DaveInDenver
Middle Income Semi-Redneck
The problem seems obvious in the 3rd video tear-down.
There's a plastic form between the internal busbar and the terminal.
Giving benefit, maybe running it insulated with a bolt was a failed attempt to be a fuse. That's a big benefit of the doubt.
This is not ideal, the guy in the first two videos is right. This is not safe mechanically as different materials expand/contract and there's no way to fix it without opening the case or/and a redesign. Even if it wasn't the electrical tie mechanically it seems kind of weak. If the plastic cracks that terminal flaps in the wind even if happens to not start arcing.
The battery itself (e.g. cells, BMS, thermal and current protection) may be safe electrically. This is a failure at the fuzzy boundary between battery and load.
The heat and arcing here is creating a failure mode that's basically the same as if you didn't do a good job connecting it on the tab. The location of the heat in proximity to the cells is more problematic, though.
Being internal in a case that is not intended to be opened or serviced it's incumbent on the supplier to do better. It would be different if the user could open the enclosure to inspect, look for deformation or loose fasteners. Maybe some iterations have a fuse or breaker to bridge this spot.
Since you can't do any of that it's on them completely. I would be concerned if these are in your system. Relying on the epoxy discoloration to indicate overheating isn't a comforting prospect.
There's a plastic form between the internal busbar and the terminal.
Giving benefit, maybe running it insulated with a bolt was a failed attempt to be a fuse. That's a big benefit of the doubt.
This is not ideal, the guy in the first two videos is right. This is not safe mechanically as different materials expand/contract and there's no way to fix it without opening the case or/and a redesign. Even if it wasn't the electrical tie mechanically it seems kind of weak. If the plastic cracks that terminal flaps in the wind even if happens to not start arcing.
The battery itself (e.g. cells, BMS, thermal and current protection) may be safe electrically. This is a failure at the fuzzy boundary between battery and load.
The heat and arcing here is creating a failure mode that's basically the same as if you didn't do a good job connecting it on the tab. The location of the heat in proximity to the cells is more problematic, though.
Being internal in a case that is not intended to be opened or serviced it's incumbent on the supplier to do better. It would be different if the user could open the enclosure to inspect, look for deformation or loose fasteners. Maybe some iterations have a fuse or breaker to bridge this spot.
Since you can't do any of that it's on them completely. I would be concerned if these are in your system. Relying on the epoxy discoloration to indicate overheating isn't a comforting prospect.
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