The Right Way To Jump Start A Dead Car Battery
![Jump Starter]()
Much has been said and written about car batteries and how to jump start a car
that has a dead one. The thing is, a lot of this info is either incomplete or wrong.
Sooner or later you will find your self in a car with a dead battery. So please read on.
Here I will give you the right and up to dated way to jump-start a car safely. Of course this is if you are stranded away from home. When you are at home the best thing to do is use a charger, not a booster or cables.
First of all I don't recommend jumping cables to the motorist, second the best options are to use a booster or just call (an expert mobile service) or take the vehicle to an expert shop. If the battery is older than 3 years or so, it could be bad.
If you must use jumper cables then here I will show the right way to do it.
Read the whole article since the info is all over the same.
First some information about batteries.
I repair many vehicles with bad batteries. The reasons the battery went bad can be many, so after jumping a vehicle you should seek professional help. Here I will tell you what can make a battery go bad, what to do to prevent it and things to do in an emergency situation.
Why a battery goes bad:
o Bad alternator.
o Bad or loose serpentine belt or off or missing serpentine belt due to another bad component.
o Excessive heat or cold.
o Age.
o Defective Part from factory. (Rare).
o Leaving the car sitting too long or driving the car in short trips not
allowing the battery to recharge.
o Too much drain, like the battery is too small for the demand. Or maybe
there are add-ons like monster stereo systems etc.
o Parasitic drain. Or just leaving the lights or something on.
o Dirty connector/terminals.
o Vibration. When there's no hold down.
o Using the wrong fluid to replenish it, like tap water instead of distilled water.
o Bad computer. The voltage regulator is there in some cars.
o Physical damage. Car accident, being dropped.
Taking care of your battery.
The best way to prevent battery failures is by doing regular maintenance on the vehicle. When regular maintenance is done the battery should be one of
the main items checked. They should clean terminals, top off the fluid if possible using only distilled water, do some tests on it, and of course test the charging system etc.
Even the best batteries will meet their maker sooner or later. They can "die¬hard" or die soft but they all die. The average life of most batteries is about 3 years, believe it or not. Some top of the line batteries can last a bit longer. I have noticed a decline on the life of batteries lately. So if your battery is about that age, have it checked or just change it to have peace of mind specially if you're making a long trip.
What to do if your battery is dead.
In an emergency when a battery is dead, the first thing that comes to mind usually is to "jump" the car. Well I don't recommend this. First of all this is a potentially dangerous action. (Doing this can cause an explosion and injure you or actually kill you (pieces of plastic going off at very high speed can cut your throat), blind you, or deafen you). The best thing will be to call someone to come and check the car or take it to a shop (there's a chance the alternator could be bad, so replacing or boosting the battery may not solve your problem). If you happen to have cables in your car then you have to find another car to boost you. This is dangerous too, because in doing so you can damage very expensive parts in both your and the assistant vehicle. There's a change of connecting the cables wrong if you're not familiar with the process, if this happens you can disable any of the two cars involved for good and incur in more expensive repairs. The best way to do this if you choose to boost the car is with a portable booster. Some have a switch that will prevent you from causing sparks. Also some models have a device that will polarize the system automatically. So it will be impossible to connect it the wrong way. Some can be connected right at the lighter port, but this takes more time because you have to let the booster charge the bad battery for a while, if you try to start the car right away you could blow the inline fuse or burn the cable.
Also after you get your car running, if you disconnect the assistant car and leave the car running to recharge your low battery this will cause serious damage to the alternator. The alternator is not designed to charge batteries that are too low or at zero volts but to keep them charged. The right way to do this is when using a portable booster to leave it connected to the car so the alternator will charge both slowly and not stress it self. The alternator has the ability to sense the battery state of charge and also the system voltage demand. It will charge accordingly. If the battery is very low it will charge continuously, hence straining it self and overheating. After 30 minutes or so you can then disconnect the booster and keep driving the car for some more time to charge the battery fully. Better yet just drive the car to the nearest service place or call a mobile service when you get home. If you're driving at night or your vehicle has day driving lights this will take a little longer. Of course after having any problem with a low battery and getting the car running, the intelligent thing to do is get your favorite tech to check you system completely to have peace of mind.
Another thing that you need to know is this, sometimes you have a battery installed and it fails soon after (one or two days) why? Well there are different reasons, the battery could be defective (very rare), or there's an intermittent problem with the charging system or a device that is putting a small drain after you turn the car off. New cars have many computers and they use a small amount of energy after the car is turned off, but it is a very small amount and it should not drain the battery in less than 3 months approximately. If it does is because one of the computers could be staying awake too long or has an intermittent short. If this happens to you, don't get upset thinking they sold you a bad battery, or that the mechanic is incompetent. The carr has to be diagnosed again to see what happened.
The right way to jump-start a car.
This is the way I recommend to perform a battery jump with cables. This takes a little longer than what most publications recommend, but is the safe way to do it. I am a professional mechanic with 28 years of experience.
Before you even think about getting your jumping cables out you should:
First of all it will not hurt to read your owners manual, there you can find lots of info pertaining the procedure. Like where the battery is "hidden" etc.
Make sure both cars are close enough for cables to reach with out cars touching.
Inspect the battery for signs of damage. A broken battery case is not a good sign. Do not jump if case is cracked or you see fluid leaking.
Set the emergency brake on both cars and turn off both ignitions and any other accessories other than the flasher as mentioned.
Keep at least one of the vehicles flashers on and any other safety device like flares etc displayed.
Battery terminals should be free of dirt and or corrosion. Use at least water and a wire brush to clean them.
Make sure both cars are of the same voltage and polarity. Some cars are grounded at the positive instead of the negative although rare. Most cars in the road have 12 volts batteries. With the advent of hybrid vehicles I will strongly recommend you just calling an expert. Hybrid cars have very high voltage batteries. 12 volts batteries won't harm you even if you touch both terminals but hybrid use much higher voltage. Also avoid connecting the cables backwards; very bad things can happen if you do.
Wear at least eye protection that includes a face protector. Gloves will be nice too. Do not allow battery fluid to touch you, your clothes or the paint job.
In very cold weather make sure the electrolyte is not frozen. (Use a flashlight etc to inspect, not a lighter).
Be very careful not to touch any moving part of the engine like belts, fans, etc while performing the procedure either with the cables or your clothes or jewelry etc.
Now the cable part, (see illustration at the end of article) before you connect any of the terminals make sure they are not touching each other to avoid any sparks. Batteries give off very explosive gasses that can kill you if they ignite. Also if the cables get hot be aware that they could be too thin or the engine could be dragging for some reason. The starter could also be bad (grounding it self). Also may be you have cranked the car too long. Check to make sure the clamps are attached properly. Let tem cool off a bit.
If anything like dome lights come on after the cables are connected, the cables are connected correctly.
The first terminal to be connected as recommended is the positive one in the donor's car then at the disabled car (both at the battery if possible).
Then you connect the negative cable at the battery terminal of the donor's car and make sure you can access the engine at the disabled car to connect the cable there.
When the cars finally starts, keep at least the headlamps on to aid in keeping any voltage spikes from damaging the delicate circuits in the many modules on today's cars.
(+) Is the positive terminal (usually red). (-) Is the negative terminal (usually black). This cable goes to the car chassis and the engine block from the battery.
Disconnecting sequence is the reversal of the connecting sequence
Smoking is not recommended any time you are working near cars.
More about this.
Never hook up batteries in a series circuit way, you will get twice the voltage and blow many things including computers.
This will certainly damage your electrical system to say the least.
Some cars with antitheft systems will activate it whenever the battery is low or disconnected. Again read the owners manual for info on this and how to reset them.
Every manufacturer use different systems.
When jumping a car you have to first charge the battery with the "donor" car for at least 5 minutes or more if possible, then try, with the cables disconnected to start the car. If the car doesn't crank or cranks slowly then recharge some more with donor car, then with cables connected try to crank the disabled car.
When selecting a set of jumper cables make sure you get a good quality set. The thicker the cable the better. Saving money here will prove a very bad choice. Cheap cables can overheat and in many cases burn or just don't work when you use them (cheap construction around the clamps). Also don't get the shortest or the longest. The middle will be best.
Never crank a vehicle more than the recommended lapse in the owner's manual (usually no more than 10 seconds) to avoid damaging the starter. If the car cranks for very long periods with out starting then you could have more serious problems than just electrical ones. Always wait some time before trying again to avoid damaging your starter or damaging the donor's battery.
If when you connect the last cable at the disabled car you see a lot of sparks make sure there isn't anything on, or the cables are connected properly (polarity), otherwise some sparks are normal since the disabled car's battery is probably very low or just dead.
There are some top-of the line cables that feature a foolproof device against connecting them wrong.
Every time the battery goes too low it gets weak. Different from deep cycle batteries on boats or RV's, car batteries are not designed for this and will after a few discharges just quit altogether
Batteries used to be better known as "accumulators" and you can guess why don't you? Yes they store electricity and the alternator's job is to keep it charged not to charge it from 0 volt, that is the job of a charger.
A battery won't get damaged if kept in the concrete floor instead of on top of a piece of wood. The way batteries are constructed today prevents this.
You don't need to go and spend big bucks for a battery at the dealer, not to mention towing costs. Any battery that meets the specification of your vehicle will do well if maintained properly. The trick here is to get the right battery, meaning the right capacity. Never use one that has less than what is required. A little bigger is better.
Some batteries have a little window that has a green or black indicator to tell you if the battery is good. Well this indicator is not very accurate for this, since it only measures the state of charge of only one of the battery's 6 cells. Another cell could be bad and you could get a "green" indicator even tough the battery has only about 10 volts, which is not enough to properly start a car. Some of the devices on your car might still work tough. The car will crank very slowly.
If by any chance acid gets in your eyes, do all you can to get it out pronto. The more it stays there the bigger the chance for cornea damage.
If you suspect a bad connection on the jumper cables, do not wiggle the connector while connected. Disconnect one on the disabled car first then wiggle the suspect ones then reconnect the rest. Remember you want to avoid making sparks.
After using the jumper cables wash them with water if possible and store them in the bag they came in. This will avoid damage to your trunk from the acid that gets stuck to the terminals.
Always work on a well-ventilated area.
The alternator. The heart of the system.
If your alternator is bad, it was the cause of the dead battery in the first place; so jumping the battery won't get you too far. As a matter of fact you probably won't be able to drive even a mile more. You could end up at a neighborhood where you don't know anyone that will be too wiling to help you.
If the battery or alternator or charging light was on before the battery died, then it is still on after you jump the car then the charging system could have a problem. It will be a good idea to contact a professional.
An alternator could be malfunctioning even if you don't see a red light in your dash telling you so.
If you are knowledgeable and want to test your charging system with a voltmeter, consider this, some carmakers have systems that will not charge when the battery is found to be full. This is done to prevent overcharging and also to increase miles per gallon (The drag on the engine is less) This also helps the durability of the alternator.
Alternators are not designed to "charge" batteries (specially newer cars, they are usually weak in this area). Their job is to keep a fully charged battery that way.
When a battery goes down for any reason, the alternator has to work overtime to bring it back to normal. The use of day driving lights is one of the reasons many alternators fail prematurely, the alternator works harder than in a regular system. But they do offer a good safety measure. Also accessories not installed at the factory like monster stereos will also put an extreme demand on a stock system not designed for such loads. There are some high amp alternators available for these cases. Also the use of multiple batteries helps. Consult an expert in this field for assistance.
Never disconnect a running car battery terminal to "test" the charging system. This was done long ago before cars started using computers. But today doing this can and will damage very expensive components. Also it can create sparks that could cause an explosion. Believe me, many people still use this method to test the alternator, yes even people that "think" they know, like some airplane mechanics.
Starting a car with the cables connected and letting it run could damage systems in either car. Things like computers etc. I have fixed many vehicles with bad alternators and computers due to this. That is why I recommend charging the bad battery by letting the good car charge the bad one for at least 10 minutes. Then you can disconnect the cables and start the car with out damaging anything. There's a theory that running two cars with the cables connected can damage the alternators. I will up date this article with some facts about this.
Push starting; it may not get you too far either.
Another way to get a car running is by push starting it. This is not recommended either. First, damage to the drive train is possible, (Expensive) especially if done often. Second, as I mentioned before, if the car doesn't run because the battery is dead, the alternator will work too hard to charge the battery when you get it started. If the problem is the alternator, the car won't run too far at all because the battery is not getting any charge so it will be depleted very soon. Push start should be done only in extreme emergency situations. As I said, be intelligent and call an expert.
I hope the information here was of help to you. As always no one is perfect. If you think there's a mistake or want to add something to this article, by all means contact me directly.
Considering the low cost of replacing the battery with a new one and after reading this information I am pretty sure you will decide not to risk performing a jump instead of replacing the battery. Unless of course, you are a professional and/or already know what I wrote here.
Today's cars are very complex machines; it is better to leave things to the experts when it comes to dealing with them. You will actually save more money (or even your own life) that way by avoiding costly mistakes.
CMT of Miami works on all brands and models of vehicles. We specialize on battery installation and alternators. When you use our services you can rest assured that you will get the right battery and professional service right at your doorsteps for a fair price.
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