Rear 'battery' powered lights with the longest run time?

[PaulB]

There is evidence, but I cant be bothered to find it re the random flashing being better. It is similar but not linked to why emergency service vehicles use multi tones, and random flashing lights (not on all vehicles yet). Basically it makes you stand out more and reduces the mesmerising bit.

[benp1]

They catch you're attention, yes

But a bright rear light on flash is hard to gauge your distance/speed against, and gets harder the brighter it is and the darker the surroundings. Try it, then try it in the rain

I'm not saying don't do it, just beware of the impact. I see lots of bikes commuting (I commute into central London), and I am one too - it's hard to look at a very bright flashing light (front or back).

EDIT - it's all relative. There's bright and there's bright. i see some that are frankly ridiculous, but partly because they are directional. Very bright where it's aimed, almost invisible from the side

Personally I run flashing and solid rear lights, and my flashing lights aren't massively bright, and then a pulsing and solid front light

[jameso]

Ben and I saying same thing, wrote this as he was posting-

There is evidence, but I cant be bothered to find it re the random flashing being better. It is similar but not linked to why emergency service vehicles use multi tones, and random flashing lights (not on all vehicles yet). Basically it makes you stand out more and reduces the mesmerising bit.

For a rear bike light that's really not what you want though, unless you're in the city centre. Assuming this is for BP use .. here goes :) ... Many (the majority? From what I recall but could be wrong) of serious injuries to riders are from cars hitting them from behind on more open roads. Some of that will be from drivers looking at phone etc not road, but some is from misjuging closing speed or distance.
All you need to do is see how it's less easy to do that with a flashing, very bright point source vs a constant and refracted light is watch both a flashing bike light and a moped light move away from you on a dark road. It's far easier to trace and judge the path of the moped. Works same in reverse as you approach in a car.

I won't use flashers unless it's in addition to a constant when riding in town or city centres. Super bright flashers are just sub standard design and cheap to make, sold to our fears of not beimg seen rather than designed to make riding in the dark safer. Some say flashing distinguishes a bike but I'm not convinced that's a benefit, I'd rather be seen as a moped tbh.
Rant over :)

To answer the OP, I'd look at anything low power but refracted or shone through a reflector made by Sigma, Spannina or other brands with good market share in Germany. If you need pure back-up light duration from a flasher there's loads that will go over 24hrs.
The other good thing to back up or make a flasher-only rear safer is to use reflectives well -
pick 2 points far apart that work to judge distance change, ie 1 on the lower rear stays area and one on rear of saddle, seapost/pack etc.

[whitestone]

The super bright rear lights are a pain to ride behind as well, you get blinded by them and lose all night vision. It's a problem with point source lighting in general. I ride with one constant and one flashing. Both are low power USB rechargeable style lights but the commuter has a StVZo approved rear light attached to the dynamo.

The Cateye "hand grenade" mentioned earlier is/was great as you could set each bank of LEDs to a different flash pattern or to constant so in one light you could have both. I'm not sure if there are any rear lights that have a constant beam with an embedded "pulse", I've seen front lights with this but not rear.

[Bearbonesnorm]

is to use reflectives well

Yep, I reckon my ProViz gilet gets me noticed in low light / dark conditions way more than a rear light does. There's the added benefit being seen from every angle.

[johnb]

In the dark on unlit roads a car driver should have no difficulty seeing you in his headlights. You often here the view from rural drivers that you can drive faster at night because you can see cars headlights coming from opposite direction before you go round a corner. As cyclists are likely to be cycling much slower I reckon it makes no difference what light you have the car driver is traveling to fast.
Now we have much brighter front lights most car drivers see your lights and are on the right side of the road when they come round the corner!
In my opinion flashing lights are a must as it indicates to a driver that there is cyclist in front and they are likely to be travelling slower than you.
I use both flashing and non flashing the aim is really to make the driver think.
Going back to my earlier statement a driver should be able to pick you out in his headlights.

[ScotRoutes]

Another issue with bike lighting (pedal and motorised) is that there is usually one light and it's on the centre line of the vehicle. This makes speed difficult to judge, whereas we can do much better when it's a wide vehicle with two lights and we can use the "change in distance" between the lights to help us. A lot of reseach was done on this when there were attempts to introduce an always-on headlamp law for motorcyclists.

[jameso]

Another issue with bike lighting (pedal and motorised) is that there is usually one light and it's on the centre line of the vehicle. This makes speed difficult to judge, whereas we can do much better when it's a wide vehicle with two lights and we can use the "change in distance" between the lights to help us. A lot of reseach was done on this when there were attempts to introduce an always-on headlamp law for motorcyclists.

Agreed, this is why I think point-source lights are a bad idea and using reflectives to create a second point for distance from any light works so well. Wider secondary points work better than verticals, bar-end position reflectors seem a good idea (or streamers )

[PaulB2]

I used to have a set of bar plug lights on my old road bike - they worked pretty well though they did corrode to pieces while the bike was stuck in a storage locker for years.

[johnb]

Went out a bit late last night to exercise the dog. Stopped to turn on rear light. I found I had 4 rear lights on the bike! The extra bright retro light, some cateye light which was on the bike when I bought it, both on the seat post. One of those R2 type cheapos on the rear rack and fourth of the same on my pannier bag. A little over the top....Blackpool illuminations.