Hot Positive Terminal Running Electric CR A/C

[MikeD930]

I want to bring heads up to make sure that those of you who are running CR A/C are aware that the positive terminal on the battery can get hot. I have posted my concern on this several years ago (CR Electric A/C). I'm surprised no one brought this up since then. Sometime it gets so hot that I can feel the battery bubbling with my fingers on top of the battery next to the positive terminal. The battery is AGM type so there's no acid venting but it's not good! To resolve this...I installed the battery terminal adaptor cable so that the positive terminal from the alternator is connected to the battery via this adpator cable. Now the generated heat is away from the battery which I tested and it works. This winter I'm planning on installing a separate cable between the alternator/starter to the positive terminal to reduce the loading on the existing positive cable while running electric A/C.

So is there anyone who noticed the same issue?

Here's my latest setup using battery terminal adaptor cable (positive side):




Following photos after 1.5 hr drive in +90 deg F temp...

Positive terminal at battery terminal adaptor cable:




Positive battery terminal on battery:




Negative battery terminal on battery:

[pmax]

Originally Posted by MikeD930

Now the generated heat is away from the battery which I tested and it works

You might have just put together a heat sink.

I assume it's secured "properly" with no chance of flopping about.
What's the clearance ?

[Nditiz1]

It would help us to know which alternator you are currently running. The next time I have it out I'll check the temp at the terminal. I haven't noticed anything, but im also not check8ng the positive terminal on the reg.

[MikeD930]

Originally Posted by pmax

You might have just put together a heat sink.

I assume it's secured "properly" with no chance of flopping about.
What's the clearance ?

Yes...I relocated heat away from the battery. The adaptor cable/terminal does not flop around...it's stiff. It will be wrapped with rubber tape/tubing.

Originally Posted by Nditiz1

It would help us to know which alternator you are currently running. The next time I have it out I'll check the temp at the terminal. I haven't noticed anything, but im also not check8ng the positive terminal on the reg.

My car has a C2 turbo (one of the previous owner replaced a stock engine with this one). I think a C2 turbo alternator puts out 90 amps...maybe 115 amps? I can't find a spec for a stock C2 turbo alternator.

[blucille]

I'm not an engineer, but the power cable to the CR AC unit seems about as large as the primary cable to the starter motor, yet the contact patch to the battery clamp in relatively small.

I'd consider swapping to a high quality battery terminal kit that would be used by high-end car stereo shops, or something similar to what was used on our long-hood, long wheelbase cars that had 2 batteries.

or host has these:

https://www.pelicanparts.com/More_Info/90161131100.htm?pn=901-611-311-00-OEM&gclid=Cj0KCQjwzdOlBhCNARIsAPMwjbyeX745iVRJiU49sxS8 D2za87k5IZK3o6rO6lT8eV1XusSCRFVGDDgaAkAXEALw_wcB

of course, you'd want to be sure you have plenty of clearance for a larger battery terminal, you might want to reorient the battery such that the positive connections are in teh gap at the front of teh car rather than tightly confined behind the battery.

[tsuter]

All that heat really depends on the type of electric compressor you are using. Hopefully it is a 300V-400V and uses a DC-DC converter. Then the current would be 12.5 amps @ 360V, so somewhere around 4.5kW draw decent but not great cooling capacity. At least nothing should get very hot and your 115A alternator will be fine.
Now if you are running a 12V compressor (no converter) like in old vehicle auxiliary coolers for beer and trying to produce even 2kW cooling capacity....all bets are off on heat and amps

[MikeD930]

Originally Posted by blucille

I'm not an engineer, but the power cable to the CR AC unit seems about as large as the primary cable to the starter motor, yet the contact patch to the battery clamp in relatively small.

I'd consider swapping to a high quality battery terminal kit that would be used by high-end car stereo shops, or something similar to what was used on our long-hood, long wheelbase cars that had 2 batteries.

or host has these:

https://www.pelicanparts.com/More_Info/90161131100.htm?pn=901-611-311-00-OEM&gclid=Cj0KCQjwzdOlBhCNARIsAPMwjbyeX745iVRJiU49sxS8 D2za87k5IZK3o6rO6lT8eV1XusSCRFVGDDgaAkAXEALw_wcB

of course, you'd want to be sure you have plenty of clearance for a larger battery terminal, you might want to reorient the battery such that the positive connections are in teh gap at the front of teh car rather than tightly confined behind the battery.

The warmest portion of the positive terminal is right at the battery terminal where the original cable goes into...not at the lug/cable from the electric compressor. So I don't think using the high quality battery terminal kit would help unless you are suggesting to replace a stock battery terminal with it.

Originally Posted by tsuter

All that heat really depends on the type of electric compressor you are using. Hopefully it is a 300V-400V and uses a DC-DC converter. Then the current would be 12.5 amps @ 360V, so somewhere around 4.5kW draw decent but not great cooling capacity. At least nothing should get very hot and your 115A alternator will be fine.
Now if you are running a 12V compressor (no converter) like in old vehicle auxiliary coolers for beer and trying to produce even 2kW cooling capacity....all bets are off on heat and amps

Are you familiar with Classic Retrofit electric A/C kit? I think the CR electric A/C draws up to 50 amps. So yeah...it's obvious this A/C does not draw 12.5 amps @ 360V.

The vent temps range from 40F to 50F depending on outside temp.

[pmax]

Originally Posted by MikeD930

Yes...I relocated heat away from the battery. The adaptor cable/terminal does not flop around...it's stiff. It will be wrapped with rubber tape/tubing.

Yes, hence my question about the clearance, mm vs cm.

[ant7]

Some of the all electric Heat and A/C systems advertised on this site after converting the stated wattage draw around 200 amps, something I actually questioned, and was told that it was correct, I will try and find the original post and link it here.

Update;
Here you go!
https://forums.pelicanparts.com/porsche-911-technical-forum/990208-classic-retrofit-six-phase-high-output-alternator-5.html

Originally Posted by MikeD930

The warmest portion of the positive terminal is right at the battery terminal where the original cable goes into...not at the lug/cable from the electric compressor. So I don't think using the high quality battery terminal kit would help unless you are suggesting to replace a stock battery terminal with it.




Are you familiar with Classic Retrofit electric A/C kit? I think the CR electric A/C draws up to 50 amps. So yeah...it's obvious this A/C does not draw 12.5 amps @ 360V.

The vent temps range from 40F to 50F depending on outside temp.

[tsuter]

Originally Posted by MikeD930

T
Are you familiar with Classic Retrofit electric A/C kit? I think the CR electric A/C draws up to 50 amps. So yeah...it's obvious this A/C does not draw 12.5 amps @ 360V.

The vent temps range from 40F to 50F depending on outside temp.

No, not familiar at all in the technical sense as I have no plans for it, but if in fact it uses a 12V compressor, then you will have issues with Amperage and heat to manage just trying to produce a few kW cooling capacity. I would want to know where the system is in stepping this up to a 300V/400V compressor which would dramatically improve efficiency, cooling capacity and cut amperage using a DC-DC converter.

Of course 300V+ DC can be a painful lesson in electricity for DIYers so be careful..

[wazzz]

CR sell electric compressors for various applications. One is the 12V version for classic cars, others are for EV and are available in 140 and 300-400 V as far as I remember.
With a 12-volt source and an electric compressor nearby with short cables, there is no real need to convert the 12 volts low voltage to high voltage. Of course the short cables need to be sized to carry whatever amps are drawn.
CR claim their electric compressor draws less than one engine HP, so that turn into something like 60+ amps to carry under 12 volts.

[tsuter]

The issue is you need BTUs to cool a car. Most will require 12,000 - 18,000 BTU/h.

So the compressor has to produce this capacity thru kW.
1kW = 3400BTU/hr
So at the low range (12,000BTU/h) the compressor must produce 3.5kW. Actually under 4kW is anemic. I believe a Sanden SD5 produces approx 7kW for comparison purposes although the RPM is not stable.
So now you see the issue with low voltage (12V) compressors. They just cannot produce the kW necessary for adequate cooling without enormous Amperage. Maybe fine in 80F but no way at 105F.

So that is why ALL electric cars are using high voltage compressors with most at 300V and higher.

I do not make or sell product but if I did I would want to look at 300V minimum.

[darrin]

MikeD930 -- wanted to follow-up on something Bluecille mentioned above -- Is the heat source the connector between the (large) cable powering the compressor and the battery terminal, or is the cable itself getting hot? An electric circuit creates heat when the current passes through a resistive element. I.e., if you ran a lot of current through a very undersized wire, the too small wire would get hot. Conversely, irrespective of current/load, a wire sized to handle the underlying load would remain cool to the touch. Wondering whether your IR thermometer would show cool temps either side of the connector at issue and whether the crimp connector is undersized/not completely attached to the cable/corroded and therefore causing resistance and the heat you're observing. Years ago, I had a similar issue where my starter (in an Audi) was failing/intermittent and I traced the issue to a crimp connector that was installed so that only a few of the starter wires (hundreds) of strands were attached to the connector -- the resistance caused by this faulty crimp caused the load issues I was having (and must have generated a LOT of heat)

[phelix]

Originally Posted by tsuter

The issue is you need BTUs to cool a car. Most will require 12,000 - 18,000 BTU/h.

So the compressor has to produce this capacity thru kW.
1kW = 3400BTU/hr
So at the low range (12,000BTU/h) the compressor must produce 3.5kW. Actually under 4kW is anemic. I believe a Sanden SD5 produces approx 7kW for comparison purposes although the RPM is not stable.
So now you see the issue with low voltage (12V) compressors. They just cannot produce the kW necessary for adequate cooling without enormous Amperage. Maybe fine in 80F but no way at 105F.

So that is why ALL electric cars are using high voltage compressors with most at 300V and higher.

I do not make or sell product but if I did I would want to look at 300V minimum.

I think you’re forgetting about the CoP?

And the CR system is a good solution. It’s not perfect. If you think there’s a better solution please do enlighten us. But simply throwing rocks isn’t very productive or helpful.

[MikeD930]

Originally Posted by pmax

Yes, hence my question about the clearance, mm vs cm.

I'm not sure what clearance you are asking about...if it's the area you pointed out above then there's no clearance between the body and the insulated portion of the battery terminal adapter. It's no different than a stock cable running along the body from the starter to the battery. But if you're asking about the clearance between the crimped portion of a battery terminal to the body...it's about 20 to 30 mm (same as a stock battery terminal).

Here are the items I used to relocate the hot positive terminal from the battery. The adapter cable is looped back instead of being 'straight'.

Originally Posted by ant7

Some of the all electric Heat and A/C systems advertised on this site after converting the stated wattage draw around 200 amps, something I actually questioned, and was told that it was correct, I will try and find the original post and link it here.

Update;
Here you go!
https://forums.pelicanparts.com/porsche-911-technical-forum/990208-classic-retrofit-six-phase-high-output-alternator-5.html

Seems your linked thread shows that the electric heater is around 130 to 135A and the electric A/C is around 60 to 70A. I believe my A/C is set around 50 to 55A. It does its job as long as the outside temp max out in the mid 90F which is fine for me since I avoid going on trips when it's 100F out anyway.

Originally Posted by darrin

MikeD930 -- wanted to follow-up on something Bluecille mentioned above -- Is the heat source the connector between the (large) cable powering the compressor and the battery terminal, or is the cable itself getting hot? An electric circuit creates heat when the current passes through a resistive element. I.e., if you ran a lot of current through a very undersized wire, the too small wire would get hot. Conversely, irrespective of current/load, a wire sized to handle the underlying load would remain cool to the touch. Wondering whether your IR thermometer would show cool temps either side of the connector at issue and whether the crimp connector is undersized/not completely attached to the cable/corroded and therefore causing resistance and the heat you're observing. Years ago, I had a similar issue where my starter (in an Audi) was failing/intermittent and I traced the issue to a crimp connector that was installed so that only a few of the starter wires (hundreds) of strands were attached to the connector -- the resistance caused by this faulty crimp caused the load issues I was having (and must have generated a LOT of heat)

The heat source is at the crimped portion of the stock battery terminal/cable junction from the starter/alternator. The cables (from the starter/alternator, adapter and to the compressor) are warm...not hot. I believe there may be some corrosion within the cable at the crimped portion of the terminal. That's why I am planning on adding another cable to run parallel with the stock cable from the starter/alternator. I used this method on my other old car ('84 Celica Supra) which helps reduce load (heat) on a stock cable.

[darrin]

MikeD - why not start by re-crimping the offending wire and see if a freshly crimped termination solves your problem? Pretty easy to determine wire gauge with a caliper and crimping kits are cheap on amazon, etc.

[dtwa]

I think your original factory terminal is corroded inside the crimp. The current from the alternator runs through that crimped connection. Any amount of resistance from corrosion will result in heating of the terminal. —Dave


Sent from my iPhone using Tapatalk

[MikeD930]

Originally Posted by darrin

MikeD - why not start by re-crimping the offending wire and see if a freshly crimped termination solves your problem? Pretty easy to determine wire gauge with a caliper and crimping kits are cheap on amazon, etc.

I'm not sure how re-crimping will help if there are corrosion in the cable at the terminal.

Originally Posted by dtwa

I think your original factory terminal is corroded inside the crimp. The current from the alternator runs through that crimped connection. Any amount of resistance from corrosion will result in heating of the terminal. —Dave

I agree with your assessment. How does one address this issue with corrosion of the cable in the terminal?

[ant7]

Any resistance you have between cables and connections ie; crimps, compression nuts and bolts connecting earth straps etc will pose greater issues the more current you try and draw through them, especially when we are dealing with a relatively low voltage of between 12 and 14v to start with, safe to say; like others have stated it is of the utmost importance that all high current cables and earth straps are clean tight, and free from corrosion.

[darrin]

[QUOTE=MikeD930;12046726]I'm not sure how re-crimping will help if there are corrosion in the cable at the terminal.


Mike, you'd need to cut off the terminal (and the portion of the wire crimped to the terminal) and strip back the insulation behind the crimp to re-crimp. This should allow you to confirm the wire's new crimping surface is corrosion-free and crimp to clean wire.