Last fall I bought this portable air conditioner (note the unit has since been discontinued so the link may die) on Amazon for $800. I had experience with a BougeRV brand “cordless” cooler and that experience was fine so I thought this might be a good purchase as well. There was one caveat, my goal was not to procure an air conditioner but rather a heat pump. As I mentioned it was the fall months in Minnesota and I was actually looking to keep an enclosed space warm, not cool.

I did my fair share of research and found there was no good reason that I should expect this device to act as a heater for me out of the box. At the same time none of the other brands such as EcoFlow or ZeroBreeze appared to offer out of the box heating either. As such I figured not only might I end up having to do some hacking to get the outcome I wanted, I may even destroy the thing in the process so why bother spending a bunch of money on a fancier brand-name.

Sure enough – out of the box the device won’t act as a heater, at least not in any environment where it’s colder than 60 degrees Fahrenheit. The time that I discovered this I had some other tasks that I needed to take care of so I didn’t get excited about my situation there and then. The non-heating unit got shuffled to the back of the shop where all the other todo projects live. Well, here we are in Minnesota springtime and I have use for low-power portable heat source again.

Disclaimer!

Standard stuff. If you break your AC, electrocute yourself, kill yourself (there is a beast of a capacitor inside that’s probably capable) burn your house down, etc… I am not responsible. You shouldn’t perform this modification unless you have a rough understanding of electrical theory and are somewhat handy.

What are we working with?

So this is the unit I hacked. While I can and will give detailed instructions on how to perform the same hack I did, the theory behind how this works will more than likely work for just about any portable air conditioner so no matter what make model you have you can probably roughly follow my instructions to achieve the same outcome. Disclaimer above still applies obviously.

Other things you’ll need
– basic electrical tools: strippers, cutters
– X-Acto knife will be handy
– soldering iron and solder
– Philips head screwdriver
– some heat shrink tubing & a way to heat it
– a drill with a step bit if you use the switch I did

Theory of the modification

So all air conditioners are also in fact heaters … more generally they’re heat pumps. They operate by extracting thermal energy from areas with a lot of energy and move it to … somewhere else. Read all about it here, but put simply there is no such thing as “making cold” … it’s just moving heat from one place to another.

The intended process of this portable AC is that it sucks air in on the front panel from your personal surroundings such as inside your tent, it sucks air in on the rear panel from the area that is not your personal surroundings, inside the plastic box it transfers heat energy from the air in the front into the air in the back, then it discharges the air back out from where it came. The device only really works if you have a barrier between your “comfortable” atmosphere and the rest of the world, such as walls or whatever. The device can be ducted on either the front of the back (super handy for our purposes here) so the device can be inside the tent discharging air to outside, or outside the tent and just moving conditioned air in and out. In order to turn this device from an air conditioner(/cooler) into a heating device all we have to do us turn the unit 180 degrees so that instead of ducting the cold air into our “comfortable” atmosphere we duct the hot discharge air into our space. Tada… done.

Except…

This device only “cools” to 60 degrees. This means if you are camping in 40 degree weather it will think it has successfully done its job and while it will still move air around it won’t be exchanging the thermal energy from one side to the other. In order to remedy this and get the device pumping heat again all we have to do is convince it that it’s warmer outside than it really is.

I took mine apart so you don’t have to

… well at least not all the way.

I’m not an HVAC expert so I didn’t know what I’d expected to find, but I knew where I expected to find it. I tore mine apart further than necessary, the only access we really needed was behind the left (as you’re looking at the front) side-panel. In order to get into that panel you have to take the rear panel off and 1 screw out of the front panel:

Once all of the screws above have been removed the back should flop off and the side should slide back to give you access to the innards.

The heart of the hack

Since our goal is to trick the unit into thinking it’s warmer than it really is, we need to find the source of the temperature reading for the “comfort” side of the unit. As logic would dictate, this is going to be at the air-inlet on the front of the unit. There are 2 thermistors in the same general area, the one we’re looking for is very much at the front and not on the side:

The thermistor is a simple circuit that has a changing resistance based on sensor temperature. Apparently, there is a standard set of resistance values for HVAC thermistors, but for my purposes and just to make sure that this unit wasn’t following some non-standard resistance values I tested it for myself. Note that in order to properly test this the connection has to be removed from the main board, this is why my unit was more torn apart than yours will ever need to be. A good resistor value for our purposes is 6.8 Kohm, it’s a standard size resistor and will trick the AC into thinking that it’s about 94 degrees Fahrenheit. Note that choosing a resistor that tricks the AC into thinking it’s even warmer will *not* change the output of the unit.

Preliminary testing

Before going through the effort of wiring this all up and closing it up I wanted to validate my concept. I cut one side of the thermistor wiring, stripped some of the insulation away on both sides and wired the 6.8 Kohm resistor inline. I put the unit outside in ~56-degree weather. The discharge temps hovered around 78 degrees – a full 20 degrees warmer than ambient. In the intended application the unit will be able to recycle its own air creating an increasing feedback loop of warmer temperatures, assuming the enclosure doesn’t leak too much. I suppose if this whole project turns out to be a bust due to lack of performance I’ll just take this page down.

Putting it all together

If you really want a hack job, simply cut the wire and wire in your 6.8 Kohm resistor and you will forever have a heater. Ultimately, I plan to use this unit as a proper AC in the summer months and that’s no issue with a little simple wiring and a single switch. Besides the 6.8 Kohm resistor I used these 2 items from Amazon:
– 3 pin male female connectors with pigtail
– 2 position SPDT rocker switch
The pigtail is a convenience thing in case you ever want to do any future maintenance and can be omitted if you so choose, however if you omit it you’ll still want to add a length of wire in its place so that you can put the switch somewhere safe. The switch type is critical however – you want specifically a 2 position SPDT switch. If you don’t like that one, choose another, but they type is critical.

The “before” wiring schematic looks something like this:

The “after” schematic looks like this:

To prepare I first put together the switch with the pigtail and also put the resistor inline. In my case the resistor needed to be on the orange wire so that it was shorted to the green wire when the switch was in the on position. Depending on how you plug stuff in your case may not be the same and you’ll want to do some testing.

Next is the integration of the switch into the AC unit. With some careful soldering, heat shrinking etc this project is pretty simple to accomplish. I’m not good at soldering small things (or large things for that matter) so it’s likely that your outcome will look better than mine:

Note that I did cut 2 wire ties to get myself some more slack. This made tying the orange wire back into the “uncut” thermistor wiring much easier.

Tidying up

Put your wire ties back on and tidy up you wiring out of the way. Make note that there are moving parts in there so be sure to avoid them, although most are quite a distance from this set of wires.

I drilled a hole in the side panel just above the power cord for my switch. It’s maybe not the best place for it, but there was lots of clearance behind it and any other sensible place would probably have required further disassembling the unit which I didn’t want to do.

That’s all. When I want the unit to operate as it did from the factory, leave the switch in the off position. If I want the unit to go into heat mode, switch in on position. I did some follow-up testing and it worked just as it did in my preliminary testing. Now hopefully I won’t have to bundle up as much in these Spring and Autumn months in the Midwest.

Bonus note

The Amazon and BougeRV website both give haphazard and often inaccurate power consumption ratings of the unit. In some quick KILL A WATT tests I found that the unit never even got up to 400 watts. This testing was in Turbo mode trying to cool a 70 degree room to 60 degrees … before the hack. I don’t know that it would ever draw more if it was say moved to a warmer or colder climate – my thermal engineering prowess cannot figure that out. That said I would definitely guess the output of this unit when it was outdoors to be on par with a 1000 watt resistive heater, maybe even more. I’ll try to gather some real statistics comparing it to a resistive heater and share that information in the future – as long as that data collection doesn’t cause me to be uncomfortable.