How to choose the power source for your device.
Have you decided what battery do you need?
Nickel Cadmium (NiCd) batteries were the typical technology for many years, but they became out of date at present. NiCd is applied where high discharge level, long life and economical price are relevant. As NiCd includes toxic metals such as cadmium it’s environmentally unfriendly and must be recycled or disposed of in the proper way.
They are heavy and have “memory effect”. When you recharge a NiCd battery that hasn’t been totally discharged, it “memorizes” the previous charge level and thus the maximum capacity becomes equal to this level. The “memory effect” is determined by crystallization of the battery's substances and can decrease your battery's life span, even make it useless. In order to avoid it, you should fully discharge the battery and fully recharge it again at least once in a few weeks.
- Fast and easy charge — even after long-time storing.
- Large number of charge / discharge cycles — if thoroughly maintained, the NiCd guarantees over 1.000 charge / discharge cycles.
- Excellent load performance — the NiCd permits recharging at low temperatures.
- Long shelf life – in any condition of charge.
- The lowest cost.
- Available in various types and sizes.
- Comparatively low energy density.
- “Memory effect”.
- Environmentally unfriendly.
- Comparatively high self-discharge — requires recharging after storage.
Nickel-Metal Hydride (NiMH) battery is less influenced by the “memory effect” and is easier in maintenance. Nevertheless, it has problems at very low or high temperatures. Although it doesn’t contain heavy metals, it can’t be completely recycled yet. NiMH battery is notable for higher energy density in comparison with NiCds. It means that you get increased runtime from the battery without extra weight.
- 30-40% higher capacity than in a usual NiCd.
- Less evident memory effect than in NiCd. Periodical full discharge/charge cycles are needed less often.
- Easy storage.
- Environmentally friendly.
- Limited lifetime — if frequently deep cycled, particularly at high load currents, the operation starts to worsen after 200 to 300 cycles.
- Limited discharge current — though a NiMH battery can deliver high discharge currents, periodic discharges with high currents decrease the battery’s life span.
- The NiMH produces more heat during charge and needs a longer charge time compared to the NiCd.
- High self-discharge — the NiMH has about 50% higher self-discharge in comparison with the NiCd. Modern chemical additives enhance the self-discharge but at the expense of lower energy density.
- Operation deteriorates if stored at high temperatures — the NiMH should be kept in a cool place and at the condition of charge of about 40%.
- High maintenance — battery should be fully discharged regularly to avoid crystalline formation.
Lithium Ion (Li ion) is the most rapidly developing battery type and a new standard for portable power. Li ion is applied where light weight and high-energy density is most important. It weighs about 20-35% less but generates the same energy as NiMH. They don’t suffer greatly from the “memory effect” unlike NiMH and NiCd batteries. Their substances are non-hazardous. But as lithium inflames very easily, they need special handling.
- Low self-discharge – the rate of self-discharge is much lower in comparison with such rechargeable cells as Ni-Cad and NiMH.
- Climate resistance – efficiency at low temperatures.
- High energy density — ability for higher capacities.
- Low maintenance — no periodical discharge is required, no memory.
- Needs protection circuit to avoid overcharge / deep discharge and shortcuts. Unprotectedlithium batteries can’t be safely applied in many devices.
- Liable to aging, even if not in usage. Battery storage in a cool place and at 40% charge level decrease the aging affect.
- Moderate discharge current.
- Expensive — about 40% higher price than NiCd.
General Battery Care
1. Store batteries in the original package. Storing batteries encapsulated in their package assures that they remain protected from environmental impacts such as humidity. It also guarantees that you don’t mix up new, completely charged batteries with old ones, and it prevents their terminals from contacting with other metals.
2. Keep batteries in a cool, dry place. When you select a place to keep your batteries, make certain it’s not exposed to humidity or extreme temperatures, as these conditions can deteriorate the battery. It will be nice if you store them at around 60°F (15°C), but keeping them at a little higher temperature will also suit.
3. Keep rechargeable batteries at a 40% charge. Rechargeable batteries with nickel or lithium chemistry should be stored at around 40% charge level. This minimizes degradation caused by aging.
4. Avoid contacting of negative and positive terminals of two batteries. If negative and positive terminals of different cells are contacting, they may conduct electricity and the batteries will be discharged.
5. Leave plastic caps on your batteries' terminals when you don’t use them. Certain batteries, among them many 9 V batteries, have a plastic cap fitted over the terminals. You need to leave these caps on during storing to prevent the batteries from losing their charge and conducting electricity.
6. Remove batteries from rarely applied electronics between usages. If batteries remain in electronic devices, they discharge faster.
7. Never keep your batteries in the freezer since this decrease their ability to charge completely.
There can be no doubt that the best instruction for storing is to consult the producers' specifications and recommendations. But there are also some general hints for storing different types of batteries:
Nickel Cadmium batteries can be kept both in a charged or discharged condition. Long storing can accelerate battery self-discharge, and result in the deactivation of reactants. Although the cells can be kept at temperatures between -20°C and +45°C, heat can provoke deterioration of the active chemicals and it’s better to keep the cells in a clean, cool, dry, non-corrosive place. After prolonged storing, 2-3 full discharge cycles may be required to renew complete capacity.
Nickel Metal Hydride batteries should be kept at 40% charge level. As NiMH cells are notable for a higher self-discharge rate, they will lose more charge during storing and will most likely demand charging before they can be used again.
Lithium-Ion. The temperature range is -20°C to 60°C but for durational storing period -20°C to 25°C is advised and 15°C is ideal. Cells should be kept with an incomplete charge (30%-50%).
Remember, the conditions of storage for batteries depend on the active chemicals utilized in the cells. During storing the batteries are liable to self-discharge and decomposition of the chemical contents. Over time solvents in the electrolyte may penetrate through the seals causing the electrolyte to dry out and lose its efficiency.
Following our prompts you can significantly increase the efficiency of your batteries and enjoy their operation for a long time!