UKC

Apologies if this in the wrong forum!

I've got an old dual lamp halogen bike light that I was thinking of rebuilding as the elderly 6v NiMH battery pack is well past its best, I also have a large stock of surplus 18650 Li-ion batteries. The original battery pack is 5 NiMH cells stuffed into a housing like this:
http://www.singletrackbikes.co.uk/smsimg/77/3068-5693-full--77.jpg

I was planning on cramming in as many 18650 cells as possible and installing a small dc-dc regulator. Ideally combined with a charging circuit as well so I don't have to pull the pack apart to charge it. Anyone tried something similar?

In reply to Reach>Talent:

Not tried this in particular, I've but done some work with batteries and regulators.
It should be pretty easy to find a small switched-mode regulator to get 6V out of a bunch of lithium cells. You're going to be limited to a maximum of about 12 cells in series though, as a regulator for over 50V will be more expensive, and more importantly you're getting into hazardous voltage range.
I think a charger will be more difficult. I don't know where you'd get a small circuit to do that many cells in series. Hopefully someone else can help - I'd be interested.

In reply to Reach>Talent:

What are you planning on running off the battery pack - LED?

In reply to Stuart (aka brt):

Unless I can find a weather sealed mr11 led at a good price I will stick with the existing halogen bulbs but enjoy a bit more battery life