Junctek Battery Monitor shunt extremely hot

Hello, I have a Junctek KH-F as well as a Junctek KL shunt battery monitors. When I am charging my 200ah LifePo4 battery with my AC charger(40A), the shunt gets extremely hot and I noticed this can sometimes drop my charger from producing it rated 40A to maybe 33A. I wanted to adjust the screw on the shunt a few days and my hand was literally burnt the moment I touched the screw on the shunt(it was that extremely hot). Wanted to ask, is this how all shunts are very hot at say 40A. I connected my charger directly to my battery terminals, and the terminals were barely warm even after almost 2hours of charging. Is this how all shunts are usually very hot or is it the Junctek that is just poorly made.

Are your connections tight and was everything clean before installation?

Yes, my connection is tight

I haven't noticed any excessive heat with mine charging in excess of 150A.
I'll quadruple check it with the IR cam next time the suns out bright and the batteries aren't full.

42OhmsPA said:

I haven't noticed any excessive heat with mine charging in excess of 150A.
I'll quadruple check it with the IR cam next time the suns out bright and the batteries aren't full.

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Wow, 150A???? And mine is just 40A. What could I be doing wrong? And whats your battery capacity to be able to pump 150A into it

What is the maximum capacity of yours and is it the one that has the thick wire bars. Mine is 600 amps and has two lugs on each side to connect to.

Perhaps the wrong size shunt?
Connected on the neg side?
Should not get hot unless over amped.
I have one of those meters, has been fine.

Easyyokefilms said:

Wow, 150A???? And mine is just 40A. What could I be doing wrong?

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What size is yours? Your 1000% certain connections are good?

Easyyokefilms said:

And whats your battery capacity to be able to pump 150A into it

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765Ah, 48V.

Quattrohead said:

What is the maximum capacity of yours and is it the one that has the thick wire bars. Mine is 600 amps and has two lugs on each side to connect to.

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Excellent question and point. I'm running the 600A as well.

Pictures or it didn't happen.

Disconnect the shunt and measure the resistance across it. From that you can hook it back up and measure the voltage drop and figure the actual watts generated by it.

Good shunts are mfg by taking the strips of metal of known resistance and casting ends around them. Then to calibrate they cut slots to get them to exact resistance.

Cheap shunts they cast the ends separately and braze or solder them into place and calibrate by reheating one end an moving it slightly or cutting a slot if it is way off. If they did a bad job it can cause high resistance internally. And because you have a unit that calibrates to the resistance with no current through it, the shunt it can still indicate accurately.

If your shunt is getting hot it either has a bad connection at one end or the other, use a laser temp gun and measure the temp at both ends and see if one is much hotter than the other that is your problem. If the insulation is softer at one end than the other you can tell that way as well.