10kWh LifePO4 DIY Battery Addition..... Here is my write up.

championc

@S' looking good 👍

SD_DRACULA

https://www.boards.ie/discussion/comment/119575695#Comment_119575695

If it's from the inverter to the BMS/isolator (like your diagram), you can also use pylontech cable kit and snip one end and put whatever lugs you need on it. Or maybe it has the lugs on one end anyway don't recall, had to snip them to put them into the 125a mcb.

Maybe add another one of those marine switches on the negative to tidy things up and have only one cable going to the inverter?

slave1

Is it possible to purchase the "insert" to battery (opposite end of the lug) for Puredrive/Pylontech and just crimp your own cables to custom length?

SD_DRACULA

https://www.boards.ie/discussion/comment/119577711#Comment_119577711

Not worth it, those round plugs for the battery connectors are not cheap (cost more than the ready made cables) and require special crimper too.

I picked up a pylon cable pack from midsummer for around 30 ish.

slave1

€30 is decent, the reason I asked is because I was gifted a dryness set for my DIY battery pack and snipped off the "connector" end, at the end of the day a crimp and not propriety (crimp) in nature

randombar

Hi Lads, does anyone know what the approximate losses in this set up are?

10kwh LifePo + Seplos + Sofar

graememk

https://www.boards.ie/discussion/comment/119588170#Comment_119588170

20% power measured in and out, via a ct

slave1

Which is why we encourage self consumption there and then as much as possible and also discourage batteries to charge an EV as there are further ~8%-10% there

randombar

https://www.boards.ie/discussion/comment/119588612#Comment_119588612

Yes, plus it's good to know when calculating the energy savings for overnight charging. It's not nightsaver vs daytime it's really nightsaver + 20% vs daytime

graememk

https://www.boards.ie/discussion/comment/119588696#Comment_119588696

What I've found is it's mostly on charging eg 15% on charge, 5% on discharge but I don't have hard numbers for that

I'd say in the summer, discharge the battery into a car, if your on a day night as your export isn't measured anyway

DC999

So that setup means you've around 20% less capacity in the battery basically (than what went into it). Am not being critical. Good for me to know when looking at battery options. All batteries have losses of course.

unkel

https://www.boards.ie/discussion/comment/119588852#Comment_119588852

No, you get about 20% less coming out of the battery than you put into it (@graememk and others have measured this). But you have also got losses even before putting it into the battery

The whole process: PV from your panels -> PV inverter converts to AC (10% loss). AC inverter (like Sofar ME3000SP) converts to DC for batteries (10% loss). Then AC inverter converts DC from batteries to AC for your house (10% loss). So overall 30% or so loss. This is less in a hybrid inverter as DC is stored directly and only once converted to AC for your house so only 10% loss in total

randombar

https://www.boards.ie/discussion/comment/119588898#Comment_119588898

I'm just working out how much I save per day charging on the nightsaver so not working with Panel -> inverter losses. PV has paid for itself already I'd say.

I'd say saving maybe 0.75 and 1.00 a day.

unkel

In my own case: 20kWh (usable) battery, day rate 27.43c incl VAT, night rate 7.90c incl VAT

So savings per month:

30 days * 20kWh * (0.2743-0.079) * 80% efficiency = nearly €100 per month saved by peak shifting...

Paid €2300 for the battery a few months ago, so you can see it will pay for itself very quickly indeed. And of course taking electricity from the grid at night when it is mostly green (from wind) and using it when it is in high demand and mostly made from burning fossil fuels during the day is a very important consideration too.

randombar

https://www.boards.ie/discussion/comment/119589051#Comment_119589051

You are using 20kWh * 0.8 (16kwh) of electricity from 8am to midnight??

unkel

Yes I'd empty the battery alright every day in winter and then some. Busy 5 person household, working from home, I use almost zero fossil fuels. Heat the house with electricity, have 3 electric vehicles. Heat the water with electricity. Have a large solar thermal and very large solar PV setup too.

slave1

Apart from EVs, I'll be able to run the home for three days with my battery backup, that's immersion, oven etc, everything (just not oven+immersion at the same time).

I'll need a changeover switch first but for the time being will go with dedicated sockets fed from EPS of inverter, the need might never arise so why plough funds into it

mrohare

Any last minute tips???

2 of my 4 boxes of cells arrived today, hopefully other 2 very soon. I have (near enough) all the other parts waiting - including ME3000SP.

how long should it take to top balance the 16 in parallel? should I just do the 8 for now and then the 2nd 8 seperately?

I have bought a capcity tester - should I capacity test each cell seperately or in groups. i.e. if 1 group is low then just test those 4 seperatly.

after capacity test, how long will the 2nd top-balance take?

for anyone who has already done this, are there any mistakes you made, or anything you have discovered that is worth giving me a heads up on?

Thanks.

munsterfan2

I would fully charge a single cell, then test it with the discharge tester while charging the next cell. It will take a number of days to work through the cells. If any of the cells arent capacity lodge complaint with aliexpress / paypal ASAP. There are time limits on these. Dont bother trying to interact with OYear, they will only look to delay you.

slave1

8 top balancing at a time, low amps first then higher, I assume you have a BMS in your setup that can manage 16 batteries, this means you don’t have to be 100% with the top balancing

slave1

Wrap your wrench in electrical tape as much as possible, you don’t want to drop it and short a battery

electricus

What BMS and inverter would you recommend for a smaller power backup pack based on 8S CALB cells? Ideally the pack will be (semi) portable with built in sockets.

Apologies if this is the wrong thread – I don’t have solar or an inverter so not looking to build anything as big as discussed here (as much as I’d like to!)

championc

You can't have 8s - the voltage will be too small. These inverters expect 48v

electricus

https://www.boards.ie/discussion/comment/119599407#Comment_119599407

Thanks, that's what I thought. I'll need a 24v inverter and a BMS that will work with it. I should probably start a new thread somewhere but asking in case anyone has tried it.

unkel

If it's a backup pack just for very occasional (emergency) use, would you not consider those all-in-one packs? They have everything built in, a charger for charging them up, an inverter for powering your applicances with 3 pin sockets, usb sockets, some even have inputs for PV.

This thread is more about large home attached power walls that are cycled every day and see some real heavy duty use.

electricus

https://www.boards.ie/discussion/comment/119600423#Comment_119600423

I looked at the backup packs but it looks like I could potentially get a much better battery for less if I built myself. I know its more trouble but hopefully this experiment will better prepare me for a future solar install (if I get get a bigger south facing roof!).

Anyway, I'll stop polluting this very informative thread.

unkel

https://www.boards.ie/discussion/comment/119600477#Comment_119600477

Any reason it has to be a 24V pack? Would need 8 CALBS and that's going to be heavy. I would just buy 4 CALBS for a 12V pack, use the busbars that come with them and buy a decent quality sine wave inverter. Tape it all together. Don't bother with BMS if you are only ever going to use it occasionally. After use just check the 4 cells individually and charge up the ones that are lower, and then just store. Rinse & repeat.

graememk

Something along these lines? What sort of power do you need?

https://youtu.be/XFn1j1mq1U8

electricus

https://www.boards.ie/discussion/comment/119600760#Comment_119600760

Very true, 50kg is heavier than I thought. I was thinking of a pack I could charge on night rate and use during the day for washer, dryer, air fryer etc. and also in case of power cuts as I work from home. Not sure how long I'd keep that up without grid tie in, so a smaller battery makes more sense if its not powering the whole house. Think I'll keep go with a BMS though to extend battery life and avoid problems.

https://www.boards.ie/discussion/comment/119600979#Comment_119600979

Thanks, looks interesting! Thinking about it, a 4 cell 12v setup will give me about 2kWh (80%) which should be enough, for now at least.

unkel

https://www.boards.ie/discussion/comment/119601139#Comment_119601139

How would you charge it up and use it during the day for washer, etc.? By micro managing the lot? Hey it's after midnight, I better plug it in to charge it? Hey the battery is full, I'd better buy a €1000 pure sine wave 2kW inverter so I can run my dryer off it? 😂

You get the picture? You either want a cheap and cheerful all in one for emergencies like I suggested above, or you want a grid tie system. There really is nothing in between that is a good solution for anything.

electricus

Thanks, that’s what I was trying to work out, I wasn’t sure if a grid tied system would be worth it without solar as most info online assumes that setup.

I was thinking of timing the charge at night. The battery would live in the utility room next to the main appliances so not too difficult to manage.

The 2kw pure sine inverters I was looking at on Ali Express we’re around €200 but maybe not up to the job.

I have a A+++ heat pump dryer which barely pulls 1kw but it runs most days during winter, same for washer which is also A+++

unkel

Your €200 "pure sine" 2kW inverter would be toast within 10 minutes, possibly taking your €500 dryer with it 😂

If you want to play with off-grid systems, start cheap and small. You'll learn. And you will definitely learn that what you plan to do on a daily basis, doesn't work with an off grid system. Unless you spend a lot of money on it. Far more money than a similar grid tie system that can do the same...

electricus

Fair enough, looks like a lot of the videos on YouTube we’re too good to be true!

Starting small is definitely a good plan, I’ll probably try a small 2-3 panel solar setup on the shed roof and play around with that to learn how it works.

If VW enable vehicle to home for my ID3 then I’ll look into that too

slave1

Just turn on the washer/dryer at night …

electricus

We do as much as possible but I don’t get up early enough to fill the dryer after the wash - planning an over complex battery solution seems easier 😂

unkel

Put washing machine on at midnight (or put it on a timer if you require more than 7 hours sleep), go to bed, get up at 7 and put dryer on. Simples.

If you don't want to get up at 7, implement a home power wall solution like the rest of us 😁

electricus

Does your system work during power cuts or is that an option?

unkel

Most hybrid / AC side power wall systems work during a power cut as they have EPS outputs. You can wire a socket to them or even a fancy transfer switch

https://www.boards.ie/discussion/comment/119601680#Comment_119601680

Dublin Fire Brigade sez no to the first bit of this.

bullit_dodger

https://www.boards.ie/discussion/comment/119601932#Comment_119601932

This one comes up all the time. Statistically more chance of your fridge catching fire, but yet people are worried about washing machines being the death of them and murdering them in their sleep. LOL

Do you plug out your fridge?

electricus

https://www.boards.ie/discussion/comment/119601680#Comment_119601680

Joking aside, I’d get a solar install with a hybrid inverter and add my own battery later - like most here. The problem is that I only have room for 4 panels on my roof so not enough to qualify for the grant.

Power wall type system are hard to find at a less than eye watering price (including install without solar+grant) right now and I’m guessing that most electricians wouldn’t be happy about grid connecting a diy battery.

That’s what got me thinking about a diy battery without grid connection. I have a good understanding of the concepts and how it all works but very little practical experience of which hardware combinations works best - especially BMS and inverters as the spec sheets for a lot of the gear on Ali Express can’t be trusted.

I looked at all in one battery packs but it looks like most affordable 2kWh packs don’t use LiFePo4 cells, which are the only type (of large battery) that I’d trust in my house.

I agree with you that my solution is not really practical for my uses and thanks for your answers, that’s what I was looking for.

By the way, what is it about the 200-300 euro inverters, like the ones on Ali Express, that makes them bad? It it there ability to handle inductive load or peak power demand?

electricus

https://www.boards.ie/discussion/comment/119601896#Comment_119601896

Can it switch to battery and isolate the mains supply automatically or is it a manual switch?

electricus

https://www.boards.ie/discussion/comment/119602001#Comment_119602001

Older hot tumble dryers too with clogged up fluff filters and dodgy charging plugs with damaged or poor quality cables are even worse.

Punchin A Keyboard

https://www.boards.ie/discussion/comment/119601520#Comment_119601520

Apparently the ID V2H enablement was meant to be done by an OTA this year. However I assume a very expensive invertor will be required but i am assuming up to 22kw DC coming out of the car.

electricus

https://www.boards.ie/discussion/comment/119602154#Comment_119602154

It was reported last year but haven’t heard anything since - VW’s software quality and update schedule hasn’t been great. I also wonder about V2H standards and if the expensive bidirectional wall box will work with other EVs

Punchin A Keyboard

I think the ccs quaser 2 has not been released yet but then there's no vehicles that officially could use it.

I believe that a standard is in progress for ccs to do bidirectional but like all official standards is taking time so I would guess slot of vehicle producer's and charger manufacturers are sitting till that is in place.

dathi

https://www.adverts.ie/other-building-materials/esb-secure-plant-storage-cabinet/27626931

would something like this be suitable to install inverter and batteries outside ?

bullit_dodger

https://www.boards.ie/discussion/comment/119602152#Comment_119602152

All very true, but this is the same with any electrical device even during the day where you turn it on and the go watch TV in another room. Electrical devices should be well maintained, have good cables, no gunk on the contact on the plugs, etc. The point that I'm making is that the risk of one of these devices today is very small.....but non-zero.

it's the non-zero element which is the interesting bit to me as people have no issues with their fridge plugged in but statistically it's more likely to catch fire than the dish washer. I find it curious that the dish washer is a fire hazard in peoples mind, but fridges are not and as such they don't plug out the fridge. If it was a real risk, then logically they should plug out the fridge also. No?

Everyone to their own of course, but the idea that dish washers/washing machines are dodgy and shouldn't be used at nighttime is a throwback to yesteryear I think, but naturally you need to do what you think is right for you and gives you peace of mind as that also is important.

DC999

@electricus, quick side note. It's defo worth your while seeing if you can really only fit 4 panels. A small shed likely fits that. We got 16 (1m wide x 1.7m high) onto a small '2 up, 2 down' house. Includes 5 of them on an extension flat roof. So I would guess it's not space that is the issue.

Maybe you already said you have other older panels or solar thermal on the roof. Or one roof is pure North (and even then it's a possible runner for a cheap DIY setup down the line). We have a few on a NW roof output is and grand up to this time if the year. Others told me that's crap in Winter but working find to this point.

Take some pics on the roof maybe and pop into into the quotes thread asking for suggestions. Some shade can be worked around with optimisers. We had vent pipes causing shade so cut them down a little in height and no more shade.

https://www.boards.ie/discussion/comment/119602001#Comment_119602001

I'm not the one advising against this. It's Dublin Fire Brigade. If you don't like their advice let them know.

Where's your source for your "statistically more chance" observation?

This lot say that their numbers come from the UK Home Office. Fridges are 5th on the list, behind dishwashers, cookers, tumble dryers and at the top of the list, washing machines.

Which domestic appliances are most likely to catch fire? – Housewares (housewareslive.net)

The same stats featured in several news reports after the Grenfell tower block fire. LOL indeed.