Quick Introduction:
In this post we are going to explore about different types of rechargeable batteries that are popularly used in commercial and industrial applications. We will explore about their general information, applications and their charging procedure so that you can pick the most suitable one for your project.
We will be exploring about the following types of mainstream batteries:
Lead-acid battery:
Lead-acid type is the first ever rechargeable battery invented by Gaston Planté in 1859 who was a French inventor. Since his invention till date lead-acid battery is one of the most popular choices for powering commercial and industrial equipment where weight, size and portability of the battery is not an issue. Lead-acid battery is also a popular choice for its cost effectiveness whereas other types of battery cost more for same energy capacity in medium to large scale.
Lead-acid batteries have one of the low specific energy density, meaning they weigh more for the same amount of charge capacity when compare to other popular types of batteries. A typical lead-acid battery has specific energy between 35 to 40Wh/Kg, but this number may vary a little depending on the optimization done by different manufactures.
A typical lead-acid battery may have low energy-to-weight ratio, but it has one of the highest power-to-weight ratio meaning it can provide a huge surge current on demand when compare to other popular types of battery, this is exactly why automobile manufacturers of all internal combustion engine use lead-acid battery for its ignition system. An automobile lead-acid (starter) battery on average provides 1000 ampere for a fraction of seconds to few seconds during ignition.
Lead-acid batteries are not suitable for long discharge cycles, if you do so it will deteriorate its plates and shorten its life, to overcome this issue deep cycle battery was introduced with thicker plates where it can provide continuous power without damaging it. A typical deep cycle lead-acid battery can discharge up to 80% of its capacity.
Technical information on lead-acid battery:
Charging procedure for a typical lead-acid battery:
Before we see how to charge a lead-acid battery, it is crucial to know a couple of concepts regarding discharging pattern of your lead-acid battery, because charging voltage is going to depend on how you are going to discharge the battery.
Charging voltage for lead-acid battery:
If you are using your battery in cyclic usage, then you may apply voltage between 14.1V to 14.4V for a 12V battery and 7.2V to 7.5V for a 6V battery.
If you are using your battery in standby mode, then you may apply voltage between 13.6V to 13.8V for a 12V battery and 6.75V to 6.9V for a 6V battery.
Note: Trickle charge can be done once your battery is fully charged; trickle charge is typically done to batteries in standby usage where the battery is applied with current equal to its self-discharge rate to keep it at fully charged state.
Charging current for lead-acid battery:
A typical lead acid battery can be charged with a current limit of 0.1C to 0.3C (C = battery capacity in Ah), this can be better understood with an example:
If you battery capacity is 10Ah then you may apply a current = 0.1 x 10 = 1A (minimum) and 0.3 x 10 = 3A (maximum).
Full battery cut-off for lead-acid battery:
A lead-acid battery should be disconnected from charger when the charging current falls to 5% of the battery capacity.
Example: If your battery capacity is 10Ah then your cut-off current is (5/100) x 10 = 0.5A
Conclusion:
In conclusion lead-acid battery can be your choice for your projects when weight, size and portability is not an issue or where there is demand for huge surge of current for short period of time or where you need to be cost conscious.
Lithium-ion and lithium-polymer battery:
Li-ion/Li-po or lithium-ion/lithium polymer battery is playing a very important role in modern portable electronics, without it the modern world that we know today wouldn’t exist. All the portable electronics from smartphones to laptops all of them are equipped with li-ion or li-po battery.
The major difference between li-ion and li-po is their chemical electrolyte that exists between positive and negative electrodes. Li-ion has an organic solvent called lithium salt as its electrolyte whereas li-po has highly conductive semisolid gel. The li-po battery is fragile unlike solid li-ion type, but it weighs less and can be moulded into different customizable shapes, this gives flexibility to manufacture to optimize the space inside a gadget and increase the battery capacity and another advantage is that li-po can deliver more current than li-ion can, but li-po battery has less specific energy density compare to li-ion.
The wide usage of li-ion/ li-po is because of their low maintenance, no memory effect and high specific energy density, meaning in a small footprint a lot of energy can be stored and has fast charging capability; this resulted in portable electronics that can be made compact and less weight. Li-ion batteries are very popular choice for electric vehicles because they can be manufactured with less weight and can travel far with a single charge.
However, this technology has its downside too. First of all they are one of the most expensive battery types. Li-ion and li-po batteries are the most dangerous too if charged poorly or mishandled they can burst into flames. They must be operated with a protection circuit to protect them from short circuit, over-discharge and high temperatures. Li-po is the least rugged and can be easily damaged physically compare to other types of batteries.
They must be charged with extreme care, we need to monitor its current, voltage and temperature. Overcharging a li-ion/li-po is a big NO, its battery chemistry cannot tolerate overcharge.
Nevertheless, li-ion/li-po technology made its way into our modern electronics despite its disadvantages, it is already safe enough for commercial and industrial applications and it will only get better as huge progress is made in this battery technology for safety and specific energy density.
Technical information on li-ion / li-po battery:
Charging procedure for li-ion and li-po battery:
Note: The charging procedure for li-ion and li-po are same. You need a power supply that has voltage and current limiting feature.
What voltage should be applied for a 3.7V li-ion / li-po battery?
You should apply 4.20V (nominal) within +/-50mV tolerance, meaning you may apply a voltage between 4.15V to 4.25V but not above this limit.
What current maximum should be applied?
Typically a li-ion / li-po battery can be charged at 0.5C safely. Example, say you have a 1Ah (1000mAh) battery, you can charge the battery at 0.5 x 1000 = 500mA.
When should you cut-off the battery from charger?
You should initiate cut-off from the charger when the charging current falls to 10% of the battery capacity, this can be understood with an example. Say you have a 1000mAh battery then you should disconnect it from the charger when the current passing to the battery falls to 100mA (i.e. 10% of its capacity).
Conclusion:
You may choose Li-ion / li-po battery type for your projects, if it needs to be portable or should weigh less, where zero maintenance for the battery is required and you can bear the cost of the battery and more importantly you have the technical capability to charge the battery safely. Fortunately, there are ready made li-ion and li-po charging modules available in the market to handle charging safely.
Nickel-cadmium and Nickel-Metal hydrate:
Nickel cadmium (wet) battery was invented in 1899 and sealed Ni-cd was the only commercial solution available for portable electronics such as camcorders, camera flash, toys, power tools, emergency lights etc. prior to 1990s, but later Ni-cd battery usage got reduced greatly thanks to alternate battery types introduced like Nickel-metal hydrate and li-ion during 1990s.
Ni-MH battery technology which is closely related to Ni-cd type was developed to reduce toxic substance usage that could harm the environment and also to increase battery capacity, a typical Ni-MH battery holds 30 to 40% more charge compare to Ni-cd of similar weight, both the batteries have a nominal voltage of 1.2V and more than 90% of the portable electronics will work happily.
Ni-cd battery suffer from memory effect, this effect makes the battery to deliver less energy than its actual full capacity after several partial discharge cycles, to overcome this Ni-cd cells has to be periodically discharged fully to 1V per cell and then recharge it fully. Ni-MH cells were marketed as free from memory effect, but the truth is they too suffer from memory effect but far less than Ni-cd do.
Ni-cd and Ni-MH batteries have a greater self-discharge rate compare to other popular battery types and recharging them is surprisingly difficult than li-ion and lead-acid types, you will understand why it is so in the next part of this post.
Nevertheless, they are not bad and have their advantages too. Ni-cd and Ni-MH can be fast charged with less stress, Ni-cd can deliver higher surge current. They are safer than li-ion type and can tolerate some degree of overcharge. They can deliver more charge / discharge cycles if you maintain them properly. They can deliver good amount current at lower temperatures and they can be stored at discharged state for longer period, only other types of batteries can dream of. You can easily purchase them from market with different sizes including AAA and AA types where they can readily replace the primary cells in your power hungry gadgets.
How to charge Ni-MH & Ni-cd batteries?
As we mentioned earlier charging these two types of batteries are difficult than lead-acid or even li-ion, you will understand after you finish reading below given charging procedure.
What is the charging voltage?
There is no fixed voltage to charge a Ni-MH or a Ni-cd battery, manufactures don’t specify them usually, but you may apply between 1.4V to 1.6v per cell for slow charging.
What current should we apply?
The amount of current you may apply depends on how you are going to charge it i.e. slow charging or fast charging.
Slow charging: The safest method to charge a nickel based cell is to charge them slowly at C/10, for example if your battery is rated at 2000mAh then 2000/10 = 200 mA of current for 12 to 16 hours is recommended. You can charge the battery with this method regardless of the initial discharge state.
Fast charging: The advantage of fast charging a nickel based cell is that their charging efficiency is higher when compare to slow charging and obviously they can be charged under 1.5 hours.
For fast charging you need to apply a constant current at 1C, for example if your battery is rated at 2000mAh then you need to apply 2000mA or 2A.
How to detect at full charge and cut-off?
Slow charging: If you are slow charging it, you need to manually disconnect the battery after 12 to 16 hours or as directly recommended by the manufacturer.
Fast charging: If you are fast charging the battery you need to cut-off the battery as soon as it reaches full charge otherwise you will shorten its life. There are two methods to detect full charge namely, delta V and delta T methods.
Implementing the above two methods are difficult in a charger when compare other battery chargers where measuring voltage and current is enough to detect full charge state.
Conclusion:
You may choose nickel based cell / battery pack for your portable and non-portable projects if you need a cost effective solution than li-ion/li-po type yet you expect a decent performance and safety. Apart from these you are okay with slow charging that cost you less for the charger or you are okay with fast charging with a more expensive charger.
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