Cessna 414.
Keith electric air conditioner.
70 amp 28v apu.
Home made power cart with 4-6v deep cycle batteries. 25.5 volts.
70 amp apu will not run a/c (circuit breaker pops on apu).
I need to add Freon or at least check it.

My current problem: The 4 battery cart at 25.5 volts will not latch the aux power Contactor. My guess is it needs 28 v to latch.
The apu puts out 28.5 volts and Contactor latches in fine.
If I add one more 6v battery that ups the voltage to about 32 volts! Is that too much?
FBO apu was inop last I checked. I’ll check again tomorrow.
I would like the battery pack to work as it may come in handy if I need a start.
Solutions.

You need a very big GPU to run an electric AC system. And very big GPU's are really expensive. I thought about all kinds of different schemes until I just broke down and bought one. You're welcome to come to KCCR and use mine for as long as you need it. Otherwise renting some time on the FBO's GPU is your best bet, assuming it's working.

Maybe try putting the GPU in parallel with the battery pack. There is probably a high current inrush that trips the breaker. The Aerostar electric A/C is typically limited to about 50 amps.

Do the math, the battery cart will not carry the load for more than a few mins at best

Your best best is to go get a MIL surplus GPU and hook it up. You're talking about 2 KW of power so it won't run off an extension cord.

Alternatively, there isn't much competition for the surplus Gen sets so I bet you could get a gas/diesel one on the cheap.

--paul

6V deep cycle golf cart batteries are 200-250 AH typically.

Strung together to make 24 volts, they will power a 70 amp load for ~ 3 hours.

Did I miss something?

Mike C.

6V deep cycle golf cart batteries are 200-250 AH typically.

Strung together to make 24 volts, they will power a 70 amp load for ~ 3 hours.

Did I miss something?

Mike C.

A 13 HP air conditioner? Really?

My vapor cycle (aka "freon") system on the V draws about 70 amps at 28 VDC, ~2 KW. I highly suspect yours is similar.

Drawing a load at C/3 (1/3 the AH rating) for a lead acid battery should get reasonably close to nameplate capacity. You aren't going to lose half of it at that moderate draw.

Cables can get warm, but that's actually not that much heat. Say it has 50 watts loss, that's still 97% efficient as far as the cable, and 50 watts into the cable will make it quite warm.

Mike C.

6V deep cycle golf cart batteries are 200-250 AH typically.

Strung together to make 24 volts, they will power a 70 amp load for ~ 3 hours.

Did I miss something?

Mike C.

A 13 HP air conditioner? Really?

Over 6 KW? Wow, what is using so much power?

It can't be the vapor cycle system, that is 3 times the power of typical systems.

Mike C.

Over 6 KW? Wow, what is using so much power?

It can't be the vapor cycle system, that is 3 times the power of typical systems.

Mike C.

So when you are operating it on engine power, your amp meters show ~100 amps per side increase when you turn on the AC?

That's really crazy, IMO. I wonder if this is normal or something is wrong with the system? Is this just one compressor?


Yes, nice little power supply.

You still need appropriate line power where you go, so that limits where you can use it.

Mike C.

Uses same plug as an EV car, a lot of hangars and airports have those accessible now, the ramp I frequent in Florida, the FBO has Hubbell connectors plumbed on the ramp so I can plug it in before departure

I can confirm that, it loads each generator about 25%, the gens are 8 kW each.

2 kW is small for a Citation vapor cycle cooling system, lots of older car system have that…