12V draw with air compressor

[Robert1380]

So I have a Viair, 12v portable compressor that has the alligator clips to connect to the car battery but I’m wondering if you can use that compressor hooked up to the battery and successfully fill all four tires without causing issues to the trucks electrical system?

On the rare occasion of using my truck at places like the sand dunes, we air down to 15-20psi and want to be able to fill the tires back up without issues. Four tires is gonna be a lot of draw and I have no idea how that works when you pull directly from the trucks accessory battery. So do you leave the truck turned on and running like an ICE vehicle so it’s backfilling from the main battery to re-charge the smaller one? Or do I need to buy a small 110 plug compressor for this?

Thanks guys

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[The Weatherman]

The simplest solution would be to buy a 120v plug-in unit. However, you might consider adding a 12v connector (cigarette lighter plug) to the one you have. There are ports front seat and back seat that are far more convenient then clipping onto the jumper point under the right hand side fender in the frunk.

Hey, that’s just me. You do what works for you.

 

[Robert1380]

The simplest solution would be to buy a 120v plug-in unit. However, you might consider adding a 12v connector (cigarette lighter plug) to the one you have. There are ports front seat and back seat that are far more convenient then clipping onto the jumper point under the right hand side fender in the drunk.

Hey, that’s just me. You do what works for you.

Yeah I thought of that but doesn’t the 12v cigarette plug pull from the accessory battery? My concern is running down that accessory battery and having issues with the rest of the truck operating correctly cuz the battery is discharged.

 

[The Weatherman]

With the truck on it should not be an issue if you have received all the BECM updates that have improved the charging logic in the vehicle. I wouldn’t let that bother me. But if it does, buy the 120v version.

 

[Maquis]

Do not connect directly to the battery. Use the jump points.
Connecting directly to the battery bypasses the BMS sensor.

 

[Robert1380]

Do not connect directly to the battery. Use the jump points.
Connecting directly to the battery bypasses the BMS sensor.

Got it. Thanks

 

[Tfarrell73]

With my ICE vehicles I always had the engine running for this or the compressor ran very slow

 

[Robert1380]

With my ICE vehicles I always had the engine running for this or the compressor ran very slow

Yeah same here. I’ve got the large Viair compressor and it’s fills very fast but it’s 12v only so I was wondering if you need the truck turned on to recharge the battery as you would on an ICE truck.

 

[NCevGuyF150]

So I have a Viair, 12v portable compressor that has the alligator clips to connect to the car battery but I’m wondering if you can use that compressor hooked up to the battery and successfully fill all four tires without causing issues to the trucks electrical system?

On the rare occasion of using my truck at places like the sand dunes, we air down to 15-20psi and want to be able to fill the tires back up without issues. Four tires is gonna be a lot of draw and I have no idea how that works when you pull directly from the trucks accessory battery. So do you leave the truck turned on and running like an ICE vehicle so it’s backfilling from the main battery to re-charge the smaller one? Or do I need to buy a small 110 plug compressor for this?

Thanks guys

Why not use the ports, or posts provided by the truck to jump off another 12 V ice vehicle. It seems like that should be where you would be able to get power for what you need.

 

[Robert1380]

Why not use the ports, or posts provided by the truck to jump off another 12 V ice vehicle. It seems like that should be where you would be able to get power for what you need.

Yeah I planned on doing that but my question is the draw to the 12v battery. I don’t wanna blow out the amps by filling 4 tires that are at 15-20psi up to the 42psi each tire takes to fill. That’s a continuous draw and a lot of it. On an ICE vehicle you simply start the engine and run it while using the compressor. I’m not sure if that is the same procedure for an EV.

 

[Runaway Tractor]

ICE vehicles have a gas engine turning and alternator to generate 12v power supplying the system and keeping the 12v battery charged.

EVs have a 400 volt DC battery, a DC-DC Converter that takes 400vdc in and outputs 12vdc for the low voltage system, with a smaller 12v battery.

The truck's computer determines when to enable the DC-DC Converter. It determines what the output voltage should be in a range of 12.8v to 14.5 volts, just like the voltage regulator on the old ICE alternator. The computer is monitoring the LV battery state of charge since it has its own little BMS and may vary the voltage up/down to charge the battery. It is also monitoring what accessories are turned on and varies the voltage. For example, when you turn the fan up to 5, it increments the voltage up. Oddly it also monitors vehicle speed. When you slow to a stop, it may increase the voltage, and then it steps down when you exceed 7mph.

To be blunt, the programming logic for DC-DC converter voltage and charge rate is absolutely moronic. This is an example of a computer program written by a blue haired college intern that has never owned a vehicle and never operated an electrical system beyond plugging in an iPhone. There are conditions where it will allow the LVDC battery to discharge or barely recharge despite having 130 FREAKING KWH of power and 100+amp capable converter sitting there waiting to do the job. It will even send you alerts about the LVDC battery being low. And it will sit there like an idiot doing nothing about it. The LVDC battery is low BECAUSE YOUR MORONIC PROGRAM ISN'T CHARGING IT.

So anyway, how does this apply to your question. Easy: Yes you can connect your air compressor to the 12V DC system. Connect it on the outside side of the little BMS attached to the LVDC battery. That way it accurately measures power in/out of the battery without your compressor skewing it. The DC-DC converter is absolutely more than capable of pushing out all the DC amps your compressor needs and then some.

HOWEVER: Due to the aforementioned useless control logic, you may need to coerce the computer to kick the DC-DC converter voltage up. It is too stupid to kick the voltage up based on, you know, the load and voltage. Turn the blower up to 5+ for example to trigger it to do it immediately.

 

[I <3 My Lightning]

The cabin 12v are 20amps. If you have the pump I think you have, it's max draw is 20 amps and has a 25 amp fuse.

This is what I use to run a compressor that connects like your does with the clamps. I have an older model of this...

https://www.harborfreight.com/autom...attery-jump-starter-and-power-pack-58979.html

Get yourself a coupon or wait till it goes on sale and get it for much less...

And after so many years I replace the battery, typically it comes with a 17ah, and I upgrade to either an 18 or 20ah depending what's available and within the 30 dollar range.

That has a built in ac charger (just a power brick with the prongs sticking out to connect to and extension cord.) that if you want you can charge off the frunk ac outlet as you run around. I have mine netted against the back wall in front of the 12v battery access panel.

 

[Robert1380]

ICE vehicles have a gas engine turning and alternator to generate 12v power supplying the system and keeping the 12v battery charged.

EVs have a 400 volt DC battery, a DC-DC Converter that takes 400vdc in and outputs 12vdc for the low voltage system, with a smaller 12v battery.

The truck's computer determines when to enable the DC-DC Converter. It determines what the output voltage should be in a range of 12.8v to 14.5 volts, just like the voltage regulator on the old ICE alternator. The computer is monitoring the LV battery state of charge since it has its own little BMS and may vary the voltage up/down to charge the battery. It is also monitoring what accessories are turned on and varies the voltage. For example, when you turn the fan up to 5, it increments the voltage up. Oddly it also monitors vehicle speed. When you slow to a stop, it may increase the voltage, and then it steps down when you exceed 7mph.

To be blunt, the programming logic for DC-DC converter voltage and charge rate is absolutely moronic. This is an example of a computer program written by a blue haired college intern that has never owned a vehicle and never operated an electrical system beyond plugging in an iPhone. There are conditions where it will allow the LVDC battery to discharge or barely recharge despite having 130 FREAKING KWH of power and 100+amp capable converter sitting there waiting to do the job. It will even send you alerts about the LVDC battery being low. And it will sit there like an idiot doing nothing about it. The LVDC battery is low BECAUSE YOUR MORONIC PROGRAM ISN'T CHARGING IT.

So anyway, how does this apply to your question. Easy: Yes you can connect your air compressor to the 12V DC system. Connect it on the outside side of the little BMS attached to the LVDC battery. That way it accurately measures power in/out of the battery without your compressor skewing it. The DC-DC converter is absolutely more than capable of pushing out all the DC amps your compressor needs and then some.

HOWEVER: Due to the aforementioned useless control logic, you may need to coerce the computer to kick the DC-DC converter voltage up. It is too stupid to kick the voltage up based on, you know, the load and voltage. Turn the blower up to 5+ for example to trigger it to do it immediately.

Wow! Now that’s what I call an explanation. Thanks bunch sir. Much appreciated.

 

[flyct]

For $59 buy one of these and plug it into your 120 vac outlet

https://www.harborfreight.com/3-gallon-110-psi-oil-free-light-duty-pancake-air-compressor-57567.html

 

[davehu]

A small 110v pancake compressor can be had for about $60 and draws only 3 amps.

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