Running 12v accessories in my m998? What’s the best way??

[papakb]

For those people not familiar with HMMWV wiring and electrical systems in general the 24 to 12 converter that MarkM posted is probably the best way to go. This converter draws off of both batteries so you don't unintentionally drain one and it eliminates the problem of accidentally connection your 12v devices across the high side battery. When you do that the ground of your device is still 12v above chassis ground and can short out and cause fires worst case.

These converters are commonly available on auction sites and a simple Google search will get you plenty of results (and prices). The converter MarkM posted is nice because of it's small size, high current output and the fact that it's waterproof, which 99% of them aren't. Couple this to one of the Pulsetech distribution boxes and you have a 12v system with everything fused for safety.

While it's nice to have a dual voltage alternator it's a fairly expensive conversion and again you should have electrical systems knowledge to install one correctly and safely. For most of us out there the 60 amp alternators will provide enough power for your needs. So unless your running massive electrical loads like high power radios or supplemental lighting systems (non-LED) the 60 amp systems are enough. Beyond that they are well understood original equipment and spares are readily available at reasonable prices.

 

[diluted]

I had ordered my 24 to 12v converter before my HMMWV arrived.. once it got here I was surprised to see it had the dual voltage alternator

 

[Mikei998]

Thank you for all your info! I’m going with the plusetech !

 

[tmobileguy]

Sorry to bring up an old thread, but I am in the process of converting my M1123 to a separate 12v system. I am going to keep the engine and main components on 24v, but instead of tapping the second battery, I am going to install a third battery in the passenger rear compartment and run 12v from it. I do have a dual voltage 200 amp alternator of which the 14v tap charges at 50a and the 28v tap charges at 150a.
I have moved the 50a alternator wire to the 12v battery bank from the 24v battery bank it was on. The only other wire I had to move from 24v bank (wired to a single battery at 12v) to the 12v bank was power wire to the TCM. The TCM relay that uses 24v to connect the TCM power wire to the TCM when ignition is supplied is still wired to the 24v system obviously.

With my 12v battery bank, I am wiring up remote door locks for my X-doors, power windows for my X-doors, and other 12v accessories such as cigarette lighter plugs for USB ports, a radio, lightbars, and some other misc stuff. Winch will probably be 12v because of price, but I do like the idea of a 24v winch better from a pure power perspective.

To keep ignition control of the 12v powered items that will only be used when the vehicle is on, I am wiring a 500a 12v relay that will be powered from the 24v ignition system. Obviously, I am going to use a 24v to 12v step down before it gets to the relay so that it is the proper voltage. To complicate it more, after it goes through the step down converter, it is going to go to another SPDT relay on the non switched side of the relay. The switched side will be connected to a button that will be wired to the 12v battery. The reason that I am doing this, is because when I want to leave the truck off but still run the radio or other things, I want to have an override button that I can turn on, and it will allow all the 12v accessories to run without the vehicle being on so I don't deplete the 24v system unnecessarily. I also have a couple of solar panels wired to each bank with charge controller to keep the batteries topped off (or in the case of the 12v system, to help charge will its running in override mode).

The door locks and a few other items (solar panels obviously) will be wired directly to the bank (through fuses when needed) for obvious reasons. Can't exactly control remote door locks if it was cut off by the ignition.

I am debated on the lights and markers. They are LED so they can be run through either system, so I toying with the idea of wiring up a turn signal switch or trying to convert over and H1 turn signal and run it 12v. Jury is still out.

Anyway, long time lurker, first time poster (well, kinda...first time posting with something that is contributing, at least)

Questions, comments and ideas are also welcome.

Thanks,

Aaron

 

[tmobileguy]

Oh, and as far as the batteries, I found a battery tray on Amazon that works perfect for 6 bucks. So I have 4 of them. They are for a Group 24 batteries, I am running 24M7 batteries by Deka that I bought from Lowes for $103 a piece. I pulled out the 24v system with the 6T batteries and the tray (which was broken) and 2 of these trays fit perfectly across. I did this switch because the whole switch cost me $350, whereas the cheapest 6T battery I could find was $260 (and most were $500+) and the stock dual 6T battery tray is $80 brand new. So same money either way, but now I have a system that costs SIGNIFICANTLY less to replace if a battery goes bad. And at a 1000 marine cranking amps (the amount of cranking amps at 32F) per battery, that is more then sufficient to turn the motor over in any weather, but with me being in Florida, its probably overkill for a set of batteries that just need to turn a 6.5L diesel motor.

 

[Action]

Obviously.

 

[Milcommoguy]

Right back at YA... Cape Canaveral. Ask a question... Get questions.

Priority ONE... Don't mess with anything necessary to start truck and ride home. That's the wayback machine. IE; leave it OEM, military 24 / 12

What's going on with the 12 Volt doors? Motors, solenoids, remote control, key fob, etc ? Why can't that be part of priority one, if known power requirement are know? (can't be a drain unless kids are working the windows? maybe a little if remote receiver)

Free ideas..........
Charge number three battery "sacrificial" 12 Volt via a "RUN" control contactor. Don't think one needs a 500 Amp job ?

Provide a dash switch energizing battery three to say "12 VOLT BUSS ON" with an LED ? switch capable or slave a contactor. Feeding the 12 Volt toys.

12 Volt winch... ??? Maybe ??? Stay out of the swamps.

Send me the money saved on the converter. LOL

Mr. R. Goldberg at NASA, CAMO

 

[Action]

How many batteries are going to be in your truck? You kept stating “12v bank”.

 

[tmobileguy]

How many batteries are going to be in your truck? You kept stating “12v bank”.

deciding between 1 and 2. But one of the reasons I was using the term ‘bank’ instead of just saying 12v, even if I only go with one battery, was to avoid any confusion between 12v wiring that is wired off the 24v like the stock configuration uses, and the actual new 12v dedicated set up that I am moving to…

 

[tmobileguy]

Right back at YA... Cape Canaveral. Ask a question... Get questions.

Priority ONE... Don't mess with anything necessary to start truck and ride home. That's the wayback machine. IE; leave it OEM, military 24 / 12

What's going on with the 12 Volt doors? Motors, solenoids, remote control, key fob, etc ? Why can't that be part of priority one, if known power requirement are know? (can't be a drain unless kids are working the windows? maybe a little if remote receiver)

Free ideas..........
Charge number three battery "sacrificial" 12 Volt via a "RUN" control contactor. Don't think one needs a 500 Amp job ?

Provide a dash switch energizing battery three to say "12 VOLT BUSS ON" with an LED ? switch capable or slave a contactor. Feeding the 12 Volt toys.

12 Volt winch... ??? Maybe ??? Stay out of the swamps.

Send me the money saved on the converter. LOL

Mr. R. Goldberg at NASA, CAMO

So one of the reasons I am going with such a big relay (or really an isolator switch) is because if I do go with a winch, they can easily pull 500a when they are really bogging down. I have a Warn Zeon 12 on my Jeep JKU and it has yet to let me down, so I’m fairly confident that it would handle the Humvee as well. JKU weighs in around 5800lbs with the hardtop, 38’s, and other add ons and modifications.
Rule of thumb from what i have always heard with winch’s is to go 1.5-2 times the weight of your vehicle. My guess is the Humvee is going to come in around 1.7….

12v doors are the items you stated. Since they are aftermarket, I would rather run them all on my aftermarket 12v set up then tie them into the OEM stuff.
TCM is the only thing getting moved and that’s because I don’t want to split the alternator wire (bad idea) and I don’t want to run an alternator switch to monitor and separate the currents. Would rather just run the 14v tap right to the new 12v bank, that way, anything that goes awry, or possibly mis wired on my part, all happens on the new stuff and the OEM stuff stays the same…

 

[Coug]

If it were me I would run a 24v-12V converter to charge up the 12V battery and leave the TCM on the original bank, as well as the 14V tap from the generator. Probably tie an isolator in so that the 12V bank gets disconnected when the truck is turned off.

My reasoning for this is that I refuse to mess with the original wiring setup as much as possible. I'd hate to have the truck stuck in limp mode because someone left the lights on or the radio or anything else.
I'd also just go with a 24V winch due to the amount of load. A 50 amp charging circuit isn't going to keep up with the draw of the winch, and if you're adding in electric doors.
The other issue you come into is the 24V starting circuit, the batteries now have nothing to keep them balanced. The 60 amp 24V only system tends to eat batteries a lot faster than the dual voltage setup.
Plus you can get a DC-DC converter that will handle a lot more than 50 amps to recharge the 12V bank faster or allow for more 12V accessories.

 

[tmobileguy]

If it were me I would run a 24v-12V converter to charge up the 12V battery and leave the TCM on the original bank, as well as the 14V tap from the generator. Probably tie an isolator in so that the 12V bank gets disconnected when the truck is turned off.

My reasoning for this is that I refuse to mess with the original wiring setup as much as possible. I'd hate to have the truck stuck in limp mode because someone left the lights on or the radio or anything else.
I'd also just go with a 24V winch due to the amount of load. A 50 amp charging circuit isn't going to keep up with the draw of the winch, and if you're adding in electric doors.
The other issue you come into is the 24V starting circuit, the batteries now have nothing to keep them balanced. The 60 amp 24V only system tends to eat batteries a lot faster than the dual voltage setup.
Plus you can get a DC-DC converter that will handle a lot more than 50 amps to recharge the 12V bank faster or allow for more 12V accessories.

So, as long as the truck starts, it shouldn’t be in limp mode because the alternator will be providing current to the bank. I get what your saying though. The only disadvantage I could see would be if your 14v tap stopped working, the tcm might be SOL at that point vs the original setup would still be charging both batteries. Load balance would be thrown off but that’s not a major issue for the short term.

I’m thinking about your step down converter idea to charge the second bank. I haven’t researched them in larger amp configurations. Have others run them successfully and what amp converter were they running?

also, why does the single alternator setup have a higher battery failure rate? Is it because 60a is not enough to keep batteries topped off vs. the 150a maintains easier? Does one float charge vs. the other one not? Never looked at the differences between the two.

appreciate the insight FYI

 

[mechanicjim]

So, as long as the truck starts, it shouldn’t be in limp mode because the alternator will be providing current to the bank. I get what your saying though. The only disadvantage I could see would be if your 14v tap stopped working, the tcm might be SOL at that point vs the original setup would still be charging both batteries. Load balance would be thrown off but that’s not a major issue for the short term.

I’m thinking about your step down converter idea to charge the second bank. I haven’t researched them in larger amp configurations. Have others run them successfully and what amp converter were they running?

also, why does the single alternator setup have a higher battery failure rate? Is it because 60a is not enough to keep batteries topped off vs. the 150a maintains easier? Does one float charge vs. the other one not? Never looked at the differences between the two.

appreciate the insight FYI

For the 60 vs 200 amp, it comes down to where they make their power. the rating on all alternators (military call generators) is rated by SAE J56, which states at 6000 Alt RPM and 72 degrees F what they can make goes on the label. So in reality with most Alts on diesels running 3 to1 of engine that means at 3000 engine rpm they reach full/rated output. but at lower RPM they make less. on the 200 amp it makes about 150-160 amps(24v only) at 2000-2100 rpm(700 engine RPM/Idle. and the 60 amp makes less than 60 at that speed. so the 60 amp becomes overloaded for awhile at idle by normal vehicles loads plus recharging the batteries after restart, unless you gun the motor or drive it at speed for awhile. where as the 200 amp can just kinda chill at idle and supply enough power to feed batteries and vehicle loads.

 

[Coug]

So, as long as the truck starts, it shouldn’t be in limp mode because the alternator will be providing current to the bank. I get what your saying though. The only disadvantage I could see would be if your 14v tap stopped working, the tcm might be SOL at that point vs the original setup would still be charging both batteries. Load balance would be thrown off but that’s not a major issue for the short term.

I’m thinking about your step down converter idea to charge the second bank. I haven’t researched them in larger amp configurations. Have others run them successfully and what amp converter were they running?

also, why does the single alternator setup have a higher battery failure rate? Is it because 60a is not enough to keep batteries topped off vs. the 150a maintains easier? Does one float charge vs. the other one not? Never looked at the differences between the two.

appreciate the insight FYI

For the 60 amp, it's because it is 24V only.
The front battery tends to charge a little higher than the second battery, and over time this means that the front battery overcharges, while the rear battery undercharges. Easily taken care of by rotating the batteries every month or two, but that rarely happens when you're talking about 70+ lb batteries.

One thing I would like to correct that you keep mentioning, the 200 amp dual voltage generator is not 150 amps of 24V and 50 amps of 12V. It's 200 amps of 24V, and up to 50 amps of 12V that is taken out of that 24V (which would be equivalent of 25 amps of 24V). I'm not sure the exact mechanism for how they do the 50 amps, if it's a separate set of windings or something else.


And yes, others have run step down converters and had no issues with them. At least the people who paid the money for decent converters. Some of the cheap chinese made converters tend to fail more often than better quality ones, but you get what you pay for.

Something like this one is about the minimum I would consider.

Amazon.com: Victron Energy Orion IP20 24/12-Volt 70 amp DC-DC Converter Non-Isolated, High Power : Electronics

Buy Victron Energy Orion IP20 24/12-Volt 70 amp DC-DC Converter Non-Isolated, High Power: Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

edit: The nice thing about doing a separate 12V bank is you can use deep cycle batteries (unless you plan to hook a winch up to it). You'll have much better battery life/performance with the lower draw/steady loads when the truck is off compared to using a starting type battery that's designed for short heavy loads.

 

[tmobileguy]

For the 60 amp, it's because it is 24V only.
The front battery tends to charge a little higher than the second battery, and over time this means that the front battery overcharges, while the rear battery undercharges. Easily taken care of by rotating the batteries every month or two, but that rarely happens when you're talking about 70+ lb batteries.

One thing I would like to correct that you keep mentioning, the 200 amp dual voltage generator is not 150 amps of 24V and 50 amps of 12V. It's 200 amps of 24V, and up to 50 amps of 12V that is taken out of that 24V (which would be equivalent of 25 amps of 24V). I'm not sure the exact mechanism for how they do the 50 amps, if it's a separate set of windings or something else.


And yes, others have run step down converters and had no issues with them. At least the people who paid the money for decent converters. Some of the cheap chinese made converters tend to fail more often than better quality ones, but you get what you pay for.

Something like this one is about the minimum I would consider.

Amazon.com: Victron Energy Orion IP20 24/12-Volt 70 amp DC-DC Converter Non-Isolated, High Power : Electronics

Buy Victron Energy Orion IP20 24/12-Volt 70 amp DC-DC Converter Non-Isolated, High Power: Power Converters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

edit: The nice thing about doing a separate 12V bank is you can use deep cycle batteries (unless you plan to hook a winch up to it). You'll have much better battery life/performance with the lower draw/steady loads when the truck is off compared to using a starting type battery that's designed for short heavy loads.

There would be no reason the 60a would charge one battery more than another in a straight 24v system unless there was some type of load imbalance going on with the batteries. The placement of the battery would have no effect on whether one battery receives more charge than another. What you are referencing is what happens on the dual voltage systems and the slight imbalance that happens because of the 12v draw)

The reason that the 60a does not fair as well, is because of the reason that mechanicjim listed above, it's because it simply does not have the power at idle to keep up with everything.

Also, the reason I keep referencing the 150a of charging power on the 200a alternator is because I have read that effectively, that's what the 200a alternator puts out. Mechanicjim seemed to also explain in detail why the 200a puts out 150a in explanation as well. To be honest, I didn't know why this was the case, just knew what I had previously read. But reading @mechanicjim 's explanation, it now makes sense to me.

My main issue with a converter is a failure. If the thing fails, and you are sending 24v power to 12v batteries, bad things can happen including batteries and devices that catch on fire, which is why I would like to keep them completely separated as possible.

After much thought, the best way to do this would be to split the 14v alternator power wire into an alternator distribution system box (like the ones that Sterling Power make

https://www.amazon.com/gp/product/B008BLYREU/ref=ox_sc_act_image_1?smid=AMVRK92LFYKXB&psc=1

)

...and let it charge the batteries accordingly. It's essentially a really smart relay, so if it fails, it will not connect the two systems like a step down converter would.

 

[Coug]

*deleted*

 

[Milcommoguy]

What's all these vehicle loads were trying to maintain?

My basic M998 currents draw. No air con, all bulbs incandesant. 185A starting and glow plugs 85A for the very short time they are on. Just running IP solenoids, fan solenoid 1A . All lights on and stop 9A. Wipers 4A, heater motor 5A. What's left?

Right after starting, engine idling, 60 Amp alternator (generator for the grunts) initially producing 22 Amps tapering to 7 Amps after 1 minute. Revving engine produced no further output and voltage stable at 28.4.

IMO... my normal truck loads are easily maintained by a 60 Amp alternator. Good set of matched batteries, charging system should be topped off before the first stop sign. The 200 Amp job is hands down in design and when it takes a dump, it's hands in the wallet too. Well, both are but 60 Amp is old school.

With the 200 Amp set-up the batteries can only take so much and if they do there is something wrong and get ready for some sparks and new parts. It does / can provide convenience for 24 / 12 equalization of the batteries. Wonder if it was another brain fart design just for 12 Volts and the 4L80E transmissions control box.

Now if your some kind of radio truck or other heavy current drains at idle... might want the extra capacity. Remember... there is a throttle control pull to spin it up a bit.

Arc welder under the hood, CAMO

 

[tmobileguy]

What's all these vehicle loads were trying to maintain?

My basic M998 currents draw. No air con, all bulbs incandesant. 185A starting and glow plugs 85A for the very short time they are on. Just running IP solenoids, fan solenoid 1A . All lights on and stop 9A. Wipers 4A, heater motor 5A. What's left?

Right after starting, engine idling, 60 Amp alternator (generator for the grunts) initially producing 22 Amps tapering to 7 Amps after 1 minute. Revving engine produced no further output and voltage stable at 28.4.

IMO... my normal truck loads are easily maintained by a 60 Amp alternator. Good set of matched batteries, charging system should be topped off before the first stop sign. The 200 Amp job is hands down in design and when it takes a dump, it's hands in the wallet too. Well, both are but 60 Amp is old school.

With the 200 Amp set-up the batteries can only take so much and if they do there is something wrong and get ready for some sparks and new parts. It does / can provide convenience for 24 / 12 equalization of the batteries. Wonder if it was another brain fart design just for 12 Volts and the 4L80E transmissions control box.

Now if your some kind of radio truck or other heavy current drains at idle... might want the extra capacity. Remember... there is a throttle control pull to spin it up a bit.

Arc welder under the hood, CAMO

View attachment 842388 View attachment 842390

I would like to be able to run my 12v ac, while winching someone out at night, with all my lights on that you can play a football game under, while cranking Metallica with a 2,000 watt stereo system, and be able to roll down all 4 windows down at the same time.

That's the dream right there.

 

[osteo16]

I’d look into something like this




Ocho out !!!

 

[Big Tom]

Get the pulsetech power distribution unit. I have them on both my 998s and they work great. Easy to install and listed on Eflea for 19.95 new in box.

the military used these before the duel voltage alternator.

I like them them because they have a built in fuse panel and the water proof and great price. Also they make the solarnizer which all fits in to one system.

pdu 735x650 12v 24v

Just looked up those pluseteck pannels they look great orders two only 14.00$ Don’t know why I never saw these . Thanks for the good info
BIG Tom