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Finished my solar powerwall build with 532 cells
Hi there

I would like to give a big thank you! I read and learned a lot here to finally figure out the ideal recipe for building my powerwall from used laptop and ebike packs. It is now fully operational and waiting for solar energy to come. Since I live in southern Germany and right now everything is covered in snow, the powerwall is getting a slow startup phase. It took about a year to harvest and build.

The components are:
  • MPP Solar PIP 3024 hybrid inverter, imported from Taiwan, basically contains a solar charger, battery charger and power inverter
  • 532 Li Ion 18650 cells
  • 3 Generic 60A 7s BMS with Bluetooth from Aliexpress
  • 3 200W mono solar panels

The first pack consists of a large 112 cell ebike battery which was donated for the project. Repacking all cells would have been a lot of work because the cells are glued together with some epoxy. Since the 8p14s pack was in good shape I split it in half and reconfigured it to 16p7s.

The second pack is made of cells from two less good ebike packs, repacked into 20p7s, the third consists of used laptop cells repacked into 40p7s.

Every pack is equipped with a BMS. It will cut off the pack when individual cells voltages are out of bounds or the current exceeds 60A.

The build process was
  • gather ebike packs from a bike shop in the neighbourhood
  • gather laptop packs from work and later from ebay because other sources were dry
  • dismantle, remove welder spots and glue
  • first charge with china TP board
  • settlement phase, sort out cells that discharged to much
  • capacity test on Opus, write capacity on cell
  • enter cell capacities in excel spreadsheet, use rePackr to group blocks
  • spot-weld with the excellent device from
A Raspberry Pi with Bluetooth speaks to the Inverter and the BMS, so I get a good systems status.

Balancing is looking fine, thanks again for this great rePackr tool! The BMS do have a litte balancing circuit too.

A master switch in my main panel allows bypassing the PIP Inverter if needed.

Right now there is little solar energy, it takes about three to five days to charge the pack. At 28 volts the PIP switches over to Battery mode and powers half of our apartment until the pack is down to 25 volts (keeping some energy for standby losses). The PIP switches to Line bypass mode until the pack is charged again. I expect it to stay in battery mode during the summer.

There is still room for one 40p7s, so I will continue harvesting cells but not actively buy more on Ebay.

DCkiwi, Church1182, Walde And 4 others like this post
Weiter so !!


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