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Norwegian 60kwh Powerwall SI8.0 REC BMS Leaf cells
Hi all,

I've been reading alot of the threads and thought it was about time to post about my project, and get some tips/help for my build.
Its based on 3 complete Nissan Leaf batteries + 3 modules, giving me 147 modules in a 14S42P setup. I will be using REC BMS and Sunny Island 8.0 battery inverter since i have a quite large solar system (22.8kwP BIPV) This will likely grow a little aswell, as i have access to very cheap solar (I sell PV through my own company in Norway)

I have seen 2 ways of connecting up the nissan leaf batteries, but have not seen anybody using fuses between the series. As my battery has a very high capasity, i thought it would be good to include fuses between the series in the design. Any input on this would be much appreciated! 

My plan for battery voltage is to keep between 3.65v and 4.05v. I would like to maximize battery life over capasity, thats the reason i'm building the battery so large.

For busbars, my plan is to use 4x15mm solid bar either copper or aluminium.

Any preference between HRC fuses and MRBF fuses? The MRBF seems small and nice, but are actually close to twice the price. (i pay 5.5usd for 160a HRC fuses and 10.3 usd for the MRBF:

Some pictures from battery picking:
Lifted the pack out from my trailer:
Open the cover:

Lifting the back half out of the encapsuling

Dismantling of busbar:

2 batteries stacked up
Redpacket, Zvonko000, chuckp And 4 others like this post
WOW!!!! Big Grin
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OMG ....quite an impressive powerwall. ^^
Batteries harvested: 2344 / Usable batteries: tbd (TBD%)

Cells tested: 1996 (Average: 1668 mAh) / Cells in production: 0 (00 %)
This is quite a setup Tongue I have a single car pack (using just 42 modules at 14s12p). I guess you are having a typo since you cannot end at an uneven number for your P or S without dismantling the modules?

Regardless the fuse - I doubt that you want the 160A fuse, since you won't be able to max out your inverter. I would suggest you go with some thick cables that can handle some peaks and reuse the main fuse of one of the batteries.

What I did with mine is re-use everything I could from the original pack. I ended up just buying cables from the bat and to the inverter - everything else was picked from the original battery. Here are some pictures of mine with a Battrium BMS (using Longmons since I originally planned going the 18650 route).

PS: Sorry for the mess Tongue
The inverter is rated to 9100w for 5 min and 11000w for 3 sec. What size of fuse would be recommended? @ 3.5v (lower than my plan) it will be 11000w/49v=225a. 250a fuse ok? MRBf fuses good stuff? Easy to get hold of 250a of those fuses. NH2 fuse holders are 4 times the price of MRBF holder.
(10-24-2019, 08:37 PM)sgrevskott Wrote: The inverter is rated to 9100w for 5 min and 11000w for 3 sec. What size of fuse would be recommended? @ 3.5v (lower than my plan) it will be 11000w/49v=225a. 250a fuse ok? MRBf fuses good stuff? Easy to get hold of 250a of those fuses. NH2 fuse holders are 4 times the price of MRBF holder.

Presumably the inverter has it's own fusing.  To me, I'd choose a fuse  'to protect the wire'  from exceeding its max amps.
100kwh-hunter likes this post
Yes, of course. On AC side, the inverter will be secured with a 40a fuse @230v. (max 9200w, and be limited to this in the software) Im thinking to protect the wires, but also internally in the batteries between the series, see the picture in first post.
For the inverter fuse, first I would look for the manufacturer's suggested value otherwise 250A HRC would be fine.
If you overloaded the inverter at either 9200W/5min or 11000W/3sec (225A), the time curve of the fuse would be longer & so would not result in nuisance blows.

Have you considered a 250A rated breaker with shunt trip? This way, your BMS can trigger shutdown if cells go out of spec.
If you can control the inverter & chargers via s/w you could get similar protection, but a shunt trip seems to combine the best features in one, eg:
- master system on/off switch (can use "fuse disconnect" units for this too)
- resettable (vs one time blow with fuse)
- can be tripped by BMS/controller

For the fuses in the battery, if you only have the one series string, then fuse = same as above. You might just use one in the middle of the pack?
Running off solar, DIY & electronics fan :-)
I woudl go with an S3N ABB Breaker on that side rated at 200 or 250A. If you cant get that one look for S5N instead that is bigger.
WuggyBuggy likes this post
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