Auto Inverter Sizing Question

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Old 07-04-13, 11:35 AM
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Auto Inverter Sizing Question

I need to buy an inverter that plugs into my Escape's cigarette lighter-like power port which is large enough to run a nebulizer -- basically, it's like a large aquarium pump that is used (when needed) by people with asthma and other breathing issues.

The other things that will be charged from it are smaller; a laptop, tablet, phone, camera, etc and we're not anticipating more than two devices to be plugged in at any time. The big question is which one is large enough to power (not charge, power) the nebulizer, but isn't too large and will add unnecessary expense.

Written in the bottom of the nebulizer, I see 115VAC, 60Hz & 1.5A our old one, which no longer works but was larger and could be the size of our next, says 120V, 60Hz & 1.7 Amps (I also see 1.7A written on the laptop cord -- who knew?)

Looking at the auto parts websites, I see several that do 120v, but the other than the number of outlets, the other distinction is the number of watts and I'm not sure how to do the math.

Any help or recommendations would be appreciated.
 
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Old 07-04-13, 11:51 AM
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First check your equipment to confirm what type of power it needs to operate. You may need to contact tech support for each item to find the answer. The reason is that most less expensive inverters generate a modified sine wave while the more expensive models generate a more true wave form. It does not matter for some devices but some (like my cordless tool's battery charger) will not operate on the cheaper modified wave inverters.



Once you know which type of inverter is needed then you can worry about wattage. Most advertised capacity is the temporary peak that the inverter can provide. So, a 1'000 watt inverter may only be able to provide 700 or 800 watts continuously. The specs should tell you both the peak and continuous capacity. As a safety margin I never like to run anything long term at it's full capacity. I like to provide a little extra safety margin.

Next, if you will be supplying enough 12VDC to the inverter. 1.5 amps is easy at 120 volts. Converted to 12 volts the amps jumps to 15 amps. Then you need to consider the inefficiency of the inverter. Cheap ones may waste up to 50% of the power they take in so you could end up needing upwards of 22 amps DC to just run the nebulizer with a cheap inverter. A quality inverter will waste much less energy but still will loose 10 or 20% requiring maybe 18 or 20 DC amps to run the nebulizer. Most auto cigarette lighter sockets are wired and fused for 10 or 15 amps maximum. What this all gets to is that may have to run special wires directly to the battery to provide enough amperage to run your devices.
 
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Old 07-04-13, 12:37 PM
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Pilot Dane covered mostly everything.
I would mention that most power ports (the current politically correct name), is on a 15A fuse which is shared with other built in devices within the vehicle.
A dedicated line would be your best bet, which is fairly easy to DIY or have done.

One other thing to mention....Consider where you want the inverter to be located and would it be used frequently enough to make it a perminent install.
If you will only use it on occation, having a dedicated power/ground line ran to a newly installed power port would be the best route. Consider the placement of the power port as you don't want to fight with cords when it use. A good temp install location is to have a power port installed near the front passenger's feet. A lot of vehicles have a pop out piece designed for installing this.
A perminent install will require a bit more thought, but would make ease of use and cleaner install much better.

Any Car audio shop can do the power cable installation. It's the exact same work powering a power amp, or a new power port.
 
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Old 07-04-13, 12:40 PM
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I'm thinking that if I call the nebulizer manufacturer and get the phone bank for the medical equipment department of this huge conglomerate, the minimum wage employee will likely tell me that they make one designed to plug into a car's power port and because the warranty on my home product is probably void if I use it in a car, they can't help me and their computer doesn't know. (I've called them about other things, before)

If anyone knows which inverter will run the nebulizer, it'd be great, but in the meantime, you say that your tool charger won't work with some inverters but it will with others. I'm assuming everything else works with whatever charger you use for your tools, so could you tell me what manufacturer or product line you use? I'm not seeing anything about waves in the various auto parts company online catalogs. I'm sure it would probably say something in the owner's manual on the manufacturer's site and I'll take a look, but if you (or someone) could give me a headstart, it would be great.

Thanks.
 
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Old 07-04-13, 12:43 PM
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Mike mentioned a lot of power ports are fused at 15 amps..... he's right. But many are fused at 10 amps too.
 
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Old 07-04-13, 12:47 PM
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For an item requiring 1.7amps at 115v you be required to use an inverter of at least 200 watts.
115 x 1.7 = 195.5 watts

You would need to try a 300 or 400 watt inverter.
 
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Old 07-04-13, 12:50 PM
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If an inverter doesn't mention the waveform then you can rest assured it is at best a modified sine wave or at worst a square wave inverter. The difference is a modified sine wave will have more "steps" than will the straight square wave device. A "pure sine wave" inverter will operate anything that normally uses utility power as long as it has sufficient output.

Multiply the voltage by the amperage as listed on the nameplate to get watts. This is not absolutely accurate but will be close enough. Add all the things that you want to use at one time and select an inverter that is at least 25% larger in nominal output than the total wattage draw of the items. It is almost a certainty that you will need dedicated wiring rather than be able to use the "power port" receptacle.

Xantrex is a highly regarded name in pure sine wave inverters. There are others. Google is your friend.
 
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Old 07-04-13, 01:21 PM
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One thing I failed to mention, I would avoid using the inverter for more then one item if that one item is a motor of some sort. Motors tend to cause issues with other devices on a smaller power source.
 
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Old 07-04-13, 02:08 PM
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Google hasn't been a lot of help because it produces a lot of people saying they run a nebulzer with an inexpensive inverter and others saying that it may not or won't work -- though the only one saying that with direct experience from the links I've clicked, said it worked like ten times, then the inverter quit. (Also listed among things that might not work is "some laptops", while Google shows me lots of people who use and charge their laptops with an inverter)

What prompted my question is that I need an inverter to keep the laptop and tablet charged or powered on a long car drive. We also do a lot of camping and if I'm going to buy an inverter anyway, I should buy one that will also power the nebulizer.

I'm not seeing Xantrex listed at any of the auto supply stores in town, but thanks.
 
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Old 07-04-13, 02:36 PM
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No, you are unlikely to find Xantrex at an auto parts store. Do the Google boogle using Xantrex as the search term. Or check out RV supply stores or solar power stores. There are other manufacturers of pure sine wave inverters, I just know of Xantrex from my explorations into solar power.

Here are some pure sine wave inverters sold by MCM Electronics. I have no connection to MCM other than as a satisfied customer.

MCM Electronics - Search Results for pure sine wave inverter
 
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Old 07-04-13, 02:39 PM
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I'm not seeing Xantrex listed at any of the auto supply stores in town
An autoparts store is generally not a source for better quality inverters. Online or marine or RV suppliers are more likely sources.

An online example: Amazon.com: Xantrex PROWatt 600 Inverter, Model# 806-1206: Automotive
 
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Old 07-04-13, 03:25 PM
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American Van has a selection of vehicle inverters. Some for hardwiring.
 
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Old 07-04-13, 04:20 PM
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I'll throw my 2 cents in here since I do use inverters on a regular basis.

I am, for the most art a truck driver by trade. I spend a lot of time on the road with a laptop, phone chargers etc. At one time, we owned a small hot shot trucking company & we ran an inverter to power any & everything from laptops, to printer/scanner/copier, Walkie Talkie chargers etc. For that, we used a 1500 watt inverter.
To run basic small inverters like you want (300 watt for example), I have bought several. Most I haven't had good luck with. However, the one's I have had very good results with have come from truck stops like Loves. Just plug it into a cigar lighter port, some vehicles now have a couple other ports like cigar lighters but are dedicated for things just like this. The last one I bought is a 300 watt.
PowerDrive RPPD300 300-Watt DC to AC Power Inverter with USB Port and 2 AC Outlet : Amazon.com : Automotive

The two previous inverters were Cobra brand 400 watt. I had both of those hard wired in to a fuse panel... NOT in the cigar lighter.

FWIW, most of the smaller ones that I have used, just do no work well for cigar plug or hardwired. These work very well without any problems.

As well, I dont know if 300 watts will run your equipment or not, I am just going off of PMax's info in post #6.
 
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Old 07-04-13, 06:41 PM
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Thanks. I'm kind of surprised that no one has spoken up who uses a nebulizer, but after some confusion about what one auto parts store has in stock and after reading a lot of reviews, I'm about ready to capitulate and buy the Diehard 425 from Sears because though I'm not finding a lot of reviews, it has a good price and the Diehard name.

Of course if anyone knows anything negative or if they have any other suggestions. Fan noise seems to be the big concern for most reviewers with all of the various brands and I've only been looking at those with the alligator clips in addition to the lighter connector because of the fuse question which was raised in this thread.

Thanks.
 
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Old 07-04-13, 07:06 PM
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Notice there is no description of the waveform it produces and the price is less than $50. Less than a third of the price of inverters that do advertise as pure sine wave. Also it is large enough for your nebulizer but probably wouldn't run anything else. Are you prepared to buy a new nebulizer if it burns up a circuit board?
 

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Old 07-05-13, 12:22 AM
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Totally agree with Ray. This is harsh but I would think you a fool to waste your money on that inverter. Maybe it will work, for a time, but it will NOT be good for your needs.
 
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Old 07-05-13, 09:08 AM
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With a piece of medical equipment I would look for a pure sine wave inverter. It will be more efficient so it will put less a drain on your battery and has a much lower chance (almost none) of damaging the nebulizer. The big drawback is the price.

Using a less expensive inverter that does not specifically say that it's a pure sine wave is a gamble. The inverter will be less than half the cost but it may damage whatever you plug into it. The charger for my lithium tool batteries will not even turn on. Some devices may work OK while others will run but the crude form of power may burn them out. It depends on the cost of your nebulizer and if you are willing to take the chance.
 
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