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Wed Jan 25, 2023 10:14 am

67 hp - 4hp = 63hp

Wed Jan 25, 2023 10:40 am

spoil sport.

At 1K RPM it's about 1.2KW input power which is only 1.5 HP.

My 50 ft speeds won't be affected.

This graph is for the actual compressor that Gilmore Enterprises puts on type4 engines.

The crankshaft pulley is smaller than the compressor pulley so it'll be sucking less HP than that off the line.

Wed Jan 25, 2023 10:46 am

Happy Hump Day All!

So, I purchased the below kit in 24V for "Cookie Monster".
https://coldmasterinc.com/product/a-c-kit-universa...ompressor/

We want to keep the original location of the A/C, so just our heads will be cool. lol

Additionally, we'll be hooking up two (2) deep cycle batteries (auxiliary battery kit from GoWesty) to handle the draw. I did look into the 120 amp alternator from Quality Power, but I like heat too and here in NC, it can get down into the low double digits.

With that, we are still trying to run down the 65 amp alt. duty cycle info.

Keep it coming guys!

Wed Jan 25, 2023 10:50 am

Give us a full review when it's up and cooling! (Hopefully before I crack my van open).

Wed Jan 25, 2023 4:18 pm

Opschief3537 wrote:

With that, we are still trying to run down the 65 amp alt. duty cycle info.

You won't find any because alternators don't have a "duty-cycle" in the sense that term is normally used, which means time on vs. time off. A car alternator is never ever "off" while the engine runs, instead it produces a constantly varying amount of current in order to maintain the system voltage the regulator is set to. And there is always a load, even all-mech diesels use a small amount of electric power to stay running, and on a gasoline engine the engine electrical load is usually around 10 amps constant. So a vehicle alternator is always "on", making some amount of current. So duty cycle as a concept doesn't apply.

What will help you in your quest is to know that rather than a maximum duty cycle, an alternator instead protects itself from overheating by lowering the voltage target as temperature increases. Voltage makes no heat, current does, and since the alternator is by design variable-current device, the only way it can regulate its own temp is by lowering current. This is a simple circuit inside the regulator that senses temp and adjusts the voltage target inversely. A lower target V will be met with less current.

So the current rating may be 65 or 90 or 120 amps, but that's the theoretical maximum at high loads but low temp. As temp climbs, the current output lowers in order to control the alternator temp. It isn't helped by being in the engine bay, but coincidentally batteries also have peak voltages that vary inversely with temp. So the temp-controlling function both protects the alternator and prevents overcharging the battery when the battery is also in the engine bay.

The problem with Vanagons is the battery (or batteries) is not in the engine bay, it stays at much lower temp in the cabin, so it would actually like a higher voltage longer. The regulator and battery work at cross-purposes in our rigs because of that. This can be solved with a remote adjustable regulator that lives in the same temp environment as the battery; the downside is the alternator will end up running hotter if there are a lot of loads all the time.

I will say that you will want that 120A alternator or even bigger. At full temp (they'll commonly get up to 200-250ºF), the alternator might not make much more than half it's rated current. I think the 120 would be maybe just adequate depending on the AC's actual duty cycle (it is described that way because it cycles on and off, although newer types always pump and vary volume dynamically instead) and how much of a battery buffer you include.

Wed Jan 25, 2023 5:11 pm

I will add a little information for posterity: the diesel Type 2 (Vanagon, T3) have the battery in the engine bay from factory.

Wed Jan 25, 2023 5:13 pm

Excellent explanation. Thanks.

I took duty cycle to mean time between failure.

Your explanation makes more sense and fits the textbook definition.

And you provide the answer to the question that should have been asked about alternator output. I had no idea the voltage regulator also sensed temperature.

I think his compressor will run all the time depending on cooling needs.

Thu Jan 26, 2023 5:42 am

Great explanation irt the "duty cycle". Now that is Marine proof!!!

This is making me reconsider incorporating the 120 amp alternator. Question to the community; Using the 120V alternator, aside from no heat in the cabin (which sucks), would this cause any other issues with engine operation, i.e., temp, etc???

Thanks!

Thu Jan 26, 2023 5:51 am

Opschief3537 wrote: Great explanation irt the "duty cycle". Now that is Marine proof!!!

This is making me reconsider incorporating the 120 amp alternator. Question to the community; Using the 120V alternator, aside from no heat in the cabin (which sucks), would this cause any other issues with engine operation, i.e., temp, etc??? Maybe we should install and engine oil cooler???

Thanks!

Thu Jan 26, 2023 2:54 pm

The air forced through the heat exchangers doesn't cool the engine, but it does cool the exchangers.

I don't know the long term results from not having this, but if you go with the 120 amp alternator, adding an electric blower to replace the alternator fan shouldn't be difficult.

Fri Jan 27, 2023 6:36 am

That's a great point Steve. I'm going to look into that.