Royally screwed up.

[Ver]

Brand new 72v 3kw kit, connected fully charged 72v30ah battery to the controller, reversed polarity…. Instantly blew the legs off the xt90s, fried my fingers a little but I’m the thankful it didn’t go any worse. Any chance my controller isn’t dead? I tested continuity over the battery leads and it beeped for a second then it appeared they weren’t shorted. Non of phase wires shorted together either.

 

[amberwolf]

Only real way to find out is to power it up and test it.

You can open it up and look for fried traces, blown parts, etc., or sit there with a multimeter and test parts, but I'd save that for later if it doesn't just work when connected correctly.

 

[neptronix]

What kind of battery do you have?

How's the battery doing, volt wise?

 

[fechter]

There is 'some' chance it will work OK. When the polarity is reversed, the body diodes in the main FETs conduct, which will limit the reverse voltage to around 2v IF nothing else blows up. It would be good to test the FETs for shorts before attempting to power up again. Unplug motor phase wires and measure continuity from each phase wire to both battery + and - wires in both directions. Each phase/battery combination should measure like a diode. If any look like shorts in both directions, something blew.
You can also blow traces off the board, so may be a good idea to open the case and look inside for any visible damage.

 

[Ver]

Only real way to find out is to power it up and test it.

You can open it up and look for fried traces, blown parts, etc., or sit there with a multimeter and test parts, but I'd save that for later if it doesn't just work when connected correctly.

Right, this might me the way. It doesn’t seem anything’s a dead short so I believe it’ll be fine, I just don’t wanna blow the connectors off again due to a damaged controller, maybe I won’t be as lucky this time. Does anyone know of an inline fuse I can use that’s got xt90s on it?

 

[Ver]

There is 'some' chance it will work OK. When the polarity is reversed, the body diodes in the main FETs conduct, which will limit the reverse voltage to around 2v IF nothing else blows up. It would be good to test the FETs for shorts before attempting to power up again. Unplug motor phase wires and measure continuity from each phase wire to both battery + and - wires in both directions. Each phase/battery combination should measure like a diode. If any look like shorts in both directions, something blew.
You can also blow traces off the board, so may be a good idea to open the case and look inside for any visible damage.

I see, I’ll tear it apart after work and check how everything’s looking and hope for the best.

 

[Ver]

What kind of battery do you have?

How's the battery doing, volt wise?

Triangle type battery, Samsung cells, 20s6p. I believe the batteries fine but in all honesty I haven’t even checked it out yet. I’ll have to see how it is later. I don’t see a reason why it would be damaged but you never know

 

[Ver]

I’m wondering if it’s possible the alarm/lock prevented any damage? I’m going to test the controller later but im hoping it could be a possibility that the lock prevented and current going into the fets? I’m not too sure how they work. Only thing I had hooked up was the alarm and the display.

 

[eee291]

I destroyed a Kelly with a incorrectly soldered xt90 once, it didn't destroy the connector like that though.
Whatever BMS is inside that pack it's not that good at detecting a short circuit event
I would have no hope that the controller still works but might as well connect it right way around and see what happens. Or maybe use a bench powersupply or some other current limited PSU.

 

[Ver]

I destroyed a Kelly with a incorrectly soldered xt90 once, it didn't destroy the connector like that though.
Whatever BMS is inside that pack it's not that good at detecting a short circuit event
I would have no hope that the controller still works but might as well connect it right way around and see what happens. Or maybe use a bench powersupply or some other current limited PSU.

I suppose the bms isn’t, the pack is designed to do 80a cont 250a pulse though, I suppose that contributed to it. I’d feel safer connecting to a limited psu instead of the battery again, but I don’t have access to a psu capable of 72v atm.

 

[fechter]

You can use a psu with a lower voltage just to see if behaves shorted.

 

[Papa]

Does anyone know of an inline fuse I can use that’s got xt90s on it?

Not specifically XT90, but will this inline cheapie do for testing? They also have HD holders rated up to 60A.

https://www.napaonline.com/en/p/BK_7822023?cid=paidsearch_shopping_dcoe_google&gQT=1

 

[99t4]

Isn't the XT90 keyed housing? How were you able to plug them together the wrong way?

 

[Ver]

Isn't the XT90 keyed housing? How were you able to plug them together the wrong way?

I had them hooked up incorrectly in the terminal block.

 

[Ver]

I took apart the controller, honestly the board looks spotless, I tested continuity between pins on all the fets and they appear to be fine. Capacitors seem spotless. Anything I should check specifically?View attachment IMG_4619.jpeg

 

[neptronix]

What's the voltage on the battery? i'm thinking it took the hit.

 

[Ver]

What's the voltage on the battery? i'm thinking it took the hit.

84v on the dot, only visible damage at all was battery side connection, nada past the terminal block.

 

[Ver]

I hooked it up to 12v, display turns on, however the alarm/lock does not function at all, wondering if it’s the alarm itself that’s damaged(internals look fine) or the controller, or if it’s the fact I’m running on 12v.. going to test on bike later today.

 

[Ver]

Tested controller, works flawlessly, can’t believe it survived that. Thank you all for your replies, i massively appreciate it.

 

[fechter]

Nice.
It looks like the connector contacts vaporized fast enough that the controller parts were saved.