Common port charging problem

Treebeard

1 µW
Joined
May 10, 2022
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I'm building a 20s8p pack with Samsung inr21700 40t cells. I have a 100A Daly common port bms. All cell and parallel group voltages were checked many times during the build. The balance wires are correctly installed, checked repeatedly, and everything seems to be hooked up properly. The Bluetooth on the bms comes up fine, corroborating all the info from the multi meter. Voltage is fine for the pack at the installed qs8 plug. I go to plug the charger in for its first run, and almost immediately white smoke starts pouring out of the connection, seemingly from the positive side. What did I do wrong? The charger is a basic 72v li-ion charger that only does 5A. Quite discouraged at this point given the time and expense already invested.
 
Without seeing a wiring diagram, pictures, etc., I can only guess that it sounds like the charger itself, or the charge port on the battery, is wired incorrectly (reversed wiring, for instance).

Note that if you get smoke out of a device (the BMS? charger? wiring? can't tell from your description), you'll probably need to replace the device before continuing, unless you have the ability to troubleshoot and repair it. The smoke usually indicates component failures; without fixing those you wouldn't be able to continue using the device the smoke came from.



Treebeard said:
I'm building a 20s8p pack with Samsung inr21700 40t cells. I have a 100A Daly common port bms. All cell and parallel group voltages were checked many times during the build. The balance wires are correctly installed, checked repeatedly, and everything seems to be hooked up properly. The Bluetooth on the bms comes up fine, corroborating all the info from the multi meter. Voltage is fine for the pack at the installed qs8 plug. I go to plug the charger in for its first run, and almost immediately white smoke starts pouring out of the connection, seemingly from the positive side. What did I do wrong? The charger is a basic 72v li-ion charger that only does 5A. Quite discouraged at this point given the time and expense already invested.
 
 

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