Outer Limits 4x4 Board

A quick question to those of you who would know more than me.
I have a 2005 Patrol with dual batteries- standard cranking (nearly 3 years old)and and aux battery - marine 70Amp/hr can't remember CCA 2years old. These are linked together with a Pirana DBS180S. I have a 9500lblow mount to install in the Nissan bar, which battery do i connect the winch to? Have heard cranking battery as this receives first charge from alternator. Or the marine aux battery as this would protect the starting battery, but recharge quickly after use?
BTW its being done Monday so all answers appreciated
Cheers
Matt

Been thru this recently on the Zook section was advised by all to connect Winch to the AUX Battery so as the car can always start and top up the AUX Battery for winching! Robb

The correct way to wire up a winch is to connect to the cranking battery and always run your motor while winching.

Best practice is to run your motor on high idle and winch for 60 second and rest for 90 while the motor remains on high idle, then repeat as many times as needed.

This style of operation allows both the alternator and battery to supply power while winching and then while resting, allows the alternator to replace the bulk of the power used by the battery while winching.

This type of operation also allows the winch to cool a bit between uses.

You could fit a marine battery switch between both batteries so you can share the load over both batteries while winching and will also allow more power to be stored in the same time, while resting.

Cheers

Thanks guys for the replies. Bogfrog, my thoughts were along the lines of yours, ie making sure the cranking battery can start the car. Drivesafe I read your thoughts when i searched this topic before posting and can understand that point of view too. But still just as confused.
Matt

connect it to the cranker, if you connect to the aux it will not maintain sufficient volts to run the winch. if you flatten the cranker you can always jump from the aux. the cranker gets all of the available current from the alt, the aux is connected usually with 6mm through the DBS and there is no way that size cable can even begin to keep up with the load of a winch

This could change depending on the isolator, but generally the alternator is monitoring the main battery voltage, and this determines the alternator output.

If you hook your winch to the auxiliary battery this battery is the one which will be drained, which is obviously the intent - to "protect" the main battery.

However, when the winch is "resting" and the alternator recharging the aux battery there will be voltage drop over the isolating device and associated wires - so the alternator is sensing a voltage above the aux battery voltage, and not necessarily charging as fast as it otherwise could.

I would connect the winch to whichever battery the alternator is sensing.

Hi Scott, not quite right. Very VERY few vehicles actually monitor the cranking battery’s voltage.

What voltage regulators do is monitor the voltage at the battery. This may seem like nothing more than splitting hairs but if you bare with me I’ll try to explain.

To actually monitor the cranking battery’s voltage, the regulator would have to first turn the alternator off, remove any current loads being caused by the vehicles use and then apply a known load for a short period of time and then a fairly accurate State of Charge ( SoC ) of the cranking battery could be determined.

Not very realistic!

Why regulators sense the voltage “AT” the battery is to allow for any voltage lose through the positive cable connecting the alternator to the battery as current demands change, to be corrected so that the regulator’s voltage setting will be supplied at the battery and not just at the output of the alternator.

this set up has a major advantage in that the battery can be a long way from the alternator but the voltage at the battery terminals will be correct at all ( most ) times.

Whether the current load at the cranking battery increases because the cranking battery is low or the auxiliary battery is low or because you have just turned on your 15 driving lights. It makes no difference what causes the current load, this increase in current demand causes a voltage drop which the regulator detects and tries to correct by making the alternator increase it’s output to get the voltage at the battery terminals back up to the regulator’s setting.

If you follow what I’m on about, you can also see why it makes sense to connect the winch to the cranking battery. The alternator is going to be working harder to keep power going to the cranking battery and the overall voltage drop to the winch is going to be lower, which in turn means that as the winch is going to be working at a slightly higher voltage, it will therefore use slightly less current while doing the same amount of work, which ultimately means slightly less ware on the winch motor.

mate i'm not much of a wiz on the electrical stuff but i do know that Most winch manufacturors won't cover a winch under warranty if it is connected to the aux battery.

From what I have read the winch should be connected to the cranking battery because that battery is designed for short heavy loads, like starting the engine or winching and recharges quicker.

Aux batteries are made for lighter loads over a longer period like fridges and lights, depending of course which sort of battery you have fitted as an auxilary.