ammeter shunt for battery box

Ive got a wizz bang battery monitor for my battery box, I've mounted the screen but now ive got to mount the shunt on the (-) end.
My question is where can the shunt be put safely? Is it gonna get too hot to mount inside the box?
I do use the batterybox with an inverter at work to run a 700w mixing drill, so im guessing the shunts gonna get quite hot with that amount of current going through it.
Any advice

It depends on the shunt's capacity. If you're inverting to produce 700W you're probably going to draw somewhere in the 55-60A range. I would expect a battery monitor shunt ought to be rated at 100A or more (and if not, the designers should be kicked) so you SHOULD be fine just mounting it in the box, but take care to keep it off the other stuff. The resistance in the shunt is very small (and precise), so it shouldn't heat up much under load anyway.

Thanks for your help Tony...
I didnt realise when I bought the battery monitor that I was going to have to calibrate it to. Ive only got a 10amp multimeter so im limited to how higher load I can calibrate at.
Im having a few issues with the unit at the moment to be honest. Ive followed the instructions to the letter to calibrate the zero load point with an external supply powering the monitor, but as soon as I connect it the source battery with no load it reads 3.5amp....anyways ive gotta email the seller to see if he can help.

Something odd ive noticed when I connect my multimeter in series with my evakool fridge, is that it reads 4amps for about a second as the fridge starts to cycle but then throughout the cycle only 0.3amp then as the compressor powers down it jumps up to 4 again for a second.

Compressors are terrible things to manage. Inside, they have little pistons that compress the refrigerant. The act of compressing the gas requires a fair bit of power.

You can consider an electric motor to have two main stages - one is its stationary stage (not running) and the other is the moving stage. When moving, the momentum of the motor (a little like a flywheel) helps keep the motor turning over so the effort of pushing the pistons in is greatly overcome by this, and the electric motor just helps keep up the pace.

When starting however, it's a different kettle of fish, and you have to generate that momentum as well as overcome the effort required to push the piston in. The power (amps) required to overcome this is referred to in the refrigeration industry (also the house air conditioning manufacturing industry) as the 'stall current'. It's usually a lot higher than the operational current.

It's also the reason why household refrigerators cause the lights to dim when the compressor kicks in. Large amounts of current required to get the compressor going hauls the line voltage down momentarily.

On top of what Old Tony has said, it can also be refereed to as "inrush current" my 12vdc knowledge isn't what it should be but in the AC world, in rush for motors and compressors is around 7 times full load current. Hence why special curve CB are used on larger motors (D curve if i remember correctly)

this is why youthat brief increase of current and it then dropping down. when stopping i can only assume it has something to do with the last compression cycle of the piston and maybe a solenoid shutting at the same time making this last cycle the hardest to compress the gas into a dead head.

Ok that makes sense.
I was expecting to get readings of around 2-3 amps whilest its cycling, but its only reading 0.3amps??.

The current spike at the end could also be back EMF.
When the motor has the power shut off to it inertia keeps the motor rotating for a brief time. The motor for this brief time becomes a generator, and depending on how tricky the circuitry in your fridge is the "generator" produces a spike of current going back to the battery.
Ever unplugged a vacuum cleaner when it was going and seen a spark at the power point?
Same theory.

Man I'm no expert but some how i dont think the spark from the power point is produced by a collapsing magnetic field, and back current. Thats more a product of braking a current path and it wanting to continue its path.

If the compressor was to become a generator(?) for that brief period because of an emf i wouldn't expect a multimeter to pick up the current that quickly, let alone 3.7amps worth. probably need an oscilloscope to see generation and probably a few hunderd millamps of current.

Stands to reason that a DC motor in reverse is just as capable of producing current as it is in drawing it.
That's what I learnt in theory and practise way back in trade school all those years ago.....
Not saying that it is capable of producing a 4A transient current (although not impossible) but until Boostin gets the shunt calibrated there's no real way of knowing.
The vacuum story is what I was taught - could be a dirty great furphy!
But never seen a spark when I pull the plug on a high current load thats not inductive like a kettle

Not sayin I'm an expert - would never claim that!!!

Just throwin some other possible theories in the mix

yeah okay i see where you are coming from. DC motor with permanent magnates would produce a current but as a ac without a rectifier? Plus i thought most DC motors of this nature would have a PCB protecting both in coming and leaving currents?

As for the spark, i have never taken it into consideration if a resistive or capacitive circuit caused more arcing just thought it was more load based. Consider me schooled and off dig out some old tech books.

Probably should have paid more attention at tech then i did

Ive been given a couple of things to try and get the meter reading accurately.
But im still wondering why the fridge is only getting a reading of .30amp on my multimeter (not my uncalibrated battery monitor) whilest cycling? Surely it should be 2-3 amps....its an evakool 70ltr

Yeah if its only using 1/3 of an amp I want one!

I'll admit 0.3A is a bloody beautiful amount of current for a cycling fridge! To be honest I'd go grab another multimeter and test with it just to get a "second opinion".