Sony lithium battery charger failed

Li+ / LiPoly batteries should be charged in a constant current/constant voltage scheme.

At initial charge, a constant current should be used, until the cell reaches 4.2V. At this point, the charger should charge at constant voltage until a threshold current is reached.

The current to charge with varies with battery. The C rate is usually good. If the battery is 4.1Wh, then it's about 1Ah. 1A constant current until 4.2V, and charge cutoff at 100mA would be a decent solution.

It is very important to *not* let the cell be charged above 4.2V, unless you want some interesting pyrotechnics.

See the

Cheers

PeteS

Thanks, Pete, just what I needed.

If I fail to access the case innards (or fail to fix it anyway), I'll try that. Without a new design to incorporate a very sensitive voltage comparator, I suppose in practice that means setting it to say 5V, 1A initially and watching my DMM closely?

Well, I would set a constant current to 1A and watch the voltage rise. If you have a fully discharged battery, it'll be about 3V.

About 70% of the charge is done during constant current mode, so simply shutting off the current source at V(batt) = 4.2V would work at a pinch.

Cheers

PeteS

What kind of capacity spec is "4.1Wh"?

Everyone seems to be worrying about charging the battery correctly, but the very basic specs quoted for the charger may suggest that it is in fact just a simple power supply, and that the charge control electronics are actually in the battery - I've seen this before, as temperature is a significant factor in Li-ion battery charging, and it's convenient to connect the temperature sensor, buried in the battery pack, straight to the charge control electronics, rather than to have to get the info out of the pack and into external control electronics.

Some camcorder charger units that I've come across, will not output any charge current, unless they ' see ' a voltage from a part discharged battery pack, across their output terminals. I've had many such chargers across my bench in the past, claiming to be faulty with no output, when in fact the problem lies with the pack that they are trying to charge, having no terminal voltage at all to get the charge cycle going.

Just a thought ...

Arfa

The link I provided above is a charge controller I am using. It pulses the output to 'detect' a battery (see if the voltage rises between pulses). It also provides for a thermistor in the battery pack (the ones I have utilise a Panasonic NTC, nominally 10k at 25C). On that note, you should not try to charge a Li+ below about 0C or above 45C.

Li+ battery packs could have the charge controllers on board, but they would be specials. Most packs come with the NTC and nothing else.

Cheers

PeteS

Good point- and it looks to be a 1160mAH capacity too- so maybe the cheapskate should just buy another one before he blows himself up

Thanks all. I'll soon know for sure whether it's a simple or complex charger, as I'm determined to open it soon. Meanwhile I'll experiment with charging the identical extra battery I bought a year or two ago. (Not such a cheapskate, Fred .)

On my To Do List for a long time has been: 'Observe Sony charger waveform'. That would have answered that point in advance of hacking into the case - but regrettably never actioned! I strongly suspect it

BTW, the battery currently in the camera still has a charge, as it successfully allowed me to transfer a score of recently-taken photos and also take a few more.

Watt hours.

Graham

Here is a message containing pretty much all I know on the subject of lithium batteries:

Chris