yep, this was meant for those who don't know, what they do ;-)

Re: Cheap (chinese) external BL-5J (and other models) battery charger: reverse engineering
 

Still alive and kicking ;)

Safety: yes, electricity and chemical reactions involved mmmhhhh sweeet! Sure, leaving the *test* charger on a cardboard box over the sintetic rug on the wooden floor.. isn't the smartest thingh to do, especially unattended, overnight and in a closed room.

But I did. :p

Ok, ok, the charger was tested with a supercap before, the code cannot lock up and as soon as something goes wrong.. components just burn.

Moreover, on almost all the assembled batteries (Lithium powered and rechargeable), there is a small (yet to analize) circuit that prevent extreme under discharge and extreme overcharge. Its a couple of small mosfet (or dedicated components I think) hidden in the plastic assembly between the phone contact and the phisycal cells that gives a small layer of protection.

I found out when I wasn't ablet to overcharge the battery above 4.3 or 4.5V (I guess), the current wasn't simply flowing inside anymore, the battery was in a high impedance status - but this was done on purpose and with the battery in a glass covered container (with vents).

However, I read somewhere, one should not charge Li-something batteries above 3.93V in order to have them last more than 10yrs without noticeable performance loss.. off course, the price you pay is the loss of total capacity.

Just for completeness, I will publish the full (stable) circuit schematics soon (hope), but there's nothing of extremely interesting inside - it's simple, crude, somewhat didactical and it works without too special components. I'm rewriting the code, from scratch - I don't feel to publish it 'couse.. it's pure evil code and "the" internet doesn't deserve such bad stuff lying around - but I'm more than available to send the source and/or the .bin file to flash the PIC and have your charger.. well, charging!

The code is pure spaghetti code full of magical numbers (had to work in fixed pint to same mem space, hence some pretty math tricks to simplify formulas) and zero comments (off course! *back then* I totally knew what I was doing..).

Re: Cheap (chinese) external BL-5J (and other models) battery charger: reverse engineering
 

Nope, the somewhat integrated charging algorithm would refuse or badly/wrongly charge the batteries. I remember the charge in the XM5800 shows a pulsed profile when checked at the battery terminals.

If it was just checking the cell voltage, you could hook up an equivalent battery (aka: 3 ni-cd or NiMH in series) - but it's wild speculation couse I don't want to risk my phone ;)

Re: Cheap (chinese) external BL-5J (and other models) battery charger: reverse engineering
 

Anybody found a half-decent cheap battery charger eg on eBay (UK pref)?

Re: Cheap (chinese) external BL-5J (and other models) battery charger: reverse engineering
 

Cheap equals trouble. Pay premium for your battery and charger and you will have no problems. Dont be pennywise pound foolish, as English would say.

Re: Cheap (chinese) external BL-5J (and other models) battery charger: reverse engineering
 

That's pretty bad advice.

Whilst there are official batteries, they use out of date technology and better ones are available.

There are no official chargers that I can see. Paying more for a charger or battery (or anything) increases chances of quality but you often get junk too.

Having said that, I don't mind paying extra if I know it will be good.