Iv had one of these for a few years now
https://purefreedom.co.uk/product/100psi-shurflo-pumpstrainer-flowmaster-controller-back-plate-copy/
It’s strange you say the flow controller has been shorting out as it’s been happening to me as well for the last few months!
It could be 1st thing in the morning and it sometimes struggles to turn on even though my battery is fully charged. My hose reel reads 13.5 amps and the flow controller says 8.8 amps (even though they’re connected to the same battery). After a lot of faffing about switching it on & off , it eventually comes on and reads maybe 13.2 amps.
It pees me of the most when it happens (rarely) in the middle of a job 😡 .
No idea what’s wrong with it though ...
What jumps out at me here is that your getting a short if the cables move or are touched. As the system is 4 years old I am guessing the wiring is of a similar age as will be the connectors. There is a very good chance the connectors and possible fuse/fuse holder are corroded. There is also a good chance there is damaged cable somewhere. Both of these will cause volt drop along the length of the cable.
Damaged or corroded connectors are also more prone to overheating. As these heat up more current is drawn from the battery and ends up being wasted to heating.
The Cables supplied with the controllers are either 1mm or 2mm Tri rated cable rated to 18amps.
I would suggest before looking at the battery replacing the wiring is the way to go.
Copper is a good conductor of electrical current however it is not 100% efficient copper will also act as a resistor to current this means a small amount of energy is lost as it passes along the cable, Commonly referred to as volt drop. For this reason all cables should be as short as possible. A longer cable run than necessary can increase the effect of volt drop along the cable length.
Connectors and terminal blocks can also be a source of volt drop for this reason regularly inspecting your connectors replacing any that are worn or damaged is a good idea. Also check connections are secure with good contact to the copper core.
Check for any damaged cable where insulation has been chaffed exposing the copper core not only is there a risk of a short knocking out the fuse the exposed core can be a source of volt drop and become very hot in some circumstance,s this heat can be sufficient to melt insulation and fuse increasing the risk of fire.
An Issue with old connectors is corrosion something that is difficult to avoid in a wet environment such as WFP so keeping connections as dry as possible by placing cable into conduit is a good idea. Corrosion will increase the resistance of the connector and in turn volt drop across the connector.
A badly worn or corroded connector can become an energy wasting resistor. If your connectors are excessively hot they either need replacing or tightening, as your are wasting precious battery power.
A good connector should only feel warm to the touch in normal use.
