Humvee Upgrade – M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories – Adjustable Converter

Humvee Upgrade – M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories – Adjustable Converter How do I power a radio or charge my phone in my HMMWV […]

Humvee Upgrade – M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories – Adjustable Converter

How do I power a radio or charge my phone in my HMMWV or M35A2 Deuce?

Since US military vehicles like the HMMWV and Deuce are usually wired for 24 volt electrical systems, installation of most consumer electronics requires some means of converting 24v to the required input voltage: usually 12v, but sometimes other voltages like 9v, 5v for USB devices, etc. There are a few ways to convert 24v to a lower voltage, which we will discuss in other articles. In this article I will show what may be the coolest method I have found… a tiny device that converts an input of 3.2-40V to an adjustable output 1.25-35V.
Humvee Upgrade - M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories - adjustable buck converter amazon

This model requires a bit of soldering, but some versions do not.

The BUCK stops here

Install an adjustable voltage buck converter to step down the voltage for your device.

If you are like me, then the idea of installing an adjustable voltage buck converter in, well, anything, never crossed my mind. I took an electronics class in undergrad, but I didn’t do very well.
Luckily, my friend John, a mechanical engineer and actual ROCKET SCIENTIST, was kind enough to show me how cheap and easy it is to put together a versatile little setup like this. Don’t worry, if you get one of the versions that require soldering, there are plenty of soldering tutorials on YouTube if you don’t have a friend like John to teach you.

Humvee Upgrade - M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories - adjustable buck converter to power intercomWhy install an buck converter?

Simple. These “buck converters” or “adjustable voltage regulators” can be had for as little as a dollar or two each, and let you adjust the voltage down to whatever your accessory device requires.
Need a 5v USB plug to power your phone?
     No problem.
How about 9v power for your intercom, or 12v for your backup camera?
    Easy peasy.

Well, this is embarrassing…

My unfortunate scenario is just one example of how these little devices can be incredibly useful. I fried the 12v input circuit in my portable aviation intercom (here is an article and video on using an aviation intercom in a loud vehicle like HMMWV) when I mistakenly hooked the input and output leads backwards on a 30A 24v to 12v converter that powered all of my 12v accessories. So, instead of stepping the voltage down from 24v to 12v it attempted to DOUBLE the voltage, delivering a bit over 40V. As soon as I hooked up the 12v power cord acrid smoke poured out of my intercom. It was fried!
Humvee Upgrade - M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories - adjustable buck converter - fried transistor

The black transistor in the center of this pic is melted in half!

… or so I thought.
Turns out, I only fried the 12v input circuit. The SoftComm portable intercom has a separate circuit to operate on one or two 9v batteries. So, I could still run the intercom off of 9v batteries. However, the 9v batteries only lasted about a week, with moderate use. Often less. I really wanted to be able to power the intercom from vehicle power, with a switch installed to turn it off when not in use. This is where the Rocket Scientist comes in… John showed me exactly what I needed to add a micro switch and power converter to my intercom. The converter allowed me to feed the intercom 9v power as if it were hooked to a 9v battery, from either the 24v HMMWV power or from a 12v source. The same setup should work for most small devices with low amp draw.

LM2596 to the rescue!

Humvee Upgrade - M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories - adjustable buck converter schematic

Found this schematic online. No idea if it is correct. It hurts my brain.

Here are the specs on the model I chose. There are other models with different input and output voltage ranges and current capacities.

  • Name: LM2596 DC-DC Buck module
  • Input voltage: 3.2V ~ 40V
  • The output voltage: 1.25V ~ 35V
  • Output Current: 3A( Max)
  • Conversion efficiency: 92%( MAX )
  • Output ripple: <30mV
  • Switching frequency: 65KHz
  • Working temperature: -45℃~ +85℃
  • Size: 43mm * 21mm * 14mm(Long*Width*Higth)

What you need

This set of tools and parts is for powering a device with relatively low current draw of up to 3 Amps. So, enough to power most phone chargers or small electronics. If you need more than 3A output, then you will need to research and figure out a higher capacity Buck converter that will handle your needs.

How to connect a converter

The basics will be the same for most installations. Here is how I did it:

Humvee Upgrade - M35A2 Upgrade – How To Install Voltage Converter For Electronic Accessories - adjustable buck converter - connection diagram

 

HMMWV stuff

More HMMWV articles can be found under the Humvee category menu above or by clicking HERE. You might also like the HMMWV section of our Amazon store where we have listed lots of replacement and upgrade parts for Humvees. We have also found a lot of HMMWV parts on eBay (link).

Suggestions?

Please leave a comment if you have suggestions on other HMMWV upgrades should consider, or you have done upgrades that we can share on Gear Report.

The Project Humvee Battlewagon

Gear Report acquired a real HMMWV (High Mobility Multi Wheeled Vehicle) from the US Army for use as our official field and shooting range vehicle. We have already posted about some of our upgrade projects (Project Humvee Battlewagon article links) and have a lot of really cool projects on the way. Consider subscribing so you don’t miss any of the cool reviews as we post them.
Here is our Project Intro (link) and our list of HMMWV upgrade projects.

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About Jeff

Jeff is the Editor in Chief of Gear Report and a National Shooting Sports Foundation Media member. He reports on the outdoor industry, reviews gear for camping, hiking, shooting, hunting, paddling, backpacking and other active pursuits. A USAF veteran, Jeff earned a MBA in Marketing and Health Services. He specializes in consultative selling and internet marketing. As the VP of BD & Marketing, Jeff provides sales and marketing leadership to MGECOM, Inc. and helps http://MGECOM.com acquire new clients in need of solutions for online merchants in need of Affiliate Marketing program management. Jeff founded and manages Cress Sales & Marketing LLC, offering online sales and marketing consulting and services to online merchants and service providers.