Even for touring the use case is pretty marginal. If you find yourself cycling in the dark on a summer tour, you’ve cocked up your planning somewhere.
(Or you’ve been to the pub)
Or you're me... On my way to Hell, I had several days where I went quite late, well into dark. I was bivviing, so basically the moment I stopped, I'd be in bed trying to sleep within 15 minutes. No point wasting daylight on that, so I'd go until it was dark, then find a suitable place to stop. I know my way round my bags in the dark, so don't need the last of the day light to make camp. One night I planned to ride a bit deeper into the night because it was forecast to be totally clear, and I was hoping for good star views. But then we've established that I'm weird ;p
Others may choose to ride at night due to temperatures by day being too warm.
When it comes to battery vs dynamo, putting aside the emotional side of it, for rides where you have easy access to recharge, then the technology has moved back in favour of batteries. But that does require you to have access to charging, you also need to be careful in calculating your power budget. As an example, my budget for the TCR is looking like this:
- Wahoo Bolt (10Wh* (Needs charging 1.6 times per day))
- Tracker (11.8Wh (needs charging every 2 days (conservative estimate))
- Mobile phone (10.6Wh (Needs charging 2 times per day))
- Head light (12.6Wh)
- Camera (4.86Wh)
This gives me a total power requirement of: (10*1.6)+(11.8/2)+(10.6*2)+12.6+4.86.
60.6Wh. per day.
With 10 hours of movement per day, giving 10 * 2Wh of power from the Dynamo (5V @ 500mA == 2.5W, assuming 80% efficiency of power bank charging). Means power deficit of about 40Wh per day. My battery pack is 100Wh, so I have 2.5 days worth of power. *BUT*, I start with all devices charged, and I can charge them fully at the end of the 3rd day. Meaning for my plan of Hotel, bivvi, bivvi, repeat. Gives me just enough power. *BUT* Now we get into the question of charging the 100Wh battery pack. Charging with a typical 2.4A 5v USB socket, you're getting 12W of power. At 100% efficiency, that 100Wh battery pack would need over 8 hours to charge. You don't get 100% efficiency, so it's nearer 10 hours. I really don't want to spend 8 hours at a hotel, let alone 10, not on an event like the TCR or RatN. Fortunately my power pack has 2 inputs, so rather than putting 2.4A in, I can put in 4.8A. 24W. 100% efficiency would give a little over 4 hours. Make it nearer 5 with inefficiency etc... Much more reasonable.
*BUT* this is without any lighting in there, other than my auxiliary head light. Let's add a light. For the sake of maths, let's use a hypothetical 3W light. Let's assume 8 hours of dark cycling (on RatN I pedalled late into the night most nights, and 2 nights, the full night). So we're now adding 24Wh of power to our calculations. So now we're at 85Wh of power, per day. With no dynamo, there's no -20Wh offset. With the same 3 day usage plan, that's 255Wh. Best case that's about 1.3kg of battery packs. And you're gonna need to have a many more charging sockets when you stop. 60Wh of power, to be in with a chance of a 5 hour stop. That's 5 USB ports at 2.4A. On top of enough ports to charge all 5 actual devices. So 10 ports total.
My 4x2.4A usb charger unit is 140g. So we're adding another 140+g for chargers.
This is getting heavy...
Now, I've talked here about events like the TCR, RatN, or my road to Hell. But the original discussion pertained to 200's for RRtY. For a simple 200, assuming a start at 0800-0900, and a UK, or western European time zone. Your worst case is that you want 24Wh of lighting power, (8 hours of lighting needed), half a top up of the mobile phone, and half a top up of the wahoo. That puts us at about 33Wh. or around the 9000Mah mark. But only about 10Wh of that will need to come from a battery pack, (I'm guessing the power for the light is built into the light).
In theory the Wahoo can do the full ride on a single battery charge. But it's close, if you're using the back light, or running a full value times, so you're gonna want to plug it into a battery pack at one of the controls (or food stops on a diy), just to top it up and reduce the "oh fuck" moment when it dies 5km from the finish.
That just leaves the question of what would be a suitable battery powered light if you went that route.
But, for all of this, for all of the maths. My preference is for a dynamo light anyway. I don't have to worry about charging it, I can literally, submit the DIY application, and hit the road the next day without needing any logistical faffing about. My light is always "charged". But that's a decision made as much on an emotional level, rather than a rational one.
Ultimately, it's a bike ride, not a trip to Mars... your mileage and power usage may vary...
J
*(Actual size, I'm not sure of, as I can't find any clear data on this)
PS Oh arse, just realised I've done all that, and forgotten that I'm swapping to Di2, which means another 1.85Wh of power needed about every 3 days. Not gonna edit all my maths now tho. sorry.