Pack #2 of 6. This one is only 8 x 27 because I used 2600mah cells. Its a bit over my target of 500Ahs but that's better than being under. I tried it with just 25 cells and it looked too odd. I had to extend the copper lug wire on the ends a little bit to make sure it still lines up with the other packs, but I'm stoked how it turned out. Loving this twisted wire busbar thing.
I have a bunch of 2200mah cells that are going into the next pack so it will be 8 X 32. Once its done I'll wire them up and put a charge in it for some testing. Stoked to have a place to share this stuff because as anyone who builds these things knows, it takes a lot of your time and sanity and its feels awesome to have a community to share it with. So thank you to everyonefor all the comments and likes!
@john mcCoy
Each manufacture is a bit different with their recommended low cut-off voltage per cell. Some makers say its safe to go as low as 2.5V, while other use the 3.5V figure. For my testing I use 3.0V cut-off. I've tested a few down to 2.5V but the curve drops off so dramatically below 3.0V that the power your getting out of the cell is not worthless compared to the stress its putting on the cell...if that makes sense.You might getan extra 50-75mah'sof energy but thedamage it can do to the cell is not worth it.When you push a li-ion to its max ( in either direction) it stresses the cell and can greatly reduce the life cycle. Since many of these cells are repurposed already, I don't want to degrade the cell any further an never go below 3.0V. If one of the cells I get from a laptop pack is already below 3.0V, then I charge it at just .050mah until it reaches the 3.7V mark and then slowly increase the current. If it holds the charge then I will cycle it three or four times to make sure it doesn't overheat or act up before I put it in the 'good' pile.
Safety for High Voltage (HV)disconnect: I havedisconnect switches (madeby SMAwhomake SunnyBoy Inverters) installedbetween my panels and the inverter (on each string), between the battery and the inverter, & betweenthe inverter and the fuse panel box. I only have the SMA branded switches because I got an amazing deal on thembut I'm sure any HV disconnect will work.I think a switch that can handle the high CURRENT is more important for most of our applications,
butit depends greatly on how your array is setup. I'll post a pic of the switches shortly so you can see the one I am using.
Thanks again everyone and I'm stoked and honored to be a member of your community.
SMA disconnect
AvgRageJoe..dude I built the bars based on your video. I love your humility man, who else would splice in the bloopers and out takes. I dig it. I'm going to check out some of your others now. I'm at the bench soldering for a few hours so I'll run your playlist. Thank again for the busbar idea.