AA Battery Chargers

[Marcos]

What are the ones that do their job properly?

I bought one that was supposedly one of the more advanced ones, but i observed that if i let it charge a set of batteries until it gave me the green light. I'd unplug it for 10mins, plug it back in, and then it would go again for hours. So clearly it doesnt really know when the batteries are full.

Tempted to get the Apple battery charger since they brag about it, I just want a charger that actually monitors the batteries and truly knows when they are charged and ready [/rant]

[Sputnik]

I've got a Technoline IC8800 and it is good but, Expensive you can even set individual batteries to different charge rates or some to charge and some to discharge.

More details of it are here http://www.techmati.com/reviews/rs900/

[mikerr]

Tempted to get the Apple battery charger since they brag about it

Apple's isn't anything special - in fact its worse than many in that it has no trickle charge to complete the charge after a fast charge cutoff (which only gets 90%)

Apple being apple make this out to be a positive:
"No trickle charge" = "lowest vampire draw eva, woot!"

I have the one MAHA C9000 below - admittedly hugely expensive - but it does show battery capacity,
and without using any of its fancy features, it will just charge when you plug batteries in:


http://www.maplin.co.uk/Module.aspx?...17893&T=Module

[Marcos]

Apple's isn't anything special - in fact its worse than many in that it has no trickle charge to complete the charge after a fast charge cutoff (which only gets 90%)

Apple being apple make this out to be a positive:
"No trickle charge" = "lowest vampire draw eva, woot!"

Thats interesting, good info!

[chrestomanci]

I bought one that was supposedly one of the more advanced ones, but i observed that if i let it charge a set of batteries until it gave me the green light. I'd unplug it for 10mins, plug it back in, and then it would go again for hours. So clearly it doesn't really know when the batteries are full.

Bear in mind that very high end chargers will 'condition' the battery by fully discharging it first in on order to prevent any memory effect, and to get the best possible charge into it, so if you put a freshly charged battery into one of those chargers, then it will spend a few hours recharging it again.

[Sputnik]

Bear in mind that very high end chargers will 'condition' the battery by fully discharging it first in on order to prevent any memory effect, and to get the best possible charge into it, so if you put a freshly charged battery into one of those chargers, then it will spend a few hours recharging it again.

Mine will by default, Charge at 200mA. To get it to condition or discharge you have to set it to do this manually.

[Marcos]

Bear in mind that very high end chargers will 'condition' the battery by fully discharging it first in on order to prevent any memory effect, and to get the best possible charge into it, so if you put a freshly charged battery into one of those chargers, then it will spend a few hours recharging it again.

Interesting!

I have a "Michael Schumacher" branded charger i picked up from HotUKDeals around a year ago, the comments said it was a rebranded "good" charger with actual brains. But its so minimal in interface I have no idea whether it is clever or dumb.

[ed^chigliak]

Technoline BL700 is same charger but max charge current is 700mA and max discharge 500mA which is better value and fast enough for normal use especially with eneloop hybrid type AA cells.

All chargers should tests and measures the actual battery capacity else you simply don't know the good from the bad. When a 2000mAh battery is only holding 800mAh you need to know and then run a refresh which loops the charge cycle until the capacity peaks. Batteries can be recovered by one or two refresh cycles and you're not using the bad cell in your equipment which drags the good cells down.

[DanceswithUnix]

What are the ones that do their job properly?

I bought one that was supposedly one of the more advanced ones, but i observed that if i let it charge a set of batteries until it gave me the green light. I'd unplug it for 10mins, plug it back in, and then it would go again for hours. So clearly it doesnt really know when the batteries are full.

Tempted to get the Apple battery charger since they brag about it, I just want a charger that actually monitors the batteries and truly knows when they are charged and ready [/rant]

Hmm, if you did that with NiCd cells then you might have gotten away with it. NiMH cells are very different beasts and must be charged in a different way. A good charger would recognise the cells were already charged by hopefully seeing their temperature rise before any permanent damage was done. Problem is the charger can just see energy going into the cell, it can't easily know if that energy is going into charging the cell or waste heat

You could go to somewhere like Maplins and spend an utter fortune on a charger intended for the radio control car/plane crowd. I guess capacity matters when your cells are in a plane high off the ground

I currently use an Energizer charger from our local Morrisons supermarket. Only does AAA or AA cells, up to 4 of them, but it was cheap and it does cells individually on fast charge and then turns off. That is the only way to charge NiMH cells, unlike earlier technologies trickle charging damages the cells.

I think all modern chargers are microprocessor controlled though, it is the only sane way to design even a low cost unit these days. The difference is in things like safety temperature sensors which allow more advanced (read potentially dangerous if it goes wrong) fast charge systems. I like "burp charging", if only for the name

In case you are wondering, yes I worked on a battery charger design in a previous job

[mikerr]

Problem is the charger can just see energy going into the cell, it can't easily know if that energy is going into charging the cell or waste heat

It can by using delta-voltage detection, which most decent chargers do.

[g8ina]

http://www.crypto.com/chargers/

I used an Ansmann for several years and it maintained my batts in brilliant condition. NOT cheap but very good :-
http://www.amazon.co.uk/Ansmann-5607...4652738&sr=1-4

hth

[DanceswithUnix]

It can by using delta-voltage detection, which most decent chargers do.

Works very well on a discharged battery, not well on one that is already charged. It can take a damaging amount of energy to record a negative delta-V on the terminals on a fully charged cell. One of these things that is simple in principle, but hard to get right when real life gets in the way.

If a charger can discharge the cell first then it knows where it is in the charge cycle and can safely switch to an aggressive fast charge. Not seen a consumer oriented charger that can do that though.

Edit to add: I notice the charger you linked to has temperature sensors for the cells, that is for when delta-V starts going wrong. Nice charger that, I would say for 50 quid that is pretty good value! Slightly worried by your comment about switching to trickle after fast charge though, I hope it only does that for NiCd as the leading NiMH cell makers stressed to us that you shouldn't ever trickle charge.

[switchmode]

I've recently been looking at a couple of videos on this type of thing, you may like to see.

An electronics design engineer talks about a 15 min battery charger.
http://www.youtube.com/watch?v=gG6rta4PuSM some mild swearing language used beware.

Part two on the theory of chargeing and temperature and changes in voltage as the cells charge up, you can measure the slope of the voltage change or the peak or the temperature or all of these.

http://www.youtube.com/watch?v=_ROhH9EkhtU

Of course no charger can easily tell the state of charge of a battery it will need to cycle the battery to do a good job I would think. If you use charge ,use charge etc etc thats the best way to look after the cells.

[stroberaver]

I second the vote for the Maha C9000. Yes, it's pricey for a battery charger but it's a worthwhile investment if you use batteries often.

I use two packs of four AA NiMH cells for my flashgun, along with a variety of AA and AAA eneloops for LED torches and various other applications. The Maha has been essential for recondtioning my batteries, grouping them into matched sets, etc, and generally getting the most out of them.

[Marcos]

What do you guys think to this charger:



"With refresh function to discharge batteries fully before recharging"

[Sputnik]

without seeing the specs for it, It is hard to say. Probably just slightly better than the cheapo ones that charge at a fixed rate.