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Car Battery Essentials – D, E and F

Written on March 16, 2016 at 2:31 pm

In this article, we continue our A-Z of car batteries with a look at the next three letters of the alphabet.

 

D is for Direct Current

A car battery, unlike a household power supply, provides direct current or DC. This means that whilst household electricity known as alternating current (AC) provides electric in the form of a wave, the power output from a car battery appears much closer to a straight line.

Essentially, in a direct current power source, the electrons flow in a single direction.

As well as producing direct current, a car battery requires direct current to charge, which is why all AC power is instantly transformed to DC when a battery is a main part of a system, as occurs in an automotive application, such as motorcycles, cars and trucks. The alternator (also known as dynamo) present in vehicles generates AC current which is instantly transformed to DC through a device called a “rectifier”, because a battery is present and most electronics need DC voltage to operate.

Domestic and commercial battery chargers, as well as quick start devices are typically supplied by AC power and feature circuitry to convert this to DC.

 

Direct Current

Image source: http://www.blogcdn.com/www.switched.com/media/2010/09/acdc2.jpg

 

 

E is for Electrolyte

An electrolyte is defined as a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water. In an automotive battery, the electrolyte is essential to how it works.

In a traditional lead acid battery, each cell contains two plates – one made of lead and the other made of lead dioxide. These plates are immersed in a strong sulphuric acid electrolyte solution. When the battery is in use, lead combines with SO4 (sulfate) to create PbSO4 (lead sulfate), plus one electron.

Lead dioxide, hydrogen ions and SO4 ions, plus electrons from the lead plate, create PbSO4 and water on the lead dioxide plate.

As the battery discharges, both plates build up PbSO4 and water builds up in the acid. The characteristic voltage is about 2 volts per cell, so by combining six cells you get a 12-volt battery.

With a traditional car battery, it is important to try to maintain a charge of at least 50% in order to prevent excessive formation of water, which will cause the battery to stop charging and eventually fail.

Modern VRLA batteries such as Gel and Agm batteries are slightly different, as the electrolyte is not stored in a liquid form but in the form of a thick gel (Gel) or contained within a fibreglass mesh (AGM). This makes them less vulnerable to leakage and therefore generally safer, as well as reducing the risk of failure in cold conditions as they do not tend to produce water buildup to the same extent as a traditional lead acid battery.

AGM batteries are also more electrically reliable, making them the favourable choice for many modern cars which feature lots of on board electronics.

 

car battery

 

F is for Failure

There are several reasons why a car battery can fail. However, with a quality battery and the right level of care and maintenance, the good news is that the majority of failures can be avoided. So what are common causes of battery failure?

Excessive Discharge
As mentioned in the previous section, it is important to maintain a charge level of at least 50% in a traditional battery. This ensures that the electrolyte solution does not undergo a complete transformation that leaves the battery with a high volume of water and no ability to transfer current between the terminals. This water build up can also cause problems in low temperatures as it can freeze.
To help avoid excessive discharge, turn off all nonessential electrical features when starting the car and ensure they are off when the vehicle is not running.

Damage
Because a traditional lead acid battery contains the electrolyte in a liquid form, damage to the housing can cause leakage. Not only can this be harmful to both humans and the wider environment, over time it will leave your battery without the essential fluid it needs in order to function and once the electrolyte has fallen to a certain level it will stop working.

Self Discharge
If a battery is unused for a significant period of time, separation will occur inside, making the battery much less likely to transfer current between the terminals when you try to start it again. Also, a gathering of substances in the bottom of the battery can actually cause the terminals to short out, discharging any energy that may remain.

At Manbat, we are experts in automotive batteries. To learn more about the technical specifications of our products along with a wealth of battery related information, visit the technical section of our website. Be sure to also stay up to date with our latest news, where we frequently publish interesting and informative battery related articles.

Noco GB40 Boost

Written on December 10, 2015 at 2:21 pm

Boost-RR-C1_GB40-small-5477

Noco GB40 Boost

New more powerful model for diesel and high-displacement engines,but still safe on engines of all sizes. The GB40 is a portable, pocket sized lithium-ion jump starter for 12-volt vehicles with single battery systems. It can safely jump start a dead battery in seconds for such applications as a car, boat, motorcycle, ATV, Motorhome, lawn mower, truck and more. The GB40 is powered by a high-density NOCO Element       lithium-ion battery  pack with a peak Amp rating of 1000A and an actual power output of 7000 joules 3s.

 

For more information please get in touch:   Call : 01743 218 500  email: sales@manbat.co.uk

What is Acid Stratification?

Written on November 26, 2015 at 11:55 am

What is Acid Stratification?

The electrolyte of a stratified battery concentrates at the bottom, starving the upper half of the cell. Acid stratification occurs if the battery dwells at low charge (below 80 percent), never receives a full charge and has shallow discharges. Driving a car for short distances with power-robbing accessories contributes to acid stratification because the alternator cannot always apply a saturated charge. Large luxury cars are especially prone to acid stratification. This is not a battery defect per se but the result of use. Figure 1 illustrates a normal battery in which the acid is equally distributed from top to bottom.

 

acid pic 1 Figure 1: Normal battery

The acid is equally distributed from the top to the bottom of the battery, providing good overall performance.

Courtesy of Cadex

Figure 2 shows a stratified battery in which the acid concentration is light on top and heavy on the bottom. The light acid on top limits plate activation, promotes corrosion and reduces the performance, while the high acid concentration on the bottom makes the battery appear more charged than it is and artificially raises the open-circuit voltage. Because of unequal charge across the plates, CCA performance, or the ability to crank the engine, is also reduced.

 acid pic 2 Figure 2: Stratified batteryThe acid concentration is light on top and heavy on the bottom. This raises the open circuit voltage and the battery appears fully charged. Excessive acid concentration induces sulfation on the lower half of the plates.

Courtesy of Cadex

Allowing the battery to rest for a few days, doing a shaking motion or tipping the battery on its side helps correct the problem. Applying an equalizing charge by raising the voltage of a 12-volt battery to 16 volts for one to two hours also helps by mixing the electrolyte through electrolysis. Avoid extending the topping charge beyond its recommended time.

Acid stratification cannot always be avoided. During cold winter months, starter batteries of most passenger cars dwell at a 75 percent charge level. Knowing that motor idling and driving in gridlocked traffic does not sufficiently charge the battery, a charge with an external charger may be needed from time to time. If this is not practical, switch to an AGM battery [See BU-201a, Absorbent Glass Mat (AGM)]. AGM does not suffer from acid stratification and is less subject to sulfation if undercharged than is the case with the flooded version. AGM is a little more expensive than the flooded starter battery but tends