There is nothing worse than a dead battery on a winter morning. You are already late for work, and the car just won’t start. How to deal with it? Can the battery be charged in the car and if yes, then how? We explain basic rules and debunk myths. Also, we advise how to effectively and, above all, safely charge the battery.

Basic terms and rules

A dead battery is always a big problem for the driver who is in a hurry. If you have been knowingly using heating on a stop or listening to music for several hours, a dead battery should not come as a big surprise.

The situation is different with normal car use. If your car increasingly often refuses to start, you have reasons to worry.

There can be many causes of it. Remember that the car’s energy balance should be stable, whereas the alternator  is supposed to produce exactly the amount of power that you use. But it only takes a minor failure, which you may not even be aware of, to disturb the balance. Sometimes the same battery in the same model may operate seamlessly in one unit even for several years, whereas in another it shows the first signs of wear and malfunction already after a few months.

It may be caused by a minor defect, e.g. a rusty ground cable of the engine, an inefficient alternator, or car misuse. When you cover short distances within the city, you often get stuck in traffic jams and intensely use heating or other power-hungry features. In such circumstances, the battery will not be able to fully charge.

In such case a good idea is to charge the battery using a rectifier. This is particularly recommended in the winter, when there is big frost, which has a negative impact on battery performance.

Can you charge the battery in the car?

Is it possible to charge the battery in the car? Many drivers will surely say yes. But with today’s new technology and advanced solutions, charging the battery in the car is unnecessary and may lead to many problems and costly defects.

Of course, a defective battery is a nightmare for every driver, and taking it out of the car, carrying home and charging can be quite a hassle. After a few days it crosses your mind to connect the rectifier directly to the battery’s clamp, which is installed in the car. “The mechanic did the same in the repair shop and everything was fine!” most drivers would think. The idea is tempting to most owners of modern cars, in which taking out the battery usually results in resetting the computer and, in extreme cases, the need to visit a repair shop, e.g. in case of complicated LPG systems with drivers etc. So, go for it or not?

Buying a rectifier – is it always so beneficial?

If you do not have a professional rectifier, or you have a modern car with lots of electronics, charging the battery without disassembling it is not recommended. Of course, you can buy sophisticated battery-charging equipment, i.e. one which is usually available in good repair shops, but the cost is several or a dozen or so thousand zlotys, which is totally uneconomic for home use.

The generally available rectifiers, e.g. in supermarkets, specialist stores or at gas stations, are unsuitable for charging the batteries installed in the cars. Such solutions do not have appropriate fire safety measures, which are necessary if you want to charge the battery installed under the bonnet. Many disruptions, or the so called voltage peaks, occur while charging, during which voltage spikes may be as high as a few dozen volts.

If the battery is charged out of the car, the effects will be virtually unnoticed. However, if the voltage spikes occur in the car’s installation, i.e. as a result of charging the battery without disassembling, it may lead to damaging the car’s electronics, e.g. computer, software etc. In extreme cases, this might even end in a short circuit, screen damage, e.g. navigation, or opening airbags. As you can see, time savings and convenience may lead to very serious consequences.

Why does the alternator sometimes fail to charge the battery?

The alternator

Apart from the previously mentioned reasons related to car use, i.e. short distances within the city, being stuck in traffic jams, intensive use of power-hungry systems etc., insufficient charging of the battery may result from an inefficient or damaged alternator. Unfortunately, there may be multiple points of failure: V-belt or ribbed belt drive, problems with brushes or bearings etc.

The most common cause of poor alternator performance are worn-out brushes. In order to check if they need to be replaced, you just turn the ignition key and then observe the charging indicator on the dashboard. If it displays a poor, hardly visible light, the alternator’s brushes should be replaced. Unfortunately, due to a complicated design and lots of default security measures, replacing the brushes at home will be very difficult, or even impossible. Instead of risking the complete damage to the alternator, a much better solution is to entrust its repair to a professional repair shop, even more so since such service should not be expensive, i.e. PLN 100-150.

Defective bearings

Another, slightly more serious problem are defective bearings. To identify the problem, you just need to race the engine. If an unidentified noise intensifies with the increase in rotational speed, it is likely coming from the alternator, or more specifically from damaged bearings. Their replacement is not expensive either and can be done by most repair shops.

Cracked alternator cover

A cracked alternator cover is a problem which may have much more serious consequences. Its replacement is virtually uneconomic, just like regenerating the entire part, since in most cases the cost will be so high that it will be much more reasonable to buy a new alternator. Is there any cheaper alternative?

One solution is, of course, to buy a regenerated alternator, which usually does equally well as the new one, but is much cheaper. 

What happens in the battery during charging?

During battery use, the number of sulphuric acid molecules in the electrolyte grows, which increases its density. Lead sulphate turns into metallic lead, which deposits on the negative plate, and lead dioxide, which deposits on the positive plate. As charging progresses, an electromotive force develops between the heteronymous plates until the value in the range from 2.4 to 2.75 V per cell is reached. 

Such state means that the entire lead sulphate has been processed, which then triggers decomposition of water in the electrolyte. As a result of the process, hydrogen is produced on the negative plate and oxygen on the positive plate. This is commonly referred to as gas discharge, which should be the first signal to disconnect the battery from the rectifier. 

How to avoid the risk of explosion during charging? 

During battery charging an inflammable and explosive gas is produced. What is important, the gas is produced both during charging with a rectifier, e.g. in a garage, and during driving, when the battery is charged by the alternator. For the reasons mentioned above, bending over an engine with a cigarette or illuminating the engine chamber with a lighter is a very bad idea.

A problem may also appear if the battery is overcharged. If you are using a damaged or improper rectifier, which is not equipped with protective electronic measures against overcharging, and you forget to unplug it, it may lead to electrolyte boiling over. This may occur during driving, if the voltage regulator is damaged. Fire can also be caused by a short circuit, which may occur if you fail to correctly connect the charger, or upon trying to start the car by pushing it or using cables.

What does the need to frequently charge the battery mean?

The biggest enemies of any battery include long-term discharge, undercharge or overcharge. Any disturbance of the battery’s natural cycle adversely affects its longevity and performance. Reasons for this may include either car misuse or too weak or too strong charging current. Sometimes you may accidentally discharge the battery completely, for example by using heating on a stop. In such case, if possible, you should fully charge it as quickly as you can.

If you leave the battery discharged for a long time, it will become sulphated. Of course you can use jumper cables, start the engine and charge the battery while driving, but this does not have a good effect on longevity. It is better to use a good quality rectifier.

If even a new battery by a renowned company shows signs of wear after a short period of use, the reason may be a defective electrical installation in the car. Sometimes all it takes to eliminate the problem is to replace the car’s old ground cable.

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