Air conditioner 12vdc/24vdc install

owner

Well-known member
Feed that 40 amps into the MPPT controller
I had that idea too. The theory seemed fine to me. But unfortunately the MPPT will suck as much current as the PSU can possibly supply, or more! In the case of more, the MPPT blows its transistors as it happily tries to pump out more than its rated for. In the other case the PSU starts glowing red hot as it tries to supply its maximum current 100% of the time.

In the end I used a DCDC converter. This device will limit to its rated current, whereas MPPT won't. I can power the DCDC from the alternator or a mains->12V PSU (an old HP server PSU) via a switch.
 

Franny

Franny
I had that idea too. The theory seemed fine to me. But unfortunately the MPPT will suck as much current as the PSU can possibly supply, or more! In the case of more, the MPPT blows its transistors as it happily tries to pump out more than its rated for. In the other case the PSU starts glowing red hot as it tries to supply its maximum current 100% of the time.

In the end I used a DCDC converter. This device will limit to its rated current, whereas MPPT won't. I can power the DCDC from the alternator or a mains->12V PSU (an old HP server PSU) via a switch.
You’re right, the DCDC converter is the way to go. Doing some looking online it‘s clear that connecting an alternator output to an MPPT is a terrible idea- sorry I suggested it!
 
Franny , any more input on this system? Still pulling the same numbers? What’s the DB level of the interior unit?
Thanks . . .
 

Franny

Franny
Hi Richard, we’re on a trip to the east coast. We’re in Maine tonight, and getting down to mid 30’s so the diesel heater is the hvac of choice. We turned the ac on in Indiana and it put out very cold air so at least it survived 500 miles.
I’ll try it out tomorrow and send a dB level and watts report.
 

Franny

Franny
Eran, I thought you did a great job on that 110v minisplit and I admire your guts! Let us know how the 24v model works. Your’s should be coming with the digital display and a remote, jealous.
Measured power and dB spl just now in a parking lot with the doors closed, relatively quite outside.
It draws 605 watts with the evaporator fan on position 2. Position 1 is a little wimpy and 3 is loud and too much.
 

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eranrund

Member
Eran, I thought you did a great job on that 110v minisplit and I admire your guts!
I thought so too, until one of the flares leaked and eventually just exploded. It turns out the flexible lines like to twist around themselves as they move and change angles, which I believe was putting stress on the connections. I couldn't figure out a way to solve that and ensures such a sucky failure does not repeat itself :(
I decided that for the relatively small cost of this Chinese AC, I'd rather give it a shot since I like the idea of being able to put it under the vehicle. I'm still on the fence about whether I will connect it to my battery, or start with a beefy 110v->24v powersupply. Those go for around ~$250 from what I can tell, but it would significantly simplify the install. When I built my battery and mounted the inverter on top of it, together with the Electrodacus-controlled high-current contractor, I didn't make provisions for attaching a secondary high-load appliance. In retrospect that was obviously a mistake...
 

Franny

Franny
I thought so too, until one of the flares leaked and eventually just exploded. It turns out the flexible lines like to twist around themselves as they move and change angles, which I believe was putting stress on the connections. I couldn't figure out a way to solve that and ensures such a sucky failure does not repeat itself :(
I decided that for the relatively small cost of this Chinese AC, I'd rather give it a shot since I like the idea of being able to put it under the vehicle. I'm still on the fence about whether I will connect it to my battery, or start with a beefy 110v->24v powersupply. Those go for around ~$250 from what I can tell, but it would significantly simplify the install. When I built my battery and mounted the inverter on top of it, together with the Electrodacus-controlled high-current contractor, I didn't make provisions for attaching a secondary high-load appliance. In retrospect that was obviously a mistake...
Looking at your blog online I see that you’ve got 16 3.2v/100ah prismatic cells wired up into a 24v system. It would be so much more efficient to just add another DSSR20 rather than inverting to 110v and then back to 24v.
How are the 6 100w panels on the roof keeping up with your electrical demands? I see you have a microwave and maybe some other high draw devices.
 
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eranrund

Member
Looking at your blog online I see that you’ve got 16 3.2v/100ah prismatic cells wired up into a 24v system. It would be so much more efficient to just add another DSSR20 rather than inverting to 110v and then back to 24v.
How are the 6 100w panels on the roof keeping up with your electrical demands? I see you have a microwave and maybe some other high draw devices.
So far when running an AC I've relied on my Honda EU2200 generator (I've used a window AC in various janky contraptions such as a fake rear wall o having it sit between the front cabin and the back since I have a cargo partition on a pile of bins and some RMax panels blocking the opening below and above it) - so I won't be inverting back and forth if I do that, only one way. Agreed that is not the most efficient or elegant solution. If I can get away with just solar, that would be awesome, but I am not sure physics work in my favor if I want to run the AC and keep the van cool the entire day. I've seen my 600W array peak at 400W but that doesn't happen often - usually there's some shade where I park and want to use an AC, and even when it happens its for a short part of the day. There's usually a tradeoff between how much shade I want to be in versus how much I want my solar to deliver. Generally my consumption is pretty low - I boil water a few times a day and microwave for a total of maybe 5 minutes. That gets replenished pretty quickly. I might be able to get away with it if I am only planning for one day use.
 

eranrund

Member
Seller told me about 4-5 weeks once it ships, I will update when they actually ship it and hopefully there's some tracking.
 

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