BMS main wires between two terminals

[k490]

This JK BMS I have the main current wires are too short to connect to the battery is it bad idea to extend them using a terminal stud. I wanted to go from the battery neg terminal to passthrough terminal to the outside and mount the BMS outside the battery box. That way bluetooth signal probably work better my DIY box is 11 gauge steel. See picture as an example waiting on proper ring terminals I thought I had all the correct ones but I decided to order 1/2 stud fastronix from amazon thinking it can handle more current didn't think about the ring terminals I have. Another issue is the wire on this BMS is 7 Gauge closest I can get is 8 gauge ring terminal to crimp on. I bought hydraulic crimpers I had used the kind hit with a hammer before it worked okay on my old 12V system.

 

[robbob2112]

Have you looked to see if the leads are soldered to the board or screwed to it? Ideally you would just replace the cables if they are not long enough.

7awg doesn't actually exist, they are using a metric size that lands between 6 and 8. That said you must go up in size not down. So if you replace or extend use 6awg not 8awg.

Make certain the wire is pure copper verse CCA. And to extend the wire use a pure copper butt splice. You can't trust the ones on amazon unless it is blue sea, temco, or another quality brand. If they are less than $3 each they are suspect. Here is a link to what you want.

Sites-WestMarine-Site

West Marine

www.westmarine.com

For the crimper I hope you bought temco or other quality brand. The dies is the cheap versions are usually metric but marked in awg, AMZCNC is one of the worst for this. And all the harbor freight ones are junk.

 

[k490]

The connectors and cabling was from batterycablesusa it's UL listed stuff I was thinking I could get this BMS wire right on the battery terminal. The terminals I just bought off Amazon seem to be UL listed they are stamped UL. Already bought the 8s see how they fit I did test fit 8 gauge terminal it fits over this soft wire on the BMS much better then a 6 gauge terminal would have needed lot of compression. The crimpers are not Temco I got them long time ago see how it works post some pictures. I haven't opened the BMS up have to do some mods to the case if I were to try and put larger wire in.

This is sort of what I was thinking I didn't see this picture until after I posted this question. I would keep my fuse on the positive terminal.

https://diysolarforum.com/threads/show-me-your-jk-bms-mounting-solutions.74867/post-949605

 

[k490]

Have you looked to see if the leads are soldered to the board or screwed to it? Ideally you would just replace the cables if they are not long enough.

7awg doesn't actually exist, they are using a metric size that lands between 6 and 8. That said you must go up in size not down. So if you replace or extend use 6awg not 8awg.

Make certain the wire is pure copper verse CCA. And to extend the wire use a pure copper butt splice. You can't trust the ones on amazon unless it is blue sea, temco, or another quality brand. If they are less than $3 each they are suspect. Here is a link to what you want.

Sites-WestMarine-Site

West Marine

www.westmarine.com

For the crimper I hope you bought temco or other quality brand. The dies is the cheap versions are usually metric but marked in awg, AMZCNC is one of the worst for this. And all the harbor freight ones are junk.

You were correct about having to upside to number 6 to fit over what they have this wire labeled as 7AWG odd that the #8 terminal I had fit must have been mis-labeled from a cheap Amazon assortment. The good news was I tested the cheap hydraulic crimpers I bought they do seem to make a good crimp. I did a pull test in the vice pulled hard as I could on that 1/0 cable could not get it to come out of the terminal.

 

[k490]

Here is what I came up with cheap hydraulic crimper wasn't working on the 7AWG wire I had to also crimp with my regular ratchet crimper put a dimple in that seemed to work.

 

[robbob2112]

Here is what I came up with cheap hydraulic crimper wasn't working on the 7AWG wire I had to also crimp with my regular ratchet crimper put a dimple in that seemed to work.

As close as I can see it looks like good crimps with little to no wings, so long as it passes the pull test should be good to go.

 

[k490]

I got it charging today at 100 amps the terminals on the B- side are getting warm 7 gauge with 6 gauge terminals around 90F warming up those wires. I probably need to try crimp it again with the other crimper. I'm wondering if I should solder this connection as well I know it's not a good idea because if it gets hot the solider can melt.

 

[robbob2112]

Solder is bad for this purpose.


If your recrimp doesn't solve the issue cut it off and do it again.

But wait, did you use no-ox-id special A or similar on the contact points?

 

[k490]

Solder is bad for this purpose.


If your recrimp doesn't solve the issue cut it off and do it again.

But wait, did you use no-ox-id special A or similar on the contact points?

Soldering fixed it wires still get little warm near the BMS now but not hot. I could not cut it off because it would be too short I would have to move the passthrough lug the wires are soldered to the circuit board. They got warm when I was charging at 125 amps I reduced charging to 50 amps because my usage on my utility looked odd 2k during peak then 12k right after peak was over. Takes longer to charge that is okay even discharging around 97 amps which is about 4800 watts it only got slightly warm now at the BMS side.

When the weather cools down little going to take the battery apart and go through all the terminals sand everything and use no-ox on it I'm getting 160 MV from the + battery terminal to the inverter + circuit board contact. There is some resistance I want to see if I can reduce it.

If I were do this over again I would buy the other JK BMS has the terminal connections. I don't like this 7 AWG wire it has 200C insulation but current seems to favor one wire more then the other. I took the BMS apart but the cases were glued in some way maybe sticky paste for heat I didn't go any further. I saw a video on Off grid garage he took it apart also wanted to change the wire but needed an adaptor on a torch flame hits one side of the metal plate use the other side as an iron. I have soldered heavy gauge wire to boards before run the risk of damaging parts probably not worth the trouble. The main issue is 6 gauge is good to 60 amps at 90C if I'm dumping 125 probably going to get little warm.