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

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Mikei998

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Lewiston NY
I just got a nice m988 and want to add some 12v stuff . What’s the best way to run my electronics ? Would like reverses lights led , car stereo, light bar and interior light . What is the best way to wire this stuff on a 24v system . Power converter , spod can I run off part of the battery? Any info would be greatly appreciated.....
 
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Mario

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Lights are easy to get in LED which normally works up to 30 volts, so no 12 volt required. For the stuff that has to be 12 volts, consider getting the two hundred amp alternator that has a 12 volt tap.

Sent from my SM-G955U using Tapatalk
 
Milcommoguy

Milcommoguy

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Many pros and cons to bring out 12 Volts from the 24 volt system.

While all of these systems use two 12 Volts batteries in series for the 24 volt needs of the truck (start, run, lights, wipers, horn, most military radios, etc) it's a good idea to keep the batteries matched, balanced, from the same lot at purchase (you get the idea) due to the need to have them work together for the total 24 Volts and Amp rating. As soon has one is abused, discharged, mismatched, brand X with brand Y, one from the old tractor, the other old one from behind the garage... Get ready for issues, just saying.

Dual output 24 / 12 Volt alternator system is a more forgiving charging system for this reason. Easiest way to grab 12 Volts for stereo's, radios of all types ham, CB, cell phones. Bad idea to run that 12 Volt winch, but some have tried. Yes you could / can run lighting, but with the multi voltage LED's, just go to the 24 Volt buss.

My guess most have the 60 Amp. 24 Volt alternator. (could be wrong) So, for all the reasons stated above about balance, I believe the 24 to 12 Volt converter (could have a 12 Volt equalized function too) is the better approach. Battery balance is key to a long lived charging system to start and run this truck. With this 60 Amp system... the minute you TAP into the 12 Volt side you just blew the balancing act. (simplified description)

Yes, you can for something of very low duty cycle and amperage. The day you forget to turn it off... read on.

At that point your going to have a dead battery. Where it gets "wacky" is when you try and start the truck. Your 12 Volt equipment Positive lead is now at the Negative leg of the good battery and POOF goes your nice stereo, etc. when you try and start as all the current as to go somewhere.

Over time (60 Amp system) the two batteries will never equalize and work effectively as one. One will over charge, the other never gets to full charge and then you can't make that beer run.

Not sure where we are going with a third battery. Diode isolated could work, but unequal charge on the 12 Volt leg in the 60 Amp system and have to stick it somewhere to bounce around.

In all cases, Ya might want to have a 12 Volt disconnect switch wired in, should you leave any 12 Volt equipment on, as in "ALL 12 VOLT SYSTEM OFF".

It's all about the juice.

CAM
 
98G

98G

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Action said:
He thought dual voltage meant a third battery for 12 volts. He doesnt know how it works yet.
Click to expand...
Exactly this. I read and learn.

My thought was to have the 12v side charge a completely separate 12v system to include a battery to run the 12v stuff when the truck isn't running.

Obviously I haven't done it. My own approach has been that if it isn't 24v I can do without it, but I certainly see why some people want 12v accessories. (My phone is dead frequently due to lack of 12v)
 
DatGuyC

DatGuyC

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98G said:
Exactly this. I read and learn.

My thought was to have the 12v side charge a completely separate 12v system to include a battery to run the 12v stuff when the truck isn't running.

Obviously I haven't done it. My own approach has been that if it isn't 24v I can do without it, but I certainly see why some people want 12v accessories. (My phone is dead frequently due to lack of 12v)
Click to expand...
I got a cheap little 24v-12v converter off ebay that I use to charge my phone in the hmmwv, works fine for little things and you dont have to worry about batteries.
 
jkcondrey

jkcondrey

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I am running a third battery, tapped off the 200 amp dual voltage alt. I run small lights, phone charger etc off that. I have voltmeters for both the 3rd batt and the other two(24v side). I have tested while running and the charges are always the same for both sides, with some fluctuation during cycles. I have had folks tell me it wont work, folks tell me why it wont work and what will happen if I try it. To date, six months later, still charging correctly, still running fine. As for your back up lights, just use 24v and tap into the harness under your shifter and put a switch in to activate them. Several posts about that.
 
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NV555

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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
 
Last edited:
someoldmoose

someoldmoose

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98G said:
Exactly this. I read and learn.
My thought was to have the 12v side charge a completely separate 12v system to include a battery to run the 12v stuff when the truck isn't running.
Obviously I haven't done it. My own approach has been that if it isn't 24v I can do without it, but I certainly see why some people want 12v accessories. (My phone is dead frequently due to lack of 12v)
Click to expand...
I know this is an HMMWV thread BUT the post is about voltage soooooo, my 2cents. On my M820 I am doing an independent 12 v system (like my travel trailer with 12 v and 110 v systems). Charging for the 12 v batts is via solar, or generator (mine has an 8 amp 12 v DC charger AND 30 amp RV AC plug aboard), or 110 v AC charger (15 amp "smart" charger) when plugged in to AC. 2 Group 78 deep-cycle AGMs give me plenty of power for the 12 v items I have in the trailer for over a week without charging other than solar. I also use the gennie to run my AC a/c in the box and charge the truck batts. (disconnected to go back to 12 v charging).

IF I ever win a lottery I would love to add a dual voltage alternator, but that's a dream for as far as I can see.
 
M

Mikei998

Member
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Location
Lewiston NY
I’m looking to run a good size led light bar in front . 2 small led lights off the back . A car stereo with wet sound sound bar and waterproof sub . Cell phone port / cigarette lighter. Can a power converter handle that or is a 3rd battery necessary ?
 
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