Sonic's Powerwall (London, UK)

Sonic01

Sonic01

Member
Joined
Sep 19, 2017
Messages
134
So after a long intro thread, things are starting to progress a bit:


image_tnlpgi.jpg


I've done voltage checks on all my cells and all are between 2v and 4.2v so should be good to go, just need to do testing cycles to check they function ok and get a reading for the mah.

My setup will be something like this:

batteries: 7s40p (24v + 100ah approx)
inverter:pIP-2424MSE
solar: 4x 250w
balancers: 7x QNBBM 1S

battery holders are on the way.

Can anyone in the UKrecommend what I should use for my bus bar and fuse wiring?
 
wim said:
Nice start...
Especially liking those bright green ones ;)
Click to expand...

i actually have no idea what they are, they are the only ones with no branding or codes written on them... they have some H&S writing on them that looks really retro but they are actually all in good condition except 2 that had popped.

Those dark purple ones were the worse... 12 had failed. all other colours had no failures.
 
Great, have you found any supplier in the UK for the inverter yet?
 
Sonic01 said:
not UK, but actually aliexpress have a german warehouse, i can get it for 295 delivered from there! linky:

https://www.aliexpress.com/store/pr...889.html?spm=2114.12010612.0.0.7d8de96aiULj87

I've also added the balancers I'm going to use to my first post now.
Click to expand...

Nice find!

I'm also UK based (Essex) but haven't reached the 'put together the packs' stage yet but was going to use 10m2 twin and earth cables for the busbars and the smallest multistrand wires I could get my hand on, probably just going to strip some speaker cables for the single strands and test a few to see if they blow at low enough amperes to me.

I was going to use this inverter:https://midsummerwholesale.co.uk/buy/sofar-storage/sofar-me3000sp.html as it has everything built in, including the limiter logic so that you can set it to never export power into the grid but just to supply your own house. You can also set it to charge overnight on S7 via a timer so get cheaper electricity over night or from your solar panels. It's AC coupled to you just plug it in!

I am thinking about puttingin a ATS to take my house off the grid if the grid fails so I don't end up having no power. I probably won't be able to bet my SolarEdge solarinverter to run behind an ATS though as it has the islanding protection built in.
 
Opus BT C3100 v2.2 finally arrived today so ill start testing all the cells properly.

I realised i made a mistake and ordered 2.5m2 twin and earth, which probably isnt enough...? though its rated at 24amp, might be enough? I wonder if i could just wind 3 strands together to make it thicker etc.

I've got some 5amp fuse wire turning up today, was only about 7.

So you're looking to properly tie yours into the mains then? I'm just going to daisy mine off an AC outlet in my shed. I'm not actually touching my house at all. Not for the moment anyway...
 
Hello,
for my 80P pack (4 x 20) I use 3 wire 2,5mm2 and I twist them with drill machine (hand electric toll)
It's give 7,5mm2. You can go up to 5A per mm2. 7,5mm2 can go up to 38A.
As there is two Twisted bus going to the lugs it's give around 75A.
Appologize for my English


... from France....
 
Sonic01 said:
So you're looking to properly tie yours into the mains then? I'm just going to daisy mine off an AC outlet in my shed. I'm not actually touching my house at all. Not for the moment anyway...
Click to expand...

That was the general idea yes. But if I ever get that far is the big question!

I don't have a shed yet but are toying with the idea of building one in my back garden at some point and if that happens then it would go off-grid or grid-tied. I've got a few crazy ideas for what else I could put in there!:p
 
cristof said:
Hello,
for my 80P pack (4 x 20) I use 3 wire 2,5mm2 and I twist them with drill machine (hand electric toll)
It's give 7,5mm2. You can go up to 5A per mm2. 7,5mm2 can go up to 38A.
As there is two Twisted bus going to the lugs it's give around 75A.
Appologize for my English


... from France....
Click to expand...

Thankscristof, perfect. This is exactly what I will do.

mormor1971 said:
Sonic01 said:
So you're looking to properly tie yours into the mains then? I'm just going to daisy mine off an AC outlet in my shed. I'm not actually touching my house at all. Not for the moment anyway...
Click to expand...

That was the general idea yes. But if I ever get that far is the big question!

I don't have a shed yet but are toying with the idea of building one in my back garden at some point and if that happens then it would go off-grid or grid-tied. I've got a few crazy ideas for what else I could put in there!:p
Click to expand...

I didn't want to have to deal with all the insurance crap + paying an electrician to wire it in + working out the deal with the power company to feed back into the grid.

Let us know how things progress :)
 
progress at last :D cell testing is finished, my 7s40p is ready to be wired up! :D got 5A fuse wire and some buss bar cable, just need some time to do it :)

I started wiring up my first pack but im having trouble getting my fuse wire and negative connections soldered to the bus bar? the bar gets super hot but the solder jjust doesnt seem to fuse to it? I'm using 4x2.5mm cables wound together.


image_efnghq.jpg

image_hwxsnq.jpg
 
Man, that was sonic fast :p

Is the solder actually flowing, just not sticking to the copper wire? If so, you probably need to apply a little flux to the copper. If not, you need a heavier duty iron. The problem is the copper could be pulling the heat away faster than the iron can produce it, so it's not sticking properly.
 
Korishan said:
Man, that was sonic fast :p

Is the solder actually flowing, just not sticking to the copper wire? If so, you probably need to apply a little flux to the copper. If not, you need a heavier duty iron. The problem is the copper could be pulling the heat away faster than the iron can produce it, so it's not sticking properly.
Click to expand...

no its not, it doesnt really seem to bond properly, it just blobs on the surface and doesnt stick well. as you say, they copper bar really heats up and it spreads fast.

I'll try with a little flux, im using a gas iron which is rated at 120W.

I tried to find something more powerful but didnt have any luck :/
 
120W should be sufficient. I'd guess the copper is just too oxidized to allow the solder to bond, and if there is any flux in the solder, it's not enough to clean. You could also use a small brass bristle brush on the copper to shine it up before soldering to it.
 
Right, my 7s40p packs are ready :D I have a couple more questions!

1. is there any way i can test the solder joints on my cells? I had a lot of trouble getting the solder to bond to my bus bar, especially on the negative side using thicker wire to the cells. I was wondering if theres a way to test the connection to each cell...?

2. now i need to look at BMS, i want something as cheap and simple as possible, would this be ok?

https://www.vru zend.com/product/24v-7s-battery-management-system-bms/
 
you can try simple resistance test. But that may not give you an accurate info. I just pull a discharge of about double my expected draw for my wall and after about 1/2 capacity removed I start checking voltages of the cells (individual 18650) while still discharging and note any big differences in voltage. That can mean a couple things. Really high voltage mans bad connection, slightly higher can mean poor connection or really good cell, lower generally means a bad cell or just lower capacity. but this is subject to lots of factors and not a definitive test
 
jdeadman said:
you can try simple resistance test. But that may not give you an accurate info. I just pull a discharge of about double my expected draw for my wall and after about 1/2 capacity removed I start checking voltages of the cells (individual 18650) while still discharging and note any big differences in voltage. That can mean a couple things. Really high voltage mans bad connection, slightly higher can mean poor connection or really good cell, lower generally means a bad cell or just lower capacity. but this is subject to lots of factors and not a definitive test
Click to expand...

but how do youtest the cells individually if they are all soldered to the bus bar?
 
Sonic01 said:
but how do youtest the cells individually if they are all soldered to the bus bar?
Click to expand...

Under a heavy load, you test the voltage on the bus bar, then you test each cell voltage. If there is a difference, there's an issue. The reason there'd be a difference is due to resistance. When there is no load, there's no resistance, and all cells will have the same voltage. That's why you test while under load and before any resistance spots. So you measure the voltages on the cell themselves, not the solder or fuse wire portion.
 
You must log in or register to reply here.
Back
Top