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Rechargeable Battery Technicals

Q1. What is NiMH and what is a NiCd? What’s the major difference between the two types of batteries?

Q2. How much better are NiMH rechargeable batteries compared to vs. NiCd rechargeable batteries?

Q3. How much performance improvement can I expect using NiMH batteries?

Q4. What is the Memory Effect of a NiCd battery? How can I avoid it?

Q5. Do NiMH batteries have Memory Effect?

Q6. Are the alkaline batteries better suited to some uses than NiMH rechargeable batteries?

 

Rechargeable Battery Technicals Answers

 

Q1. What is NiMH and what is a NiCd? What’s the major difference between the two types of batteries?

 

Answer NiMH refers to Nickel Metal Hydride and NiCd refers to Nickel Cadmium. The major differences between the two types of batteries are is capacity, memory effect and environmental friendliness. NiMH batteries have high capacity, no memory effects and environmentally friendly. If you are under the illusion that rechargeable batteries are not very good then the chances are that you have been using older Alkaline rechargeable batteries (which are rubbish) or NiCd batteries suffering from memory effect and you have not been aware of the effects of Memory Effect.

 

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Q2. How much better are NiMH rechargeable batteries compared to vs. NiCd rechargeable batteries?

 

Answer NiMH batteries are the results of recent technology advance. NiMH batteries last much longer than NiCd batteries per charge. NiMH batteries also are environmental friendly because of elimination of cadmium toxicity concerns.  Today, more and more high-drain devices consume battery power quickly. Consumers will greatly benefit from the value proposition delivered by NiMH.  Not only do they deliver more power, lasting longer in high drain devices, but they also can be charged up to 1000 times. NiMH batteries are much better than NiCd batteries.

 

 

NiMH batteries' advantage over NiCd batteries

PERFORMANCE

NiMH batteries will greatly out-perform standard NiCd batteries in high-drain applications.

CAPACITY

The amount of energy stored by the battery. NiMH has more than twice the capacity of standard NiCd. NiMH batteries have much longer runs times (hours played, number of pictures taken).

MEMORY EFFECT

NiMH batteries can be charged or “topped-off” at any time without affecting battery life. In order to achieve optimum performance from NiCd batteries, they must be fully discharged before recharging. Unlike NiCd batteries, NiMH has No Memory Effect.

ENVIRONMENTALLY FRIENDLY

NiMH batteries have no Cadmium added.  Cadmium is hazardous to the environment.  NiMH is much more environmentally friendly

VOLTAGE

The power produced by the battery. Both NiMH and NiCd have virtually the same voltage.

                                               

                                                Comparison between NiMH and NiCd rechargeable batteries

 

NiCd

NiMH

AA Capacity
(mAh)

600 - 800

1,800 – 2,000

AAA Capacity
(mAh)

200

600 - 700

Service Life

Up to 750 cycles

Up to 1,000 cycles

Voltage

1.25V

1.25V

 

NiCd batteries can generally perform well in devices such as TV controls, clocks, radios or torches for example, where they will happily operate until they run flat. Modern power hungry devices like digital cameras, video cameras or remote control toys on the other hand are better suited to NiMH.   

 

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Q3. How much performance improvement can I expect using NiMH batteries?

 

Answer NiMH rechargeable batteries will easily outperform throwaway alkaline batteries. Have you ever noticed that when using high powered alkaline throwaway batteries in your digital camera that things can soon start to slow down and you eventually need to replace the batteries a lot sooner than you'd like to?  DO NOT throw these batteries away (well not yet!) as you will probably find that they will work perfectly satisfactorily  in less demanding equipment such as radios or TV controls. The battery still has plenty of power but is no longer able to deliver it quickly enough. That's why everything stutters and slows down. It does not matter which make of alkaline battery you try to use as there is no getting away from the fact that alkaline batteries are quite simply not capable of operating today's power hungry digital devices due to the outdated chemistry of alkaline batteries. Alkaline batteries can store the power, it's just that after a relatively short period of use, they simply can't delivery it quickly enough in modern digital equipment when full power is required “in a flash”. 

 

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Q4. What is the Memory Effect of a NiCd battery? How can I avoid it?

 

Answer  If a NiCd battery has not been entirely emptied before the next charge, the charge will not be complete and will set a new lower energy capacity. Over time it will appear that the battery is no longer holding a charge. This is called the "memory effect". To avoid this, it is best to occasionally discharge NiCd batteries entirely as this will ensure optimum performance and help lengthen the life of the battery.  You should discharge NiCd cells before every fifth to tenth process of charging in order to avoid the feared memory effect. The memory effect has the consequence that the not used parts of the cell due to partially discharging are no longer in a position to receive and produce energy. Consequently their operating times become shorter and shorter and the cells have to be recharged more frequently. This often misunderstood feature of NiCd batteries has possibly given some users a bad impression of rechargeable batteries in the past. NiMH batteries don not have memory effect.

 

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Q5. Do NiMH batteries have Memory Effect?

 

Answer NiMH batteries have no memory effect.  Memory is a type of problem that traditional NiCd batteries usually develop. You probably have heard that in order to maintain the life and performance of rechargeable batteries, you have to fully drain the batteries before recharging them. Thanks to "memory free" technology used for NiMH batteries, you can charge them anytime you wish, regardless if the batteries are fully drained or not.

 

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Q6. Are alkaline batteries better suited to some uses than NiMH rechargeable batteries?

Answer This really depends on what you are using the batteries for.  For most high drain electronic devices, like digital cameras, rechargeable batteries will continue to work much longer than alkaline batteries. In fact in devices like digital cameras, NiMH batteries will run on a single charge for 3-4 times as long as they would on an alkaline battery. Alkaline batteries can be the better choice than NiMH or NiCd for some uses.  Alkaline Batteries are more suitable for use in low-energy consumption appliances like digital clocks or remote controls.  Rechargeable NiMH batteries are the better choice for high drain applications. They lat much longer on a single charge and don’t have to be discarded after a singer use. Alkaline batteries are comparatively very expensive.

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