Why Laptop battery reduces its efficiency? Tech Focus 9


Laptop battery is a kind of Lithium Ion ( Li-ion) battery which has features like high efficiency, slow discharge rate, best energy to weight ratio etc.Unlike other rechargeable batteries, Lithium ion battery uses Lithium as the active material. During discharge, the lithium ions move from the negative electrode to the positive electrode. The flow of lithium ions reverse during charging. Lithium Ion battery outperforms other types with its features like High open circuit voltage that deliver high power at low current rate, Low self discharge rate of 5-10% per month etc. But along with these advantages, lithium ion battery has demerits also. Memory effect, self discharge, over heating etc are the most important drawbacks of Laptop battery. Let us see how this happens and the solutions to prevent this.
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How to maintain Maintenance Free Battery? Tech Focus 5


“My UPS is not giving sufficient back up”. This is the most common complaint raised by PC users. It is not the fault of the UPS, but is due to the poor maintenance of its battery. Sealed batteries are used in UPS, Emergency lamps etc do not require water and acid top up. There is no water loss in these batteries during the charge/discharge cycle and it can be positioned in any direction like vertical, horizontal etc. These sealed batteries are known as SMF (Sealed Maintenance Free) or VRLA (Valve Regulated Lead Acid) batteries and they work on the oxygen recombination principle. SMF battery is totally maintenance free and has longer cyclic life, thus compensating the initial higher cost. One of the important aspects of battery life in relation to the use of equipment is the cut off voltage set in the equipment. If properly maintained, the sealed battery can give sufficient back up time. Let us see the tips to increase the life of UPS and Inverter battery.
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What causes premature battery breakdown? Fact File 32


So many factors. Battery needs care to maintain its chemistry and its energy efficiency. The aging process starts at the moment the battery leaves the manufacturing factory. Self discharge ,sulphation, capacity loss, overcharging, dendrite growth, grid corrosion, excessive heat and water loss etc are some common reasons for the premature battery failure.

If the battery is not cycling for long period, self discharge takes place @ 4 % per week at 27 degree. For example, a 125 Ah battery shows self discharge @ 5 Amps current per week if it is not discharging through the Inverter. Sulphation is another important factor affecting battery efficiency. The lead sulphate accumulating on the plates prevents charge release/ acceptance cycles. Usually the lead sulphate crystals will be removed during water filling and charging. So it is better to charge the battery as soon as possible to prevent sulphation.

Another important reason is overcharging. The battery used in backup systems should have a charger cut off facility, otherwise the battery will get over charged due to float charging. When the battery is overcharged, the charge voltage increases above the Gassing voltage. This causes formation of excess hydrogen. The Gassing voltage of a 12 V lead acid battery is 14.3 at room temperature. The battery voltage crosses the gassing voltage level if one or more cells are damaged or weaker. The weaker cell will charge last since its resistance is lower than the good cells. So higher voltage appears across the good cells and may increase the voltage above the gassing voltage level.

By using the battery equalization method, it is easy to make the battery fully charged. All the cells in the battery will not be equally good due to aging. Some cells accept charge very fast and some in a slow rate. If this happens, the battery will not hold sufficient charge and will discharge very fast through the load. Equalization is done by giving slight overcharge to the battery even after the terminal voltage rises to maximum. Due to this overcharging, the weaker cells also get time to accept full charge. A fully charged 12 volt lead acid battery will show 13.8 V terminal voltage and a 12 V tubular battery will show 14.8 V in the fully charged state.

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Why Emergency Lamp is not doing well? Fact File 18


It is not its fault! But ours. We search for the emergency lamp only when power fails frequently. Otherwise it will be a dust depositor somewhere. To make the emergency lamp in good condition, proper care is needed. The emergency lamp battery is SMF (Sealed Maintenance Free) type and need not require water topping and can be placed in any position. It is rated 6 volts @ 4.5 Ah backup current.

 

The electrolyte of most SMF battery is a gel of Sulphuric acid mixed with Silica fume which makes the resulting mass gel like and immobile. This gel electrolyte reduces the electrolyte evaporation, spillage etc. One important feature of Gel battery is that the lead plates contain Calcium instead of Antimony to reduce water loss. Because of the presence of calcium, the gel battery charges very slowly compared to other batteries. Another important feature is its thermal sensitivity so the battery is vulnerable to thermal run away due to abusive charging. Over charging leads to its premature failure.

The Emergency lamp battery requires equal charge and discharge cycle. That is, it should be charged and discharged daily or once in two days. If it is always plugged in for charging, overcharging occurs leading to its permanent damage. If the battery is kept without charging for few days, self discharge takes place and the battery develops Memory Effect so that it will not charge fully. Deep discharge is another problem that can affect battery life. When the emergency lamp is kept switched on till it completely shut down, two adverse effects happen. The battery will not charge fully in recharging and the ends of tubes turn black due to filament damage. So it is better to switch off the lamp, when its light intensity drops.
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Battery Level Meter


With this circuit, you can assess the voltage level in Lead Acid Car battery or Inverter battery. It gives LED indications in Dot Mode display to show the level of voltage in the battery. A Lead Acid battery attains 13.8 volts and tubular battery 14.8 volts in the fully charged state. If the battery voltage level drops below 10 volts, it needs immediate charging, and if it is not attaining full charge, it cannot be used to drive the load.

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Inverter Battery Charger with Cut Off


The Blog Stat shows that most of the readers are interested in Battery Maintenance as indicated in the Tag cloud. So I wish to post a Friendly Charger circuit for the battery. This Battery charger can replenish any kind of 12 V Inverter battery or Car battery and keep it in top condition. The charger never allows the battery to Over charge or Deep discharge. It automatically charges the battery when its terminal voltage drops below 12 volts and switch off the charging process when the terminal voltage rises to 13.5 volts. So that the battery can be kept unattended.

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