Raypal RPL-2261, to-be-seen head/tail lamp on Li-po battery

Pictures to come.

I wrote on the main page:

2016-3-6: Some time ago I spotted some to-be-seen headlamps and taillamps using a LED strip (these are allowed in NL, using to-be-seen headlamps is not allowed in Germany if that lamp is mounted on a bicycle). I doubt they are really good (as in not having blinding direct light) but I might order one to see what they are like. E.g. Raypal RPL-2261 which seems to be a knockoff (or actually original from the same factory?) of a design called 'Comet' by moon-sport.com (which is Hong Kong based). Moon also has a design called 'Nebula'. Pretty pricey if it's no good (if good then the price is fine if the quality is good). I may first order the RPL-2261 and if it's any good try the Nebula. There are no proper reviews and what I saw on youtube is not useful, I need to try one myself.

Tested from 2016-4-14:

I tested the headlamp first, to see if the concept is any good.

Power input is from mini-USB, why not micro-USB? The lamp can light while the battery is charging from the USB input, this means you could extend the runtime using a powerbank...

The light output is interesting, a LED strip which even in the lowest brightness is already too bright, but still not as annoying as many taillamps with single red LED that don't have optics to distribute the light. Here the light doesn't appear to be distributed when running on very low power (you can see the LED cores then, when the battery is nearly empty) but the LED dies are definitely bigger than those of 5mm clear LEDs.

For to-see the lamp is barely usable (even though it puts out a lot of light on the highest setting, enough to light up a small room which again shows how important proper light distribution is and that cutoff lamps are always much better than non-cutoff), so I'd say this is a lamp for use within cities where there is enough streetlighting, so no need to light up the road, just that you are seen by other traffic. I will do some experiments running the LEDs at lower power to see what happens. Then if possible I will modify the lamp to run at lower power which will still give plenty of visibility. Some data: 46 g with holder, LED voltage 2.49 / 2.67 / 3.02 V at the 3 power levels. So the LEDs are run in parallel. At the lowest level the LEDs seem slightly flickery so not current driven (but pulsed). This means a possible easy (though not optimal) modification with a resistor in series with the LEDs. Direct current measurement of LED current gives 0.09A, 0.18A, 0.36A (DCeff). On the battery is printed 3.7V 500mAh which would mean a runtime, assuming an efficiency of 80% of the driver, of about 6.60h / 3.08h / 1.36h. The box says: 6h 20m / 2h 45m / 1h 40m.

So the LEDs are too bright, and I was concerned about heat: The LEDs are mounted on a heatsink, but the heat can't go anywhere as it's all encased in plastic. Another issue is that runtime on low is 6 hours, and I want more. So there were 3 reasons why I wanted to run it at lower power.

24-4-2016: Now doing the mod that I had in mind: I started by putting a 10 Ohm resistor in series with the LEDs: Voltage (DCeff) over the LEDs is 2.42 V | 2.55 V | 2.77 V (note Vresistor= 10 Ohm *current /(Ohm A)), current (DCeff) is 0.028 0.056, 0.112A (Vresistor=0.28V / 0.56V / 1.12V). This mod gives plenty of light and an expected runtime of 19.5h / 8.5h / 3.4h assuming driver efficiency of 80%. The LEDs seem pulsed at least in low mode, so this is all a bit inaccurate (running the LEDs off of a lab power supply gives a different forward voltage for the same current), but, it's good enough to see what can be done. I am doing a runtime test to verify the runtime on low.

20 Ohm also works. 5 Ohm would be better for giving a higher maximum brightnes, but what is needed/useful? More on this after my evening test on how bright I experience the lamp now.

Examining the way it works: Starting at the lowest power level on my lab power supply, which is 0.001A, it's interesting to see the LED dies light up, which seem to be behind or part of a larger die layer, and this looks to be part of why the LEDs don't give the annoyance of 5mm clear LEDs (the other reason is that the LED dies are already larger). Only at larger current do the LEDs shine such that the entire layer becomes emitting. So this method works but at a too high brightness, and there is plenty of room for improvement in this sort of lighting.

Test at night: with the 10 Ohm resistor it is definitely bright enough, even at the lowest mode. I feel this value is the right choice as it gives a good range of brightness levels and a long enough runtime.

Runtime test with 10 Ω resistor: After ca. 17h on low it was still going on full power and checking again after 19h the brightness was a lot lower and the higher settings get barely brighter, but it's still working and you are still very visible... At about 19.5 hours the light is flickering and dim, so runtime is about 19h on low. That means if riding 5 days a week for an hour in the dark, 4 weeks. That's plenty :)

After this modification I quite like the lamp as it's bright without being annoying, it now has a long runtime and it's useful to have a white front backup light in case something happens with your dynamo lamps (or wiring) and it can be used to light up your work area in case you need to do a night time repair of the bike or fix a flat tyre etc. For this purpose it is better than a torch, which are blinding when you look into them which happens when letting the lamp lie somewhere to light up an area...

In operation there are a few nuisances:


For the price of the RPL 2261 (about € 12) you get a nice package, but to be truly useful you need to modify it as I did.

Alternate versions?

Of course there is moonsport's Comet, but I ordered a set of front + taillamp from a supplier in the UK, which are said to have a battery of 1200mAh. I will see... (looking at the size of the battery, and comparing the volume to a 18650 of which the highest capacity available is 3500mAh I would expect a possible maximum of ca. 1000mAh)

I've got them, from Planet-X, which has the Jobsworth Canopus lamps (look exactly like the Raypal, except the taillamp has a saddle mount) on offer along with tyre levers from Ekip which are the same shape as the Specialized tyre levers, and as these are the best ones so far so I wanted some spares. I hope these are as good, but if any of them break, well, I bought a bunch so plenty of spares :).
1. I can more clearly see the LED dies...
2. the power-off is quicker.
3. It uses micro USB!
4. Charging indication is not as good as the Raypal, the orange LED stays too long in the ON position.
5. The PCB is completely different, looks a bit more crude...
6. The mounts are more tight, too tight, hard to get the lamps in/out.
7. The status LED is too bright...
8. Switching off (long press) doesn't switch modes first and switching on is always back to the low mode...
9. The screw that fixes the mount's other side on the lamp has a flat head, and a bubble head on the Raypal. This bubble presses into the battery.

So a quite large list of differences...

The taillamp looks to have a low enough low level, perhaps because of the red LEDs instead of white, it's not because the battery was almost empty as after a short time it was full. On the battery is printed 500mAh, so not 1200mAh that the planetx website says. The packaging also says 500mAh. More details/investigations/measurements to come.

Red taillamp: Voltage over the LEDs: 1.20V / 1.56 V / 2.13V (a lot lower than the white LEDs in the RPL 2261). Current: 0.09A / 0.18 A / 0.38 A. So the same as the white LEDs in the RPL 2261, but lower forward voltage. This could mean a runtime of 14h on low if the driver efficiency is 80%. I will test... Using a 10 Ohm resistor current is 0.05 A / 0.10A / 0.20A and looks bright enough to me (I will test it this evening). Current over the LEDs+resistor in this case: 1.62 / 2.46 / 3.97 V (Vresistor is 10 * current = 0.50V / 1.0V / 2.0V) so for the taillamp this mod would not improve on the expected runtime but only lower the intensity (as I said in the beginning, this is an inefficent mod, and that is because of losses in the resistor. For the headlamp I wasn't worried about this, the main thing was to get the starting brightness lower and that it then runs for 17-19h on low instead of ca. 6 is a bonus).

Runtime test for unmodified red taillamp: Just a little under 5 hours! This means either a completely retarded (immensely inefficient, ca. 30%) driver or the battery is not actually 500mAh. Voltage of the battery under load at switch-off is ca. 3.00 V). Perhaps the RPL2261 taillamp is better...

Charging test to see how much is going into the lamp/battery to fully charge it: 611 mAh * 5.1V is about 842mAh at 3.7V which means the battery is indeed about 500 mAh (ca. 80% efficiency of charger and about that too for the battery as it gets warm, need to put in more than the energy you can get out of it). So the driver is garbage... The runtime could be about 3 times as long with a proper driver running from the same battery...

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