Discussion of combining 24 and 12 volt systems

[tm america]

I got whipped on this site talking about chargers for 12-24 volt battery systems so I will avoid.
One good thing that came out of it though was there was a fella making some special brackets here where you guys could put up 12 volt alternators. Best idea yet. I would think almost any alternator would do, as long as it fit, but of course, that is assuming you use the 12vdc side for low current applications, meaning less than ten amps or so for lights, computers, special applications, but definitely NOT hooked up to your starter. Ha!

You can probably find him through the search engine using the right keywords.

the lowest amp alt that fits my brackets is a 40 amp the biggest is 100+amp..you can run winches,hydrualic pumps.. lights,, radios.blower motors,heaters whatever they make in 12 volts with less than 100amp draw so that doesnt limit you much at all

 

[rat4spd]

If anything I say is in correct I welcome being corrected and educated.

Do spelling errors count? Just kidding....

 

[3dAngus]

the lowest amp alt that fits my brackets is a 40 amp the biggest is 100+amp..you can run winches,hydrualic pumps.. lights,, radios.blower motors,heaters whatever they make in 12 volts with less than 100amp draw so that doesnt limit you much at all

There you are. OK, so this would be my first mod when I get my first vehicle. I like it.

 

[FireFighterHill]

The next option I wanted to bring up which is almost the same as using a 24v to 12v converter is a battery equalizer. Which in my opinion is the next best thing to having a separate 12v system.

Pros: Give the option of pulling both 24v and 12v for accessories from the equalizer. Discharges both batteries equally. Charges both batteries separately avoiding over or under charging. Can be utilized in 2, 3, 4, or more battery configurations depending on the equalizer. Some models have setting to avoid completely discharging your main batteries that are used for starting.

Cons: EXPENSIVE.
You still run the risk of discharging or damaging your main starting batteries if something goes wrong with the equalizer.
Can not handle the loads of a separate system.
Can be susceptible to damage from exposure to elements normally experienced in an MV.
And I said it once ill say it again, good equalizer's that can handle a decent load are not cheap.

 

[fasttruck]

Find out whjat the Army itself did with the M915, 916 eyc as tghey have a spil 12 and 24 volt capability with four ea 12 volt batgteries and one alternator. Is essentially a 12 volt vehicle with a 24 volt starter and botyh 12 and 24 volt lighting capabilities.

 

[FireFighterHill]

FT, I believe they do the same as the CUCV which is to use 2 separate 12v alts charging 2 12v batteries. or a an alternator like wolverine sells that puts out BOTH 24 and 12 volt. The alts don't see each other or the other battery as they are isolated from each other. The starter and glow plug though draws voltage from both batteries to get the 24v they need. That's the way I understand it, can anyone confirm this?

 

[tm america]

Find out whjat the Army itself did with the M915, 916 eyc as tghey have a spil 12 and 24 volt capability with four ea 12 volt batgteries and one alternator. Is essentially a 12 volt vehicle with a 24 volt starter and botyh 12 and 24 volt lighting capabilities.

i'm guessing those use the same type of electrical system as the hwmmv uses with a dual voltage alt....they have a separate regulater to turn on and of the 12 volt side and 24 volt side separately..it's a pretty complicated system and very expensive.. the alt itself sell for 1700..and a replacement regulater goes for 750..and even then the 12 volt side is only rated at 25 amps..If you have uncle sams money you can do what ever you want the rest of us have champagne tastes on a beer budget..

 

[plym49]

One issue you need to decide upon up front is what you are after. Maximum redundancy? Least number of components? Simplest installation and troubleshooting going forward? Or???

For maximum redundancy, 4 batteries provide the best flexibility. 2 for your 24 v system, 1 for the 12v system and a spare. With the right hookup you can swap them around so you always have power to start and run the motor. With the right switching you can just keep your original 24v alternator. Charge pairs of batteries at a time when running and then switch off/isolate the one being used for 12v stuff. Before it gets flat switch off to the next, restart the motor and then switch in the flat batteries -- etc. Perhaps operationally difficult to keep track of where you are at, but a tremendous amount of flexibility.

For minimum parts count, and if your 12v ampacity needs are modest, then tap off of one of the two batteries from your 24v system. If you have some 12v accessories that do not ground to the case (like some driving lights that have separate ground wires) you can run these off of the other battery to balance the load. But you need to understand how to wire lest you introduce a nice short, and forget about someone else working on your rig and figuring out what you did.

For a straightforward installation and ease in operation and troubleshooting, just add another alternator. Makes things really simple.

 

[OPCOM]

I combined 12/24V systems on my previous M35. I ran three #6 wires from the battery box 0-12-24V points up to a 2-pole contactor and from there to a battery equalizer. The 0 was connected to the 0 terminal of the EQ and the other two were switched. The contactor had 30A/440V AC contacts intended to be used to energize motors, so it was more than sufficient to run 100A intermittently (some may argue but consider LRA locked rotor amps ratings).

The contactor solenoid was 24VDC and actuated through an ON-off-ON switch so that in one ON position the contactor was energized, and in the other ON position it was energized when the truck power switch was turned on. The cold solenoid terminal was simply connected to the 0 wire.

From the battery EQ terminals ran 12 gauge wires for 0/12/24VDC under the cab and up in front of the firewall so they could be accessed under the hood and then cone into the firewall for accessories (RT246, CB, GPS, aux dash lamps, cigar lighter, etc)

Also from the battery EQ terminals ran three #6 wires for 0-12-24 up into the S-280 shelter. The o wire was bonded to the shelter's DC system ground (this shelter had that). the 12 and 24 wires ran to the pair of 100A DC magnetic circuit breakers. Some will complain that #6 is too small for 100A, but the breaker is 100A and the load was no more than about 50-60.

From the other side of the 100A breakers, I distributed the 12V and 24V throughout the shelter. I set up a 12v and 24v set of breakers so that there was a 24V bus and a 12V bus.

To the busses could be connected (by more of these breakers) two sets of 12/24V AGM batteries rated 95AH, and through other breakers each individual piece of radio gear and other accesories in the shelter.

This way, many things could be done by turning on the appropriate breakers. Note these kind of breaker is usable as a switch. I also installed two regulated 12V 35A DC power supplies in series and set them to 13.65VDC so that batteries could be eternally floated on that source. Aslo of course they were the primary power for all the gear in the shelter.

1. use the truck to charge the shelter batteries
2. use external 120V with the power supplies in the shelter to charge the truck batteries, either bank of AGM batteries, or all
3. use the onboard generator to perform #2 above.
4. charge one set of batteries while using another
5. boost-start the truck by switching all AGM batteries and the truck's batteries onto the DC bus in an emergency

There are wiring diagrams and pictures of a couple of the black surplus 'rockwell collins' breaker panels of this at the link below. It shows what the breakers look like. These breakers can be bought surplus for $5-10 each in many Amp-ratings. This solution is far better than fuses and also better than thermal breakers and self-resetting breakers. It is very rugged both electrically and mechanically.

Last pint - -I soldered every wire connector and lug. Crimped then soldered. That is impotant. There was never any sort of issue and this was run for >5 years. The ultimate goal was safety and plenty of power.

This is perhaps more than most people want, but there is no need to build out more than you want. I hope the wiring diagrams and the pictures are useful.
M35 Commo Truck 23 June 2007 - Field Day" with the Irving Amateur Radio Club

 

[Unforgiven]

The alts don't see each other or the other battery as they are isolated from each other.

That's not necessarily true. I found out the hard way that if you accidentally leave the lights on after shutting off the truck the 24V batteries will back-drain through the12V alternator to the +12V side of the 12V battery. The headlights will glow dimly (b/c it's only seeing 12V of potential difference). Eventually that would drain the 24V batteries & overcharge the 12V battery. Luckily headlights are visible. An "invisible" closed circuit might not be detected in time to prevent battery damage.

I'm running Wolverines system right now w/ a total of 4 batteries, 2-12 & 2-24. I did this so that I could jump start myself in case the 24V batteries have problems.

http://www.steelsoldiers.com/deuce-...off-switch-fuse-box-wiper-install-w-pics.html

If you install battery cutoffs on the + side of the batteries it will eliminate this potential problem.

 

[plym49]

I combined 12/24V systems on my previous M35. I ran three #6 wires from the battery box 0-12-24V points up to a 2-pole contactor and from there to a battery equalizer. The 0 was connected to the 0 terminal of the EQ and the other two were switched. The contactor had 30A/440V AC contacts intended to be used to energize motors, so it was more than sufficient to run 100A intermittently (some may argue but consider LRA locked rotor amps ratings).

The contactor solenoid was 24VDC and actuated through an ON-off-ON switch so that in one ON position the contactor was energized, and in the other ON position it was energized when the truck power switch was turned on. The cold solenoid terminal was simply connected to the 0 wire.

From the battery EQ terminals ran 12 gauge wires for 0/12/24VDC under the cab and up in front of the firewall so they could be accessed under the hood and then cone into the firewall for accessories (RT246, CB, GPS, aux dash lamps, cigar lighter, etc)

Also from the battery EQ terminals ran three #6 wires for 0-12-24 up into the S-280 shelter. The o wire was bonded to the shelter's DC system ground (this shelter had that). the 12 and 24 wires ran to the pair of 100A DC magnetic circuit breakers. Some will complain that #6 is too small for 100A, but the breaker is 100A and the load was no more than about 50-60.

From the other side of the 100A breakers, I distributed the 12V and 24V throughout the shelter. I set up a 12v and 24v set of breakers so that there was a 24V bus and a 12V bus.

To the busses could be connected (by more of these breakers) two sets of 12/24V AGM batteries rated 95AH, and through other breakers each individual piece of radio gear and other accesories in the shelter.

This way, many things could be done by turning on the appropriate breakers. Note these kind of breaker is usable as a switch. I also installed two regulated 12V 35A DC power supplies in series and set them to 13.65VDC so that batteries could be eternally floated on that source. Aslo of course they were the primary power for all the gear in the shelter.

1. use the truck to charge the shelter batteries
2. use external 120V with the power supplies in the shelter to charge the truck batteries, either bank of AGM batteries, or all
3. use the onboard generator to perform #2 above.
4. charge one set of batteries while using another
5. boost-start the truck by switching all AGM batteries and the truck's batteries onto the DC bus in an emergency

There are wiring diagrams and pictures of a couple of the black surplus 'rockwell collins' breaker panels of this at the link below. It shows what the breakers look like. These breakers can be bought surplus for $5-10 each in many Amp-ratings. This solution is far better than fuses and also better than thermal breakers and self-resetting breakers. It is very rugged both electrically and mechanically.

Last pint - -I soldered every wire connector and lug. Crimped then soldered. That is impotant. There was never any sort of issue and this was run for >5 years. The ultimate goal was safety and plenty of power.

This is perhaps more than most people want, but there is no need to build out more than you want. I hope the wiring diagrams and the pictures are useful.
M35 Commo Truck 23 June 2007 - Field Day" with the Irving Amateur Radio Club

It would be hard to not call that setup best practice. Really nice.

And crimping and soldering - that's the right way to do it. Followed up with shrink wrap and/or self-vulcanizing tape.

 

[jdgreen]

Has anyone tried to put dual alternators on the 250 cummins in the 809 series yet?