Bms replacement and the order of the eleven wires

[papangua]

Hello, this is my first post on the forum, it's about my replacement bms, it's 10s 36V, the 11-pin ribbon cable fits exactly, but is the cabling in reverse order or is it my idea? See the B+ and B- signs in the picture. No worries if you are not sure, I still get the blame, so guesses are welcome!

 

[A-DamW]

Sure looks to me like the order is reversed.

Can you unplug the ribbon cable from the battery so it is not live?

You can re-pin your ribbon cable by CAREFULLY(don't short the pins if they are live) inserting a pin/sewing needle/razor blade tip
under the pin latches(red arrows in picture).
You may have to split/separate the ribbon cable wires a little to have room to work.

 

[papangua]

Pff I hoped to avoid this chore. Each cable is soldered to the battery groups of poles, i guess that's what we mean live? The new bms came with it's own ribbon. I could also cut the existing battery cables at positions not adjacent with each other, join them, isolate them, one by one, with the matching cables of the new bms. It seems safer than repining. What do you think?

 

[A-DamW]

If you have a soldering iron, I would just solder the bare wire ends of the new ribbon cable into the old cable housing in the correct order.

Or if you have heat shrink tubing, remove one pin at a time from the old housing, put heat shrink, solder to new wire, heat shrink the joint to isolate, next joint...

 

[docw009]

I found that some BMS connectors can be inserted flipped, if the two guides on the ribbon cable connector are removed, but the pins must be in the center of the connector. The latter isn't always true. I did that once because I had no slack in the harness to rewire.

 

[A-DamW]

I found that some BMS connectors can be inserted flipped, if the two guides on the ribbon cable connector are removed, but the pins must be in the center of the connector. The latter isn't always true. I did that once because I had no slack in the harness to rewire.

That is a great point, I have done this before, and it works.
@papangua , Take a look at your old connector by holding it up to the bms connector in the correct direction, and see if cutting off the two yellow areas in the picture will allow the old one to fit.

 

[papangua]

I did the flip thing. It wasn't centered, I even cut / trimmed a bit of the heatsink to make it fit. Now I need to solder these two thick cables to the new bms board. There are holes there, I suppose i could use em. My soldering iron is a simple one and I have experience only with thin wires

 

[papangua]

I plugged the charger in and it does not seem to charge. 2A charger reads 42.4V and after a quarter of an hour the battery still reads 36V. Connections on the bms, negative from battery to B- and negatives to motor and charger to C-. Nothing on P-, I copied the connections from the failed bms. All contacts checked visually and with the dm. If I remember well, maybe I had plugged the battery's ribbon cable, which was wired with vice versa polarity, to the new bms, and left it like that for some minutes. I don't recall it as an image, but I recall having the thought that, I could do it safely since the charger is not connected to the bms. Maybe I even connected it and then realised the opposite polarity. I have fried the new bms right?

 

[docw009]

If you connected the harness backwards for a few minutes, yes, you fried the BMS with or without the B- lead soldered up, You weren't the first to connect one backwards.

 

[papangua]

B- surely wasn't soldered up... I remember readings from groups of batteries at 22V... so this voltage in reverse killed it. I only imagined current running from the charger to the bms and not from the battery. I feel ashamed and humiliated but it's sometimes good. Anyway thanks a lot!

 

[docw009]

I wired up a Daly BMS backwards a few years ago, and the red epoxy case by the connector bubbled up and melted while I was wondering why it didn't work,

Recently, I took a harness out of my bin and soldered it up properly, but not seeing that it was reversed for a different BMS. That one threw a big spark because I touched the grounded lead first and it hit the positive end. Didn't damage the BMS. They tell you to insert the connectors with the negative end first, Maybe for that reason.

 

[papangua]

it's a pity coz we waste time, money and resources. Many times i wish i didn't need to mess with anything. Less fun and convenience but more relaxed