What maximum power inverter for car?

Looking into high power inverter to run off the car. But for 1000W, it's likely draining 80A or 90A from the alternator. Does that mean the battery will die even when the engine is running?

I believe most alternators are around 50A, so max power of 600W?

Reply to
edward.ming.lee
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Looking into high power inverter to run off the car. But for 1000W, it's likely draining 80A or 90A from the alternator. Does that mean the battery will die even when the engine is running?

I believe most alternators are around 50A, so max power of 600W? =======================================================

Yes, the battery will still be discharging to make up whatever the alternator can't source, and yes, the alternator won't be happy for too many hours at max output. I don't know if the low end is really down at 50 or

60A , but many cars have alternators rated at 130A or more and I think 80-100A is typical. What kind of car do you want to do this with? Go to an auto parts website like autozone.com or rockauto.com and look up a replacement alternator for it, and they should list the specs. For grins I chose a 2010 Toyota Camry 4 cyl completely at random and autozone says 100A. Make your inverter connection to the output stud on the alternator and you'll save the voltage drop in the wire from alternator to battery.
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Regards, 
Carl Ijames
Reply to
Carl Ijames

Got a Toyota Sienna. I think it outputs 50A at idle and 120A at 5000RPM or so. Do i need to step on the gas to get the higher RPM, even when the car is not moving?

Perhaps tieing a controller into the throttle when voltage is getting too low?

Reply to
edward.ming.lee

ICBW but IIRC if one messes with the voltage regulation they can deliver much more voltage at rated current, increasing output power greatly. That does mean using a separate alternator for your power abstraction - and a suitable belt.

NT

Reply to
tabbypurr

You need to look up the specs for your car, so that you don't have to preface statements with "I think".

Having some way to make it do a high idle is probably a good idea, although a modern car will probably try to defeat you at every turn. Amateur radio operators probably know how to do this, although a lot of the really serious ones I've met drive SUVs, and probably know how to get a camping package or an aftermarket alternator that puts out more juice.

Given that the Sienna is a fairly large minivan there may possibly be a camper kit that you could put on it -- limber up your fingers and meditate to maximize your Google-Fu, and get to it.

Failing that, if you know your battery then you should know how long you could operate at full power before you need to go to high idle or drive around for a bit.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

No- the regulator will just back off the field current to keep the battery voltage at 14.4V.

No.

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Reply to
bloggs.fredbloggs.fred

I'm curious. How do you know the amperage needed to run that inverter? (Or any inverter). For example, I have a 300W inverter that plugs into the cig lighter in a car. I dont know how much amps it draws, but it has to be less than 20A, because cig lighters are usually fused at 20A or less. I use this inverter mostly for a laptop computer, so I can use the laptop at WIFI spots from inside the car. I know the laptop dont need the full 300W, but it still uses some power. I have run that inverter for as much as 6 hours, without running the car engine. Only once did I drain the battery enough that the car would not start, but that was over

6 hours use on a weak battery, and with the dome light turned on most of the time too. (I had the battery tested after that, and it needed to be replaced).

I have a friend who bought an older Ford van, which came with a camper package, including a TV, VCR, and a built in 1200W inverter. The van's altternator was 140A. For some reason that alternator or the regulator kept failing, and he said it cost a fortune to repair. He said he did not need or use the inverter, so he disconnected it. He dont use a VCR, and the analog TV is worthless without a converter box for on the air tv. Anyhow, after spending lots of money on alternator repairs, he changed it to a standard 60 or 65A Chevy alt with built in regulator. (That took a little modification of the brackets). He has not had any problems since. Aside from a few extra (dome) lights in the rear, it's just a basic vehicle now, without the inverter and tv/vcr. So he dont need all that extra amperage.

Reply to
oldschool

Lots of work in a car with a serpentine belt, but possibly doable if there's room.

A herkier alternator is probably better, if you want to get into things that deep.

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Tim Wescott 
Wescott Design Services 
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Reply to
Tim Wescott

Got a Toyota Sienna. I think it outputs 50A at idle and 120A at 5000RPM or so. Do i need to step on the gas to get the higher RPM, even when the car is not moving?

Perhaps tieing a controller into the throttle when voltage is getting too low? =========================================================

Rockauto and autozone both say a 2015 Sienna has a 150A alternator. I haven't seen any official specs for idle output but you should get full output by 2000 rpm or 2500 for sure. The voltage regulator is listed as "internal", but I don't know if the pcm can modulate that or not so it may do better at idle than 50A. I know that on later GM's the pcm controls the alternator output but I'm not familiar with Toyotas. My guess is yes, if you want full output to an inverter you will have to step on the gas a bit to get the rpms up, and shut off everything you can like headlights, drls, and climate control (kill both the compressor and the internal fan). The engine shouldn't overheat but keep an eye on it. Get a clamp-on dc ammeter good for 150-200 A, clip it on the alternator output wire, turn on all the loads you can (headlights on bright, foot on the brake, ac fan on max, seatwarmers on, anything you can plug into the cigarette lighter like a spotlight or air compressor) and see what the output is at idle and above. You say 1000W, but is that continuous or an intermittent load? If it's intermittent you could probably get away with idling, and let the battery carry it on the peaks.

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Regards, 
Carl Ijames
Reply to
Carl Ijames

What the heck are you running in the car that actually NEEDS 1 KW?

Jon

Reply to
Jon Elson

On an old car with lots of space, fairly easy. On a new extremely compact one with lots of things running on 1 or 2 belts, not as easy.

NT

Reply to
tabbypurr

Good question. Knew someone would ask. Running a 1200W food warmer for an hour, until i can hook it up to the engine heat/cool system. Might not need 1000W, but at least 700W to 800W.

Might be easier just to hook up a bank of batteries.

Reply to
edward.ming.lee

Good question. Knew someone would ask. Running a 1200W food warmer for an hour, until i can hook it up to the engine heat/cool system. Might not need

1000W, but at least 700W to 800W.

Might be easier just to hook up a bank of batteries. ========================================================

Will you be stationary? I guess I was assuming that before, from your idling questions. If so, just get one of those $89 on sale harbor freight

700 watt generators if that would be just enough, or the 4000 watt one for about $300. If you are driving around but it is a temporary fix until you plumb into the heater loop for hot water, then just use the 1000W inverter and don't worry about idling unless you spend a lot of time doing it. It may not be optimal but it will get you up and running for now. The battery will go down a bit at idle but will charge back up when you start moving again. Get one of those $10-15 ebay voltmeters that plug into the cigarette lighter if you want to keep an eye on the system voltage while the engine is running and the battery voltage with engine off, there's even a cute one with two usb ports for phone charging.

(If the inverter draws 80A and the alt can source 50A at idle that is a battery draw of 30A so the battery will last about three times longer idling than with engine off and my guess is that on just battery it could last

40-50 minutes completely discharging the battery, so my swag is that you could idle for 20 minutes at a time without discharging the battery too deeply before you need to rev the engine back up. Brief stops as an ice cream truck ok, parking for two hours as a roach coach not so much :-).)
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Regards, 
Carl Ijames
Reply to
Carl Ijames

If you run it long enough, the surplus power will, of course, come from the battery -- until the battery is unable to keep the engine running!

You may find that you cook the diode trio in the alternator before that point -- alternators aren't intended to run at 100% duty cycle.

Also, consider how you're going to get that power *from* the battery terminals to your load. If you're stuck with a 12V supply, you'll want to keep those cables very short to avoid large IR losses.

If your need is only temporary, consider tossing a spare battery in the trunk with a *light* feed from the engine (behind a diode) to pick up part of the load. Then, when THAT battery runs flat, you can still drive home.

(Trunk is a better location for a battery, regardless. Under the hood is just a matter of convenience -- and shorter wire run to starter)

Depends on the alternator and vehicle. My buddy's truck has a *pair* of 150A alternators and a pair of oversized batteries (for the 7L diesel)

Are you sure you really *need* 1000W? Just because the thing you are powering CLAIMS to be rated at 1000W doesn't mean it will actually DRAW that!

Reply to
Don Y

Power = Amps * Volts

With all things consumer, there's a bit of tongue inserted in cheek. I.e., they may assume your battery is at 14.4V instead of *9* (which is where it will be when the engine is cranking). And, may simply indicate the *rating* of the components used inside -- I've got a

2200VA UPS plugged into a 15A mains circuit (clearly the branch circuit won't be able to supply that 2200VA!)

Laptop is probably 40-60W. I have a portable inverter for emergency use that is wired directly to the *battery*, with its own internal fuse.

Often, all you have to do is replace the diode trio ("bridge") inside the alternator. Usually a handful of dollars and 10 minutes of your time (given that you have to plan on removing and reinstalling

*an* alternator, regardless).
Reply to
Don Y

Yow! How about tow a gas generator behind the car? Really, general passenger cars are NOT made for these sorts of electrical loads. And, many inverters are horribly inefficient, so if you need 800 W into the warmer, you might need a much larger inverter to not have it burn up on you.

Jon

Reply to
Jon Elson

Use the exhaust heat.

NT

Reply to
tabbypurr

Possible. But rubber hosts (for coolant) is easier to route than metal pipes (exhaust gas).

Reply to
edward.ming.lee

Less consideration re CO too. But cooling water isn't doing what you want, a flexible exhaust hose system will.

NT

Reply to
tabbypurr

Using the waste heat of the engine is a good idea.

Anyway, burning the hydrocarbons in a ~20% efficient engine (optimistic

- it is unlikely to be running at the optimum power level), and then running the mechanical output through an alternator and then an expensive inverter, only to dump whatever tiny proportion is left into a resistive heater is surely not a good use of the fuel.

Camping stores have a variety of cooking equipment that heats food using burning hydrocarbons, with much higher efficiency. Once that is done, put the hot food into a vacuum flask if one wants it to stay hot whilst the car is moving.

Reply to
Chris Jones

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