Heat from battery monitor shunt?

[LittleSister]

Does the shunt in the negative line for a battery monitor give off any significant heat?

I am considering the best location to mount the shunt for a battery monitor, and having limited space/options I'm considering mounting it under the fridge, but would not want heat being generated there.

It's a 500A shunt, but I don't have anything that consumes that amount of current. Biggest draw I have is for a small bow thruster, nominal 350A IIRC, and that would be used infrequently and only for brief bursts. In normal use the small fridge is the biggest draw, then autohelm, lights, domestic water pump, etc.

 

[geem]

Does the shunt in the negative line for a battery monitor give off any significant heat?

No

 

[KLBH]

It should produce no heat.

 

[LittleSister]

Thank you both. (I thought not, but wasn't sure.)

 

[kwb78]

Shunt resistors do give off heat - they are just resistors, albeit with quite low, but known resistance.
A shunt resistor creates a measurable voltage difference between its terminals, and that's what the ammeter will read to determine the current flowing. The resistance for a 500A shunt that produces a typical 50mV full scale would be 0.1mΩ.

If you use the formula P=I^2 x R, the power dissipated while 500A is flowing would be 25W. That's definitely not nothing and is enough for a shunt to become noticeably warm or hot, but as long as it's not in a sealed box somewhere it won't be an issue. This is partly why high current shunts tend to be made of multiple plates, as that gives more surface area for heat dissipation.

For your usage with a maximum of 350A for only short periods it won't get hot enough to cause any problems. The rest of the consumption won't be high enough to cause any significant heating.