Dual 12v / 24v system?

Here is a question I challenge the most savvy electricians to answer: I have a Toyota 4X4 that is American and runs 12v's. I have a 24v Warn winch and I would like to run a dual battery system that runs 12v's normally and can run 24v's while winching. I have heard equally from multiple sourses that it can and/or cannot be done (safely). Are there dual output alternators that push out 12v and 24v, similar to U.S. military Huvees? Can a 24v battery be installed into the system and charged this way? Can you switch from dual 12v batteries in parallel to 24v's in series while winching?

Well, I think this is one the toughest tech questions to date that I can think of. What say you?  

It would be best to use a battery isolator and keep it a 12 volt system for the vehical.  Go to your local marine dealer and ask them about it.  

A Perko dual battery switch available from any marine supply house would allow you to run a second battery wired serial to produce 24v. Then you can use the switch to control the second battery's connection from either a 12v parallel connection for charging or a 24v serial connection for winching. You would not be able to charge and run your winch at the same time.

This is a common thing in boating applications where a 24v trolling motor is used.  

You would not be able to have a 24 volt system connected to the 12 volt system of the vehical.  In order to make a set up work like ftgiles suggests, you would need two battery swithes so you disconnect from the vehical electrical when you have the batteries connected in series for the 24 volt winch.  One switch disconnects from the vehical electrical and the other to connect the two batteries in series.  You would not be able to have the engine running when you have the 24 volt system in use.  A battery isolator would be used so you can charge both batteries when the engine is running.

It used to be common for ellectric trolling motors to be a 12/24 V, but it was either switched internally in the trolling motor or with wiring connection switched in the boat.  Not with a battery switch as suggested by ftgiles.  Sorry, no offense to you ftgiles.  Most trolling motors now are iether 12 volt only or 24 volt only.  The 24 volt system always is a pair of batteries connected to the trolling motor only.  A 24 volt system is NEVER connected to the boat 12 volt system.

Perko has been around for a long time and they are ok, but my first choice in battery switces would be Blue Sea Systems and the second choice would be a BEP Marine.

I would recommend using a 12 volt winch or switch the entire vehical system to 24 volts to use a 24 volt winch.  

No offense taken. "Common" meaning people do it, not common that it is right and certainly not that the boat was set-up in a full-proof way. If the switches are not in the correct position for each curcumstance (user error) bad stuff will happen.

I totally agree with you and it also sounds like some of the opinions he's already received that it could work but be somewhat risky.

The people I have seen using a 24v trolling motor this way, have had three batteries. They used a disconnect switch between the first and second batteries and then two switches to control the connection (serial or parallel) between the second and third batteries. I've also seen plenty of people wing nut their connection back and forth for charging.  

The attraction to a 24v winch would be the longer duty cycle. Since it would only draw half as many amps doing the same work, it would run a lot cooler.

But doing tons of winching, taking advantage of the longer duty cycle, and not having the engine running  would greatly lessen the advantages of the longer duty cycle. And the hassels of "switching", ya, probably not a solid plan.

"Free stuff" sometimes gets expensive. Unless the winch isn't free and then it's probably not a good overall value.  

couldn't you run a couple of diodes to isolate the second battery (the 24v circuit) from the main vehicle circuits and just have two seperate circuits... that way both batteries are being charged, the vehicle is running standard 12 volts, and you have a single circuit at 24 volts to run the winch... use the diodes same way you would run a one-way valve in plumbing... that way you can't backfeed that 24 volts into the 12 volt system... it would be tricky to setup... but if done right i don't see why it wouldn't work...  

problem is... once you get all the wiring in place... you're going to have an empty wallet... and if something does fail you risk frying your entire wiring harness...