8.4V Nickel–metal Hydride labeling - Nominal Capacity VS Minimal Capacity

[Kiriakos GR]

I am currently exploring this last significant detail at 8.4V NiMH labeling, regarding Nominal Capacity VS Minimal Capacity specification.

We get out shopping for a new 8.4V NiMH, we seek high capacity products, we make our purchase according to product label.
For example, we got an 250 mAH (Nominal Capacity), but under testing, actual capacity this is close to Minimal Capacity specification.

Over the years, I have read too many technical documents, but no one clarifies of why we should accept Minimal Capacity as this be normal to happen?

Indeed an 8.4V NiMH, this is consisted of seven interdependent cells.
This is now a battery pack of stacked cells.
In theory, all cells must be in identical condition, regarding electrical performance and capacity per cell.

But, here gets in, and another factor (parameter), this named as quality control at battery cells production.
An factory with severe issues at quality control at manufacturing stage, this will deliver uneven in capacity NiMH cells (1.2V).

In theory, a serious factory of 8.4V NiMH E-Block, this it should run Burn-in tests in all their products, so the ones with issues, them to never arrive at the market.
Brand xxxx this informs of 72 hours Burn-in test, but is that sufficient?

An 8.4V NiMH E-Block this requires 16 Hours for charging, along of 4.5 Hours as discharge test.
An single test cycle this will require approximately 21 Hours.
72 hours Burn-in test, this divided by 21 Hours this is equal to 3.5 test cycles.
And or at three complete cycles, when there is also calculated and included, a small resting period, between its new test.

-------------------------------------------------------------------------------------------------------------------------------

The new question, this is if the factory, it does perform such testing at all products?
You are paying for 280 mAH capacity, and you get  274 ~ 289 mAH   
You are paying for 250 mAH capacity,  and you get  224 mAH   

At a manufacturer with high standards at quality control, the difference  between Nominal Capacity VS Minimal Capacity, this is at 8% at 8.4V NiMH E-Block.
The worst percentage that I discovered due my tests this is 12%. 

What consumers should know, this is if measured capacity this is less than 15% at any NiMH E-Block or at a single cell, this must be returned as damaged.   

-------------------------------------------------------------------------------------------------------------------------------

Why the awareness of actual Minimal Capacity this is of high importance?
Answer: Because if you do not exceed this limit at battery discharge, you are performing a normal use of the product.

[Kiriakos GR]

What else it can influence at a fresh NiMH cell, it actual battery capacity? 
 
This information comes from the mouth of Duracell.

The negative electrode has excess capacity compared to the positive electrode and is used to handle both overcharge and over discharge.
Thus, the useful capacity of the battery is determined by the positive electrode.

And therefore, build quality of the positive electrode, this is essential. 

At the end of the day,  when we spot NiMH cells with average to low performance, this translates that this factory does not have or use advanced Know-How.
Panasonic and FDC (Japan), both are knowledgeable at making best performing positive electrode, along of special coatings these extend positive electrode service life.

This is of why 95% of made in China cells, they cannot compete at the service life and performance with the Japanese products.
Unfortunately for us,  the manufacturing of 8.4V NiMH E-Block this is now abandoned by the Japanese.

This is of why ITTSB Europe, this now also focusing at the offering of awareness, regarding the few 8.4V NiMH E-Block these available in EU.
And especially for products, these claiming that they are Low Self discharge and Pre-charged.   

An assembled 8.4V NiMH E-Block, this is consisted by the number of seven positive electrode, and the combined number of losses, this forming the number of  Minimal Capacity (useful capacity).

-------------------------------------------------------------------------------------------------------------------------------

This information comes from the mouth of Duracell.
Typically, under a C/5 charge/discharge at normal ambient temperatures (20°C or 68°F), up to 500 cycles can be achieved with the battery delivering at least 80 percent of its rated capacity.

In other words, Duracell this considers as minimum accepted useful capacity this be 20% lower than Nominal Capacity = product label.