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What is the best way to combine the 3 wires from BMS C- or B- into 1 terminal/wire?

sawmonandnatalie

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Jan 22, 2021
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North Vancouver, Canada
Hi all,

What is the best option to combine Overkill Solar BMS wires for either C- or B- into 1 wire so it can be hooked up to Battery negative? I think each wire is 10 AWG.

Can we put a ring terminal on each end and connect to a piece of copper bar and have a wire coming from the battery negative also connected to the copper bar? Also instead of copper bar maybe we can use Stud Type Junction Blocks.

 
Strip off enough of the insulation, twist them together if you want and cram them into a single cable lug. However, before you do the crimp, arrange the wires and lug on the target terminal. That way the wires sit well in the lug without any stress. Then do the crimp.

Three 10 gauge wires is equivalent to one 5 gauge wire.


I combined the three wires into one lug for one of my batteries. The other battery I used one lug on each wire. The three wires into one lug method worked a lot better and was a cleaner install.
 
Thanks for the tips. For my install, the wires from the bms need to longer so I'm curious if anyone has thought about combining the three wires to one larger wire using a single crimp connector for a clean install. This would avoid crimping two or more lugs/wires just to connect the lugs with a bus bar or a nut and bolt. The finished connection would resemble a a butt slice.
 
Thanks for the tips. For my install, the wires from the bms need to longer so I'm curious if anyone has thought about combining the three wires to one larger wire using a single crimp connector for a clean install. This would avoid crimping two or more lugs/wires just to connect the lugs with a bus bar or a nut and bolt. The finished connection would resemble a a butt slice.
I used a 1/0 butt splice for 6 wires that came off a 200a 8s jbd bms. I used a slightly smaller gauge crimping die than the 1/0 in my hydraulic crimper to make sure it was a good solid crimp. Had to file the wings it created off.
 
Thanks for the suggestion. I had 2 awg wire available and used a 1/0 butt connector. With a bit of patience and a slight trim on the 2 awg, all wires could be snuggly fitted into the butt connector that I cut in half. Still need to crimp and add heat shrink, but I'm pleased with the results.
 

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This answered my question exactly! Thanks! So all 3 wires into one lug, or 3 separate lugged wires.. either way, electrically it's the same for both B- and C-?
And why 3 wires for the 4S 12v bms, and only 2 for the 8S 24V bms? Is this just because a 12V bank typically carries higher Amps? Does that mean 1 wire carries the charging load, and 2 carry the discharge load?
 
This answered my question exactly! Thanks! So all 3 wires into one lug, or 3 separate lugged wires.. either way, electrically it's the same for both B- and C-?
And why 3 wires for the 4S 12v bms, and only 2 for the 8S 24V bms? Is this just because a 12V bank typically carries higher Amps? Does that mean 1 wire carries the charging load, and 2 carry the discharge load?

More wires means more amps. The 24v version doesn't need to handle as many amps (half) as the 12v version.
 
More wires means more amps. The 24v version doesn't need to handle as many amps (half)
Any way to determine which wires are incoming/charging and which are outgoing/discharging? If in fact that is how they are designed. Seems logical to me, but I really don't know.
 
Any way to determine which wires are incoming/charging and which are outgoing/discharging? If in fact that is how they are designed. Seems logical to me, but I really don't know.

I don't know. I have three wires on my BMS. I thought all three were used for both charge and discharge since mine is a common port BMS.
 
Any way to determine which wires are incoming/charging and which are outgoing/discharging? If in fact that is how they are designed. Seems logical to me, but I really don't know.
All 3 blue wires are the same. All 3 black wires are all the same. A common port BMS uses the same wiring for charge and discharge.
 
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