r/18650masterrace • u/MyBatteryGuys • 13h ago
Thoughts?
Hey guys, wanted to get opinion on my custom battery build.
I had a client reach out about needing a battery for an old electric scooter.
The battery had specific requirements as he had old battery bay - it was a tight fit. 330x178mm and about 74.6mm of height to work with, so if the layout looks weird it’s because of the dimensions.
Specs:
- 7S8P - 56x EVE 40P 21700s (25.9V)
- About 32Ah, around 830Wh
- DALY 7S 60A smart BMS
Used 3d modeling and created custom holders for tight spacing to fit the measurements so I also Laser cut the copper busbars myself - modeled the pack in Fusion first, pic is the cut strip next to the CAD. The C ring cutouts are the spot weld lands, one per cell.
External battery level meter, Anderson SB50 output, comes with a 29.4V 4A charger
2 year warranty on the build
Charged $475 all in - design, cells, BMS, meter, connector, charger, assembly and full test cycles. One off custom job, not production work.
Two questions - anything you would change on the build? And was $475 reasonable, or should I have charged more or less?
The cost of cells was ~$220 and the charger, bms, anderson connector, and other misc (fish tape) probably another $80. So call it about $300 in parts, which left maybe $175 for the design work, modeling, cutting the busbars, cell matching, spot welding, assembly and the full test cycles.
The hours I put in definitely don't math out at $175, but it was a one off and I ate some of the learning curve. Curious where you all would have landed on price.