Outer Limits 4x4 Board

i didn't put this in electrical as i am sure 80% never look there.

what size in mm2 are you using for a 12 volt highmount with a 6 hp.

i looked up and calculated the resistance and therefore voltage drop and was quite surprised.

I assumed current 500 amps

resistance specs from tycab (we supply their pvc for the cable (v90ht) which is 105 degree stable as well as uv stable)

used v=ir and got voltage drops for 10m of cable as follows

120mm2 0.805 v
95mm2 1.03 v
75mm2 1.36 v
50mm2 1.93 v

i chose 10 m as 1 have 2 batteries in the tray with the winch up front and am sorta allowing for the contact resistance and the worst possible routing case.

my view is that estimating the factory cable (std batt up front situation) at 50mm2 and 2m long i get a drop of .386 volts which is still far better than 120mm2 with the batts tray mounted.

do you notice the drop in speed due to the voltage drop which must be close to 10% worse than the factory setup?

shall i just get 95 or 120 and get over it??

don't want to go 24v even though resistance will half

cheers bru

what about the internal resistance of the battery ?

i am assuming this is fairly low. the batteries are fairly decent ones
delkor 31-900. 900cca each, 160 reserve, amp hour (20hr) 100

http://www.delkor.com/language/eng/product/specifi.asp

by what you are suggesting is the internal resistance the limiting factor anyway, thus the cable is an overkill.

cheers bru

nup - didnt meen it like that, just wondering if the battery did contribute much to overall voltage drop. I have no idea.

i maybe not thinking right after a few rums but hw are you getting less resistance with a 24V motor than a 12V

im looking at voltage drop formulas but im getting different answear to you not sure with difference to AC and DC though

for the same power , twice the voltage = 1/2 the amps. less amps = less voltage drop. resistance stays the same.

Do you have the room to mount the batteries closer to the winch? Or do you want them there for weight distribution.

You have assumed the worst-case scenario for cable length and power consumption though.

You certainly won't have 10m of run. That is crazy long.

I'm using 2/0 welding cable. 67 mm2. That is much more than enough. Most people don't go over 1 gauge (42 mm2).

Remember, speed is proportional to voltage. Torque is proportional to amerage on these motors.

120mm is an overkill and not fun to work with, espically trying to run it around a car. if you are worried about voltage you can parrallel up 2x 50mm2 cables which should also be allot easier to work with. in a high current situation like this you would stick to a voltage drop of 10% max. if it does drop anymore the motor will be working harder and inturn try to draw more current. inturn creating more load on the batteries and then increasing more voltage drop witch can cause the motor to stall creating massive current in the motor windings which inturn create heat which will more than likely end up burning out your motor.

How will you be charging these batteries? will the alternator be ran back to the batteries via another cable or will you charge these from a point in the cables that will be running the winch.

if you charge from the same cable thats running the winch and the charge point is closer to the winch it will then see the higher voltage from the alternator and draw all it can from the alternator till the alternator can not produce anymore currnent then it will get the rest of it's power from the batteries this is normally ok if you have a good heavy duty alternator but you have to be careful with some of the factory alternators and factory wiring from it.

Cheers.

95mm is perfect mate. It is easier enough to work with and is the choice amongst most winch challenge trucks. I would replace all wiring on the winch with it to.

LudaCris

the only reason i ask is 120 is the same price as 95 as i have 2 different sources. the batteries are there for waight dist. the cable length was over dramatised but will be close once its run under the cab to the other side and back to the front prob 7 mt.

Ive got 24v into a 6hp warn motor and the batteries at the back of the chassis. I used 75mm2 Narva (made by Piralli) automotive starter cable and with engine running charges at 28-30 volts a have a volt meter at the winch soleniod (relay) box and it drops to 24 volts with the winch working real hard. The winch works supurbly and wouldn't change a thing.

Wally