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Cell Matching of rechargeable batteries

PostPosted: Dec 16, 2012 11:52 am
by harrym
In order to get the most out of your rechargeable batteries and lights, it is best to match cells of similar capacity. This means that the batteries that you put in your light should all have similar capacities.

How do you do it?

Here's my technique:

I used Enloop 2500mAh NiMH AA batteries, and charge them with a Maha Powerex MH-C9000 smart charger.


Since the Enloops are white, I use a black permanent Sharpie marker to number each battery. As I recondition each battery on the smart charger, I get a reading of each battery's actual capacity. This information is recorded in my battery log.

Using a log I can monitor the performance of each battery over time, and I can tell when it is time to discard a particular battery. Batteries naturally lose some capacity with time.

In order to match batteries in my lights, I can refer to my battery log. But there is a better way.

I made a chart of battery capacities and assigned a "dot" for each category. For instance:

Actual capacity
>2000 mAh = no dots
1980-2000 mAh = 1 dot
1960-1980 mAh = 2 dots
1940-1960 mAh = 3 dots
1920-1940 mAh = 4 dots

The lower the the capacity, the more the dots. These dots are maked on each battery with a Sharpie marker to indicate that individual battery's capacity.

Using this method, it is easy to match cells.

Just grab 2 or 4 batteries with the same number of dots and load them into your light.

Re: Cell Matching of rechargeable batteries

PostPosted: Dec 17, 2012 1:21 am
by Smells_Familiar
I do the exact same thing but I haven't evolved to the dots yet. That is a great idea though. That way you just add an extra dot when a particular batt drops below the next capacity threshold. I have two battery logs; one is a battery charging log which I only record my yearly battery Break In and my 6 month Cycle (for batts that haven't been used much) statistics including internal resistance (which is measured by the formula Ri=(ICV-V2-0.09V)/1.97A), and the other log is a battery usage log.

I like having two separate logs. This way the battery Break In/Cycle log isn't cluttered with usage info and vice versa. The usage log and the numbering system work well together as I can quickly tell if I'm using the batteries with equal frequency to prevent me from leaving some batteries on the shelf and only using a select few by accident.

BTW, I just got done with my yearly Break In of all 36 of my batteries and it took me 2.5 weeks! :yikes:

Re: Cell Matching of rechargeable batteries

PostPosted: Dec 17, 2012 7:44 am
by harrym
I also use rechargeable batteries in my scuba diving lights, camera and strobe, so I have 42 AA and 16 AAA batteries!