How to charge a bike light battery (stupid newbie questions!)

Batteries and Chargers Chargers
1

I have a bunch of questions about safely charging a li-ion battery pack.

I recently bought a bike light off ebay, like this one:

http://www.ebay.com.au/itm/SolarStorm-2-CREE-U2-5000LM-LED-Bike-Light-Cycle-Bicycle-Headlight-Lamp-Battery-/181400293928

The battery pack is 4 x 18650 batteries (8.4v I believe). The charger that came with it has no auto cutoff, which is kinda dangerous with li-ion batteries from what I understand. So I’m looking for a good charger for this battery pack.

My dad’s suggestion was to buy something like this (doesn’t have to be this model):

http://hobbyking.com.au/hobbyking/store/\_*6478IMAX_B6_AC_Charger_Discharger_1_6_Cells_GENUINE*.html

So my questions are:

1. If i chop the lead off the cheap charger and wire it up to the imax charger will that do the job?
2. What is “balance” charging? Am I right in thinking that evenly charges all batteries in the pack? Do you need a special lead from the battery pack to do this? (additional to the main charge lead).
3. Is there some benefit to balance charging for this battery pack? Do I even need to worry about it?
4. Is there some other cheap(ish) alternative to this idea? As in, can you buy a simple charger for this battery pack with some sort of safety cut-off when it reaches full charge so they don’t blow up?

More worried about the safety angle than anything but kinda interested now in the whole technical aspect of batteries and why you need high end chargers for them. Does it increase the battery life? etc.

Any answers to clear up the confusion appreciated, feeling kinda lost here, thought this would be a simple thing!

2

for future light purchases, avoid buying these kind of kits, and buy a 4*18650 battery carrier, you can install quality cells there, and charge them outside in a reliable charger. The increased runtime, and the possibility to charge the cells individually, and not having to trust an internal balance circuit that can or can not be well designed,is a plus for me
If you are interested in this solution i can try to find the link

3

box like this

battery x4

charger x4

you can use your batterypack with charger to but stick around if you charge for safety

4

Ah, much better solution.

Can you get such chargers off ebay? Are they trustworthy? I’m in Australia so it can be difficult to get this stuff cheaply here other than ebay.

Also, can I just disassemble the battery pack that came with the light and use those batteries? Or should I buy new ones? Really not concerned about any of this being top quality, just looking for a cheap working option :slight_smile:

5

that’s the box i was talking about. nice selection on batteries and charger.
DX has free shipping, and you can find these items in a variety of shines/HK shops

6

Yeah, poor choice in hindsight, but I bought one of these when we needed another bike light:
TrustFire TR-D001 LED 600lm 4-Mode White Bicycle Light - Black (2 x 18650)
http://www.dx.com/p/trustfire-tr-d001-cree-xm-l2-t6-600lm-4-mode-white-bicycle-light-black-2-x-18650-330662
(also available from FT and other places)

This comes with a shrinkwrapped 2-cell “battery pack” — 18650s — and an AC wall wart charger.

The battery pack fully charged reads 4.20v (so it’s 2 cells in parallel, makes sense)

The wall wart has a multicolor LED — red for “charging”; orange for “yes-it’s-still-charging-be-patient”; and green for “this ought to be charged by now”
Imgur
the charger board says “C-05 V1.2 140120”

The switch for the light has colored LEDs in it that should show
— green for going on near 100 percent charged
— blue for 30 to 70 percent charged
— red for not much and flashing red for going down fast

But the thing never shows better than “blue” with the battery pack supposedly fully charged.

The instruction sheet packed with it shows a 4-cell battery pack, but all the places selling it show the 2-cell pack.

I’m puzzled, guessing
— maybe it’s really meant for higher voltage/more cells, or
— maybe it’s meant for more cells in parallel, or
— something else.

One nice thing about this light is, there’s a purple screw-on cover on the back of the light — inside that is the driver board, no heatsink at all, floating free, but easy to get at.
So if it needs a charger board transplant, and/or heatsinking for the driver board, that’s doable.
This Trustfire 2-cell thing gets improved somehow.
SO — ideas welcome.

I’ll dig into that once the genuine Yindings (better bike lights)
Info here: (use a code “yinding” — MTBR forum) get here

EDIT — I should also have checked the manufacturer’s website on this “deal” light.
Trustfire no longer even carries the TR-D001 model on their webpage, and the 2-emitter TR-D002 is out of stock.

I bought a damn antique.

Nothing goes out of date faster than flashlights, except computers, cell phones, and fresh fruit……