Winch wiring question (12V)

Anonymous Poster · Dec 10, 2002

Gary, I highly recommend installing a battery disconnect switch right at or near the battery. More vehicles burn for the want of a $25- switch than should.
I just had to replace the "automotive type" winch cable running to an electric crane on the back of a truck I bought cause it constantly drew the battery flat sitting overnight.

gws · Dec 10, 2002

Re: Winch wiring question (12V)

One issue I see is the plugs. The male plug should not be on the source voltage side (battery). This will usually leave exposed postiive voltage that could come in contact with the frame ground. Source should be female.

You can charge the trailer battery off the truck, but you should consider getting a battery isolator to keep back feeding and over charging.

dummy · Dec 10, 2002

Late reading this and it's a little confusing. The breakaway battery on my trailers are already wired into the accessory side of the wiring harness. As long as the truck is plugged in, they get charged through an isolation circuit. I assumed this was a standard design with the breakaway kits.

dummy · Dec 10, 2002

Meant to add a picture to the previous. The box in the lower left corner is the charger/isolator circuit.

TWINKLE_TOES · Dec 10, 2002

What do you think is inside of those fancy overpriced isolators?

One or more diodes. What I'm saying is they don't keep the Aux battery charged to it's full capacity.
If you would research this a bit I'm sure you will find this to be true.

Gary_in_Indiana · Dec 10, 2002

"I highly recommend installing a battery disconnect switch right at or near the battery"

I'm thinking just unplugging the winch from the battery will accomplish the same thing for about $25 less. /w3tcompact/icons/clever.gif

I think I may well need ot clarify a few things here. I don't intend to leave the winch on either the trailer or on the back of my truck unless I'm using it so it'll only be connected to battery power then.

The trailer sits far more than it moves so the idea of hooking up to it AND then connecting the trailer battery to the truck battery had some appeal so I could charge/top off the trailer battery that way for it to operate the hydraulics on the tilt bed even if I don't ever put the winch on.

Odds are I'll only use the winch for "dead" vehicles and will just drive the others on. I just thought that it'd be like running jumper cables between the battery on the running tow vehicle to the trailer battery to charge it or, in a worst case scenario, to power the hydraulics motor through the trailer battery in a pinch. Does that make any sense?

Anonymous Poster · Dec 10, 2002

If I'm reading what youre writing right, I'd opt to save a lot of time wiring the truck, and get myself a 30 foot set of plug in jumper cables to run back to the trailer when needed.
If the distance you'll be towing the trailer justifys it, I'd equip the truck with a #12 wire running from the ignition terminal to the battery on the trailer via the trailer plug to top off the trailer battery in route. I'd also equip that line with a 20 amp circuit breaker and a DIODE to prevent backflow from the trailer to the truck. Then again, what do I know, I've only been building equipment for 41 years effective Friday the 13th.

TWINKLE_TOES · Dec 10, 2002

Franz,

You can lead a horse to water......

Anonymous Poster · Dec 10, 2002

Twinkle my man, I'm an old fart who has been doing it for a lot of years, and unless and until you can show me where the diode in an expensive battery isolator delivers one bit more power downline to a battery than a single diode does, this horse ain't gonna drink or swim, let alone do the backstroke.
Right now I'm running several vehicles with lantern chargers, my service truck where the generator battery is charged thru a diode, and a few trailers that maintain their batterys via a diode, as well as handlanterns that charge thru a diode, and have yet to have a problem. Then again, I'm old enough to remember when a 5u4 vacuum tube was called a valve on one side of the Atlantic because it acts like a check valve to electricity.
When something works 100 0r more times, I'll take a lot of convincing it doesn't.

TWINKLE_TOES · Dec 11, 2002

Good response /w3tcompact/icons/smile.gif

unless and until you can show me where the diode in an expensive battery isolator delivers one bit more power downline to a battery than a single diode does, this horse ain't gonna drink or swim, let alone do the backstroke.

Nope, not going to do that, isn't any difference. The point was, a diode in the line only allows the battery to charge to ~ 50% of it's capacity whether it be from an expensive battery isolator or from one you might add. For the winch application this don't work. Your application sounds significantly different than a winch that wants to draw 400 plus amps plus under load.

To understand why, you need to examine the charge source and the battery chemistry. A modern alternator is a single wire device with internal voltage regulator. The regulator output voltage will vary from ~13.8 volts to ~14.4 dependent on the connected loads and the battery charge current demand. The automotive battery has a pretty easy life, supply high current during starting and after that the alternator supplies the connected loads. In normal operation the auto battery depth of discharge is only slight.

The auxillary battery will typically see a deep depth of discharge and deep cycle batteries are appropriate. The chemistry of the lead acid battery under charge will cause the terminal voltage to gradually increase until it reaches a transisition voltage of ~13.8 voltage, at which time it rises abruptly. High current charging above this potential will boil the electrolyte away. At the transisition voltage the battery capacity is ~50%. The alternator continues to supply reduced current to the battery until the voltage reaches~14.2-14.4 volts.

The following table (battery manufacture unique) is typical of the terminal voltage and state of charge for a battery that has been rested for 48 hours:

100% 12.80
75% 12.60
50% 12.40
25% 12.20
0% 12.00

You can see from this that the terminal voltage difference between a full battery and an empty battery is only 0.80 volts.

I you now subtract the forward diode drop 0.7 to 1.0 volts (dependent on forward current) from the requlator output 13.8 -0.7 = 13.1 V and 14.4-0.7 = 13.7V, you can see that the Auxilliary battery never gets above the transisition voltage for lead acid of 13.8 volts.(~50% capacity)

Some isolators use Schottky diodes with lower forward voltage drops (0.4 to 0.6 volts)at the expense of high reverse leakage and lower breakdown voltage, but the payback is small and there are better ways to work this problem.

older alternators with remote requlators can be rewired to compensate for the diode drop. Several manufactures offer adjustable regulators and dual output requlators in addition to smart (three state regulators) Battery combiners (voltage sensing switchs) are also offered.

What were the five tube types in the universal AC/DC superhetrodyne receiver?