Question about rechargeable batteries

[SolaresLarrave]

I have a question about the numbers followed by a dimensional (mAh). What do they mean?

I had a first batch of Duracell rechargeable batteries (AA type) that are the NiMH type, and said 2400 mAh somewhere. Then, I bought a couple of other packages and later saw they had a 2500 mAh. Much later, I needed additional juice for my Nikon F5 so I bought another pack... and these ones say 2650 mAh.

I have the faint notion that these numbers indicate the speed at which the batteries recharge. However, I wonder if is safe to mix them in cameras or flashes; i.e., to use the 2400 along with the 2500 and 2650.

Could someone help me understand? Thanks a big lot! 🙂

 

[ZeissFan]

No, that number represents the battery's capacity as measured in milliampere hours.

Basically, the higher the number, the more capacity the battery has to store energy and the longer it should last.

However, there are other factors that come into play, the biggest being that rechargeable batteries lose a portion of their charge every day, regardless whether they're being used.

I've found that some of the cheaper off brand names don't hold a charge for as long as they should and/or can't be recharged as many times. That's just my experience, and it's likely that others have different experiences.

I'm sure someone on the Internet who doesn't have a real life has tested and compared these and has a massive chart showing the length of charge, discharge rate, number of shots per charge, etc., etc.

 

[payasam]

Most camera manufacturers warn that cells of different types (manufacturer or rating) should not be mixed. I follow this rule without knowing why.

 

[fidget]

One reason not to mix different capacity cells is that the discharge and charge of each cell may vary, with some or one cell having plenty of charge left when the others (one or more) go flat. If use continues one cell may be "reverse charged" by the others. This is very bad for a cell. It is probably a primary factor in shortening the life of cells.

It's not so bad if the equipment is able to shutdown automatically, but applications where manual switch off is required are risky.

Never fully discharge a group of cells. If a full discharge is needed, then discharge each cell individually. I often check for poor cells by trying each one for several minutes in a single cell torch.

Dave

 

[Roger Hicks]

Sanyo's new eneloop (sic) batteries hold 85% of their load after 1 year and are sold charged, ready for use.

The first rechargeable AAs I had, over 25 years ago, were 800 mAh. Today, 2400+ is normal. I don't mix manufacturers because they're ALL different amp-hour ratings; in fact, I don't mix different mAh ratings, for the reasons given by others (reverse charging).

Cheers,

R.

 

[Nickon51]

I think you have to take the specs with a grain of salt. If the batteries you have are the same weight, they should be about the same capacity. Some of the Asian batteries are much lighter and only measure about half their rated capacity.
The comments about mixing and matching are good advice, avoid it if you can.
Just as a footnote, I don't think the difference in performance of a 2400mAh cell and a 2650mAh cells will yield a noticeable gain in performance. Its more likely to depend on where the cells were made and by whom.
Cheers
Greg

 

[spyder2000]

Even if you do match cells by capacity, each cell can age differently so you never really avoid the possibility of one battery serving as a power source to the others. Heat is the biggest destroyer of the cells, so charge and discharge them in such a way they do not get too warm. Some packs include a thermal breaker to help with this and it works while both charging and discharging. If you aren't aware of this, you'll recharge a battery that doesn't need it yet, the same one that will work again after it has cooled a bit.

 

[snip]

I have achieved an advanced state of Ni-Mh happyness by marking my batteries in groups of four, so they allways stay together in their original sets;

And using an intelligent charger that takes eight at a time and discharges each cell individually before charging them using some sort of interstellar circuitry that charges them just right and then shuts down 🙂

 

[SolaresLarrave]

Thanks for all your replies! For some reason, I never mix and match batteries with different mAh numbers. It seemed unwise at the time, and I see that it is actually unwise.

Will have to look for some more of those 2650 mAh thingies...

Again, very many thanks! 🙂