Electric a/c for Minis

[MPlayle]

Starting a separate thread to discuss/track this.

Post up what you find on the A/C, in fact we should start a thread on just that as I'm looking into it too for my hot rod Mini.

I had a guy bring an electric compressor over yesterday so I could see how big and heavy it was, and where I might mount it. My understanding is that they all draw about 50 amps on start up then run at about 30, so you'll need a healthy alternator to keep up - fortunately the one on the hot rod is 150 amp, so I'm good there.

I'm not sure but I think you can get one with a heat strip in the evaporator assembly too, which I would love - instant heat and defrost!

My thinking is to mount the compressor right up on the bulkhead so the hoses will be shorter, then I just have to supply power from the back. It was interesting on this compressor that the inlet and outlet for the hoses were on opposite ends of it. I already have the condenser but I still need to figure out the mounting, hose runs etc. I was thinking I would like to make hard lines for almost all of it, just a short run of rubber hose off the compressor. The one he brought also had rubber mounting "feet", and I would have to make a bracket to support it up on the bulkhead..

Not sure what size cable I'll need, the wires that went from the inverter/controller on this one only looked to be about 10 gauge. Seems like it would need to be bigger than that to supply 50 amps. Not sure on that yet. Lots to learn!

I am still researching the topic.  A while back, another Mini related friend sent me an article where a UK outfit had installed a setup into a classic Mini destined for Singapore.  I have been consulting with them and some of their sources - in particular for a high output alternator that will fit our Minis.  I am still waiting on feedback regarding the alternators.

Most of the kits I have found recommend an alternator putting out at least 120 amps at idle/low rpms.  I did a quick consult with one of the kit suppliers in the US (Miami, Florida based) and they can supply with a variety of condensor sizes (I am considering the 12"x14" for tucked into the rear subframe) and a variety of evaporators (both "cool only" and "heat/cool").  I have a couple of models under consideration that are 14.5" wide, 12.5" deep, and 6" tall.

It sounds like the compressor you have test fit is the typical one now being used.  They are often listed as being dual-scroll type.

[MPlayle]

One thing I have been finding in my research: the cooling capacity of the 12 volt electric compressors is better than it used to be, but not yet comparable to belt driven compressors.

As long as you are realistic about your expectations, they are still a viable option for our Minis, just don't expect to get 40* output.  You are most likely going to get 60*-70* output, which for me is vastly better than 90*+ ambient in a Van with sliding windows and wispy little USB dash fans for when stopped.

If I can get the alternator output requirement solved, I will likely go forward with the effort.

[MiniDave]

I figure with such a small area to cool it should be adequate, plus too and also, I'm not out driving on 95* days if I can help it!

To me, it will help just being able to close the windows for less travel noise.

[MiniDave]

Looking at several different brands and suppliers it seems I was wrong, none of them use a heat strip for heat, they all use the engine's coolant. That's a disappointment as I was hoping not to have to plumb water to the unit.

I've seen BTU's of 12K, 13,800 and 18K.....makes me wonder just how much I would actually need for 1/2 of a Mini interior? (no back seat in the hot rod)

[MPlayle]

Most of the BTU ratings I have seen on the 12 volt compressor kits turn out to be the rating of the evaporator versus the capability of the compressor.

I am still trying to figure out/learn the differences and relationship between the two.

[Merlin]

Here's some data from the AC compressor attached to my JDM mini.
The compressor is a Unicla UP90 (As far as I can tell) The cut sheet is below.
https://www.supercool.com.au/unicla/up90-upf90/
The compressors is designed for 2-3Kw applicaitons which translates to 6,800-10,000 BTU/Hr. This is compressor BTU
Looking at the data in the cutsheet, it gives us power consumption at RPM. The pulley on the compressor is the same as the crankshaft damper (120mm) giving a 1:1 ratio. Assuming that we are steady state at 1,000 rpm the HP consumed is roughly 1hp (750w). Running that backwards into Amps at 13V and adding a 90% eff, that would require 64amps to operate an electrical A/C compressor.

So let's gut check this. There are electrical cars and they don't belt drive their A/C Compressors. There should be a system out there that would work?
https://openinverter.org/wiki/Tesla_Model_S/X_A/C_Compressor
The Tesla units operate on a 350VDC system pulling nearly 4.5kw (6hp!!) which is more than we predicted with the engine driven one above. They offset the need for high Amps by upping the voltage. Checking the chevy volt system as a comparison and its a 350VDC system.


My only thought here is this... Move to a 48V system with its own dedicated battery.
https://www.guchen.com/compressor/48v-electric-ac-compressor-for-truck.html
This unit is capable of 3.5Kw which is at the max of the required need. The cc/rev flow rate is lower at 20cc/rev but it can operate constantly at 6000RPM which means it can move as much freon as the Unicla above. The numbers make the most sense here. Using a 48V lithium battery like the one below would give you the voltage and nearly the amp draw required. The battery states it can do 60A draw, but the BMS says 30A. At full load, the compressor is pulling 33A. We can reel it back a bit, still hit the BTU rate and stay under the battery requirements.
https://www.vevor.com/batteries-c_14008/vevor-48v-electric-scooter-battery-20ah-ebike-lithium-battery-pack-with-30a-bms-p_010464838800?adp=gmc&utm_source=google&utm_medium=cpc&utm_id=23748664457&ad_group=195029942043&ad_id=805057579869&utm_term=&gad_source=1&gad_campaignid=23748664457&gbraid=0AAAAACq8bLWtC1hNskacoNW9DoBg0woRN&gclid=CjwKCAjwirLWBhBBEiwAlItbEuIBtaDomHAmvgcrCeKXxLTSTMPrkprE89vUj1LKlKCh8-2bSbIyBBoCy9MQAvD_BwE

Battery states 20AH, which would be about a 40 min run time. The compressor would not run constantly so this could be an option for shorter trips. Adding a DC/DC charger could help offset. This could add 400W to the system, which could be used for demand or for charge. Adding batteries could be used to double or triple that range if require at the cost of weight. https://expion360.com/products/orion-tr-smart-12-48-8a-380w-non-isolated-dc-dc-charger?variant=46373429739683&country=US&currency=USD&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&utm_term=&utm_campaign=WP+-+PMax+-+NOCO+%2B+Victron&utm_source=adwords&utm_medium=ppc&utm_id=23326401726&hsa_acc=4475371194&hsa_cam=23326401726&hsa_grp=&hsa_ad=&hsa_src=x&hsa_tgt=&hsa_kw=&hsa_mt=&hsa_net=adwords&hsa_ver=3&gad_source=1&gad_campaignid=23331492140&gbraid=0AAAAACkQ-wRiaIQCjat0gIUycjFaZMGsg&gclid=CjwKCAjwirLWBhBBEiwAlItbEkhGua-m08o-TtJApp0b-Nd-S22CeR_3s8Dboh0sq6nB-sFrst4Q8xoCSzMQAvD_BwE


This is math problem limited by physics. 12,000BTUs of cooling require ~1.5hp. How you get it is up to you.