U2: what is your rechargeable strategy?

I am buying a U2 and wonder what rechargeables you use?

I have some Pila 168S that I use for my L4, and I have a few miscellaneous protected 4.3v JSB 123s.

What should I do? What do you do?

I have 5 18650 Li-ION cells that are 2400 mAh that I use in my U2.
I get about 1.5 hours on level 6.

I also have 8 OLD 18650 cells out my OLD laptop battery that I use, if I were to guess, they are about 1700 mAh.

Get some 18650 cells from www.batteryspace.com (the 2400 nAh ones)

Then get a $13 charger from CPF member AW or Emilion.
It chrages at a slow 350mA rate, but I replaced the stock wal wart with a 1200 mA (1.2 amp) one, now it charges much faster /ubbthreads/images/graemlins/smile.gif
NOTE: make sure the wal wart you use is still 5V, and NOT more mA than the cells mAh.

Yes, the UN-Protected bare 18650 cells are perfectly dafe in the U2, it wont drain them too low.

~John

What jtice said. I have 4 of these 2400mAH cells for my U2 /ubbthreads/images/graemlins/wink.gif

Will

I'm using the 2400 mAH Li-Ion in a bored out C2 body with a KL5 head on it. It runs in perfect regulation for 1½ hours. Only drawback is it takes a long time recharge the cell, but I can see now that there is solution to that. /ubbthreads/images/graemlins/cool.gif

John, the 1.2 A wall wart you use - is it regulated do you think? What I mean is that most cheap wall warts are not voltage regulated. They have a nominal voltage stamped on them, but in fact the output is to some extend dependant on the load, and has quite a lot of ripple. Thanks.

Jan
BTW that package you sent me has now left the States. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/thumbsup.gif

JanCPF, I figure its only alittle regulated, its a regular run of the mill wal wart. So it will have some variation, but I figure the one that comes with the charger is not fully regulated either.

I have charged a 18650 2400 mAh cell about 4 times now, still works /ubbthreads/images/graemlins/icon3.gif

5V is a pretty common voltage requirement for digital logic circuits. There may be circuitry inside the charger that depends on this voltage being reasonably stable. That said, I haven't seen any 5V wall warts that are not regulated for this very reason. If it is a switching power supply (small and lightweight, versus a big heavy brick) then it is almost certainly regulated.

And, of course, if it's not regulated, and the batteries and charger still work, I wouldn't worry about it too much.

I'll know for sure when I get some 18650s and the charger, for my "new" U2 I just received /ubbthreads/images/graemlins/smile.gif I am still waiting for nightfall to test it!

The original wall wart of the charger has 5.5V/350mA. Is it reasonably safe to use one that provides only _5.0V_ (and a higher mAh for faster charging)? The 5.5V ones are hard to find.

-Connor

After some expert advise and input /ubbthreads/images/graemlins/wink.gif

I am fairly sure that both the stock charger, and the 1.2 amp charger I am using are regulated.
So you may want to be careful with a non regulated setup if you are planning to pushing the mA up.

I do have the Pilas...does anyone use Pilas in the U2 instead of the unprotected 18650s?

Ive used Pilas in my U2 also, they work fine, the 18650 cells just get alittle longer runtiem thats all.

A Pila 168s works fine. Pila 168a will fit in a U2 need to
load it /place it in from the top end/bezel/head it will fit works great if you have Pila's handy use them.
Topper /ubbthreads/images/graemlins/smile.gif

Connor,

I ran an experiment with a 5V 1.5A transformer with the same battery charger/holder as the one with the kit from AW that has the original 5.5V 350mA transformer.

I first drained the 2400mAH by running the U2 on high for at least two hours in front of a fan. There was some light output left, and the battery was about 3.17V or so after this.

I then used the new 5v/1.5A transformer and sure enough after barely a couple of hours (much fast than twith the stock unit) the green light came on. However, the voltage of the cell was NOT the usual 4.20 volts, but 4.05 volts or so. The cell was NOT warm or hot to the touch, but I was not there exactly when the light turned green. I did touch the cell during charging and never felt the cell being hot/warm.

I am now re-charging the cell with the stock transformer (5.5v/350mA) and I am expecting to of course get back to the 4.2V or so.

So it looks like using a 5.0V/higher current does work, but does not charges the cell to its full potential. It should not be a HUGE difference (4.05v vs 4.20 volts), but there "is" a difference.

I have a 5.8v/700mA transformer to test/try as well, but given that the transformer's voltage seems to be directly related to the final/charged voltate cutout, I am not going to try it since it could overcharge the cell. If simple math holds:

5.5 => 4.20, and
5.0 => 4.05, then
5.8 (should be approx) => 4.4v-4.7v - which would be TOO HIGH /ubbthreads/images/graemlins/crazy.gif

So, based on these limited tests, it "seems" that it is best to stick with 5.5v to get the best charged voltage, but using a 5v is safe, even if the cell is not trylly "fully" charged - at least at 1.5A it charges up VERY quickly and you can then use the oroginal transformer to top the cell. I would also recommend AGAINST using any transformer with a voltage rated to higher than 5.5 volts (by the way, all of these measure slightly higher under no load).

Hope this helps,
Will

wquiles,

hey, thanks *alot* for that info. I got my DSD charger from AW just today. When the LG 18650 2400mAh cells I ordered have arrived, I will start experimenting with the charger. Hopefully I will be able to get a 5.5V/~1200mAh transformer somewhere.

Thanks again for the great information!

-Connor

Connor,

No problemo dude /ubbthreads/images/graemlins/wink.gif

The cell just finish charging (using the 5.5v/350mA) and the cell came up at 4.16 volts. It only took about 1.5 - 2 hours to top, so by using the 5v/1.5A I did save LOTs of time /ubbthreads/images/graemlins/happy14.gif

Like you said, finding a 5.5v/1.5A is most likely the ideal /ubbthreads/images/graemlins/grin.gif

Will

Thanks alot Will.

Mine is a 5V 1.5 amp charger, lookes like I need to find a 5.5V one /ubbthreads/images/graemlins/smile.gif

I forget what mine was off charge, ill check this weekend

Cognitivefun,

I use Pila 168a exclusively just because they're straightforward and safe. I also use a stock charger -- the Maha C777 PlusII.

Paul

I think when my U2 arrives I'll use Pilas also /ubbthreads/images/graemlins/smile.gif

I've been very happy with them and I have peace of mind with them.