Batteries are constantly falling in price and the idea of replacing all batteries with them is becoming more and more attractive. But if you take the first available batteries for this, their resource can turn out to be depressingly low – and not because they are bad. But because the battery must be selected for each type of equipment separately – taking into account the load, operating mode and other characteristics.
Battery form factors largely repeat those of batteries: AA, AAA, C, D, “crown” – the sizes are familiar to everyone. But new ones are also added – purely battery-powered: 18650, 16340, 26650 and so on. At the same time, some are very close in size to “battery” ones. So, a 14500 form factor battery has the same dimensions as AA (and 10440 – like AAA), but the voltage is 2 times higher. Therefore, when changing a battery to a rechargeable battery, find the form factor designation and install it only after you make sure that it matches.
Battery form factors have developed historically, there is no special meaning in their names.
For cylindrical batteries, form factors are more systematized: the first two digits indicate the diameter, the rest indicate the length. So, the 18650 battery has a diameter of 18 mm and a length of 65 mm.
Lithium polymer batteries can be of any shape and size. They do not have established standard form factors.
Lithium polymer batteries are selected according to the voltage and size of the battery compartment.
Nickel-cadmium – the oldest type of batteries, today they are almost not produced.
They have a lot of disadvantages, the most significant of them are a small capacity, a small number of charge-discharge cycles (about 200), a strong self-discharge when idle, and a memory effect. Due to the last drawback, the battery must be completely discharged before charging, if you put the battery on charge with 50% of the charge, then the next time it is discharged, it will give out only 50% of the capacity.
However, Ni-Cd batteries have not completely disappeared from the shelves, as they also have advantages:
high discharge current;
high charge current – charging speed is higher than other batteries;
does not lose performance in the cold;
Nickel-metal hydride batteries are still the most popular batteries.
Their popularity is facilitated by high capacity, low price and a high number of charge-discharge cycles (1000 on average, up to 3500).
The memory effect of NiMH batteries is much less pronounced than that of Ni-Cd, but it is still recommended to fully discharge the battery before charging to maximize battery life.
But Ni-MH is more sensitive to temperature changes – in cold weather, battery life decreases.
Lithium-ion batteries are the best batteries for normal use.
They have maximum capacity, absolutely no memory effect; there are models capable of delivering high currents from 20 A and above.
But Li-Ion batteries are more expensive and more demanding. Their resource is greatly reduced when working in the cold and when discharged by currents above the permissible ones – and it decreases irreversibly. For Li-Ion batteries, a full discharge is unacceptable, this can lead to rapid cell degradation. Therefore, conventional Li-Ion batteries can only be used in devices with discharge control, which turns off the battery when the capacity drops below a certain limit. If there is no such control, batteries with built-in protection should be used.
And Li-Ion batteries do not tolerate overcharging and are demanding on charging conditions, so they can only be charged with specialized chargers prepared for working with lithium-ion cells .
Lithium-polymer batteries are similar in characteristics to lithium-ion, the main difference is the shape.
In Li-Pol, it can be any, which allows you to use the internal space of the gadget as efficiently as possible. Therefore, Li-Pol batteries are usually used in miniature devices where the volume is limited – mobile gadgets, drones, radio-controlled models, and so on.
Lithium-cobalt batteries are a subspecies of lithium-ion batteries and correspond to them in most characteristics. They have a high capacity, but the specifics of the device do not allow the Li-Cob battery to operate at high currents, so they are not used in powerful devices.
Battery capacity determines how long your gadget will last on a single charge. If, for example, the gadget consumes 500 mA, and the battery capacity is 2500 mAh, then the gadget will work 2500/500 = 5 hours on a 100% charged battery. It’s in theory. In reality, things can be a little different.
First, the nominal capacity may differ from the real one. The manufacturer declares the nominal capacity for the entire line of batteries, but each individual instance will have its own capacity, due to various factors that have developed during production. The real capacity, by the way, will not necessarily be lower than the nominal one – it will be close to it with an error of ± 10%. These are from honest manufacturers. For unscrupulous, the real capacity may differ from the nominal one for the worse at times. Therefore, for batteries of little-known manufacturers, it is better to be guided by the measured capacity – if it is, of course.
Secondly, the battery capacity depends on the discharge current. If it does not exceed 0.5C (half the capacity, i.e. 500 mA for a 1000 mAh battery or 1 A for a 2000 mAh battery), then you should not be afraid. But with an increase, there can be subtleties:
For Ni-Cd batteries, the capacity at high currents almost does not drop – capacity decreases begin only at discharge currents from 3C, and even then they are insignificant.
For Ni-MH, a decrease in capacitance becomes noticeable at a discharge current of 2C: ~5% at 2C, 10% at 3C, etc.
For Li-Ion, it all depends on the device of the battery. Without familiarity with the documentation, it is not recommended to remove high currents from a lithium-ion battery, since some models give a 5% decrease in capacity already at 1C and 10% at 2C. Further excess of the discharge current can lead to the destruction of high-capacity Li-Ion batteries (Li-cob, NMC, Li-Al). At the same time, some types of lithium-ion batteries can operate at currents up to 10C (Li-Mn, Li-Ti), and some – up to 25C (LiFePO4).
The dependence of the capacitance on the discharge current can be estimated from the parameters capacitance at a current of 250 mA to a voltage of 1 V (mAh) , capacitance at a current of 1 A to a voltage of 1 V (mAh) and capacitance at a current of 2 A to a voltage of 2.5 V (mA h) . If you know the current consumption of your device, you can choose the most suitable battery for these parameters.
Please note that the nominal voltage of the batteries varies over a fairly wide range. The voltage of most batteries is 1.5 V, and cylindrical batteries can deliver a nominal voltage in the range of 1.2 to 3.7 V.
Keep this in mind when replacing batteries with rechargeable batteries. Note in particular that most “battery” form factor batteries are 1.2V, while batteries of the same size deliver 1.5V. 1.5 V.
The number of recharge cycles shows how many times the battery can be recharged before the capacity drops by 20%. This means that a battery with 200 charge-discharge cycles does not have to be thrown away after two hundred charges – it will continue to work, just the capacity will be below 80% and continue to fall. Another thing is that the decrease in capacity is exponential, and after a drop of 20%, most batteries quickly degrade until the resource is completely depleted.
The number of recharge cycles is not constant and depends on the operating conditions of the battery. Low or too high temperature, overcharging, overdischarging, high charge or discharge current – all this can reduce the number of cycles, and at times. To avoid this, do not use the battery in unsuitable conditions and charge only with suitable chargers .
Suitable for food
To determine which type of battery is suitable for powering a particular device, you should understand the conditions under which the device is operated, what current it consumes and whether it has overdischarge protection:
For MP3 players, portable audio players, phones, digital cameras, wireless mice and other computer equipment, high capacity Li-Ion batteries are best. These devices are operated under normal conditions, do not consume high currents, but they are expected to have long uninterrupted operation. You just need to be sure that the device has overdischarge control or install only batteries with protection.
For watches, flashlights and other household devices, it is more expedient to use Ni-MH batteries: they are not afraid of a full discharge, while they have good capacity and resource.
For toys, you can use both Ni-MH and Ni-Cd batteries – they are cheaper and more unpretentious. A Ni-Cd battery can be “forgotten” uncharged in a toy – this will not lead to its degradation. But keep in mind that the contents of Ni-Cd batteries are toxic – if there is a danger of damaging the battery case, it is better not to put it in toys.
For remote controls, you can install any cheap batteries – the current consumption in them is negligible, the resource of any battery is enough, so the question of price becomes decisive here.
For alarm panels, it is better to use Ni-MH or Ni-Cd – they will not freeze at sub-zero temperatures and will not suddenly stop working when the overdischarge protection is activated.
For power tools, flashlights and other equipment with high current consumption, either Ni-Cd batteries or Li-Ion batteries should be used – but designed for high currents.
For drones and compact gadgets, it is usually more convenient to use flat Li-pol batteries of suitable voltage and capacity.
Some batteries are equipped with a built-in charger – they do not need a special charger to charge them, they can be charged from the USB connector on a computer, tablet or standard charger. Some batteries have a microUSB or miniUSB connector for a cable, and some do not even need a cable – just remove the cover and plug the battery into the connector like a USB flash drive. Convenient, but this option reduces the battery capacity and increases its price.
To replace the batteries, you can use the batteries of the appropriate form factor – ” little finger ” or ” finger “.
If the device on which you are changing batteries to rechargeable batteries is demanding on the supply voltage, choose among batteries with a voltage of 1.5 V – like conventional batteries.
To power devices that have to work for a long time in the cold, use Ni-Cd batteries .
To make the device last as long as possible, choose among high-capacity batteries .
Batteries with USB charging do not require a special charger, they are convenient to use to power wireless mice and other computer devices – when the battery is discharged, it can be quickly recharged without leaving the place.