lordxenu
Member
- Joined
- Aug 17, 2018
- Messages
- 61
Hey all,
I came here after finding several YT vids that turned out to be members here and I've decided to join in on the fun.
As chance would have it, I happen to have about 312-320 brand new cells including
92 x Panasonic NCR18650B @ 3400mAh
100 x Panasonic NCR18650BE @ 3200mAh
120 x LG B4 @ 2600mAh
So since I already have these cells, and they were doing absolutely nothing on my shelf I've decided to use them to build a powerwall. I am by no means an expert, nor an electrician ... but I do like DIY and electronics and I have built some off-grid systems in the past with lead acids and currently have a 4kW grid tie solar PV system at home with hot water diversion unit.
So I've decided not to go grid tie with this system, but instead to use an independent set of solar panels already mounted on the roof that provide (in theory) 960W - with 3 x Canadian Solar 320W panels all in series, one reason is that here in the UK we don't do net metering, instead we provide what the goverment calls the feed in tarrif; which is basically a system that says I get paid about 0.14 per kWh that my system produces ... and they just "assume" 50% of it gets exported, so I get another 0.04 on top of that. But this tarriff says you can have a maxmium of a 4kW system... so for that reason, and because I want a backup system that can operate when the grid goes down I have decided to go for a hybrid inverter that will charge batteries from solar (and AC if necessary) and includes a transfer switch to transfer loads to AC when the batts are dead.
I have a few devices that I'd like to stay on in the event of a grid failure (which to be fair is rare, but has happened about twice in the last two years for about 10 minutes) so I'll hook them into the inverter and let them run from that and they can swap back to grid AC if the batteries don't get charged enough.
I have decided that I'm going to use a 14s system and i'm going to arrange my packs like this
84 x NCR18650Bs in 14s6p = approx 20Ah at 58v (going to charge them to 57.4v ~ 4.1v per cell)
98 x NCR18650BEs in 14s7p = approx 22Ah
112 x LG B4 in 14s8p = approx 19.2Ah
All in all i should have somewhere close to 3.5kWh pack to play with. I'm going to mount it outside my house and bring the wires in (only on the wall outside, 1-2 metres max) to the inverter which i'll then connect to my stuff inside.
What I have not decided yet is if I should make one giant battery pack, or split them into three. Splitting has the advantage that all the same type of cell will be bonded together. One large cell means it's easy to use a BMS like batrium with only 14 longmons ... not 14 x 3...so that point I'd like to ask if anyone has any advice on?
Today I purchased the 48v 3000W hybrid inverter. Not really heard of this brand but it looks very similar to the MPP Solar style ones.
This one is 230V AC (I live in the UK) not sure if links are ok so i'll just post a pic. With today's ebay discount, I saved 50 on the total price of it.. so I'm really hoping this one works
Let me know what you think of my proposed design and I'll be updating and adding images as the stuff arrives.
I came here after finding several YT vids that turned out to be members here and I've decided to join in on the fun.
As chance would have it, I happen to have about 312-320 brand new cells including
92 x Panasonic NCR18650B @ 3400mAh
100 x Panasonic NCR18650BE @ 3200mAh
120 x LG B4 @ 2600mAh
So since I already have these cells, and they were doing absolutely nothing on my shelf I've decided to use them to build a powerwall. I am by no means an expert, nor an electrician ... but I do like DIY and electronics and I have built some off-grid systems in the past with lead acids and currently have a 4kW grid tie solar PV system at home with hot water diversion unit.
So I've decided not to go grid tie with this system, but instead to use an independent set of solar panels already mounted on the roof that provide (in theory) 960W - with 3 x Canadian Solar 320W panels all in series, one reason is that here in the UK we don't do net metering, instead we provide what the goverment calls the feed in tarrif; which is basically a system that says I get paid about 0.14 per kWh that my system produces ... and they just "assume" 50% of it gets exported, so I get another 0.04 on top of that. But this tarriff says you can have a maxmium of a 4kW system... so for that reason, and because I want a backup system that can operate when the grid goes down I have decided to go for a hybrid inverter that will charge batteries from solar (and AC if necessary) and includes a transfer switch to transfer loads to AC when the batts are dead.
I have a few devices that I'd like to stay on in the event of a grid failure (which to be fair is rare, but has happened about twice in the last two years for about 10 minutes) so I'll hook them into the inverter and let them run from that and they can swap back to grid AC if the batteries don't get charged enough.
I have decided that I'm going to use a 14s system and i'm going to arrange my packs like this
84 x NCR18650Bs in 14s6p = approx 20Ah at 58v (going to charge them to 57.4v ~ 4.1v per cell)
98 x NCR18650BEs in 14s7p = approx 22Ah
112 x LG B4 in 14s8p = approx 19.2Ah
All in all i should have somewhere close to 3.5kWh pack to play with. I'm going to mount it outside my house and bring the wires in (only on the wall outside, 1-2 metres max) to the inverter which i'll then connect to my stuff inside.
What I have not decided yet is if I should make one giant battery pack, or split them into three. Splitting has the advantage that all the same type of cell will be bonded together. One large cell means it's easy to use a BMS like batrium with only 14 longmons ... not 14 x 3...so that point I'd like to ask if anyone has any advice on?
Today I purchased the 48v 3000W hybrid inverter. Not really heard of this brand but it looks very similar to the MPP Solar style ones.
This one is 230V AC (I live in the UK) not sure if links are ok so i'll just post a pic. With today's ebay discount, I saved 50 on the total price of it.. so I'm really hoping this one works
Let me know what you think of my proposed design and I'll be updating and adding images as the stuff arrives.