Flash tests
8 December 2025 10:27 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
igenlodeI have spent the last couple of days running tests on my USB bike lights to try to work out what they will and will not safely do -- I thought I should remember the significance of all the times/figures I jotted down, but of course I don't :-(
But the general conclusion seems to be that they will indeed run for very long periods uninterrupted -- I accidentally left my front light on flashing mode for about nine hours or so overnight and it was still flashing in the morning and not showing its low battery warning. (Which is what one ought to expect, really, given that although I don't know the exact model of this light similar USB white headlamps in this style advertise run times of over a *hundred* hours in lowest power-consumption mode.)
However the moment I switch them off after a long run, it then becomes questionable whether they will immediately start displaying a low battery warning if I switch them on again. I ran the light in flashing mode from 2pm to 5.50pm, switching it off every half-hour or so to check, and it was fine; this is much longer than the 70 minutes' or so run that caused problems on Wednesday. I ran it on steady low mode (being sick of all that high-intensity flashing going on in the background!) from 1.25pm to 9.30 pm, switching off every hour or so to check, and it was fine. I then left it on from 10.35 pm until 3.20 am this morning without recharging in the intervening interval, and it was fine... but showed red as soon as I switched it off, though it did consent to restart at 5.45am this morning, albeit with the warning from the start. I don't know how long it ran under those conditions because it was off again when I woke (or rather when my alarm woke me after a few hours of sleep...)
So my provisional conclusions, from what I can remember of my test data, are that it should be perfectly safe to cycle for, say, an hour and a half, spend a few hours on various other activities and then cycle home again, provided you don't attempt to switch the lights *off* in the interim :-O Which means having them flashing away in the bottom of your bag in the cinema, say, and hoping it is sufficiently lightproof -- obviously you can't leave the bike parked and drawing attention to itself outside with the lights left on. It is the trauma of starting up on high-beam that seems to flatten a battery that should in theory have hours of continuing power left in it.
Alternatively, it would probably work if you can remember to switch them off briefly every half-hour or so while riding, which seems to contradict the previous result.
My tests, however, do not seem to confirm the observed practical journey data that leaving the lights on for just over an hour will immediately trigger the low-battery state (I started off yesterday's tests by leaving the light on from 1.25 to 3.05 pm, and it was still working at 9.30pm, with various periods of an hour and a half or so between test switch-offs). So I'm not sure how reliable they are :-(
The trouble is that every time you switch the light off to test there is immediately a possibility that it won't come on again, which if you're out on the road at the time is fairly disastrous -- so the only *safe* thing to do is simply not to switch it off at all. Which probably means running on low-beam rather than attracting traffic attention via high-beam flashes, because the latter are simply so obnoxious when not in traffic... which means that my lights are theoretically present but not necessarily particularly safe, given that their only actual function in town is to highlight my existence to the cars at risk of hitting me through inattention :-(
But the general conclusion seems to be that they will indeed run for very long periods uninterrupted -- I accidentally left my front light on flashing mode for about nine hours or so overnight and it was still flashing in the morning and not showing its low battery warning. (Which is what one ought to expect, really, given that although I don't know the exact model of this light similar USB white headlamps in this style advertise run times of over a *hundred* hours in lowest power-consumption mode.)
However the moment I switch them off after a long run, it then becomes questionable whether they will immediately start displaying a low battery warning if I switch them on again. I ran the light in flashing mode from 2pm to 5.50pm, switching it off every half-hour or so to check, and it was fine; this is much longer than the 70 minutes' or so run that caused problems on Wednesday. I ran it on steady low mode (being sick of all that high-intensity flashing going on in the background!) from 1.25pm to 9.30 pm, switching off every hour or so to check, and it was fine. I then left it on from 10.35 pm until 3.20 am this morning without recharging in the intervening interval, and it was fine... but showed red as soon as I switched it off, though it did consent to restart at 5.45am this morning, albeit with the warning from the start. I don't know how long it ran under those conditions because it was off again when I woke (or rather when my alarm woke me after a few hours of sleep...)
So my provisional conclusions, from what I can remember of my test data, are that it should be perfectly safe to cycle for, say, an hour and a half, spend a few hours on various other activities and then cycle home again, provided you don't attempt to switch the lights *off* in the interim :-O Which means having them flashing away in the bottom of your bag in the cinema, say, and hoping it is sufficiently lightproof -- obviously you can't leave the bike parked and drawing attention to itself outside with the lights left on. It is the trauma of starting up on high-beam that seems to flatten a battery that should in theory have hours of continuing power left in it.
Alternatively, it would probably work if you can remember to switch them off briefly every half-hour or so while riding, which seems to contradict the previous result.
My tests, however, do not seem to confirm the observed practical journey data that leaving the lights on for just over an hour will immediately trigger the low-battery state (I started off yesterday's tests by leaving the light on from 1.25 to 3.05 pm, and it was still working at 9.30pm, with various periods of an hour and a half or so between test switch-offs). So I'm not sure how reliable they are :-(
The trouble is that every time you switch the light off to test there is immediately a possibility that it won't come on again, which if you're out on the road at the time is fairly disastrous -- so the only *safe* thing to do is simply not to switch it off at all. Which probably means running on low-beam rather than attracting traffic attention via high-beam flashes, because the latter are simply so obnoxious when not in traffic... which means that my lights are theoretically present but not necessarily particularly safe, given that their only actual function in town is to highlight my existence to the cars at risk of hitting me through inattention :-(