Electronics noob with a big torch to mod

Hi all - I managed to aquire an x21 for a steal recently. I had reservations about it due to the fact it is a direct drive light and not rechargeable. I am travelling RTW with the giant cannon and finding quality d alkalines will be near impossible in a lot of places - I do not want to lug it 40,000 miles to only use it a couple of times.

The torch is to be used for landscape lightpainting with my photography. I dont mind sacrificing runtime as long as I can have a similiar output of light and throw to using alkalines.

SO as the title states I am an electronics/torch mod noob and while I have tried to search these forums for x21 modding or similiar, my lack of knowing what words/acronyms to use is failing me.

I note Led Lenser advise against the rechargeable D cells, I assume because of voltage/mah issues? But would love some more explanation. I have read of people using them anyway but have complaints of running hot if on for extended periods, and people advising that it will shorten circuitry lifespan.

I was wondering if I could build a custom rechargeable pack that matches 4 alkaline d's as closely as possible in power. Am I right in thinking there is 2/3rd size "D" cells that are 1.2v rechargeable. How about using 5 of these in series and then using the 2/3rds space left over for a charging point or some type of circuitry/spacing.

I'm also led to believe that I will run into regulation problems...... Need help there. Ha.

Reading above makes me wish I knew much more about electronics!
I hope the tech-heads can understand my simpletonian and school me in some modding suggestions. Look forward to utilising the CF community and putting some pics and details of the x21 project soon.

Cheers
Tim

Since your light is a direct drive that means as the batteries get weaker so does the amount of light. Keeping that in mind; Alkaline D cells are 1.5v when new sometimes a bit more than that. After you put them in your light that 1.5v drops pretty soon to about 1.2v which the battery stays at for a while but all the while the voltage is slowly declining. There are alkaline discharge rate charts on CPF that would give you an idea. Basically alkalines just get weaker and weaker till they are dead. Now you could get some NiMH recharagable D cells which are different than alkalines. They come off the charger at about 1.4v and then settle down to about 1.2v-1.3v. Now here is the good part of NiMH cells they STAY at 1.2v while you use them. They hold that voltage level. So if you had two x21 lights side by side one with new alkalines and one with fresh charged NiMH cells you might see the one with alkalines being a bit brighter at first. BUT after a few minutes both lights would look the same and then after 20 minutes you would see that the NiMH is now brighter and you'd also notice that the NiMH one is staying that same brightness until the cells were depleted. The alkaline light would continue to get dimmer and dimmer and dimmer.

As for NiMH cells hurting your electronics I can't see how as the voltage is less, there is the possibility that using NiMH would keep the bightness up longer than LedLenser wants and that in turn could heat up the light too much. Does it get blazing hot with fresh alkalines at first and then cool down? I wouldn't sweat it too much. Now you don't have to buy D cells, you could get AA cells and use a battery holder. Lets say you get 2000Mah AA batteries. Your light uses 4D batteries so you would need 12 AA cells in a special holder, which hold the cells 3 in parallel and four of those 3 packs in series. Don't get one of those holders that would put12 cells in series as that would be 12 * 1.2v = 14.4v a bit too much when you need 6v max. Think of it as 3 AA is replacing one D battery. As for recharging the cells you can do that a hundred ways, individually in a cheap recharger is the most inexpensive. A good hobby charger will do it faster and give you more options and will do a better job. Hope this helps. Hell you could just test it out with 4 AA just roll up some cardboard/ plastic tube whatever will take up the space around the little AA and fill out to D size. Then just put a bolt to take up the extra space as 4AA is shorter than 4D. Layout the 4D next to 4AA to see what size spacer you need. You could spend money on some fancy holders that allow you to charge the battery pack as a whole or put a charging jack in the tail of the light. Do a search on CPF for charging jack/battery pack charging etc. Just to complicate it a bit more, there are basically 2 types of NiMH cells the usual ones you find everywhere and what they call Low Self Discharge (LSD), these LSD cells don't discharge after a month like regular NiMh cells. They hold 80-85% of their charge over a years time. Nice to have these type if the light sat for a month. These type of cells usually say "pre Charged" on the label, some brands are Eneloop, Duracell, Rayovac etc get these type and watch for sales on Amazon etc.