Question for electrical gurus: Wiring a dual battery setup to support a 24 volt winch

[StG58]

I'm looking for a way wire a dual battery setup in a TJ to support a 24 volt winch. I read @ac_'s write up on installing dual batteries, and that helped. I've also read a ton of other resources on line about 12-24 volt systems and all I got was confused. Please use small words, I'm electrically stupid beyond the basics.

 

[Steel City 06]

The way I see it there are at least 2 ways to accomplish this:
1. 24 volt battery bank with a step up module to charge the bank
2. 24 volt battery bank with a separate 24 volt HO alternator to charge them independently (keeping stock alternator and battery)
3. 24 volt main battery and alternator with a step down module to charge the remaining vehicle circuitry


The step up module would be the cheaper way to go, but you would need a much larger battery bank because the step up modules are limited in the current they can provide. You would probably see better results with a 12 volt winch on a 14 or 16 volt car battery.

The independent alternator would be the best way to go, but also the most expensive. A HO alt should be able to provide about 7 horsepower continuously, which would power most of the winch, with the peaks being taken up by the 24 volt battery.

The step down module would be a
decent way to go, but the power remaining for the 12 volt system would be limited by the module.

Is there a reason you want a 24 volt winch as opposed to a 12 volt winch?

 

[Steel City 06]

What the car audio enthusiasts often do for 10,000 watt + systems is to use a 14 volt or even 16 volt AGM battery bank, as many as four 350+ amp HO alternators tuned to provide 16 or 18 volts charging, and then a step down module to convert the nominal 14-16 volts into 12 volts nominal to power the OEM circuitry.

 

[pagrey]

Is there a reason you want a 24 volt winch as opposed to a 12 volt winch?

Cheap humvee winch is my guess.

 

[StG58]

Rigging to 12 volt batteries in series gets me my 24 volt output for the winch, but the battery isolation side and charging is beyond my tech skills.

The difference in performance between the 12 volt and 24 volt version of the same winch makes it interesting enough to at least explore.

 

[Jerry Bransford]

I wouldn't do it without a 24v alternator, two 12v batteries wired in series will be drained pretty quickly without a 24v alternator to help keep them charged. Find a 12v winch.

 

[StG58]

Cheap humvee winch is my guess.

Nope. Fairly expensive Sherpa Mustang winch. The line speed difference between 12 volt and 24 volt is around 35-40%.

 

[Wildman]

You can do it making your own switching system or buy a switch. The hardest part Is going to be able to find a switch or relays that can handle the needed amps for the winch.

https://www.amazon.com/dp/B000KOQ3D4/?tag=wranglerorg-20{creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4583795260682522&psc=1

https://www.bing.com/search?q=series+parallel+battery+switch&FORM=R5FD1

 

[Steel City 06]

If you’re concerned about performance, consider buying a 12
volt winch and a HO alt. The 12 volt winches bog down when they exceed the alternator output and the voltage drops from 14 to below 12. A single HO alt can put out as many as 370 amps at 14 volts, which will power all but the most powerful winches at the stall load.

The HO alts can be reprogrammed to charge at up to about 18 volts, so you could run a 16 volt battery system on a 12 volt winch, and use a step down module to charge the OEM battery and power the OEM systems. Feeding 16/18 volts to a winch designed to operate on 12-14 will significantly increase performance at the cost of reduced duty cycle and increased risk of burning up the motor. (This statement is speculation.)

Personally I would not take the risk and just install a 12 volt HO alt and 12 volt winch, and tune the alt to charge at about 14.4 or even 14.6.

 

[Jerry Bransford]

You can do it making your own switching system or buy a switch. The hardest part Is going to be able to find a switch or relays that can handle the needed amps for the winch.

https://www.amazon.com/dp/B000KOQ3D4/?tag=wranglerorg-20{creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4583795260682522&psc=1

https://www.bing.com/search?q=series+parallel+battery+switch&FORM=R5FD1

You're advising something that just isn't going to work in reality. Coming up with a system to allow a 12v alternator to keep two batteries charged that are wired in series that actually worked would not be something I'd attempt despite my electrical/electronic background. Potentially doable by NASA? Probably. Would NASA approve it for use in space? Not likely. They'd either use a 12 volt winch or a 24 volt alternator.

 

[Wildman]

Why can't a alternator charge two 12 V batteries? Mine does with my dual battery system. With the switch it wouldn't be charging them in series but in parallel. I'm not agreeing or disagreeing with the OP's desire to run a 24V winch but he asked a question. People have done this before so it isn't rocket science. The hardest part will be finding a switch or relays that can handle the amps the winch will draw.

 

[Boinked]

Why can't a alternator charge two 12 V batteries? Mine does with my dual battery system. I'm not agreeing or disagreeing with the OP's desire to run a 24V winch but he asked a question. People have done this before so it isn't rocket science. The hardest part will be finding a switch or relays that can handle the amps the winch will draw.

Simple answer when you wire 2 12v batteries in series you not long have 12 volts. Its 24 volts.

When most people run 2 batteries in a jeep they run parallel. It remains 12 volts but has twice the capacity.

 

[Steel City 06]

A 12 volt alternator cannot charge both batteries in a 24 volt system at the same time. It would have to charge one, then the other.

When winching with a standard 12 volt or 24 volt system, a significant portion of the winch power is directly provided by the alternator. Without the alternator simultaneously charging both batteries, one will be required to supply the ENTIRE current required by the winch. Thus it will discharge rapidly. If the one battery gets depleted, the remaining battery and the alternator will reverse charge it and destroy it, which could cause a fire or explosion.

It can be done, but it is extremely difficult to do safely.

 

[StG58]

Luckily, this is all academic at this point. I didn't think about getting into the alternator when using the winch (duh!) The additional line speed is attractive, but not THAT attractive.

Thanks folks, for the sanity check. 12 volt it is.

 

[Steel City 06]

Luckily, this is all academic at this point. I didn't think about getting into the alternator when using the winch (duh!) The additional line speed is attractive, but not THAT attractive.

If you want a high end alternator, check out the following manufacturers:
DC Power Inc
Singer Alternators
Mechman Alternators

Any of those 3 companies will make you a bolt in 370 amp alternator (or any size 160 amps to 380 amps) for your Jeep. I recommend singer and DC first, but Mechman is also a good option. There are other companies out there as well.

Then you can keep your winch powered entirely on the alternator, so it will always see 14 volts instead of 12, so you WILL get the advertised line speeds, instead of bogging down once the alternator reaches its limits

 

[pagrey]

You might look into the Sec8 from Milemarker, it's 3.3 vs the 3.8mpm of the 24V Mustang. Not quite the speed but not too bad either, better than the Mustang 12V

 

[Wildman]

Luckily, this is all academic at this point. I didn't think about getting into the alternator when using the winch (duh!) The additional line speed is attractive, but not THAT attractive.

Thanks folks, for the sanity check. 12 volt it is.

A stock alternator will recharge your battery/batteries but it will take longer. Having a higher output alternator will recharge them faster. I have a dual battery setup in my TJ that isolates the two batteries for normal charging and so that they don't drain from each other. And then if needed you can connect them together in parallel when you need those added amps. It still doesn't stop the winch from draining the batteries but it helps.

https://www.dirtyparts.com/store/detail.cfm/BATTERY-MANAGER-CONTROL-KIT/pid-80492

This is the kit I have in my TJ. They also make a dual battery tray you can by as a complete kit.

This one is made for if you have A/C.

https://www.dirtyparts.com/store/detail.cfm/DUAL-BATTERY-KIT-97-02-JEEP-TJ---LJ/pid-80419
Non-A/C

https://www.dirtyparts.com/store/detail.cfm/DUAL-BATTERY-KIT-97-02-JEEP-TJ---LJ/pid-80418

 

[Boinked]

Due to my limited knowledge on diesel engines. I have found a few things.

Some larger trucks do use a 24v starting system. To my knowledge once glow plugs are hot the do not require power. So a relay will supply 24v to the starter while killing 12v power to the vehicle. Then one the start button is released it returns to 12v.

This system will not work on a jeep. Once 12v is lost the engine will die.

This is only about 24v start with 12v system.

There are some 24v vehicles mostly military.

If i am off base someone correct me.

 

[StG58]

The additional line speed appeared to be a cool gimme on the surface. Under closer scrutiny, it's not worth the effort. I do explore the fringes though, because that's where the progress comes from.

 

[Steel City 06]

Most lower amperage combination systems either use a step up or step down module to convert between 24 and 12 volts. IIRC, a Prius has a 200 volt main drive system, and then a 12
volt step down module to power the accessories.

The issue is that the step up or step down modules can only support a limited amount of amperage. So whichever system doesn’t get the alternator is almost entirely reliant on the battery to take spikes in power consumption.