Power adapter from cigarette lighter - questions

[John Farley]

These probably will seem like dumb questions to you techies out there, but I am a low-tech chaser trying to go a little more high-tech. I have read some related threads to my question, which only makes me more concerned and confused.

I just ordered a Jensen - Dual Vehicle Power Outlet Adapter to let me plug two things into my cigarette lighter. One is my laptop, for which I have ordered a laptop auto car adapter from laptoppartsnow. The adapter is designed for my particular computer (Acer Aspire 5610). This basically looks like what you use to plug the computer into the wall, with the power-supply box thingie, except that instead of a wall plug, it has a plug for the cigarette lighter. I found that if I rely on the computer battery, it tends to die in the middle of the chase - very annoying! So, I wanted a continuous power supply. The other thing I would like to plug in is the signal amplifier for the antenna for my Sprint aircard, which comes with the cigarette-lighter plug.

So here are my questions: Is this too much power to draw from the cigarette lighter? Will it run down my battery? Will it cause a fuse blowout, which someone on another thread mentioned having happen? Will using this setup damage the computer or the amplifier? If indeed this is too much, I guess I could just plug in the computer and leave off the amplifier, except for short times in areas with poor cell reception where the amplifier would be really needed, and in those times run the computer on the battery and plug in the amplifier, but obviously it would be much better to have both continuously if that would not cause a problem. Advice?

[David Drummond]

You can try it, most likely it's going to pop the fuse. If it does, it's too much and needs a direct to battery wiring. Don't just put in a bigger fuse, unless you enjoy car fires though. ;)

[Adam Lucio]

I use a simple DC to AC power inverter that plugs into the cig lighter I got at best buy for 65 bucks. Ive had 2 laptops running with no issues and this will be my 3rd year using it. Im not sure how much more [if any] juice the cell amp would use. Just make sure both units dont exceed what your adapter is built to handle and you should be ok. Definitely dont run them when the car is off, that will kill your battery, if the car is on the alternator will take over and your battery should be fine.

You may also want to speak with a mechanic to recommend a battery that allows for the extra output. Which just reminded me of the fact my old chase vehicle sitting in my garage with a blown head gasket has the battery...I need to do a swap.

[Skip Talbot]

Hey John,

Laptops and amplifiers are very power hungry. Those two items draw the most power in my setup. Do try it like David said, but if your amp stops working and your dash lights or radio goes off in the middle of a chase, you'll know what happened and make sure you have some extra fuses. I don't think you risk damaging the equipment, it just might not work. I know I can't run my laptop through a splitter plugged into a cigarette lighter, but then agains its a large performance model. In the end its best to just run some heavy gauge wire under the carpet and through the firewell and terminate with an inline fuse where it connects to the battery. Its kind of chore, but its not too difficult and I can help if you have any questions or problems.

[David Drummond]

Some cars the outlet goes dead when you turn the key off, like the RAV4 I rented recently.

Once your car is running, the size of the battery really means nothing, as everything (at least in a healthy system) will be running off the alternator. It's a common misconception that the car runs off the battery. It will only default to that if the alt is malfunctioning. I'm fairly certain all modern alternators should be able to handle a few additions ok.

[John Farley]

Thanks for the responses. But that raises another question - would I be less likely to blow the fuse if I used a DC-AC power inverter, or would I be drawing about the same amount with either setup? The amplifier for the aircard has cords to run off either AC or the cigarette lighter, so it would be possible for me to use either the setup I first described or get an inverter and plug both the computer and amplifier into it. Is there any difference in the likelihood of blowing a fuse depending on which of these setups I use?

[David Drummond]

Those plugs technically aren't meant to handle more than one item. Most have a 10 or 15 amp fuse on them. I ran a backup inverter I had the other day on the rental. It was 300 watt but with the laptop/camera plugged in it I don't think I was pulling all that many amps.

If this is more or less a permanent setup in your own car, I highly suggest running dedicated power wires from the battery, and as stated before, fuse them at the battery. The hardest part will be finding an entry point from the engine compartment to the passenger compartment (or creating one), but once you have it in place, and wired properly, you won't ever have to worry about it again. Then you can plug a power strip in the inverter and plug in several devices as long as you don't outstrip your average watt rating for the power inverter and you get the added benefit of the power surge protection. I have used this setup for years and years and it's virtually trouble free.

[John Farley]

Thanks, David. I would have to hire someone to do this, as I am a complete mechanical dummy. However, it turns out my car has at least two cigarette lighter/accessory plugs, rated 20 amp. What I am wondering now if I would be OK just plugging one thing into one of them and another into a different one.

I am looking at my owner's manual to try to figure out how they are fused, but that seems to be pretty much useless. There is no fuse marked accessory, so I am guessing maybe the "infotainment" one would be the relevant one. But I am wondering if the fact that the two accessory plugs are separate from one another would mean that each could accommodate up to 20 amps? If so, maybe I am ok. Again, anything you or anyone else on the forum knows about this that would be useful would be appreciated! BTW the car is an '09 Chevy Traverse.

[Skip Talbot]

John, they should be separate lines. The two in my van definitely are, and I believe most cars would follow suit.

[John Farley]

John, they should be separate lines. The two in my van definitely are, and I believe most cars would follow suit.


Thanks, Skip. In that case I should theoretically be OK. According to their instruction manuals, the computer takes under 5 amps and the cell amplifier about 3. Of course if I do blow a fuse, I will be clueless about which one to replace, since none are labelled to indicate that they are for the accessory plugs. But if the lines are separate, maybe I will be OK.

[David Drummond]

Check your can user manual, find the page where it shows the fuse layout, and see if it shows two separate fuses for it.

[Wesley Luginbyhl]

My '99 Jeep has 2 power outlets (one up front and one in the cargo area), but they are ran through one fuse in the fuse box. I figured that out after I blew the fuse for one and the other stopped working. My cigertte lighter is on a seperate fuse though.

You definitely want to run a dedicated fused wire from the battery as David said, and save yourself a lot of headaches down the road. If you do try it yourself, you can get a good fuse block from the automotive/stereo section in Wal-Mart. For a big enough gauge wire you should try Radioshack. They have every gauge you might want, you just have to ask them to go and cut it in the back.

[John Farley]

Check your can user manual, find the page where it shows the fuse layout, and see if it shows two separate fuses for it.

There appears to be one fuse marked "power outlet" in the fusebox under the hood, so perhaps the outlets are all on one fuse. That said, if the combined amps of the computer and the cell amplifier are less than 8, and the system is designed for up to 20 amps to be plugged in, as the manual says, I would think in theory I would be fine, right? In theory being the key words, of course.

The car in fact has three different cigarette-lighter type outlets in the front, middle, and rear, so I would think it is intended to have more than one thing plugged in, so long as the total does not go over 20 amps.

Thanks to all for the comments and suggestions. I guess I could have figured out some of this from reading the owner's manual first, but like I said I am pretty low-tech, so that didn't occur to me until I started reading a couple of responses here. The manual was how I figured out I had more than one outlet; it said I might have as many as 4 but I could find 3. I had never really looked until then, assuming there was only the one under the instrument panel.

[David Drummond]

Should be fine. If it's not, it hits over 20 amps it should pop the fuse. Just don't whatever you do put in a bigger fuse. ;)

My chase van even has one of those outlets all the way in the far back by the lift door where no one will ever use it. With all the ones I have added I have 11 total. LOL

[Dan Robinson]

Weak spots I run into with cigarette lighter plugs are the wire gauge, cable length and the plug contacts. If the wire is too long or of too small a gauge, there is often enough of a voltage drop to trip the inverter's alarm when running a high-wattage device like a laptop. If the contacts are bad at the plug, that's a major weak link and a source of arcing/cutouts if the plug moves/vibrates at all. Most cigarette lighter plugs I've seen are pretty flimsy to carry any appreciable load.

[Tony Propp]

Hey I used one of those all this week, I did alot of driving and my computer was on the whole time, I also have an Acer and it worked great! I am almost positive it won't blow a fuse, like I said I used it all day for most the week and no problems at all, and that is also with the radio on and lights and AC and everything else, I never busted a fuse so have fun!

[Mark Blue]

Thanks for the responses. But that raises another question - would I be less likely to blow the fuse if I used a DC-AC power inverter, or would I be drawing about the same amount with either setup? The amplifier for the aircard has cords to run off either AC or the cigarette lighter, so it would be possible for me to use either the setup I first described or get an inverter and plug both the computer and amplifier into it. Is there any difference in the likelihood of blowing a fuse depending on which of these setups I use?

John,

Another thing to have on hand is both types of replacement fuses. At auto parts stores they have a kit where you can buy a box with compartments in it and a fuse puller that includes every fuse you would need if you blew one in your car. Last year I had a penny fall into the cigarette lighter plug (we keep change in the ashtray) and when I tried to dig it out it shorted and blew the fuse. Replacing it was a cinch since I had the kit.

The other thing to keep on hand is some 2 or 3 amp old style glass fuses as the cellular amplifier has a fuse inside of the cigarette lighter plug. You just remove the tip where it is threaded and inside of there is an old style fuse. You can get boxes of 5 of those at auto parts stores for like a buck a piece. I've had two or three of those blow out in as many years, so I now carry a box of those just in case.

I think you'll be much happier with a DC power adapter than you would with an AC power inverter. I first bought the AC power inverter, then converted to a DC power adapter (like you bought) and was much happier in the end. It just makes more sense for me since my laptop is built for gaming so it draws quite a bit of current and the DC power adapter seems to work better in the car.

It's good to hear that you have 3 cigarette lighter plugs in your car as that's what my new SUV has and it's nice to be able to split up the gear amongst different plugs than to try and double them up and run the risk of blowing fuses and what not. I think you'll be fine with your current configuration, just keep an eye on your cigarette lighter 2-in-1 adapter (touch it every once in awhile), as if you buy an el cheapo it can get really hot. I use one of these as it's the best one I could find as far as quality goes: http://www.lindelectronics.com/cgi-bin/store/shop.cgi/!ORDERID!/other/PROEM-00043/dbx_gen_detail_product/ (http://www.lindelectronics.com/cgi-bin/store/shop.cgi/%21ORDERID%21/other/PROEM-00043/dbx_gen_detail_product/)

Thanks,
Mark