Chevy Volt specific bms harness

Two required for 20s to 24s lithium conversion.
Parallel up to 3 modules.
Also used on solar power wall.
Universal fit 6s, 12s, 16s. Wire 18p to 18p pin to pin.
Use JST-XH as needed.

Also make pcb that plug into stock 2011 to 2016 modules, and fit in original bms enclosure.

Top picture parallels 6 12s modules. Used mostly for power wall, but hey, make a 100 mile Gem. :slight_smile:

bms harness 6p12sgem4kwh harness

BMS-24T $350 delivered conus.
In usa stock
Auxiliary fast charger 1500w 103v 25a, $350
Works with original charger for quick charge from two circuits.
All chemistry. Even LTO and pb.
C10325 search

Dave, this looks a lot more user friendly! The only issue I see is length of cables. Older GEMs had batteries run the front which would make for a longer cable run.
Kudos on what you have done. This may make a few more people take the plunge.

If you get frustrated there’s always the harness. Your way will look much neater if you can pull it off.

Interested in your harness. Have 3 48 volt Chevy volt modules from 2018 . Was sent harnesses from Ontario that don’t work .
I want to tie them in to my Chargery C4012b Bms.
I can send you a pic of what I have I have, if that helps so you can give me a price.
Let me know,
Thanks, Tim

Those were most likely my harnesses. Kelvin? Were they configured for Gen1 modules?
I believe that 2018 is the same as 2016. Gen2.
If yes, the harness can be reconfigured, unless some wires have been cut.
$50 + 25 reconfigure + $12 shipping.
Even if I configure it for you, it must be tested before plugging into charger.
Also there is a good possibility of blowing .68a module fuses with 1a balance current.

Boy I am glad I found you. I’ve read some of your posts, your knowledge is beyond belief! You would not believe the nightmare I have endured with this 6.9 kWh system relying on an “expert” It should have been up and running early October. Anyways it is now up at my cabin 6 hours north of Vancouver at my cabin. Snow is piling up and my system is down.
Below is a link to a video and some pics. Make sure you watch the video as I test these…".yellow bird harnesses " Also note that my 2018 batteries show a couple of real low voltage cells. I was told these batteries were tested for a week before shipping and now am offered an explanation that it may be an incorrect reading on my BMS.
So those are the major 2 issues… Low voltage cells and harnesses that are wired wrong. And getting my Generator to charge batteries.
Any help will be incredibly welcomed! Keep in mind I am 6 hours away from the system and will not be up there until the end of month. Thank you! Link…!AtvQznYuiIN11CqaGEpLMv9ZT6qy

The harnesses seem ok. I’m sure he tested them.
He may not be aware of the balance line fuses. High balance current of Chargery products will blow fuses.
You can plug harness into one battery at a time to see which fuse is blown in each module.
The all need to be replaced, or balance turned off. Let me look for a picture.
I clean and tin the top fuse connection and jumper each with a fuseable link.
A single strand of the yellow wire will work.
Not all 18 wires from plugs are needed. Cut a piece from a loose end.

May be different, you will only have 12 fuses in yours. This is a Spark module.
No small job doing it “hot”. Be careful or get help.


Wow! Thanks for getting back so quick. Would appreciate a picture of your fuse solution. Can you comment on the low voltage reading? with the 3 Chevy volt modules , should 36 cell readings show up on the BMS.?

I hope you forgive my limited experience in lithium systems.
I have done lots of dc and ac wiring but need to be walked through this fuse repair
They all need to be replaced, or balance turned off. Let me look for a picture.
I clean and tin the top fuse connection and jumper each with a fuseable link.A ysingle strand of yellow."
You circled 2 fuses.Is that all I need to be concerned with?
Explain what you mean by " clean and tin”
1 yellow wire for each battery?
Fuses and fusible links required .Can you give me specs and amounts on what I should purchase before I go back up? tk

You might as well jumper them all. 3 x 12 = 36 fuses. Ask Kelvin if he did this already. Then we need look for something else.
Not the complete yellow wire. One single strand is enough. This small wire will melt if there is a fault in the external balance wire circuit. ie. fuseable link.
All you need is some small electrical solder and a tool to clean the conformal coating that waterproofs the fuses.
My Tomberlin may have Gen2 modules. If it does, I can get a picture. I’m using small balance current, so I may not have bypassed the fuses.

Only 12 cells need to be monitored, as all 3 modules are locked in balance with the harness. Unless of course a fuse blows.

Does this make sense?
I tested at 2 amps to be sure.

Again…Thankyou… I think I get it .Thin wire becomes a fuse. I am jumping across the fuse housing . I am assuming I throw away old fuses. . Definitely something I can manage. Should I be concerned about low voltage reading on a couple of cells or this may be caused by the fuses being blown?

Leave the old fuses in place. Not worth the risk of removing them.
If fuses are blown, readings will be wrong or zero. Each fuse affects adjacent cell readings.
You might ask Kelvin. I’m in the dark as to what he did. Can only assume he tested it and fuses are blown.
Easy to check voltages once you are on site.

Finally … I am out of the dark on what’s going on… I’ll keep you posted when I get back. I hope you don’t mind dumb questions I can’t thank you enough…tk

I’m interested in a harness to interconnect a group of gen 1 12s batteries. Are the connectors or harnesses available?

Yes they are. How will they be connected?

I have 15 that are connected in parallel. I would like to connect them together in 2 groups. 7 in one group and 8 in the second group.

To be more accurate, I have 14 of the 12s modules and 2 of the 6s modules paralleled together. The two 6s modules are in series to equal a 12s module.

This is what the battery arrangement looks like if its helpful.

Need more information than that, unless you want to buy a bunch of harness and configure yourself.
Standard harness connects 3p similar modules to jst-xh plugs.
Expander/splitter connects two modules to one plug of standard harness.
PCB connects up to 3 standard harness to terminal strip.
Special harness connects two 6s modules to make it look like a 12s module.
… Custom made, but I can sell the parts to make your own.
… Male to female wires and correct plugs.
…Time consuming but not rocket science. :slight_smile:

I’ll add pictures.