# Can an Eos jump start another car?



## hobbittcar2 (Oct 16, 2007)

My wife's battery died, so I dug out my manual to make sure I followed all the proper hookup steps. I knew that the EOS battery is in the trunk, and there are terminals in the engine area.
I was surprised to see that only the positive terminal is available. When _getting_ a jump, the negative side is supposed to be grounded, so we don't need a negative terminal to receive a jump.
But, when giving[I/] a jumping to another car, the battery is supposed to have the cable hooked up to its negative terminal (at least according to every car manual I've ever read).
We ended up getting our neighbor's car just to get it done, but I'm wondering if I'm missing something. Can we really not jump another car with the Eos?
I didn't see anything in the manual regarding this, but I admit I may have missed it.


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*

You probably could boost another car with your Eos, but.....
I believe general wisdom is not to use a vehicle with a complex computer systenm on board to boost another vehicle. This is because there is a risk of a power surge coming back to your vehicle when the boosted vehicle starts, and this could damage computer components.
This eliminates pretty much every vehicle on the road today.
There are ways to reduce the risk if you are in a situation where you have no other options. Leaving your car (the boost car) turned off while boosting is the best. This is actually the recommended boost procedure, but I often see people leave the boost car running, even revving up the engine, to provide a little extra juice to the dead battery.
A good solution is to purchase a Booster Pack from your local auto supplier. I bought one on sale with a deep cycle battery for under $100 cdn and once charged it holds the charge for a long time so it is ready if/when you need it. The problem is it is a bit bulky to carry with you all the time, so it is really most useful only if you are having problems close to home or have a friend or family member who can respond and help you out.
The reason for making the last connection on the frame of the car rather than the negative battery post is to prevent sparking near the battery. Batteries produce hydrogen gas when charging which can, in rare cases, ignite and explode the battery.
Kevin

*NOTE: Here is an excerpt from an article on boosting vehicles.*
_Regardless of the reason for a battery becoming discharged, a boost is usually the first thing attempted. Getting a boost means using heavy cables to supply battery power from one vehicle to another. Some car manufacturers do not recommend boosting a vehicle, They state that damage to electronic controls can occur if voltage surges flow through the electrical system during boosting. Instead of boosting, the auto manufacturers prefer that a fully charged battery be installed in place of the dead one or that the dead battery be charged. This is often impractical because of where the vehicle is sitting so most people with a dead battery boost their vehicle - but several important steps must be followed to prevent damage. 
First of all, to prevent damage, turn off all electrical accessories on both the vehicle being boosted and the one providing the boost. If there is an electrical surge, this will prevent damage to those accessories. 
Many people leave the engine running on the vehicle providing the boost, but as soon as the starter is cranked on the vehicle with the dead battery, the alternator on the running vehicle produces maximum electrical output. If the cranking takes too long before the dead vehicle starts, the alternator can be damaged on the running vehicle. To prevent this, connect the booster cables and let the running vehicle charge the dead battery for several minutes. Then turn off the running vehicle before cranking the other vehicle. 
When connecting the booster cables, the red cable ends should be connected to the + or positive posts on the batteries of both vehicles. On many new vehicles, the battery is concealed under the rear seat, in the trunk or beneath plastic covers in the engine compartment. Fortunately, the manufacturers usually provide a positive connector under the hood to provide a connection point for boosting. Look for it under a bright red plastic cap marked " battery" or with a + sign. 
The black booster cables should be connected to a metal bracket or mount directly on the engine. Do not connect the ends to the battery negative posts or a spark can occur. Hydrogen gas generated in the battery could be ignited by the spark created when connecting the cables and the resulting explosion could spray battery acid on the operator. Be careful to keep sparks and flames away from batteries. 
Don't be surprised if the horn starts honking on the vehicle being boosted. Many newer vehicles have security systems activated when the car is locked. Because the battery was dead, the system did not disarm when the car was unlocked but now there is power supplied by the other vehicle and the alarm triggers. Simply unlock the vehicle again using the key fob or the key in the driver's door to deactivate the alarm. 
With the cables connected, the dead vehicle's engine can now cranked. Don't crank the starter for longer than 15 seconds or the starter motor may overheat. Allow the starter to cool at least one minute between each 15 second crank attempt. With the engine started, remove the booster cables carefully so that none of the ends touch each other or the vehicle until all the cables are disconnected. 
Hopefully, you will never need a boost but if you do, following the procedure carefully will help prevent harm to yourself and your vehicle. _



_Modified by just4fun at 2:14 PM 2-14-2009_


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (just4fun)*


_Quote, originally posted by *just4fun* »_You probably could boost another car with your Eos, but.....

But how would I? There's no negative terminal available. Wouldn't I need that?
And believe me, one of the first things I thought of after this was getting a booster pack, but as you mention, they're not exactly convenient to carry around.


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*


_Quote, originally posted by *hobbittcar2* »_
But how would I? There's no negative terminal available. Wouldn't I need that?


No, you can ground to the frame or engine instead of directly to the negative terminal on the battery. Usually any bare (non painted) metal surface under the hood will suffice. Try to stay a reasonable distance from the battery whenever possible.
Most often it is recommended that the negative (black) clamps on booster cables are connected to ground on both vehicles rather than to the negative terminal. It just ensures no sparking at the battery.
Kevin


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (just4fun)*

*NOTE: *The Eos owners manual also suggests that BEFORE DISCONNECTING the booster cables after starting the car you should turn on the headlights and rear defroster. This will pull a draw on the electrical system and help absorb any power spikes that could occur when you disconnect the cables.
The Owners Manual only gives detail on boosting the Eos to start it, not using the Eos to boost others.
Kevin


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (just4fun)*

I know I'm harping on this, but please don't take offense.









_Quote, originally posted by *just4fun* »_
Most often it is recommended that the negative (black) clamps on booster cables are connected to ground on both vehicles rather than to the negative terminal. It just ensures no sparking at the battery.


I'm no electrical engineer, but that makes no sense to me. Let's agree that booster cables consist of 2 wires, red and black. Let's also agree that they are separate and don't touch in any way. So, we should be able to agree that one could pull apart the booster cables and have 2 standalone wires. (similar to pulling apart the red and white cables of a VCR's RCA cables into 2 separate cables). It's simply a matter of convenience that that the cables are bundled together.
So, let's think about jumping with 2 separate cables, red and black. I hook up the reds to the positive terminals first. Now, if I hook up both ends of the black wire to grounds on the cars, and neither one is hooked up to any battery, it's that kind of useless? I'm grounding a ground to another ground. How would it prevent a battery from sparking if it's not touching any batters? I might as well just remove the cable and only use the red for jumping. Now, if one end of that black is connected to a battery and another to a ground, well, that's different and now we're doing something useful.
Incidentally, both my current car owners manuals, all previous owner's manuals I remember, edmunds.com (http://www.edmunds.com/ownersh....html), the cartalk website (http://www.cartalk.com/content....pdf ), and every other link in the search results of "how to jump start a car" talk about hooking up the negative terminal of the charged battery to a ground, not putting both black cramps on grounds. 
As much as I respect your advice in this forum, I'm not sure the above it correct.


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## mark_d_drake (Aug 17, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*

I have wondered about this too. The only other solutiion I can think off would be access the battery terminals in the trunk. Presumably if you take the -ve on the first battery and +ve on the second battery you have full 12V. However I'm certainly not recommending expermenting with approach. 
My solution was a standalone JumpStarter from Kragen/Autozone/Pepboys etc.


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## cb391 (Mar 12, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*

I believe you are missing one point. The negative battery terminal is connected to the engine block and the car's body by a piece of cable. This makes the whole metal structure "ground" even though it would not be an "earth ground" like that used for wiring of buildings. You want to clamp your negative cable on the car being jumped to the ground away from the battery so if a spark occurs, it won't ignite any stray hydrogen generated by the battery. If you cannot get to the negative battery terminal on the car doing the jumping, then you would connect the black (negative) jumper cable between the bodies or chassis of the two cars. It's not the ideal way as it is not the best electrical connection, but it does work.


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*


_Quote, originally posted by *hobbittcar2* »_As much as I respect your advice in this forum, I'm not sure the above it correct.

No problem, and don't think of it as harping, it is simply discussion.
The negative terminal of the battery is connected directly to ground (the frame) of the car. By connecting the jumper cable to the frame/engine/body of the car it is essentially the same as connecting to the negative terminal of the battery.
Pretty much any metal surface on the frame, engine, or body of a vehicle will function as ground. There are occasions when you can't get a good ground in a certain spot because for one reason or another the ground connection is insulated or broken.
For example: when you install an electrical device or option into a vehicle, the positive (red) wire needs to be run back to a suitable power source, but the negative (black) wire can be connected to the nearest ground point and you will complete the circuit. Some manufactures recommend running the negative wire back to a specific grounding point, this is to ensure a good uninterupted ground, but in theory, pretty much any bare metal point on a car is a potential ground.
When you make the final connection with the booster cables, you can, and most often will, get some sparking, but if you make this connection on the frame or engine it is at a distance from the battery where there _potentially may_ be a build up of hydrogen gas. (keep in mind that it may be necessary to try a couple different spots to find a good solid ground)
Connecting the booster cables directly to the terminals on both batteries will certainly work to boost the car, but isolating the negative connections away from the battery is safer.
FWIW I learned first hand that batteries can explode. Back in the day new batteries were delivered dry and you had to add electrolyte to them and charge them up for a few hours before installing them. I was 15 or 16 at the time working at a local service station. I had a new battery charging on the bench, without thinking I replaced the caps on the battery before disconnecting the charger, then disconnected the terminal connections without first turning off the charger. The terminals sparked and a large chunk blew out of the top of the battery hitting me in the forehead hard enough to give me a good gash. I was fortunate that none of the battery acid splashed into my face or eyes, but I did get some on my hands which I washed off quickly and didn't get any serious burns. In this case the battery was on a hard charge and lots of hydrogen gas was being created, but the risk is real, it can happen.
I believe that todays sealed batteries and gel batteries are less suscepitble to explosion, but I still routinely see advice NOT to connect booster cables directly to the negative terminal so I have to assume that the risk is reduced, but not eliminated.
Always connect your positive terminals first. Making the final (negative) connection to the frame/engine is an important safety step, but making both negative connections onto the frame will still work, and further reduces any chance of sparking near the battery.
Kevin
NOTE: In the excerpt I posted above I believe the author is recommending connecting both ends of the negative cable to a bracket on the engine away from the battery. He doesn't specifically say both, but he uses the plural "ends" rather than the singular "end" when refering to the black (negative) cable.

*IMPORTANT NOTE:* cb391 clarified this nicely while I was busy writing this novel











_Modified by just4fun at 9:57 AM 2-15-2009_


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (just4fun)*

cb391 and just4fun,
Thanks! I was wondering if indeed the negative terminal was connected to the chassis in some way.
To summarize for those that may pick up on this thread:
Jump starting using an EOS as the "charging" car is possible, but not recommended?
I'll think I'll go for the booster pack


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## solarflare (Mar 28, 2007)

*Re: Can an Eos jump start another car? (hobbittcar2)*

I just wanted to point out that if voltage spikes are possible with these modern cars when jump starting there's little that can be done to mitigate that risk other then disconnecting the charging vehicle before starting the charged vehicle. One can turn off the radio and climate controls but even these have a constant 12v which will see the voltage spike not to mention the dozens of various controllers/computers that you can't turn off if your car is running.
I can attest to that fact that these portable 12 volt power boosters will start a car. I've had to use mine, a Xantrex, twice to start my Eos after I killed the battery installing an aftermarket Ipod adapter (since returned). I couldn't even unlock my door with the remote. After connecting the powerpack and waiting a few minutes the engine cranked over, albeit slowly, and then started. I threw the powerpack in the trunk and off I went. IMO, much easier then dealing with having to get another car close by. The unit also has an A/C inverter so that it can be used for emergency power to run lamps, radios, tv during a power outage or to run small power tools remotely without having to untangle that extension cord







It's a very useful item to have around the house. The Xantrex can stay plugged in on trickle charge year round so that it's always ready to deliver.


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (solarflare)*

Anybody have any other personal recommendations for a booster?


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*

Can't really make a recommendation on brand, but would suggest a minimum of 800-900 peak cranking amps, especially if you ever need to do cold weather starts.
Kevin


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## solarflare (Mar 28, 2007)

*Re: Can an Eos jump start another car? (just4fun)*

I don't think you need a booster with 800-900 peak cranking amps. That will amount to a regular car battery. My power pack uses a 21amp/hr AGM battery which is probably somewhere in the area of 200 CCA. It just needs to be enough to put a charge on the existing battery to boost its capacity. Like I said this unit worked great for me with a drained battery. If you have a defective battery, one with perhaps a shorted cell, these small power boosters may not do the trick. I have not been in that situation yet so I can't say for sure. But if that is your situation then it's probably best to replace the battery rather then jump starting because you'll probably be taxing the alternator to try to charge a 10 volt battery to 13.5 which will never happen. 


_Modified by solarflare at 1:40 PM 2-16-2009_


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## kghia (Nov 16, 2006)

Good information to know!
I have kept my car running while boosting another, but then my other cars don't have computers.
I'll have to remember this advice for other people's cars (and my Eos)
I have one of those trickle-charged packs that does *air inflation* as well as provide 12v accessory outlets. In hindsight/future purchases, I would buy one that does all 3-- battery boost, air compressor, 12v accessory plugs. The only issue is that those seem to be twice as much (around $90)
You could also buy the two separate types (battery boost & air compressor), but of course they would take up twice as much space, in any place you put them.
The air compressor is _also_ more convenient when you don't have to pull another car up close and run the cord from a plug out the window.
Those 12v outlets are *very nice to have* to charge phones, etc inside with a car plug, or for using car items inside while the power is out.
William


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (kghia)*

Air compressors! I'm all over that!
When I change tires in spring/fall, I end up manually pumping up 8 tires using a bicycle pump. Yes, yes, I know I could drive down to the local station, but it's nice to just have it all done in your garage. You should see my deltoids though


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## hobbittcar2 (Oct 16, 2007)

*Re: Can an Eos jump start another car? (hobbittcar2)*

I picked up a Duracell "Powerpack 300" at BJ's for $50.
Jump starts, has an AC outlet (up to 300 Watts), DC outlet, air compressor, and flashlight.
I was pretty impressed with all that for $50. It will probably blow up in my face when I go to use it


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## just4fun (Oct 29, 2006)

*Re: Can an Eos jump start another car? (hobbittcar2)*

I've had mine for over a year and have yet to use it.
I'm sure for as often as your unit gets used it will be there for you when you need it.
Good score for $50 http://****************.com/smile/emthup.gif 
Kevin


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## liquid stereo (Feb 26, 2003)

*Done it twice with no problem*

I have given a boost to two people and have had no problems.
Cheers!


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