFePO4 itself has no problem operating as normal as long as the temperature isn't below zero degrees when you try to charge it. And I presume your attic rarely or never goes below zero? The inverter and batteries themselves create quite a bit of heat too because of charging and discharging losses of near 10% each way.

If you build your own battery, you can decide what settings you want to use in the BMS. If you use a proprietary battery like Huawei, Givenergy, etc. you will have to contact the manufacturer to tell you what those settings are.

HotSwap

https://www.boards.ie/discussion/comment/120610173#Comment_120610173

Huawei will operate down to -10C; but the charge and discharge start to fall off once it gets below 5C. And at least they are upfront about this and include it in the documentation. As to how much the rates decrease as the temp drops below 5C you would need to open a support ticket to get that info.

I would think it’s not too many days a year your attic will below 5C. And I would think as long as the battery is in use it will generate some heat itself.

These are designed to be installed outside; so I think an attic will be fine. Although if you do it and it gets below 5C I’d love to know what happened :) please update us if you do it.

unkel

@HotSwap - "These are designed to be installed outside"

Which ones, the Huawei? Like the Tesla Powerwall? I wouldn't touch either of them then with a barge pole if the install was to be outside. The Huawei will do feck all colder winter days / months. And the Tesla has a massive elephant in the room: it uses a built in heater to keep the temp of the battery high enough to be able to charge / discharge even when it is sub zero. This effectively means that the system could cost you more money than it saves for long periods of time in winter.

DrPhilG

Insulation baby!

HotSwap

https://www.boards.ie/discussion/comment/120610635#Comment_120610635

Designed to be capable of being installed outside I should say. Mine is inside.

The data sheet says it works down to -10c; and only starts to de rate itself at 5c. I’d rather ask Huawei for the de rating curve and see what they say. I’ll ask and let you know.

casey80

https://www.boards.ie/discussion/comment/120610617#Comment_120610617

I think there would be some nights during the winter when temp drops below 5C in the attic. Unlikely it would drop below 0C though.

So, would be good to understand the extent to which charging is affected in 0-5C range, as ideally I would like to be able to charge battery overnight on the cheap night tariff.

Did anyone install LIP batteries outside and what was the performance during the winter? Could not find much info on this, and battery manufacturers are not very transparent in specifications regarding reduced charging capability in single digit above 0C temperatures.

con747

https://www.boards.ie/discussion/comment/120618319#Comment_120618319

I know a couple of people fitted something similar to this https://www.diy.ie/departments/goodhome-basic-5x3-pent-grey-shed/5059340270623_BQ.prd at the side of their house and insulated the inside so the heat off the inverter and batteries keep it from being too cold.

ELM327

https://www.boards.ie/discussion/comment/120605988#Comment_120605988

Would you not find it difficult to get a BMS that works with 15S? My dyness batteries are 15S and I was initially intending to parallel it with 15S calb cells but "the internet" said that was not a good idea, for multiple reasons, one of which being the difficulty that finding a bms working with 15S was problematic.

What would you think of paralleling 15S Calb (or EVE) cells with existing Dyness server rack.

unkel

https://www.boards.ie/discussion/comment/120631011#Comment_120631011

No, the JK BMS will work with any number of cells in series from 8S to 24S, just change the number of cells in the settings in the phone app, 5s job. Done. In fact I did it late on Sunday evening and I'm now running 15S 😁

So paralleling two different packs is perfectly fine, as long as they are the same chemistry and same number of cells in series. I did this before as I have a 100Ah 16S server rack pack too. This is now for sale as I no longer can parallel it with my main 15S pack!

graememk

https://www.boards.ie/discussion/comment/120631011#Comment_120631011

That would work, the JK bms will work with 15s.

You don't have to worry about communication either, just connect in parallel and let the dryness work away

ELM327

https://www.boards.ie/discussion/comment/120631167#Comment_120631167

Could you put the EVE/Calb cells as the main battery in that setup using the JK bms, and then set the dyness to slaves.

I actually think that would be better than trying to sell 1 year old dyness batteries, if I could put 15S calb or eve cells into the setup and add capacity that suits me better.