I have been using heavy duty cables to restrict the voltage into a forklift pack,

This is a heavy duty 72volt forklift charging cable approx 14ft long. if I connect it to the end of a 66ft long 64 sq cable running from my 330watt x 72v array on the lawn to the 48 volt x 400ah forklift pack, i can restrict the incoming voltage to the pack down to 53 volts, Open voltage in the nearby andersons can be 85+ but the moment it is connected to the pack, it drops to 53v and refuses to rise above 53v absolute max..even in prolonged sunlight.
So i remove the forklift cables

by undoing these pair of Biff special bolt on connectors, insulated with plastic from water bottles,and taped together with ordinary insulating tape,,crude but rather effective. Then I gently connect up a set of 64sq cables and clamp them on to the forklift pack,

and as you can see the voltage jumps up into the late 50s. it will peak @ 59 volts no matter how strong and long the sun shines.The only thing you have to watch is the danger of the acid in the pack sizzling and fizzling away. So it is not a good idea to leave it such, unattended while not under load.. I have had this pack for a good few years now. I built the shed with it, the same 330watt panels can dish out 450 watt. The system drove my little cement mixer, drove the grinders and drills,charged cordless,s without ever being discharged. The whole lot was looked after by a 1kw chinese controller/inverter which can still perform perfectly when needed.
It is interesting that a large lump of copper cable at the end of the 66ft of 64sq can act like a controller. It does have an anderson connector in the middle of it,,if that would make a difference but i think it is just the amount of copper that the volts and amps have to try and push through to finally get to the pack that creates the resistance and lowers the voltage.
So one could work out the weight and the length of the copper required to keep a set voltage from a set array, to a set pack under control without getting too fancy.
Biff