Anyone with 12v Air Conditioning Experience?

[adamis]

Having spent the better part of a week in a hot, dry and smokey campground that doesn't allow generators to run (I posted previously about this issue in another thread) it got me to thinking about some possible options... From what I can figure, the only real need for a genset is to run the Microwave and the AC unit. My problem with this however is that the generator isn't allowed in many places, is loud and sucks propane. That got me to thinking about eliminating the genset entirely and just using the space to house more LiFePo4 batteries. I think I could probably get 4 100AH batteries in the same space, coupled with the current 100AH battery that would get me 500AH of batteries to play with.

From a previous post and article discussing different air conditioning options, it seems that the van life community has created some interesting options for us that were not available even a few years ago. One potential contender is the Nomadic Cooling 3000 12v. Now it is pricey, nearly $4290! I guess these digital nomadic van life millennials have cash to burn.

Anyway, for the princely sum of ~$9k, one could have a 12v DC air conditioning that will run for hours on battery. Throw on 400w to 600w of solar and now you can stay cool in just about any situation. If money wasn't an option, I would probably do this in a heartbeat but sadly it is so it is hypothetical for now. One thing I could do is to space out purchasing of batteries and add to the capacity a little each year. Even with 200AH to start with, that should be enough for 30 minutes to an 1 hour of cooling, good enough for a quick lunch on the road side. The best thing about this is that unlike propane which requires refueling at a station, I can charge that battery bank through solar or DC to DC from the truck.

I know some of you have already done similar setups, being able to run AC off of batteries. I am however not aware of anyone who has ditched their genset entirely and gone with a 12v AC unit. Has anyone taken this extra step or contemplating it?

[time2roll]

Here is one more 12v-24v vendor to look at:

https://undermountac.com/

[3_tons]

HMS Beagle wrote:

adamis wrote:

HMS Beagle wrote:
Not sure I'd build a camper with a 24V system. On the boat there are many high current devices (AC, watermaker, 3 winches, windlass, inverter) so a lot of big cable. With 24V you get half the current and can withstand twice the voltage drop, so the difference in cable size is quite large.

I'm curious HMS Beagle where you keep your boat up in the North Bay? My folks have a 47' Gulfstar Sail Master in Sausilito that they stay on 50% of the time. When I was in college at San Jose State I used to drive up there on a regular basis to visit. I'm now in Gilroy so I can't get up there that often but still try to visit on occasion. My dad is an active sailor (was a Merchant Marine for 30 years before retiring and buying the sailboat) and loves taking his boat out. He's also been sailing in the Master Mariners Regatta. Guessing you might be involved in some of the same circle of people as my Dad.

The sailboat is now in Brickyard Cove at Pt. Richmond. It took us about 12 years to get there from Toronto where it was launched. I'm not tied into the local crowd that much, as I don't race or belong to a yacht club. I also keep a small trawler up in the PNW - had the sailboat there for 4 seasons but there is no wind there so I sailed it home. A lifetime of boat ownership has gained me a lot of experience in DC systems!

If I were to choose to go this route (full disclosure, I’m not) I might consider the 24v unit were there to be a loooong cable run, and use a dc to dc converter to power up all other 12v devices…

3 tons

[HMS_Beagle]

adamis wrote:

HMS Beagle wrote:
Not sure I'd build a camper with a 24V system. On the boat there are many high current devices (AC, watermaker, 3 winches, windlass, inverter) so a lot of big cable. With 24V you get half the current and can withstand twice the voltage drop, so the difference in cable size is quite large.

I'm curious HMS Beagle where you keep your boat up in the North Bay? My folks have a 47' Gulfstar Sail Master in Sausilito that they stay on 50% of the time. When I was in college at San Jose State I used to drive up there on a regular basis to visit. I'm now in Gilroy so I can't get up there that often but still try to visit on occasion. My dad is an active sailor (was a Merchant Marine for 30 years before retiring and buying the sailboat) and loves taking his boat out. He's also been sailing in the Master Mariners Regatta. Guessing you might be involved in some of the same circle of people as my Dad.

The sailboat is now in Brickyard Cove at Pt. Richmond. It took us about 12 years to get there from Toronto where it was launched. I'm not tied into the local crowd that much, as I don't race or belong to a yacht club. I also keep a small trawler up in the PNW - had the sailboat there for 4 seasons but there is no wind there so I sailed it home. A lifetime of boat ownership has gained me a lot of experience in DC systems!

[Siletzspey]

stevenal wrote:
Have you checked the RVIA electrical codes?

I took a pass at trying to understand the relevant industry "codes / standards" and wire gauge x amperage tables, and my debrief WITH LINKS TO THOSE CODES is here.

http://www.barbless.com/share/lifepo4/TJG-Wire-Fuse-Sizing.pdf

Many codes that are stereotyped as "housing" codes do cover low voltage DC systems, and in fact are what the boating and RV standards build off of! IMHO the boating industry with its ABYC standard is the most comprehensive, mature and utilized standard for low voltage DC systems, not only for boats, but for RVs. The RVIA standard is sparse in comparison, and I've seen multiple comments that utilization of the RVIA standard is voluntary and sparse.

IMHO the biggest misunderstandings on various forums are: 1) confusing VOLTAGE DROP tables with THERMAL CURRENT-LIMIT tables and 2) arguing that you only fuse to protect the wire, which means all RVs with 10AWG DC wiring rated at 105C should be fused at 60A.

I'm not an expert, but I am putting my work WITH CITATIONS out for critical inspection and feedback.

--tg

[adamis]

HMS Beagle wrote:
Not sure I'd build a camper with a 24V system. On the boat there are many high current devices (AC, watermaker, 3 winches, windlass, inverter) so a lot of big cable. With 24V you get half the current and can withstand twice the voltage drop, so the difference in cable size is quite large.

I'm curious HMS Beagle where you keep your boat up in the North Bay? My folks have a 47' Gulfstar Sail Master in Sausilito that they stay on 50% of the time. When I was in college at San Jose State I used to drive up there on a regular basis to visit. I'm now in Gilroy so I can't get up there that often but still try to visit on occasion. My dad is an active sailor (was a Merchant Marine for 30 years before retiring and buying the sailboat) and loves taking his boat out. He's also been sailing in the Master Mariners Regatta. Guessing you might be involved in some of the same circle of people as my Dad.

[HMS_Beagle]

Not sure I'd build a camper with a 24V system. On the boat there are many high current devices (AC, watermaker, 3 winches, windlass, inverter) so a lot of big cable. With 24V you get half the current and can withstand twice the voltage drop, so the difference in cable size is quite large.

[Kayteg1]

I had 24V coach in the past.
Don't know if wire weight saving on 16 tons vehicle was crucial, but keeping 3 different voltage wiring systems in working order sure could be confusing.

[HMS_Beagle]

Also why my boat was wired 24V for everything that possibly could be. I probably saved 300 lbs in wire just from that.

[pianotuna]

Kayteg1 wrote:

Still would I build big solar system, not likely I would put 100 lb of cables to connect it to battery.

One would go MPPT with a 100 volt or larger input voltage.

I've often advocated for the charge controller to be as close as humanly possible to the battery bank.

I aim at less than 1% voltage drop, but I agree #8 wire is ummmmm a fuse at 400 amps.

[pianotuna]

HMS nicely said. Thanks.

[HMS_Beagle]

I think the Chinese codes are suspect. 8 ga AWG wire has 0.62 ohms/1000 ft. if of good quality. 18" of wire therefore has only 0.0009 ohms which doesn't sound like much. At 400A that is still only 0.37V drop which also doesn't sound like much. But it will dissipate 149 watts which sounds like one hellava lot! In fact it will do that for only a very short few seconds before the insulation melts and it is red hot. Wires are often sized for voltage drop, as apparently here, but there are also ampacity specs based on insulation temperature ratings, and #8 is typically 80 amps unless a very special high temp insulation - but never 400 amps!

So based on voltage drop of 3% - a typical metric for battery powered systems, #8 is fine because the run is so short, but based on ampacity you need at least 3/0, which is independent of run length.

[Kayteg1]

Still how can 400 amp unit be supplied by wires rated for 40 amps?
Meaning between RVIA and Chinese codes used for inverter, the true will lay somewhere between.
In my inverter application, I used the small cable to paralel 2nd battery, when main inverter connection is #2 wire. Just becouse I had it on the shelf and I know that voltage drop on inverters can be crucial.
Still would I build big solar system, not likely I would put 100 lb of cables to connect it to battery.

[stevenal]

Kaytag1,


I never purchased the standard, but from https://archive.org/stream/ansi-rvia-lv-standard-for-low-voltage-systems-in-conversion-and-recreatio... #8 stranded is good for 40A. But if the wires are part of the inverter, they should be covered by its listing, and RVIA would not apply.

[Kayteg1]

The issue was solar wiring.
This year I bought 3000 W inverter, who came with about 18" of connecting cable.
So for 400 amp potential current, I measured the attached cables to be.... wait for it..... #8 gauge.
What RVIA says?