Thanks for your comments and suggestions. I´ll investigate these new options. However, one must take into consideration the availability and mainly the cost of this solution. An expensive solution for a cheap product doesn´t match well. Regarding to using higher currents to charge I agree, provided that the battery doesn´t be "uncomfortable" with the treatment... Surely you added a good contribution to the subject. Thanks again.

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This was a real "Research & Development" article. Fully detailed in every aspect.
If your intention is to use NiMH cells I propose to you the Eneloop type produced by Panasonic. (It was invented by Sanyo, which has been bought by Panasonic and Panasonic kept the original marketing name Sanyo had given to this product).
They are designed to have very low leakage current, which means that once you charge them fully,they remain 80% charged after one year of no use. I think that this is ideal for the use you make with this head light. (I am not paid to advertise these batteries. Simply I am using them permanently and I know what I am saying about them).
The LiIon type looks better, but it is intended for everyday charge discharge cycles. If you store it either fully charged or discharged it deteriorates with time. These cells need to be stored (I.e. Not used for long time) having only 75% of their full capacity, which is difficult to achieve every time before storing them without using special instruments or sophisticated chargers. (I personally use the Turnigy Accucel 6 in its "storage" mode for this task).
The second proposal to you is to use higher current in order to reduce the existing long charging time within logical limits (I.e.7 hours, or 10 max.). In order to do so, you need to recalculate the capacitance of the input capacitor (practically to increase its capacitance), but keep in mind that above 100mA of output current these transformerless P.S.Us are not the best preference...
You need therefore to select another solution.
Thanks for sharing your experience!

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Muchas gracias por sus observaciones. Saludos.
Thanks for your comments. Greetings.

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Right, Mikael. Perhaps this is the reason why I achieved only 9 hours of autonomy. It was just the first test. I´ll take care of this. Thanks

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Thanks for your comments, Imoudu. However I am not genius, just a man that thinks that all one is going to do must be well done. In my case, as a retired man, I have time to spend in searching the subject in internet and also spend more time in preparing the tracing of the circuit. However, I am aware of the fact that, when one has a repair shop, it is not possible to spend so much time in a repair. Many thanks for your post.

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Thanks for your comments, Parasuraman. I always have a concern in adding a didactic explanation of how a circuit works. For this purpose, I generally carry out a reverse engineering, tracing all the circuit and drawing it. That's the reason why the drawing is so ugly, as done with my hands. Even so, an activity like this takes some hours... but enough to address the didactic purpose. Thanks for your encouraging words.

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Thanks a lot for your comments, Albert. About the zener diode you are correct. I carried out in this way as I didn´t have in hands a more robust diode. However I thinked in two things: 1) The power dissipation can be improved by adding a transistor associated with the LED (which I didn´t do yet), and 2) The worst to happen is the zener becomes shorted-out, which is quite suitable, as it works in this case as a crowbar circuit, effectivelly protecting the LEDs. Better to replace one cheap diode than 12 LEDs……
About the use of Li-ion, you are right. I´d really considered this when I was planning to do this retrofit. An extremely sound proposal. It could be so, with success too and with the advantages you pointed out. The link you suggested is quite valid. As I have yet an emergency lamp to retrofit in sequence (mentioned in the article), there is a strong possibility I use your suggestion. More experience ahead!!!! And perhaps another article for this Jestine Yong´s site.

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