Battery Models & Terminologies
1. Which battery models do exist?
2. For which applications are the different batteries suitable?
3. Which battery is the right choice for which device?
4. What has to be considered when buying a battery?
5. Can primary batteries be completely replaced by rechargeable batteries?
6. What means "life cycle"?
7. What is the "memory effect"?
8. Are there rechargeables without “memory effect"?
9. What is a "self-discharge rate"?
10. What is a "maintenance charge"?
11. What is a short-circuit at batteries and how can you avoid it?
12. Which types of rechargeables do exist and how do they differ from each other?
13. What argues for the usage of NiMH-rechargeables?
14. How do I obtain the highest capacity of NiMH-rechargeables?
15. How long does a rechargeable battery charge?
16. Which criteria are important when buying a charger?
17. Can rechargeables be charged without interruption?
18. Is it a malfunction, if rechargeables heat during the charging process?
19. Which factors determine the lifespan of a rechargeable?
20. Which factors maximize the lifespan of a rechargeable?

1. Which battery models do exist?
There are one-way batteries and batteries, which are rechargeable and can therefore be used several times.
One-way batteries are also called primary batteries. They are not rechargeable and are hence disposed after usage. The popular types are alkaline, zinc-coal, lithium-oxide and zinc-air cells.
Rechargeable batteries can be recharged and used up to 1.000 times, dependent on their terms of use. The popular types are nickel-metal-hydride (NiMH), nickel-cadmium (NiCd), lithium-ionic (Li-Ion), lithium polymer and lithium iron phosphate (LiFePO4) rechargeables.

2. For which applications are the different batteries suitable?

3. Which battery is the right choice for which device?
The current consumption of the electrical device determines finally, which battery model is the right one. Because in general it is effective: electric devices with a high consumption of electricity also need higher power and that constantly for a long time period. Here most of the time rechargeable batteries are the better choice.
The longest life-span at a high current consumption is offered by NiMH-, LiIon-, LiPO- and LiFePO4- rechargeables. They can be recharged up to 1.000 times and are therefore much cheaper than one-way batteries on the long run.
Alkaline batteries are especially suitable for devices with a tempered current consumption, as e.g. flashlights. At a low current consumption, e.g. at remote controls or clock radios, zinc-coal batteries on the other hand are the better choice.
Examples:

4. What has to be considered when buying a battery?
Despite the higher acquisition costs, for one-way batteries alkaline cells are more economical than the zinc-coal ones. Because they offer at a high current flow a 5-10 times longer life-span.
Purchasing rechargeable batteries is in general more expensive than buying one-way batteries – especially if the adequate charger has to be bought as well. But on the long run rechargeables are much more economical, as they can be recharged and used up to 1.000 times. Even though NiCd- and NiMH-batteries are really similar regarding their qualities and both offer the same nominal voltage of 1.2 Volt per cell, NiMH-batteries survive much longer. They keep up to twice as long as NiCd-batteries till they need to be recharged again.

5. Can primary batteries be completely replaced by rechargeable batteries?
Yes. Especially at items with high power consumption the nowadays current NiMH-rechargeables are an ideal substitute – and that despite the higher voltage of the primary batteries of 1.5 Volt. The reason: as soon as the discharging procedure of the one-way batteries starts, the capacity declines constantly. The average voltage of alkaline batteries is during the whole discharging time about 1.2 Volt – close to the voltage value of NiMH-batteries.
Also the stability of the capacity is an important factor: alkaline batteries just make it to 1.5 Volt right after the beginning of the discharge process. Afterwards the voltage is declining constantly to below 1.0 Volt. Different to NiMH-rechargeables: here the voltage of 1.2 stays almost constant at 1.2 Volt during the whole discharge cycle.

6. What means “life cycle“?
Life cycle means the possible number of charge- / discharge cycles of a rechargeable before its capacity declines. In general the life cycle is regarded as being ended, when the capacity is only 60 to 80 percent of the nominal capacity. When that is reached is depending on the particular charging- or discharging conditions.

7. What is a “memory effect“?
The „memory effect“ occurs, when a rechargeable is getting charged before the energy is completely consumed. In this case, the battery stores the amount of the remained capacity before beginning charging. If the battery is always being recharged, before the whole energy is consumed, the service time and the life-span of the rechargeable reduces with each charging cycle.

8. Are there rechargeables without “memory effect"?
Yes, thanks to new technologies besides lithium-ions-rechargeables (Li-Ion) also nickel-metal-hydride batteries (NiMH) without, respectively with a very low, „memory effect“ are offered on the market (see also question 12).

9. What is a “self-discharge rate“?
Is a fully charged NiMH-battery not being used, its voltage reduces successively. This effect is called “self-discharge”. The self-discharge rate at an average room temperature is about 15 to 20 percent per month.
For NiMH-high performance cells this value lies much higher.
LiPO, Li-Ion & LiFePO4 cells have a significantly lower self-discharge rate of 5-10 percent per month. Though, here the amount is also higher for high performance cells.

10. What is a “maintenance charge“?
The maintenance charge is a very low charge current, which is just sufficient to keep the battery in a fully charged condition without overloading it. This is e.g. important for wireless phones which are often connected to the charging base.

11. What is a short-circuit at batteries and how can you avoid it?
A short-circuit occurs, when the positive and the negative pole of a battery are being connected by a conductor, e.g. by a key ring or a paper-clip. A possible consequence: the temperature of the cells is increasing and the inner gas pressure is accelerating. The battery can leak. To avoid a short-circuit, you shouldn’t keep new or just charged rechargeables together with possible conductors as coins or keys.

Rechargeables & Chargers

12. Which types of rechargeables do exist and how do they differ from each other?
Lithium-Polymer-Rechargeables (LiPO)
Lithium-Ions-Rechargeables (Li-Ion) are very light and offer a specifically high energy density (3,6 - 3,7 Volt). Therefore they are suitable for midget devices with a high consumption of electricity, e.g. cell phones, notebooks, smartphones, PDA’s, etc., which are the trend today. These are most of the time included when buying the mobile device. Lithium-Ions-Rechargeables are more expensive to produce and for this reason more expensive to purchase. In addition they react more sensitive to false treatment than other rechargeables. One advantage: they can be charged at each time and not only when the battery is empty.

Lithium-Iron-Phosphate-Rechargeables (LiFePO4)
Nickel-Metal-Hydride-Batteries (NiMH)