Shunt very warm to touch

[frthompson]

Pictured is the system in my travel trailer with my newly built batteries barely visible though the center opening (8 eve 280 AH cells configured as two 12 V batteries), 2 JBD 150 A BMS, and some other Victron equipment. I was testing every thing out and when drawing 200+ amps the battery side of the shunt and two copper bars on the red disconnect in the bottom of the phot get very warm but not hot. At 100 amp draw they are not even warm. The four black wires on the right side of the disconnect are the negative wires from the two BMS. Does this sound normal or OK? I already checked and cleaned all the connections, and no other connections are even warm. Out of sight is my Victron multipluss 3000 and mppt charger.


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[DThames]

Resistance times the amps squared will be the power dissipated, so 200amps would make 4 times the heat of 100amps.

 

[Browneye]

That's a LOT of juice.
500A shunt?
Make sure ALL connections are tight, no washers under those lugs.

 

[mikefitz]

The heat is most likely from the disconnect switch, you could take this out of circuit for confirmation. Very few isolation switches operate without heating up at 200 amps.
Note if you operate the switch the Victron shunt will lose SOC value.

Mike

 

[frthompson]

I suspected the disconnect too. I will rarely if ever will be actually pulling 200 A, that was with the air conditioning running off the battery. Thought I should test it nonetheless, thanks for the quick replies!

 

[HRTKD]

That looks like a Blue Sea switch. It should be up to the task. It looks like your copper bus bar hanging off the switch is unsupported. It's short, but I would feel more comfortable if it was supported. I had a tough time getting the connections on the switch tight enough. I sure wish the studs were on top, not the bottom.

How thick are your copper bus bars? I have a similar setup and my copper bus bars are 1" x 3/8" and I've drawn almost 200 amps out of my battery bank to test charging an EV and running the air conditioner. Everything stayed reasonable temps - no hot spots.

FWIW, a switch is usually on the positive side, not the negative side.