new battery´s in magicshine 878

Hi,

i would like to change the 8 x18650 1100 mAh to 8x panasonic 3400 mAh ( http://www.dx.com/p/panasonic-recha...llowish-green-black-4-pcs-291759#.U8Ti5F4sq5E) in my dive light magic shine 878 ( http://www.dx.com/p/mj-878-sst-90-4-mode-2200-lumen-white-led-diving-flashlight-set-8-x-18650-121152) .

can i do that, or would there be any problems with the new battery´s ?

one more thing, charging the light now takes 8 hours, so with the new battery´s it would take a whole day. can i build or buy a quicker charger?

The charger i have now saids
input: 100-240VAC 50/60 Hz
charging Current: 2.5A MAX.
Output Voltage: 8.4VDC

Im kind of new in these things so i hope you would help me.

/Seiko1980

Wow, that's a beast of a light!

First of all, Panasonic rates that cell at 3350 mAh typical, 3250 minimum. Note that the pictures on the web site carefully avoid showing you all sides of the cells. It's not a big deal, but just gives you an idea who you're dealing with. Here's the genuine data sheet: http://www.panasonic.com/industrial/includes/pdf/NCR18650B.pdf

As for a faster charger, it is generally advised to charge LiIon cells at 0.5C to 1.0C, and specifically Panasonic recommends 0.7C. At that rate the bulk of your charging would occur in 1.4 hours. Topping off (the final 15% or so of the charge) generally takes around twice as long, so maybe 4-5 hours total. If it's already taking 8 hours, your charger is underpowered for the 1100 mAh cells. It would be grossly underpowered for the Panasonics. Unfortunately, a higher current charger could overload the charging jack or other parts of the light, as the recommended current would be over 9A. Correction, that would overload the jack. I would recommend removing those cells from the light for charging. Once you do that, you have a wide range of possibilities.

On the other hand, BatteryUniversity.com says there's no ill effects from charging at lower currents, so if you have time, go for it. A 3.0A charger should get you a charge time of 12-15 hours (I suspect your charger is closer to 1.7A than 2.5), and it should be okay for the light.

Also, given the sensitivity of LiIon chemistry to charging voltage, you may want to consider a better quality charger anyway. I've bought several MagicShine dive lights, and the quality can be pretty scary. At the very least, you should check the final charge voltage.

That said, those cells would probably work fine in that light. The only possible problem is that cells vary somewhat in diameter and/or length from one model to another. They are NOT 18mm x 65mm, but only close to that. Make sure there's room for the ones you choose.

Oh, one more thing. Since topping off is the majority of the charging time and only represents 15% or so of total charge, you could take your cells off the charger long before it says they are done, and you only lose a little in battery run time. This is actually good for the long-term life of the cells.

And yes, I know 'topping off' isn't the right term. But it does get the point across better than 'saturation charging' or 'stage 2'.