After the Razor battery charger failed to peak charge and over charged the SLA batteries in my son's stand up scooter, this is what happened.
I got those out of the garage and made a 7S6P 25.9V 9Ah battery out of left over Sony Konion 18650V cells. I JB Welded 5.5 mm bullet connectors and a 7S balance connector to the side of the scooter. The result works great, the top speed is pretty much the same but the torque and acceleration is much better than before as reported by my 8 year old boy. He reported a ton more range also compared to the 7Ah SLAs.
I cut the ribbing at the bottom to make room and put some 5.5 mm bullets on the controller.
The connectors JB Weld to the side
After equalizing all the cells, I joined them in 6P strings, fully charged each string and assembled into a 7S6P pack. Then a final balance charge as a whole pack to test the connections.
Even with the ribbing trimmed at the bottom, there's a tiny bit of bulging on the metal strap. Not enough to worry about it.
First recharge after running all afternoon.