rechargeable AA batteries any good?

Another vote for Eneloops.

I am using an old Prodigy charger which is set for regular NiMh charging and it does false peak about 50% of the time. But it is being supplied by a variable voltage so that does not help it.

I check the mah input and go for about 2500 mah if they were flat. Works well in torches and my digital camera.
 
A few points

The low discharge batteries like the Eneloop are much better. They are still usable a year or more after charging and they last. My 4 year old batteries still produce their rated 2Ahrs and they have always been charged at 1C. I wish my boat batteries could do this especially when they are often 100% discharged.

Be very sceptical of the mAhr claims many bear no resemblance to what the batteries will do. Genuine very high capacity batteries have a very high self discharge rate, so they are only useful if you can use them just after charging, they also tend to have a short life.

The good chargers will reliably pick the end of charge, by noting the slight voltage drop when fully charged that is characteristic of these batteries. If you use a trickle charger you need to be sure the batteries are fully discharged before you start. Modern batteries are easy damaged by overcharging, older low capacity NiCads tolerated this well.
 
oldharry said:
Many of the problems reported with rechargeables arise because most of the cheaper chargers do not do the job properly. Rather than monitor the actual state of charge, they simply apply a current for a set time. If the battery is still part charged, then they get overcharged which can damage them, while if they are fully discharged, they are not kept on charge for long enough so never reach full capacity. This also can damage them - particualrly the cheaper types.

If you are going to use them regaularly it is well worth buying a proper charger which gives you control over the charging rate, and senses the battery voltage to ensure it is fully charged.

One of the cheap plug in chargers I have now thrown away only took a discharged battery up to around 75% before switching off.

Since investing in a proper 'smart' charger, I find batteries holding a higher charge for noticeably longer. In my DSLR camera for example four 2500ma AA will now allow over 500 frames, whereas previously I was lucky to get 350 - 400 from the same set. Using cheap chargers I would sometimes find them failing after less than 300 frames.

My Techno Line BL700 charger cost just under £40 from Amazon. It charges each battery individually, will give me an exact reading of the state of charge of each individual battery, can measure the actual capacity of each battery so that I know when one is beginning to fail, and has a restore function which works a battery through several full charge discharge cycles at optimum levels which extends the service life of an older battery very considerably (Several batteries which showed up as reduced capacity have been restored and are now working properly again, so it is well on the way to paying for itself! Its not the easiest to use, and needs a little perseverance to get the best out of it - but its well worth it.
Click to expand...

+1 on the Technoline charger.

I use high-capacity NiMh batteries for devices that eat battery power, alkalines for clocks and similar stuff that runs for years on one battery. If I had to use alkalines for cameras and flashguns I'd spend a fortune on batteries.

One advantage of NiMhs is that they don't seem to leak goo no matter what you do to them, whereas alkalines can and do occasionally.

interestingly "Which" tested throwaway AAs recently and found LIDL Aerocell alkalines at £1.99 for 4 were very, very close in capacity to much more expensive Duracells and Energisers.
 
Ok - this has been my experience with rechargeables ...

Best thing I ever did was to buy a UniRoss Sprint 90 charger - charges 2 x 2300 AA's in 90 mins or 4 x AA's in about 2hrs 15mins. (depending on residual charge...) I wouldn't charge any faster than this ... due to old-fashioned prejudice.

Actually, I bought 2 of these chargers - 'cause the first was 'faulty' - and then the second developed exactly the same 'fault': which was refusing to switch off, thus risking over-cooked batteries.
Eventually this was tracked down to using 'em in the kitchen, just within range of steam from an electric kettle - the humidity from which was just enough to keep the power MosFET gates triggered. Using the chargers in another room instantly cured the problem.

Having 2 chargers is great - it means I can always have one set of batteries fully charged and trickle-charging on 'standby'.

Re: brands of batteries ...
recommend you avoid BTY from China. Cheap and nasty, and have about 1/2 their claimed capacity.

Vapextech 2400 - very poor quality control - bought 2 packs of 4, of which 2 batteries were dead on receipt.

UniRoss 2300, 2500 - excellent batteries, but curiously the 2300 last longer than the 2500s (go figure).
Encore 2500 (by UniRoss) - excellent - used as 'lithium-battery savers' in my hand-held GPSs, and only need to be recharged every six months.

UniRoss Hybrios - despite what everybody else says, I find these very disappointing, and now have 2 sets of 4x AAs up for grabs if anyone wants them. Maybe they don't like the Sprint 90 chargers - dunno - but I've learned not to trust them in excess of 2 months after charging, which is no use to me.

I've recently bought an obscene quantity of 'RS' brand 2300s - dunno who makes 'em (anybody know ?) - it's still early days, but so far they are proving to be very good indeed.
 
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electrosys said:
Ok - this has been my experience with rechargeables ...

Best thing I ever did was to buy a UniRoss Sprint 90 charger - charges 2 x 2300 AA's in 90 mins or 4 x AA's in about 2hrs 15mins. (depending on residual charge...) I wouldn't charge any faster than this ... due to old-fashioned prejudice.

Actually, I bought 2 of these chargers - 'cause the first was 'faulty' - and then the second developed exactly the same 'fault': which was refusing to switch off, thus risking over-cooked batteries.
Eventually this was tracked down to using 'em in the kitchen, just within range of steam from an electric kettle - the humidity from which was just enough to keep the power MosFET gates triggered. Using the chargers in another room instantly cured the problem.

Having 2 chargers is great - it means I can always have one set of batteries fully charged and trickle-charging on 'standby'.

Re: brands of batteries ...
recommend you avoid BTY from China. Cheap and nasty, and have about 1/2 their claimed capacity.

Vapextech 2400 - very poor quality control - bought 2 packs of 4, of which 2 batteries were dead on receipt.

UniRoss 2300, 2500 - excellent batteries, but curiously the 2300 last longer than the 2500s (go figure).
Encore 2500 (by UniRoss) - excellent - used as 'lithium-battery savers' in my hand-held GPSs, and only need to be recharged every six months.

UniRoss Hybrios - despite what everybody else says, I find these very disappointing, and now have 2 sets of 4x AAs up for grabs if anyone wants them. Maybe they don't like the Sprint 90 chargers - dunno - but I've learned not to trust them in excess of 2 months after charging, which is no use to me.

I've recently bought an obscene quantity of 'RS' brand 2300s - dunno who makes 'em (anybody know ?) - it's still early days, but so far they are proving to be very good indeed.
Click to expand...

Fujicell and Encore off Ebay very good, Vapextech off Ebay junk, Hybrio not very good
 
7 or 8 years ago i bought into the rechargeable idea, starting with NiCd and progressing to Nimh, I've gradually gone off them. The in drawer discharge rate is the main problem, and the lower voltage means that they can't be used with some of my equipment.

Now source alkaline and zinc batterys from the likes of pound shop, Wilkinsons or B&Q when they have special offers. Not had any probs so far, and the ease of use outweighs any financial saving.

Got a drawer full of Nimh cells and chargers, free if you collect.;)
 
oldharry said:
Many of the problems reported with rechargeables arise because most of the cheaper chargers do not do the job properly. Rather than monitor the actual state of charge, they simply apply a current for a set time. If the battery is still part charged, then they get overcharged which can damage them, while if they are fully discharged, they are not kept on charge for long enough so never reach full capacity. This also can damage them - particualrly the cheaper types.

If you are going to use them regaularly it is well worth buying a proper charger which gives you control over the charging rate, and senses the battery voltage to ensure it is fully charged.

One of the cheap plug in chargers I have now thrown away only took a discharged battery up to around 75% before switching off.

Since investing in a proper 'smart' charger, I find batteries holding a higher charge for noticeably longer. In my DSLR camera for example four 2500ma AA will now allow over 500 frames, whereas previously I was lucky to get 350 - 400 from the same set. Using cheap chargers I would sometimes find them failing after less than 300 frames.

My Techno Line BL700 charger cost just under £40 from Amazon. It charges each battery individually, will give me an exact reading of the state of charge of each individual battery, can measure the actual capacity of each battery so that I know when one is beginning to fail, and has a restore function which works a battery through several full charge discharge cycles at optimum levels which extends the service life of an older battery very considerably (Several batteries which showed up as reduced capacity have been restored and are now working properly again, so it is well on the way to paying for itself! Its not the easiest to use, and needs a little perseverance to get the best out of it - but its well worth it.
Click to expand...

Very true. According to studies and documents I've read from expert sources, NiMH are supposed to be charged at a varying rate (and quite rapidly at the end of the charge to avoid the heat build up - the heat build up at end of charge is bad - crystalisation etc.)
Strangely, the NiCads that have fallen out of favour are SUPERIOR to NiMH in some applications. NiMH arrived owing to their "no memmory" business, but NiCad like to be used vigorously and perform better at heavy duty jobs. Also, the memory affect on Nicads can be reversed (fiddly, but you just have to break down the crystallistion affect that has built up over time- you do it by discharging them to a very low voltage, very slowly - then re-charge and they are like new again - but very fiddly)

So it is all in the charger. (As far as these two types are concerned anyway)
 
Apart from their well-known 'memory effect', NiCads had a rather bad habit of growing crystals inside themselves if they were left discharged for an extended period.
If those crystals (or 'dendrites') grew to such size that they bridged that cell's terminals, then the cell was goosed, well and proper.

OK, if you were techno-minded, then it was possible to blast those dendrites to smithereens by discharging a large capacitor across the cell's terminals - but that didn't always work, and most folk simply consigned them to the bin.

No such analogous problems with NiMH cells (which is why I love 'em).
 
Trouble with NiCad or Nimh, batteries are that they have high self discharge. There are also Lithium Iron AA size batteries which last well over a year, and appear to have about 3 times the capacity of alkaline batteries. They are apparently not recharegable. I have 4 in a digital SLR camera, and they provide much more power for flash work than any other sort of battery. My current set are 18 months old, and I have taken over 2000 pictures. 7 day shop is a good source
 
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