Rechargeable batteries is it a con?

[ericmark]

My wife proudly said how she had got a pair of 800mah for a pound compared with the 4 x 2500mah batteries I got for £2.98. But did I really get the better buy? Hers were ready charged and are claimed to hold charge for 1 year and mine had to go straight into the delta V charger.

There's many types of rechargeable batteries, the main ones are NiMH (Nickel-metal hydride battery), Nicad and LiPo (the latter, Lithium Polymer) are rare in AA form at this time), they all hold charge at different rates.

Nicads discharge the quickest, NiMh the second whereas LiPo can hold their charge very effectively for up to a year. They all perform differently too.

Do you know whether the two batteries you're comparing are of same type? Nicad's will generally be cheaper than NiMh's. Also, are they both 1.5v, generally the cheaper rechargeable's tend to be 1.3v.

Both batteries are NiMh's you can't buy NiCad's any longer except for military or medical use. And although there are some odd re-chargeable alkaline batteries at 1.5 volt these are rare and in the main you can't use a Delta V charger to charge them.

Most rechargeable AA cells are 1.2/1.3 volts the 1.5 volt is rather rare. The problem is the amp-hour ratting this varies from 600mhA to 2500mhA reading Wikipedia it seems there are 2700mAh versions.

There are a number of factors Ah rating ability to hold charge, voltage and internal resistance but in the main the normal punter only looks at the rechargeable tag. Add on to this the charger paramours and it goes well beyond the ken of the normal punter.

This is my point to my mind it seems there is a big con with some retailers marketing batteries well below the norm but at a good price and conning punters to buy cheap rubbish.

 

[MJN]

Both batteries are NiMh's [...]

Whilst they are both NiMH the batteries your wife bought were of the low self-discharge variety by virtue of them utilising a different form of electrode separator (evidenced by the fact that they came fully charged - a normal NiMH battery would discharge sat on the shelf).

Whilst the charge capacity of low self-discharge batteries are lower than their conventional NiMH counterparts they may prove far better performers in circumstances that have long periods of inactivity e.g. remote controls (particularly LCD/backlit ones), flashguns, toys etc. In such cases a standard NiMH battery, even of a higher capacity, will self-discharge in a matter of weeks even sat not doing anything, whereas the lower capacity LSD NiMH will end up lasting much longer in such short duty cycle situations. These so-called 'hybrid' batteries are arguably one of the greatest improvements in battery technology in recent years.

There are a number of factors Ah rating ability to hold charge, voltage and internal resistance but in the main the normal punter only looks at the rechargeable tag. Add on to this the charger paramours and it goes well beyond the ken of the normal punter.

The same goes for practically everything. Your average man in the street has no clue and compares everything using nothing more than headline figures such as print head resolutions for printers, sensor pixel count for digital cameras, speaker power output for HiFi... All figures that, by themselves, are practically meaningless as measurements of quality/performance. If consumers aren't willing/able to educate themselves then you can hardly blame manufacturers and retailers for pandering to the lowest common denominator and keeping things 'simple' by merely stating that a battery is rechargeable coupled with some form of numerical figure to allow direct comparisons to be made. To take the digital camera comparison, the fact that Camera A has a 10 megapixel sensor whereas Camera B has only 6 megapixels says absolutely nothing as to which is 'better' by any sensible definition of the term. Unfortunately, if they were the same price then the common man would probably end up buying Camera A because 'bigger number is always better, innit?'.

This is my point to my mind it seems there is a big con with some retailers marketing batteries well below the norm but at a good price and conning punters to buy cheap rubbish.

That may be a valid general point, but your particular battery situation is not necessarily one of them because you are inadvertently comparing apples with pears given the apparent difference in battery type (LSD NiMH vs standard NiMH). That said, 800mAh for an LSD NiMH battery is significantly on the low-performance side by modern standards so on the outright capacity front, and in the absence of any other details about them, they could be better.

Mathew

 

[Space cat]

Your average man in the street has no clue and compares everything using nothing more than headline figures --

Sad but true. The average man in the street is barely capable of buying a decent pint of beer:

"Low carbohydrate lager! That'll be good; I can drink it without getting fat. "

 

[ericmark]

I do see your point when compared with cameras mega-pixels rule OK forget the ISO of the CCD or the 8 bit (Jpeg) v 16 bit (RAW) options.

Oddly it is flash guns that I use the rechargeable AA cells for and there is a problem where the internal resistance is high in that the gun will either fail to charge or charge very slowly.

I select AA cells from charger on the day I go out with camera and don't install in flash until required and I have found non rechargeable just can't supply current required so has to be rechargeable.

With the 800mAh I will be lucky to get 20 flashes from a pair of batteries but with 2400mAh I can often last the day without changing them. Not a precise figure as the flash is thyristor controlled so does not give out same light with each trigger. But because the batteries fail well before they are what most would consider as flat it means I have to select them with care.

I do find NiMh batteries are a pain in there is little indication as to their state of charge. My camera will go form showing full charge to flat in three shots, my phone also will show all bars then fail one hour latter with a flat battery. As a result with both I carry spares. I will give IPhone their due the battery meter does seem to work better than most. However the inability to change the battery should one forget to charge it coupled with the non compatible blue tooth with most car radios means I only use Iphone to show pictures and play games I use a proper phone (Nokia) to phone with.

The problems with NiMh therefore is not limited to the battery it reflects on the equipment being powered by them and I note my father-in-laws Panasonic camera very carefully lists what batteries can and what can't be used with NiCad and Alkaline rechargeable batteries both being on the DO NOT USE list.

So now to next project I want to boost the output from my 30W radio to speakers from 300mW to around the 2W mark so I can hear it in my car. But I have never understood speakers. If I drive two 30W speakers from a radio why am I not using at least 6A on a 12 volt system? My car radio is on a 3A fuse which has never blown even when my daughter is plugging her Iphone into the USB socket to charge and turning the volume to max?

My 30W transceiver does draw around 10A on Tx which is what I would expect so why does a stereo with twin 30W speakers not draw around 20A?