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How To Boost A Car Battery
After driving for more than 20+ years, I’ve never had to know how to boost my vehicle’s battery. Someone was always around to do it for me–until this past winter.
Here are step-by-step instructions for how to boost your car’s battery. Feel free to print them out, put in a plastic sleeve and tuck into your car’s glove compartment.
First:
- You’ll need someone with a running vehicle to give your dead battery a boost plus a set of booster cables.
- You can either turn off the running vehicle before applying booster cables, or leave it running. Your choice.
Admin Edit – Correction Made From the comments area below:
Connecting the black (ground) jumper cable (of dead negative grounded vehicles) to the sheet metal of the vehicle rather than the negative terminal of the dead battery is a very important safety feature. Batteries can and do emit gas and if you get a spark while connecting the cable to the negative terminal of the battery the close proximity to the gas can result in a battery exploding in your face. Generally, you only make this mistake once.
How To Boost A Car Battery
- Pull the running vehicle up close to the dead vehicle. This can either be side-by-side or hood to hood. Just make sure the vehicles are close enough for the booster cables to reach both vehicle batteries.
- Take out the booster cables and make sure to never touch the ends to each other at any time.
- First work with the running vehicle. Take one end of the battery cables and attach them to the battery which is usually up front near the corner of the car when the hood is popped up.
- There are always two posts on a battery, one is positive and the other is negative. The positive post is usually bigger than the negative, has more wires going to it, is frequently colored red and has a + sign beside the post. *See Pictures Below
- Working with the same end of the booster cable (one red clamp and one black clamp):
- Clamp the red end of the booster cable to the positive post on the battery.
- Next clamp the black end of the booster cable to the negative post.
- Now you should have both clamps from one end of the booster cables attached to the battery of the ‘working’ vehicle.
Very Important: Make sure to NEVER let the clamps of the booster cables on the loose end touch each other or you will have flury of sparks.
- Working with the ‘dead’ vehicle and the other end of the booster cables, follow the exact same procedure above. First attach the red positive clamp to the positive post, and the black negative clamp attach to a grounded piece of sheet metal of the vehicle (read comments below).
Important: Make sure to attach the red positive clamp first, then the black negative clamp.
- Now both ends of the booster cables should be attached, one end to each vehicle. Red clamps attached to each positive post, and black clamps attached to the negative post on the running vehicle and the other negative clamp attached to a grounded metal part of the other vehicle.
- First turn on the ‘working’ vehicle giving you the boost. Then try starting the ‘dead battery’ vehicle. If it doesn’t start right away, you may need to let the running vehicle run for a minute or two to charge the dead vehicle, then try starting the dead vehicle again.
- If the dead vehicle still doesn’t start, make sure the clamps are on the battery posts properly and have not fallen off.
- Once the vehicle with the dead battery is running, do not shut the vehicle off. Keep it running so it recharges the battery.
- Remove the booster cables from one vehicle at a time.
Important: First remove the black negative clamp, then the red positive clamp.
- Hold the detached clamps in one hand away from the other end while removing the second booster cable end from the second vehicle–or sparks galore again.
- Once the booster cable has been removed from both vehicles, it’s safe to wind them up and put them away.
Pictures
*Note changes made, the negative clamp on the dead battery should be on grounded metal instead of on the negative post of the dead battery.
Looking from behind, here is a picture of a truck battery with the posts on the side, the positive post has a red cap that first needs to be lifted off. You see the negative (black) post on the right, no cap, and looks just like a nut and bolt. That bolt is where you clamp the booster cables to:
Here is a view looking from the front of the hood, you’ll notice the top of the red cap hanging off and the clamps from the booster cable are attached to each post:
Here is a picture of an older vehicle’s battery, the posts are on top, uncapped and quite a bit larger to work with (instead of just a nut/bolt). You would clamp the booster cable onto each circle of the metal post. You can see the post on the right is tagged red (positive) and is a little larger than the negative post on the left:
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Great post, but a couple of tips I have learned over years of driving “beaters” in the north.
When connecting the clamps to the batteries start with the dead car and attach only the positive lead, let the negative clamp dangle or set it on some plastic. Then attach the positive lead on the good car, then the negative on the good car. This way you have not exposed yourself to any potential voltage because you have never handled a live positive and a ground at the same time. Now you can connect the ground on the dead car, but not necessarily to the battery post, any bare metal (no paint) will do. Find a spot that is not going to have any chance of contacting the positive and has no flammable materials near it. When you make this connection watch for a spark, if there is none check all your connections and try again. Removal would be reverse of application.
Oh, and if you wonder what the difference between the $10 cables and the $40 cables is:
$10 cable = charge for 5 minutes then start
$40 cables = start car immediately
cheap cables can’t pass the full power to start a car so a little patience or $ will save time
Also smaller running cars to larger dead cars, especially trucks I have noticed the small car might need a little throttle, just over idle, to generate enough power to run the larger starter motor.
Wow, fantastic info there Mike, thank you
!!
Question: If you want to charge a bad batter with a good one from another car can you just hook up the jumper cables and leave them for a while or do the cars need to be running? Thanks!
I’m pretty sure they have to be running Tara.
Thank you very much Mike , Really I need these Information for a research in my homework ^_^
thanx !
“Question: If you want to charge a bad batter with a good one from another car can you just hook up the jumper cables and leave them for a while or do the cars need to be running? Thanks!”
Well it’s relative really. You can charge a battery with another car if this car is running but it’ll take time and probably won’t get to the maximum charge.
When you have batteries set up in both car, you don’t have to start your car in order to charge the battery but sometime you do when the battery is very low or it needs a lot of power! Usually we start the car in order to give a boost!
The reason we run the car with a low battery it’s because the alternator(electronic device) make your battery charge as long as your car is on.
What we should do instead of leaving our car on while giving a boost is to stop it before! Let your car charge the battery from the other vehicule (about 5-10 minutes) then stop your engine!
Here’s the short and sweet explanation: the alternator on the running vehicle will produce maximum electrical output when the other vehicule have a hard time to start! This means that you can damaged your alternator.
By doing this you save yourself over 100$ and you just made someone happy!
these directions are wrong you dont connect the black cord to the negative on the dead batter you connect it to a metal ground like a bolt or something
John the directions aren’t wrong, you hook the negative clamp on the negative battery post. Doing it your way is another option.
Why is the print at you site so small?
it can not be read
Dont tell your mechanic about your booster cables, one kept mine, so i have no clue who in the last year it was. LoL.
The main thing to remember is POSITIVE + first.
Connecting the black (ground) jumper cable(of dead negative grounded vehicles )to the sheet metal of the vehicle rather than the negative terminal of the dead battery is a very important safety feature. Batteries can and do emit gas and if you get a spark while connecting the cable to the negative terminal of the battery the close proximity to the gas can result in a battery exploding in your face. Generally, you only make this mistake once.
Allan thank you for that info, after all these years living in “cold country” and all the battery boosting over the years, we’ve never known that. The original instructions were to a “T” what my husband was taught both in shop class and by his father.
I’ve corrected the info above. Although the original instructions will boost a vehicle (and how Mr. Tipnut has boosted batteries for over 25 years with no incident), it’s best to be as safe as possible and take necessary precautions just in case.
I can guarantee we’ll be boosting batteries the safer way from now on, thank you again
.
Ok, I just came back from trying to start my dead mazda rx7 off my live durango. The rx7 has been sitting all winter..yes the battery was still connected, don’t ask. It didn’t want to start, lights worked, sounded like it was trying, checked all hookups. SHould I have been more patient, it usually starts right away in past.
thx
If you both use an Absorbed Glass Mat style battery like a Deep Cycle Optima Blue Top then you don’t have to worry about hooking to the dead vehicles chassis, straight to the battery -.
AGM batteries do not output the charging-reaction gas and are sealed.
Here’s a tip for all you folks that have problems with boosting your car (with suspected starter problems):
If you are able to receive a charge from someone who was nice enough to stop to help you but you notice that your starter is not engaging or the engine is simply not turning over you can try taking a crow bar or some other long thin heavy metal object to knock the starter while you have someone try turning the key on the ignition. The reason: OLDER VEHICLES (HIGH KM VEHICLES) SOMETIMES HAVE STARTERS WITH STUCK WORN BRUSHINGS. GENTLY KNOCKING THE STARTER WILL HELP MOVE THE STUCK STARTER’S MOTOR BRUSHINGS TO START THE CAR. I know this works because its happened to me.
God Bless
Thank you so much! You saved me from much embarrassment when my girlfriend woke me up to help the cute neighbour boost her car. I was able to walk out and be the hero without either one of them being the wiser.
Now I just hope my gf forgets how rude I was to her because she woke me up early when I’m on nights. Got an article for that? lol
OK, I am dumb when it come sto cars. Mine has in the last two weeks, taken 3 tries before it starts, and runs not so smoothly. Not sure if it’s because the weather has been getting colder, but as of yesterday, the car would not start (really cold here now) and just hear clicking noises from engine area. The panel will light up, and I believe the window went down and defrost came on. Going to try a boost soon, but does this sound like it’s just battery???
Hi John, this is what my husband said: He suggests taking your car to a mechanic and getting both the battery and the alternator tested (I don’t think this costs very much to get tested). It could be either your battery or your alternator (meaning the alternator is not charging the battery). If it’s the battery, it will take a boost and get you running for a bit, but will start dying off. Hope that helps, but this is something you’ll want to take care of asap before you get stranded (getting too cold for that!).
Thanks for the info. A buddy of mine has suggested once the car is running after the boost, and the booster cables are off, to disconnect the positive side (red) of my battery, and if the car still runs, then it’s not the alternator. Does that sound right?
Yes, hubby says that’s right. Good luck! [Edit To Add]: My husband isn’t a mechanic btw, he’s just really good with this mechanics stuff
.
Can’t you leave one car running and THEN hook up the jumper cables–this way we wouldn’t drain the “booster battery”.
Hi. My car battery was dead, and we tried boosting it with another car. But the car with the dead battery just doesnt start. There is currents going through the jumper cables to the dead battery, but the dead battery just wont start. Is there a problem somewhere else in the car?