Don in Austin

I dropped my Magicshine battery pack ion the toilet -- please don't snicker! The second time I went to use the light after that it didn't work. I took the battery pack apart and found it has micro-circuitry between the battery and the cable. For whatever reason connection to the battery was lost in this circuit board. I moved the negative (black) wire directly to the battery output and now everything seems to work properly. I have the three different brightness levels and two flash modes and the charger seems to be working the same. I have bypassed some kind of function but i have no idea what.

What the hell is this circuit board for?

Don in Austin

zzyzx_xyzzy

It is protective, to prevent undercharge or overcharge of the battery. It is supposed to cut out if the battery voltage drops to a certain level. You might have a greater chance of damaging the battery if you let the light run down too low.

helicomatic

You can also damage a lithium ion battery from overcharging it.

Overheating a lithium ion battery can cause thermal runaway past a certain temperature, where the increased heat will cause more increased heat, until the battery breaks open, and catches fire or explodes.

GlowBoy

Absolutely right! NEVER use or charge a Li-Cobalt battery without protective circuitry in place! There are a number of conditions (undercharging, overcharging, excessive charge current, excessive drain current, physical damage, short-circuiting) that can cause a Li battery to overheat and go into thermal runaway. Li battery fires are extremely powerful and intense, can also be explosive, and also spew extremely toxic fumes. That circuit board is designed to minimize the chances of these things happening. Sure you can probably get away without using it, but it's a bit like driving without a seatbelt.

These dangers are in fact exactly why I've stuck with NiMH so far for my homebrew lights, and will go directly to Li-Manganese or Li-Phosphate for my next battery.

znomit

I think it stops the battery catching fire when it over discharges. Throw it away and order another.

Don in Austin

I will just charge it outdoors then.

Don in Austin

Don in Austin

So it probably has a thermistor that isolates the battery from further charging above a certain temperature.

Starting to make sense.

I won't charge it except outdoors removed from anything combustible.

Thanks....Don

ItsJustMe

As others have said, it's protective circuitry, REQUIRED when charging LiIon OR when using - if you don't have protective circuitry in place, and you short out the output, the batteries will at least get extremely hot (hot enough to melt through the plastic and burn the hell out of anything close) and will probably catch fire or explode.

I wouldn't go nuts about it though. Dry it all out, then give it a try. It'll probably be fine. When you've determined it's OK, just stick it in a ziplock or wrap it with electrical tape and just keep going.

cyccommute 

You are correct in that you shouldn't charge a lithium ion battery without a protective circuit and that there are a number of conditions that can lead to problems. It's not overheating that's the problem. Overcharging and overdischarging can lead to a reduction of the lithium from an ionic state to a metalic state. Metalic lithium (elemental lithium) is extremely reactive. It will react with the materials (water, usually) in the cell and release hydrogen. It has enough energy to cause the hydrogen to combust. Alkali metal fires can't be put out with water (the water reacts and forms more hydrogen and makes for a bigger explosion). In labs where we use elemental alkali metals (sodium usually) we have to have D class fire extinguishers. These are filled with sodium chloride or a copper based dry powder that dissippate the heat and absorb the alkali metal.

tatfiend 

I just bought a 18650 flashlight and batteries and made sure to get the protected cells. I would presume that Magicshine is using unprotected cells and one external protection circuit to lower costs. I know that Battery Junction offers unprotected Li Ion cells but does not recommend them for consumer flashlight use.

Wanderer

Why not just contact Geoman, and see what replacement options are - they ARE pretty consumer oriented.....

Don in Austin

I already ordered a second battery from Geoman -- should be here soon. Because I dropped the battery pack in the toilet and subsequently took it apart, I don't really feel there is a warranty issue.

Don in Austin

Garfield Cat

Now thats a battery flush

Iowegian

I asked Geoman about getting a replacement PCB (printed circuit board) when mine shorted out in the rain a few months ago. At the time, they were not available. I did find the specs on 2 of the 3 IC's on the board on the net and they are generic LI battery controller/protector IC's. I couldn't find any info on the third IC and have no idea what it is. Fortunately, the problem with my board was a blown resistor and I was able to obtain a replacement at work. I soldered it in and my light works as new.