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Anonymous Poster #1

Max Electrical Power Output Of A Car

07/30/2017 11:47 PM

what is the max electrical power that can be safely drawn out of a running car ?

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#1

Re: max elctrical power output of a car

07/31/2017 12:06 AM

I bite! Where from in which car, what for?

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#3
In reply to #1

Re: max elctrical power output of a car

07/31/2017 12:16 AM

an average diesel/gasoline car

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#2

Re: max elctrical power output of a car

07/31/2017 12:08 AM

It depends . Depend on type of power source you are using , the batteries , and other factors . Here is a site which tells you about some of the most powerful electric cars made. Tesla S is just the tip of the iceberg . But Tesla S is a good electric car.

https://www.mnn.com/green-tech/transportation/blogs/4-insanely-powerful-and-expensive-electric-cars

It also depends on which sense are you judging the car. By its speed or acceleration or what ?

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#4
In reply to #2

Re: max elctrical power output of a car

07/31/2017 12:16 AM

not an electric car, a gasoline one

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#33
In reply to #2

Re: max elctrical power output of a car

08/01/2017 6:41 AM

Who says its an electric car?

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#5

Re: max elctrical power output of a car

07/31/2017 12:17 AM

Depends on the battery size, alternator size, wiring and existing internal protection sizes, how long you want to discharge for (is it short duration seconds or long duration hours), etc. Also is it one big high current circuit or a combination of numerous lower current circuits.

Is it a stock (unmodified) vehicle or are modifications to upgrade the electrical system allowed?

What is the application exactly, what are you trying to do and what currents are you thinking you want?

The question is quite vague and this will help narrow down our answer.

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#6
In reply to #5

Re: max elctrical power output of a car

07/31/2017 12:26 AM

the power needs to be drawn for about 10-20 minutes. it's one high current circuit. No modifications are made to the vehicle electrically. i'm expecting at least 100W of power output, while the headlights and the infotainment systems are running. possible?

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#7
In reply to #6

Re: max elctrical power output of a car

07/31/2017 12:32 AM

Well 100W may be possible using the vehicles existing Cigarette lighter port, which now days has been repurposed into an accessory socket.

https://en.wikipedia.org/wiki/Cigarette_lighter_receptacle

It depends on the fuse size protecting the socket (which is independent of the other circuits in the car), but anywhere from 2-10A or more is possible, and 100W is only about 8.3A.

I am not sure, there may be a higher current circuit available at the fuse box of the car but it is probably not going to be wired up as standard to a convenient set of terminals so additional wiring will likely be necessary from the fuse box to your load.

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#8
In reply to #6

Re: max elctrical power output of a car

07/31/2017 12:36 AM

100 watts at 12v = 8.34 amps average alternator output in average car ~60 amps....

Should be no problem....most cigarette lighters are 12 -15 amps

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#9
In reply to #6

Re: max elctrical power output of a car

07/31/2017 12:37 AM

Let's just imagine that the battery is 60AH (reasonably typical). If you draw 60A for 15 minutes the battery would still remain 75% charged. 60A x 12V = 720W. The wire (and fuse) will need to be sized for the amp draw you need.

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#39
In reply to #9

Re: max elctrical power output of a car

08/01/2017 9:43 AM

OP hasn't been 100% clear, but it seems more than likely he wants his 100W with the engine running, not draining the battery.

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#10

Re: max elctrical power output of a car

07/31/2017 2:02 AM

Alternator output can range from 50 to over 200 AMPS.

So, your question is not answerable without specific details.

It's like asking "how fast can a car go".

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#11

Re: max elctrical power output of a car

07/31/2017 3:16 AM

It is determined by the rating of the protective devices, usually fuses, in the wiring. The vehicle's wiring diagram and user manual can not be seen from here.

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#12

Re: max elctrical power output of a car

07/31/2017 4:56 AM

First of all do a google search for the specification of the alternator for the car your going to use. So, search for say

"Chevrolet cavalier replacement alternator specification"

I ended up with this spec:-

http://www.autozone.com/batteries-starting-and-charging/alternator/duralast-alternator/352089_938138_0

It's probably reasonable to assume that you could take 30% (~360 W) of this power over a long period or almost 100% over a very short period.

Of course you need to make sure that you have the necessary wiring and fuses in place.

This is of course purely hypothetical as your chances of finding a 2000 Chevy cavalier which will start are vanishingly small.

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#13

Re: max elctrical power output of a car

07/31/2017 5:18 AM

Hello,

In Australia we have a 7 pin trailer socket that runs the standard trailer accessories and then there is a 12 pin option that includes a system to charge accessory batteries and such while travelling. The battery circuit is protected by a 15 Amp fuse, so 100W is no problem for a standard car.

There are multiple cars that have additional headlamps (spotlights) for remote driving with light capability over 100W for those lights only. again, should not be a problem.

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#14

Re: Max Electrical Power Output Of A Car

07/31/2017 7:33 AM

In Europe, typical alternator rating is 55 or 70 amps giving about 770 or 1000W at regulated voltage about 14 volts (though there are lower and higher outputs).

Your 100W shouldn’t be a problem, even with the other loads you mention. You could draw a lot more than that over a short period. If it’s temporary job you could connect direct to the battery. Then there’s no issue of fuses blowing, and you can take current above alternator rating, the battery supplying the difference. The alternator is self-limiting for current, so there’s no immediate risk there, but if you take maximum output for extended periods life, specially brushes, might be shortened. It might be a good idea to have an ammeter in the circuit, so you can see what you’re doing. Also the alternator gives maximum output at about 10000rpm, so you might need to rev the engine.

If you want to do it while the car is being driven, you need to connect somewhere appropriate, and ensure the relevant wiring and fuse are up to it

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#15

Re: Max Electrical Power Output Of A Car

07/31/2017 7:43 AM

"what is the max electrical power that can be safely drawn out of a running car ?"

1.21 gigawatts, if it is a certain DeLorean DMC 12.

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#17
In reply to #15

Re: Max Electrical Power Output Of A Car

07/31/2017 9:41 AM

Holy crap!

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#20
In reply to #15

Re: Max Electrical Power Output Of A Car

07/31/2017 3:32 PM

Technically they needed the fictional value of 1.21 Jigawatts as stated in the films by both future (present) Doc, past Doc and future (present) Marty.

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#21
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Re: Max Electrical Power Output Of A Car

07/31/2017 3:36 PM

"J" or "G"... it's all in the pronunciation..... Jim went to the gym.

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#23
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Re: Max Electrical Power Output Of A Car

07/31/2017 4:25 PM

...but it is not pronounced jugawatts

It is Gigawatts, like you got a new gig, get it? Not jig, as in jigger's up drunks!

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#43
In reply to #23

Re: Max Electrical Power Output Of A Car

08/01/2017 10:59 AM

Giggity!

Quoting Quagmire from Family Guy.

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#44
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Re: Max Electrical Power Output Of A Car

08/01/2017 12:00 PM

OR did you mean, Jiggly?

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#26
In reply to #21

Re: Max Electrical Power Output Of A Car

07/31/2017 9:20 PM

The American pronunciation in the "Back to the Future" movies where this came up were very clear in my mind and not open to misinterpretation in my opinion. "Jig" and "Gig" are very different sounds and it was clearly "Jigawatts" both actors were saying.

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#36
In reply to #26

Re: Max Electrical Power Output Of A Car

08/01/2017 9:20 AM

What we have here is a failure to "respect my authoritah!" Gigawatts is spelled with a "G" for a reason. Now get yur butt to units detention facility!

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#38
In reply to #26

Re: Max Electrical Power Output Of A Car

08/01/2017 9:31 AM

Jack, read this. Also check out Merriam Webster's pronunciation.

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#46
In reply to #38

Re: Max Electrical Power Output Of A Car

08/01/2017 3:49 PM

Interestingly other dictionary references and my experiences with the European and American power industry don't use Jiga either in spelling or pronunciation. Perhaps like the article says it is one of those old references that is no longer used (like 'cycles' changing to 'Hertz').

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#47
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Re: Max Electrical Power Output Of A Car

08/01/2017 3:58 PM

Just saying, I think either pronunciation is correct, but the spelling is still "gigawatts".

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#48
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Re: Max Electrical Power Output Of A Car

08/01/2017 4:39 PM

According to Merriam-Webster's 11th Collegiate, you are correct.

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#50
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Re: Max Electrical Power Output Of A Car

08/01/2017 7:28 PM

Other dictionaries I looked at said no however hence my comment above.

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#51
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Re: Max Electrical Power Output Of A Car

08/01/2017 8:15 PM

I don't recall that, either, but I wonder what was said in the movie "Back to the Future".

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#49
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Re: Max Electrical Power Output Of A Car

08/01/2017 7:27 PM

I have never met or seen on video an American power Engineer who has said Gigawatt with a hard 'J', certainly no European or Australasian I have heard talk.

Anyone come across this or is it just me? How about a you tube link or something.

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#52
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Re: Max Electrical Power Output Of A Car

08/01/2017 8:19 PM

It's stupid, seems like an old pronunciation from ancient Greek.

https://wheels.blogs.nytimes.com/2008/04/08/you-say-gigawatt-i-say-jigowatt/

http://insideenergy.org/2014/10/10/ie-questions-what-the-hell-is-a-jigawatt/

https://www.youtube.com/watch?v=cMP9LvUb3Ig

http://www.deloreanmotorcar.com/ec/jigawatts.htm

It would seem neither of us is incorrect, in fact I say it with a hard "G", I'm just saying when Doc Brown said it with a "J", he was still saying "gigawatts". Something like "Gigolo", or "Gigantic"....

Kind of got serious over a response I made as a joke....

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#40
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Re: Max Electrical Power Output Of A Car

08/01/2017 9:45 AM

That's not a typo. Jiggawatts is similar to Bazillionwatts. Gigawatts is an actual unit.

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#22
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Re: Max Electrical Power Output Of A Car

07/31/2017 4:09 PM

What the hell is a Jigawatt? Is that related to Dan Fielding on Night Court?

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#27
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Re: Max Electrical Power Output Of A Car

07/31/2017 9:22 PM

GREAT SCOTT!! Does no one remember the American movie classics from the 80's?

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#32
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Re: Max Electrical Power Output Of A Car

08/01/2017 5:13 AM

One could always go back in time and sort all of it out.

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#45
In reply to #32

Re: Max Electrical Power Output Of A Car

08/01/2017 3:41 PM

Time travel is relatively simple compared to finding a serviceable Delorean to build it into. I think you can still buy Mr. Fusion on Ebay.

Ok, now I think we are starting to stray off topic.

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#16

Re: Max Electrical Power Output Of A Car

07/31/2017 8:17 AM

I have looked into details of Battery used in Ford Fiesta Car.

It is 400A peak current at 12V. Usable power in KW hours may be only 1kW hour. That sets the upper limit.

Drawing 10A at 12V is 120W as I*V. It is feasible to use such power for 10 minutes even when car isn't running if battery is fully charged.

Draining too much power, car may not start and to be at safe side make sure, battery is good and fully charged.

While car is running, it may be feasible to tap power even from generator which is charging the battery.

It may be a very good idea to tap the battery power using an intelligent circuit which can estimate available power on the battery like the way one knows in mobile and Laptop. If your car has any such display then have a look at it before start draining the power.

Short circuit in the device may be a disaster and hence, protection device which may limit the maximum current and its duration or total power must be in place, is sure a wise idea. Short circuit can happen simply due to defective cable.

I like this idea as I often tap power from Batteries. I also know these problems that do happen in real life. Some time cable can melt in your hand if it is short circuited.

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#24
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Re: Max Electrical Power Output Of A Car

07/31/2017 4:28 PM

And you and I both hate grilling 3rd degree burn lines into the palms of our hands when wires melt. I just hate when that happens! LOL!

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#53
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Re: Max Electrical Power Output Of A Car

08/02/2017 2:48 AM

It is indeed nasty to have very hot short circuited wire in hand with molten sleeve which sticks to skin. We often save our hands and let the battery go to hell, and it sure does.

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#55
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Re: Max Electrical Power Output Of A Car

08/02/2017 10:33 AM

I would rather not have that entire event take place to begin with, and thank you so much for sharing that "lively" experience with us.

Goshee that has to hurt. It is as though someone picked up a branding iron out of the fire by the wrong end!

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#18

Re: Max Electrical Power Output Of A Car

07/31/2017 1:20 PM

Assuming you may place the drive wheels of said "running" car on a dynamometer, I would say it is very nearly the sticker horsepower rating.

Otherwise, you are limited by the amount of power you can pull off the alternator.

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#19

Re: Max Electrical Power Output Of A Car

07/31/2017 2:14 PM

Look into automotive sound systems. They typically use around 100W and there's a lot of info on how they do that.

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#25

Re: Max Electrical Power Output Of A Car

07/31/2017 6:32 PM

Apparently after all my time spent working on higher powered electrical and electronics systems I must have become jaded.

To me a short term 100 watt load on a common vehicle 12 volt system is inconsequential. In my books the 3000 watt continuous (6000 for 5 minute surge capable) inverter I am working on getting part together for for my service truck is something worth putting some consideration into.

So far I just aquired the third 12 volt ~110 Ah group 31 deep cycle battery for it so I can install everything as I need to now.

The plan is to use 1/0 from each battery to the inverters two power lugs and a 2 ga feed from the alternator for charging with the likelihood of installing a 140 - 180 amp alternator if the one of the oddball high powered ones I picked up used works or is fixable.

To me that's a high power 12 volt load!

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#28

Re: Max Electrical Power Output Of A Car

07/31/2017 10:54 PM

I just googled "max amperage alternator" and found a 370 Amp E Series Alternator with Black Finish for Select 1994 - 2003 GM 2.2L SOHC Engine Vehicles, $699. This is a apparently a bolt on accessory. Of course, you might need some hefty cables from the alternator.

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#34
In reply to #28

Re: Max Electrical Power Output Of A Car

08/01/2017 9:06 AM

Forget cabling, that bad puppy needs silver plated bus bars!

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#35
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Re: Max Electrical Power Output Of A Car

08/01/2017 9:15 AM

Is that a matt black finish, to look cool?

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#29

Re: Max Electrical Power Output Of A Car

07/31/2017 11:06 PM

There are two limiting factors: Battery capacity and alternator capacity. Everything else can be compensated for. This is a common question when adding a winch to a vehicle/trailer. A larger battery can supply a larger amount of power until it's discharged; how long it takes to recharge is dependent on the alternator. Sometimes a second battery is added to ensure that you still have starting power from the main battery, so that you don't get yourself stranded. You could also make a trailer with 12vdc power tools for a mobile shop, with its own battery that's recharged from the tow vehicle via a large wire from the alternator thru the trailer connector to supply a large amount of "recharge current" to the trailer's battery. The point is that the battery can act as a buffer for large loads when the alternator can not supply it in real time. How fast the recovery time is from that deficit, depends on how fast you can recharge the battery.

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#37
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Re: Max Electrical Power Output Of A Car

08/01/2017 9:21 AM

Please define "everything else." That appears to be a fairly wide class of objects.

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#41
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Re: Max Electrical Power Output Of A Car

08/01/2017 9:53 AM

Well, you got me there. I was referring to collateral items like cables, fuses, connectors,etc. But, for for that matter, I suppose that even the battery(s) and alternator can be upgraded also, as long as space/mounting-brackets, etc, can support it.

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#30

Re: Max Electrical Power Output Of A Car

08/01/2017 1:18 AM

Are you talking about from the piddly little alternator on the engine? OR, are you thinking about putting the car on a set of rollers, which are attached to a large generator, and using the energy, that the spinning tires could produce from that set up?

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#42
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Re: Max Electrical Power Output Of A Car

08/01/2017 9:56 AM

If he only wants 100W, even in addition to usual loads, the piddly little alternator on the engine would be fine.

Before alternators came in output of a standard dynamo was 22A (in UK, can't speak for USA). So even a small alternator isn't that piddly by comparison.

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#31

Re: Max Electrical Power Output Of A Car

08/01/2017 3:46 AM

If you check out various US cars you will find a series production socket for 110v supply which is far higher than a normal 12v system allows, using a 12v DC Invertor.

Also there are 12v power winches fitted to SUV's that draw 500+ Amps at full load.

In addition there are certain vehicles ( Land Rover for example) that can run hydraulic power take-offs from the gearbox which is yet another form of power. These hydraulic systems can be used to run Generators, one was 240V 5KvA 21 Amp.

Some also used a belt driven system from the motor.

Current new vehicle architecture is using 48v systems to power stop-start, Aircon, Power Steering etc.

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#54

Re: Max Electrical Power Output Of A Car

08/02/2017 7:39 AM

Is this a question about dynamometers?

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#56
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Re: Max Electrical Power Output Of A Car

08/02/2017 10:34 AM

Should have been, IMHO! Alternator smallternator, let's see some real power here.

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#57
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Re: Max Electrical Power Output Of A Car

08/02/2017 2:21 PM

That is what I asked in post #30.

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#58
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Re: Max Electrical Power Output Of A Car

08/02/2017 4:41 PM

#18

Re: Max Electrical Power Output Of A Car

Same thing I said in post #18.

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#59

Re: Max Electrical Power Output Of A Car

08/03/2017 12:33 AM

If you run a lead from the battery to the outside world: Power drawn from the battery, say 40A, assuming 40AH battery and you are going to run for about one hour. If you run longer, reduce current drawn from battery. The lead from battery to alternator is rated at about 100A continuous, determined by its diameter/circumference (not its cross-sectional area), to get rid of heat. So alternator/100A + battery </= 140A for one hour. =100A max all day.

If you run a lead from the alternator to the outside world, the limit is say 40A from battery plus alternator rating, for one hour. Alternator rating only if all day.

If you run from elsewhere in the wiring loom, the limit is set by fuses in circuit and the conductors between take-off point and battery/alternator.

I have not allowed for ignition requirements. I assume you are not moving, have vehicle doors closed, you are in daylight, nothing switched on other than ignition, no other external connections, and you don't smoke (don't light up using the electrical system).

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#60
In reply to #59

Re: Max Electrical Power Output Of A Car

08/05/2017 5:16 AM

Diesel engines require very little power when running, you can safely ignore it.

My car has a cooling water heating system, that warms the water when the engine is cold, but we only use it in winter time.

But due to that, it has a 12 volt nominal, 120 amp alternator from the manufacturer.

Most of this would be available, without using the battery at all if need be. Your 100A cable would be too thin.....In such cases I always use starter cable, its usually good for 400 amps or so, and is reasonably priced.....of course a proper fuse would also be a good idea as well for safety.....

Also, a long time ago, someone here mentioned "after market" alternators, that can be fitted to cars/trucks, giving quite large current outputs of either 12 or 24 volts.....but I cannot remember who or where, sorry! But more than my car's alternator, that I do remember....

Also, someone added an alternator quite cleverly to a boat's engine , fairly recently on CR4.....not that much different.

Of course the OP has been exceedingly sparing with details, so he has really left us all in the dark and guessing.......

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#61
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Re: Max Electrical Power Output Of A Car

08/09/2017 11:17 PM

I totally agree with you, Andi. Diesel engines need the power to start the starter and to sustain very minimal electrical stuff especially those old engines.

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#62
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Re: Max Electrical Power Output Of A Car

08/10/2017 3:00 AM

That's right, in the good ol' days you didn't need a battery at all, tow start it and away you go. Of course that's road vehicles, small stationary engines and petrol/TVO tractors with magneto ignition and swing start don't have a battery anyway.

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#63
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Re: Max Electrical Power Output Of A Car

08/10/2017 10:42 PM

You are correct... I do remember those olden day. But now modern diesel engine needs a contious supply of electricity to power its ECU. Technology at its best!

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#64
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Re: Max Electrical Power Output Of A Car

08/11/2017 3:37 AM

You slightly missed the point to my mind, it was actually mentioned by myself in passing too:-

Yes, it needs power, but it needs only milliamps for itself!!!!

Certainly far less than 1 amp!!! Probably only 500mA or less.....

But lets go with say 5 amps! To include the valve control solenoids and stepper motors (which are only used when needed, not continously!) and the like!

Still unnoticeable in the big scheme of things!! Many cars today have 120 amp or more Alternators........

The "average" power drain, seen over hours, will be quite small!

See here:-

Engine_control_unit

I hope this helps better understanding of the amounts of power needed.

By the way, I have explained for any ECU on cars, but in reality, Diesel engines will use even less total power....few controls, less data.

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#65
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Re: Max Electrical Power Output Of A Car

08/13/2017 10:37 PM

Oh yeah sorry about that!

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#66
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Re: Max Electrical Power Output Of A Car

08/14/2017 4:14 AM

I forgot to add in #62 - in the old days of dynamos, before alternators you didn't need a battery to start a petrol engine, just tow it to give engine speed enough to close the cut-out. Then keep revs up and cut-out closed and it will run all day.

Unlikely to work with an alternator as usually not enough residual magnetism in the rotor, and anyway it's risky to run with battery disconnected.

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#67
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Re: Max Electrical Power Output Of A Car

08/16/2017 9:14 PM

Yes, that is absolutely correct codemaster.

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