$60 xml bike light- too good to be true?

[Vancbiker]

Are you measuring that voltage under load? Most of the "budget" 18650s have a fair bit of voltage sag under load. That may explain the light shutting down when a no load voltage reading is 3.4V.

[claytonedge]

Argh! No, very good point! Thanks, will run the battery down a bit and have a look.

[zarr]

tagged for future reference

[Action LED Lights]

Originally Posted by claytonedge

My suspicion at the moment is that once either pair of cells drops below 3.4v the power from the battery is cut. This is a bit annoying since it's really 3.2v before we start getting any damage to these cells....but it could well be that the temperature we're riding in is influencing the cut off voltage.

claytonedge,

Here is a typical discharge curve for a 4400mAh 2S2P pack under load. Your light probably pulls about 1.5A on average so the red line would be about right. You can see that by the time it reached 3.4V per cell or 6.8V it's headed south pretty fast so the difference in run time between 3.4 and 3.2 would be pretty small. However, this test was on an assembled pack and ran down to 5.6V without the PCB cutting out. I believe the cutoff under load is 5.4V.
I don't know about your pack but the Magicshine and Gemini packs have a balancing lead between the pairs to monitor and charge each pair separately.

[claytonedge]

Thanks Jim - very kind of you to post the discharge chart, and to share your experience.

On these batteries there's certainly no balancing lead between the pairs (I've attached one myself), but it is good that the fancier/pricier batteries do have some mechanism to balance the charging.

For others reading as well - the capacity of these cheaper batteries is more in the 3400mah region than the 4400mah....but I'm even quite dubious of this!

[Action LED Lights]

Oops, now that I look closer at the graph is see this particular test was with a 5200mAh Gemini pack. The shape of the curve is the same with 4400mAh, just shifted a little to the left.

[claytonedge]

Updates here.

Full charge, cell1 4.2v, cell2 4.2v
Cut out after 90 mins of riding in freezing temps
Voltage, cell1 3.7v, cell2 3.7v both under 0.7a load.
After charging the battery normally takes 3400mah from empty, but from this cut off state only took about 1300mah.

It appears the protection circuit is cutting in very early when it gets cold.

Have ordered another battery, an rc type Lipo and will see how this goes.

[shellshocked]

Ordered the $60 ebay light and got it three days later from a US seller. I have to say I was very impressed with the packaging and the overall design. No short-cuts that I could see, OP reflector, etc... It has three light levels plus strobe. This is my first bike light but this thing puts out an incredible amount of light. I will ride with it next week. The only flaw I see with the light is the mounting bracket is designed to fit a thinner bar - not the 31mm MTB bar. Seems like it will work ok with the provided rubber band mount but not ideal.

[hernluis]

i just pulled the trigger on one with a smooth reflector. Hopefully i will get it soon. I did see that the ones from over seas are on sale and last time i looked about a 1000 had been sold they are going at about $42 shipped? not bad.

[fevans]

Originally Posted by J_Hopper

I have an original P7 MS900 with the new, replaced-under-warranty Geoman battery. I'm having difficulty with the switch on the back of the MS900 (I have to push it very hard to get it to change modes, hard enough that it's difficult to maintain the pressure for 2 seconds to turn it off). I'm considering upgrading to the newer XML version. I'm trying to decide, is it worth it?

I've had this problem a few times with my MS light. The problem is that the retaining nut that holds the light puck in place inside the head gets loose over time.

All you have to do is take the crown off and remove the reflector to get to the retaining nut. It has two holes which are used to tighten it. You can use a pair of needle-nose pliers to do this.

[torreyaz]

Riding with mine tomorrow AM in Az. Probably dark for an hour ride time. I charged it to green (about 2.5 hrs). It's maiden voyage and I'll report back on the performance.

[nathan59801]

Are most people using this light on their handlebars or helmets? If using on your helmet, is there enough cord to run the battery to a pocket on your jersey? If stuffed in you pack, does the battery get hot?

[Sourloter]

I bought the exact same light about 3 weeks ago, for 38 euros. It's amazing! I am using it for about 2 hours and the battery can keep for more.

I haven't used it on my helmet yet, but i'm sure it's gonna be stable enough.

[shellshocked]

Rode with my light tonight. Rode an hour on bright and no problems. The amount of light is excellent. Overall I am extremely pleased. If I had one change it would be to make the beam pattern a little wider as where I ride has a lot of tight switchbacks and with the light on the bars having more light on the turn before I actually turn the bars shining the light into the turn would be nice but it is still pretty good as is. Someone asked if the cables are long enough - short answer is yes no issue - I have the battery mounted on my seat post and the light on the handlebar and still have about a foot of extra cable.

[Action LED Lights]

Originally Posted by shellshocked

If I had one change it would be to make the beam pattern a little wider as where I ride has a lot of tight switchbacks and with the light on the bars having more light on the turn before I actually turn the bars shining the light into the turn would be nice but it is still pretty good as is. .

See our Wide Angle Lens.

[shellshocked]

Action: Thank you - I just placed an order with you.

[Mr. Lynch]

The wide angle lens from Action LED works great. I have one in my MS light and it was a perfect fit. On the knockoff MS lights all you have to do is leave the stock lens in place and put the wide angle on top. It then fits great and the light still seals nice.

[Action LED Lights]

Originally Posted by Mr. Lynch

The wide angle lens from Action LED works great. I have one in my MS light and it was a perfect fit. On the knockoff MS lights all you have to do is leave the stock lens in place and put the wide angle on top. It then fits great and the light still seals nice.

I would suggest you put the stock lens on top smooth sides together with the ribs pointed into the reflector. The effect is the same either way and then the glass protects the plastic lens. This won't work on a true Magicshine as it won't seal with the added thickness.

[Mr. Lynch]

That's exactly what I did. wide lens, then stock lens on top with smooth sides together. It has held up great thru some really nasty conditions. I just listed the pieces wrong above, but anyone installing the lens would figure that out quickly!

[xycarp]

Just checking in to provide an update and some extra info...

1. Update - It's been pretty darn warm in Michigan the last few weeks and the light has been working much better. I am able to get 3 20+ minute rides out of it without recharging.

2. Extra info - The rubber ring that holds the light on the bars broke. It's an oddball rubber ring that I could not find in the hardware store. I am not surprised as I have been riding in some pretty crappy and extreme weather (like 7 deg F). I ended up making my own ring out of surgical tubing. That stuff is awesome. If your ring breaks, buy a few inches of tubing and make a ring. Not to mention the stuff is so strong it's worth keeping in your riding toolbar for misc trail repairs.

The light is working fine!

[zarr]

Originally Posted by xycarp

Just checking in to provide an update and some extra info...

1. Update - It's been pretty darn warm in Michigan the last few weeks and the light has been working much better. I am able to get 3 20+ minute rides out of it without recharging.

2. Extra info - The rubber ring that holds the light on the bars broke. It's an oddball rubber ring that I could not find in the hardware store. I am not surprised as I have been riding in some pretty crappy and extreme weather (like 7 deg F). I ended up making my own ring out of surgical tubing. That stuff is awesome. If your ring breaks, buy a few inches of tubing and make a ring. Not to mention the stuff is so strong it's worth keeping in your riding toolbar for misc trail repairs.

The light is working fine!

can you explain about the tubing.(more detail)

[claytonedge]

Introduction

Ok - I've done as much experimenting on this as I am likely to. I embarked on this as the light draws about 1A of current, and from a 4Ah battery I'd expect about 4 hours. When using this in the cold from Monday to Thursday, I would get about 2.5 hours. Admittedly this was in the depths of winter - when it's super cold anyway. This experiment is to try and understand what is going on.

First some vital stats on the light - current drawn at
A - high - 0.93A
B - low - 0.36A
C - off - 0.02A

Executive summary - the light draws a fair amount of current even when it's switched off. The battery performs worse when it's cold. The available capacity reduces the longer it is left in the cold.

Methodology - carried out three discharge tests - each discharging at 0.7a until the battery voltage dropped down to 6.0v. All tests were done discharging the cells individually by passing the protection circuits.

Test1 - charge battery to full capacity, and discharge at room temperature. This is the top line in the chart.

Test2 - charge battery to full capacity, freeze battery over an hour, and discharge in a cool box. This is the middle line in the chart. Temp started at 0c (32f) and finished at 4c (39f).

Test3 - charge battery to full capacity, freeze battery for four days, discharge in a cool box. This is the bottom line in the chart. Temp started at 0c (32f) and finished at 4c (39f).

Results
Battery will cut out at about 6.4v if left to its own devices.

Test1 - around 4000mah
Test2 - around 3700mah
Test3 - around 3500mah

Conclusion
When it gets cold - for several days - the capacity of the battery drops - even when it's not being used.

This in part explains why the performance of the light was impaired in cold temperatures.

Secondly - the light when plugged in, even without being switched on, draws 0.02A of current. The light on standby would therefore drain a fully charged 4Ah battery in 174.59 hours - about a week.

My usage of the light would see it operating over four days, a total of 2.5 hours on high - and a total of around 90 hours on standby. Thus - 2.2Ah consumed by the light while being used on the bike, and around 1.8Ah being consumed by the light while in standby mode.

Recommendation
1. Keep your battery warm to get the best power out of it.
2. If you want your battery to last longer - when not in use either unplug it, or manually install an in line switch and turn it off.

[Buddha43]

I have 4 of these batteries (disassembled) if anyone wants them. Pay shipping and there yours, PM me.

They have been charged 4 times.

[sc redneck]

I bought this light and gave it a 1 1/2 hour workout last night. It performed flawlessly.
Biggest bang (brightness) for the buck...
$32 shipping included off ebay.



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[mappable]

do you mind posting a link to the light and battery that you purchased?

Originally Posted by sc redneck

I bought this light and gave it a 1 1/2 hour workout last night. It performed flawlessly.
Biggest bang (brightness) for the buck...
$32 shipping included off ebay.



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