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Newbie
09-30-2004, 08:04 AM
How does the mah of a NiMH battery drops over time.

What I mean is, if I buy a 2200mah battery, after 4 cycles it will reach its full capacity. After 50 cycles, what will be its effective mah(or what can it be compared to), after 100 cycles, 150, 250 and 500.

Also, will the drop be the same if its a 2400mah or if its a 2100 mah.
Like, if after 50 use, the 2400 drops to 2100, would a 2100 drop to 1800 ?

If someone knew about that, it would be nice to know.

Rhys
09-30-2004, 08:56 AM
How does the mah of a NiMH battery drops over time.

What I mean is, if I buy a 2200mah battery, after 4 cycles it will reach its full capacity. After 50 cycles, what will be its effective mah(or what can it be compared to), after 100 cycles, 150, 250 and 500.

Also, will the drop be the same if its a 2400mah or if its a 2100 mah.
Like, if after 50 use, the 2400 drops to 2100, would a 2100 drop to 1800 ?

If someone knew about that, it would be nice to know.

i don't think it's that simple. There will be other factors involved such as:
1. whether the battery is fully discharged and recharged fully as soon as possible
2. whether the battery is partially discharged and left for periods before being used or recharged.
3. whether the battery is fully charged and topped up constantly.
4. The temperature/humidity in which the battery is stored/used.
5. The manufacturing quality of that specific battery.
6. variables such as chemical impurities in the battery etc.

As an example, 20 years ago, I bought a set of alkaline batteries. I use them occasionally in my radio. They've been there for 20 years and when I checked them with the meter, they were still all in pristine condition. Equally, I have a set of "prestigious" duracell batteries that were flat within a very short time.

Batteries are a chemical technology and like all chemicals aren't 100% predictable.

Newbie
09-30-2004, 03:21 PM
Okay, then without getting a perfect prediction... is it possible to get an approximation of what it would be in those conditions.

1. The battery is ALWAYS fully discharged and always fully recharged(not topped) within 18 hours. After 48 hours, it is used frequently until fully discharged. Under an average temperature and humidity(I don't know 20C and what is avg humidity ?)

2. The battery is ALWAYS fully discharged and always fully recharged within 48 hours, it can be left unused for periods up to 10 days. Under average temperature and humidity.


Finally, I know its better to always FULLY discharge the batteries and I always do that, but I do not always recharge the battery right away when they are discharged, I'd rather wait to charge them little time before I will have to use them. I do not discharge them in one use, but I'd say that it takes about a week for me to discharge the battery completly.
Any suggestion on how this impacts the battery's performance ?

D70FAN
09-30-2004, 04:14 PM
Okay, then without getting a perfect prediction... is it possible to get an approximation of what it would be in those conditions.

1. The battery is ALWAYS fully discharged and always fully recharged(not topped) within 18 hours. After 48 hours, it is used frequently until fully discharged. Under an average temperature and humidity(I don't know 20C and what is avg humidity ?)

2. The battery is ALWAYS fully discharged and always fully recharged within 48 hours, it can be left unused for periods up to 10 days. Under average temperature and humidity.


Finally, I know its better to always FULLY discharge the batteries and I always do that, but I do not always recharge the battery right away when they are discharged, I'd rather wait to charge them little time before I will have to use them. I do not discharge them in one use, but I'd say that it takes about a week for me to discharge the battery completly.
Any suggestion on how this impacts the battery's performance ?

Overall Rhys has already answered you questions. There is no real rule of thumb, and the primary variables lie mainly in the manufacturing processes, and chemical compounding, used by each manufacturer. Full charge and full discharge also vary in meaning, and different chargers can actually have a profound affect on the actual fully charged state.

I have a question: Is there a reason behind your questions?

Incidently, its mAh (mili Ampere hours). Ampere is a measure of current (force). Voltage is a measure of potential. Both named after people, hence the capital letters.

Newbie
09-30-2004, 05:40 PM
The reason behind my question is that I'd like to know more or less how fast the power yielded by the batteries goes down. So in other words how a battery's mah will be affected at certain moments in the life of a battery.

Of course, if the numbers given are only approximations or approximations based on a certain battery type, then it would be fine... Mostly I'd like to have an idea of the curve the mah capability evolves in time.

D70FAN
09-30-2004, 05:57 PM
The reason behind my question is that I'd like to know more or less how fast the power yielded by the batteries goes down. So in other words how a battery's mah will be affected at certain moments in the life of a battery.

Of course, if the numbers given are only approximations or approximations based on a certain battery type, then it would be fine... Mostly I'd like to have an idea of the curve the mah capability evolves in time.

Just google it. There's a ton of info out there.

Robert Besen
09-30-2004, 06:39 PM
If you have access to a technical library (like at an engineering college) look for "The Battery Handbook", edited by David Linden. This will answer your questions about capacity vs. cycle life for all types of batteries.