Can anyone recommend me a good quality AA/AAA battery charger at a reasonable price. Or tell what to look out for when choosing one.

Also has anyone used the Eneloop XX cells? They have a higher capacity (2500mAh compared to 2000 mAh of the standard Eneloop AA) but have a higher self discharge rate (not much of a problem imo) and are only good for 500 recharges compared to 1500 for the standard Eneloops (a bit more of a problem depending on how much you use them).

Cheers,

Huge.

Huge,
I'd stick to the normal Eneloops - you'll be taking a spare set underground anyway so the small loss of capacity makes little practical difference.  The low self-discharge is so useful because you don't have to charge them the day before you go underground!
(I've also had good results from the '7dayshop' brand of low self-discharge 'Good to Go' batteries.  Much cheaper.)

I'd look for a charger that charges and monitors each battery separately.  Much better for the long-term performance of the batteries.
Avoid ones that have to charge pairs of batteries, or don't specifically say that they charge each battery independently.

I've had a 'technoline' IC8800 charger that I've trusted for years.  I think they're variously titled 'Technoline', 'La Crosse' or 'Voltcraft' - the case and display certainly look similar.

K.

Cheers Korky, I'll take a look.

I have a couple of the chargers that are sold at Lidl for around ?14.00. Using batteries from the same source I have had no problems in the 3 years I have used them. The newer version has LED indicators to show charge and they both will handle one to 6 AA batteries.From batteries  that have seen 6 or 7 hours use to full charge is normally less than 2 hours. I cave once or twice a month although I have never used the same batteries for more than 7 hours on one trip. Lidl also sell "Low discharge" batteries that I use in my backup lamp, I charge them every couple of trips even if I have not used them. On test they powered a duo for 7 hours after being stored for 2 weeks and they may have lasted longer.

Cheers Alex, that's very interesting.

You need a 4-channel smart charger
Go for the regular eneloops they will be more robust in the long run

korky said:

(I've also had good results from the '7dayshop' brand of low self-discharge 'Good to Go' batteries.  Much cheaper.)

Click to expand...

I bought and tested some of the 7dayshop AAs and they were reasonably good - capacity not quite as much as claimed, but not too far off.
However, some own-branded AAAs I got from them were rather poorer in terms of capacity than I'd expected/hoped.
I can't remember the figures at the moment, but (if I can find the cells) I'll stick some through my analyser and report the results.

Stuck a couple of the '2100mAh' 7dayshop-branded 'good-to-go' cells in my Maha C9000.

The cells are couple of years old but pretty lightly used, and came out as 1700mAh (1704, 1707) capacity on refresh/analyze, which I think is not far off what they tested at when they were new.

My C9000 does seem a bit pessimistic - all the Eneloop 2000s I've tried seem to pretty universally come out as being 1900mAh or a touch less although other people seem to report them as being typically mid 1900s and upwards.

So on that basis, I'd reckon that the 7dayshop AA cells may be close to Eneloop 2000s in capacity, but a little worse. OK for the price, assuming the self-discharge is similar.

Thanks all for the advice. I thought I'd let you know what I ended up with.

I bought a Technoline BL-700 for ?36 from Battery Logic through Amazon. It seems to do everything you'd need. It will charge up to 4 batteries individually. There's a choice of 3 different charging currents (the lower the better I assume?). It can also discharge, capacity check or refresh the batteries (continually charge/discharge until old batteries have reached the maximum capacity they are going to attain). It will charge different batteries at different currents and you can charge, discharge and refresh different batteries at the same time, if you should ever wish!

The big selling point though was that it came with 4 AA Eneloops in a limited edition graphite sparkle colour!!!

Cheers, Huge.

There are some people who say that smart-charging cells at low rates relative to capacity (anything less than 0.5C) is wrong/risky because a smart charger might fail to detect a cell is full and so fail to terminate charging when it should.

However, there are quite a few smart chargers around that seem to charge at rates of ~0.3C with no obvious problems (like overly-warm cells when charging stops), and I've homebuilt smart chargers that are perfectly happy charging single cells or multicell packs at rates around 0.2C without any problems missing terminations.

(the 'C' is a number relative to battery capacity, so for a 2000mAh cell, a 1C charge would be at 2000mA, a 0.5C charge would be a charge at 1000mA, etc)

The charge rate depends on your cells. You want it to pick up on the voltage dip when it's fully charged. We charge our eneloop AA's at 700mA, the chargers reliably terminate appropriately. Crappy cells are more problamatic, and different chargers use different algorithms to determine when to stop. Here, I'll just post an excerpt from an article written about batteries and charging by Brian Stoltz (knows his stuff very well) 'cuase it will explain it better than I can and it is safe info to use:

?So exactly how does a smart charger work?? I?m so glad you asked!! As a cell is charged, the cell voltage
increases. Just after being fully charged, the voltage actually peaks, and takes a dip. The smart charger
looks for this drop in voltage, called negative delta V (-dV), then it terminates charging. But here is the
catch, and something important to understand if you have a charger with selectable charge rate (like
the two mentioned above). You have to charge the cell at the correct charge rate in order for this -dV
signal to be visible enough for the charger to detect. For NiMH cells, that is 0.5-1.0C, where C stands
for capacity. So, for example, a 2100mAh cell should ideally be charged at 0.5-1.0 it?s capacity, or 1050-
2100mA of current. This also means a full charge from being fully depleted would take 1-2 hours. If you
charge slower than this on a rate-selectable charger, you risk missing the -dV signal and cooking the
cell. The myth of ?slow charge is better/healthier? is incorrect in most all cases. If you charge faster (like
the 15 minute chargers) you also cook the cells. 0.5-1.0C is the sweet spot for optimal cell longevity and
performance.

As for Huge's question, for the BL-700 (and the similar Lacrosse BC-700) and Eneloops, most of the the recommendations I've seen online are for using the 700mA rate.

As far as the rest is concerned, at the risk of drifting off topic, all I can say is that a couple of commercial smart chargers I have have rates of ~700mA (so a 'bad' 0.35C on 2000mAh cells, and 0.3C on 2500mAh cells) and they appear to terminate pretty well.

The Lidl 6-way charger I have seems to tend towards heating up cells, depending on cell make, but it supposedly charges AAs at 1A, so charges at a 'good' 0.5C for the cells I put in it.

Until it eventually died, a 2-way one which came with a digital camera and charged at 550mA seemed to have no problems terminating 0.25C charges without excess heat and (according to my analyser) appeared to fill cells up pretty well.

Design seems more important than charge rate for the commercial ones I have.

I've made smart chargers that charge NiMH cells and packs up to 4500mAh, (typically ~3700mAh) with a 700mA charge rate, and termination seems pretty reliable from voltage readings alone.
The analyser version which permanently displays all the relevant info (voltage, mAh in, dV, etc) seems to put in the expected amount of charge after a known amount of discharge from full, and the dV info displayed shows a usable signal starting at the right kind of time.
Now, being aware of what people do say, I did my best to make sure it would terminate, sticking a clutch of similar-but different termination triggers in the charging program to cover various bases, but that approach could never have worked if there was no usable information to trigger off in the first place.

Standard enloops are fine particularly if used with the Technoline BL-700. If you discharge and recharge the capacity is generally over 2000 mAh. I only bought one lot of xx'x and they don't charge consistently often less than the standard eneloops

Regarding the 7dayshop 'good-to-go' cells, I just bought some more, this time the 2150mAh variety, and though I can't speak to the self-discharge or the cycle life, the capacity is good.

Bear in mind my Maha analyser seems to be a bit pessimistic, giving lower figures for Eneloops than most people report (even trying out 20-30 cells), usually low 1900s for Enelopps ad somewhere in the 1700s for the '2100' good-to-go cells

As tested on arrival without charging I got 1693-1751 out of 16 '2150' cells, which is fairly respectable given they may well not have been fully charged in the first place, and is a fairly tight result across 16 cells.

On testing 4 cells immediately after a cheap smart charger indicated 'full', I got 2165-2185mAh

After an overnight charge (and possible slow trickle top-up), out of 8 cells, I got  between 2180 and 2240 out, so all results better than the claimed nominal capacity (which is a first for any cell on my Maha), with the best ones getting close to 100mAh over spec, on an analyser which is typically a few percent down.
I really didn't expect that.

They're heavier than Eneloops by 1-1.5g, and fractionally thicker, so best not rammed into snug-fit flashlights, but fine for Duos, etc.

I'll try and do a short (~1-2 month) self-discharge test on some of them once they're broken in enough to give consistent readings.

I missed this post at the time, sorry Potholer, thanks for your insights.  I have indeed avoided the 1.5v Li-Ion AAs and got a simple smart charger.

Logic BL 500 Chipmunk

The selling point for me was the choice of a set of Eneloop AAA or AA or Pro batteries or 10x Fujitsu AAs for a pretty decent price.