I have had the Magicshine Headlight (not the torch but the headlight) for several months and I love it. I can't say enough good things about it. However, I had a little scare tonight on my commute home...

My ride is approx 40 minutes each way. Light worked fine on the way in, was fully charged from about 1 week ago. About 10 minutes into my ride home, the green button went red...and about 10 minutes later the light went totally dark. On an unlit, dark road.

Fortunately I have a backup light (a fenix L2D CE Q5, the "it" light of 2008) so I was able to limp home safely. But it was unnerving.

My understanding is that the MS light is supposed to have 3-4 hours of burn time, but clearly today it lasted less than an hour. I should add that although I like the light, I have not used it a ton and the battery has probably been through "only" about 15 charge cycles.

Any thoughts or suggestions?? I suppose I should charge up the battery and run the light again to see if it only lasts 1 hour again, or if today was maybe a fluke?

Doug

edit: I doubt this matters, but the temps today were approx 40F. Cool but not that bad.

I love Magicshine lights as well but have concerns about the quality. For that matter no light is 100% reliable and like you I always carry a backup light.

I can only guess at the issue with your light. I find that sometimes it is difficult to make a solid connection. Is it possible that last time when you charged it up you didn’t have a good connection and did not charge it up at all? I verify the connection to the charger by unplugging the charger and plugging in the battery. If there is a good connection then the current in the battery turn on the LED in the charger. I then gingerly plug in the charger and let it charge overnight. Just a thought.

Mine died in what was probably less than optimal time once too, possibly after sitting for a while. I think it's just that the cells are cheap and they don't hold charge for days very well. They also don't like cold, I think ( like, down below 10*F or less).

You may not be recharging it frequently enough. Li-ION batteries shouldn't be too deeply discharged. Try re-charing every 2-3 days rather than just once a week. Also, do not recharge in an unheated area.

From Battery University (https://www.batteryuniversity.com):


-Do not discharge lithium-ion too deeply. Instead, charge it frequently. Lithium-ion does not have memory problems like nickel-cadmium batteries. No deep discharges are needed for conditioning.

-Do not charge lithium-ion at or below freezing temperature. Although accepting charge, an irreversible plating of metallic lithium will occur that compromises the safety of the pack. Not only does a lithium-ion battery live longer with a slower charge rate; moderate discharge rates also help.

When the green button turns red, that's your cue to switch to low beam.

My evening commute averages around 40 minutes this time of year (I have daylight in the morning). Today I tried to get a third run out of it before charging, and wound up doing the last half of the ride on low beam after getting the low-voltage warning. So I guess my four-month-old battery is good for a little less than two hours of runtime on high (temperatures have been a few degrees below freezing here).

ItsJustMe, how is your 8-cell battery working out?

There are two issues here. One is to not depend on a light that has been charged a week ago. Charge them more often and know how long your lights will run. Lithium does not like to be deep cycled. You can even damage the battery if you cycle them too deeply. They should have protection circuits to keep this from happening but if you go too deep the protection circuit will disable the battery completely. If the charge gets too low, you'll end up going into cell reversal and reduction of the lithium ion to lithium metal. That is very bad, hence the protection circuit.

The other issue is redundancy. Over long years of night riding, I've learned not to depend on a single light source. I run 3 lamps and have had occasion to need all three. A recent crash took out the two handle bar lights and did a number on the helmet light. At least it got me home. You at least had a back up but a better choice would be to run a second light system. You'll have more light and you'll won't be limping home.

You guys said it - I charge every other day for a 40 minute each way commute. Only once have I had to switch to med/low beam, and it got me home just fine. Never would I trust a rechargeable light that was charged a week ago.

Wait a second, let me see if I get this...

If I fully charge up my MS batteries, then don't ride for a week, I shouldn't expect a full or nearly-full charge to remain??!!??

I don't connect the battery to the light so the trickle-loss from the LED is not there.

Doug

Batteries can self discharge. Some battery chemistries are worse than others and the amount of discharge can depend on several other factors as well. Li-ion batteries are also susceptible to aging and loss of capacity. Deep cycling and high current draw (like lights do) can cause the batteries to loose capacity too. Bad chargers cause problems too.

Most people mistreat their batteries...even experienced users with years and years of experience and a good knowledge of the battery chemistry...because they are unaware of the problems. You may have done something wrong...deep discharged them, gotten them hot, shorted them, dropped the pack, etc...long ago and it's just now manifesting. Or it may just be the battery. If you want some light reading go here. The Batteries in a Portable World is one of the best places for battery information around.

LiIon should NOT self-discharge very much in a week. I've picked LiIon off the shelf after months and still had significant charge in it.

I would only expect to have lost perhaps 5% of the charge after a week. However, these are budget cells, certainly not stress tested before being shipped, and it's possible there's one or more cell in there that might self-discharge a little fast.

The Magicshine has a 2s2p battery pack -- two cells in series, two in parallel.

Cell reversal is an issue for NiCd/NiMH cells -- the weakest cell's voltage drops to zero, but the other cells keep things going, so it gets `reversed' which makes it even weaker. But if you have eight cells, and one goes bad, you still have seven good cells so the voltage reduction is relatively minor.

However, it's unlikely to ever be an issue with a 2s pack, simply because by the time one cell is dead, you're looking at less than half the original voltage, probably significantly less, and usually whatever is powered by the battery is already not working any more. And the protection circuitry makes it even less likely to happen.

LiPos/LiIons don't actually have to be reversed (dropped to zero volts and beyond) to be damaged -- they're damaged by going under 3 volts (or over 4.2 volts.) The protective circuit should prevent both conditions from happening -- and yes, it may kick in and make the cell entirely non-functional -- it may never work again, unless you bypass the circuit and charge the cell somewhat. This is done because abused LiPo cells can, under some conditions, catch fire and nobody wants that.

NiMH and NiCd cells are fine with being discharged to zero (but going beyond is bad) and are also fine with being overcharged as long as the charge rate is low. So they don't really need any protective circuitry. But LiPos certainly do ...

In any event, if one cell's circuit decides that this cell is no longer good, it basically takes it out of the picture. This reduces the capacity of your pack by one half. The way one tests this is by using a volt meter to check the individual cells ...

Cell reversal was the wrong term to use. Sorry. It's not like NiCd or NiMH but rather a reduction of the lithium ion from a +1 charge on the atom to a neutral charge. A neutral charge is lithium metal which will react...spontaneously and violently...with water to form hydrogen and heat. Lots and lots of heat. The same happens if you go too high in voltage. That's why the protection circuits are needed. It's also why the protection circuits will not allow you to use the battery again.

I don't use mine enough to use up a full charge. so I just charge it the night before I ride. I'm doing 1-2 commutes a week