Woosh Advice requested - powering e-bike lights

[Bad Machine]

I think you're overstating the effect the resistance has when the dynamo is on - those of us who do ride dynamo-option bikes/trikes won't notice a huge difference when actually riding. Theoretically, yes. In Practice, No.

Sure, put the dynamo-hubbed wheel into a stand, and compare the free-running of the wheel when dynamo is "off", then "on" (for a hub dynamo - connected or not to working lights). Yes, then you can see there's additional resistance, but when riding ? Nah, I'd suggest that most non-competitive cyclists wouldn't notice the difference when out riding. And the option of having working lights when the e-bike battery has run out of juice ? Yes, for those that have that concern, fit a dynamo light system, and then you can (at least those of us with a trike, hah !) sit back and forget.

I'd totally disagree with you on dynamo lights being "as good as useless". If that's your experience, then you've been choosing the wrong lights. Riding on unlit roads with hugely overpowered lights is tiring on the eyes; what makes for better lighting is a system where the light is focussed where it is needed - and not blinding those occasional car drivers who also use those same unlit roads.

 

[danielrlee]

Many of you forget that once your ebike battery is too far discharged to sustain 15-20A that your motor requires to operate, it's still capable of outputting 1A that your lighting requires to shine for a long while after the motor cuts out. That's why (to me at least) powering lighting directly from the main battery makes sense more than any other method.

Out of interest, has anybody who actually does run their lighting from their bike battery, ever been left without sufficient energy to do so?

 

[Nealh]

Never been without lights when lvc has been reached as voltage is still plenty to run lights , voltage also rebounds to ensure voltage climbs above lvc and riding unassisted in PAS 0 to get home if need be.
I usually only use PAS level 2 so load on battery is low at about 2- 5a max or less then 0.5c per cell.

 

[vfr400]

I think you're overstating the effect the resistance has when the dynamo is on - those of us who do ride dynamo-option bikes/trikes won't notice a huge difference when actually riding. Theoretically, yes. In Practice, No.

Sure, put the dynamo-hubbed wheel into a stand, and compare the free-running of the wheel when dynamo is "off", then "on" (for a hub dynamo - connected or not to working lights). Yes, then you can see there's additional resistance, but when riding ? Nah, I'd suggest that most non-competitive cyclists wouldn't notice the difference when out riding. And the option of having working lights when the e-bike battery has run out of juice ? Yes, for those that have that concern, fit a dynamo light system, and then you can (at least those of us with a trike, hah !) sit back and forget.

I'd totally disagree with you on dynamo lights being "as good as useless". If that's your experience, then you've been choosing the wrong lights. Riding on unlit roads with hugely overpowered lights is tiring on the eyes; what makes for better lighting is a system where the light is focussed where it is needed - and not blinding those occasional car drivers who also use those same unlit roads.

You have to pedal 8% harder if you have 3W total lights and normally pedal with 60W input. You can't change the laws of physics (first law of thermodynamics) no matter how much you wish you could.

Here's some lab test results that show that my estimate was about right, a bit underestimated if anything. Note that they only use a 2W load and their cyclists are somewhat fitter than your average ebike one. Basically, they show that you have to put 7W in to get 2W out at 15 mph.

How Much Does Dynamo Hub Drag Really Slow You Down? Lab Testing Results - CyclingAbout

If you've ever tried to spin the axle of a dynamo hub, you'll know they feel incredibly 'notchy'. Let's look at how dynamo hub drag affects cycling speed.

www.cyclingabout.com

 

[Bad Machine]

From the article you quoted:

"Given the leverage of a wheel and the flywheel effect of the rotating mass, dynamo hub drag only has a small effect on your speed.

The result for most people is likely to be an extra three to six minutes riding time over 100km, all while getting a good charge to your electronics (or while running lights). "

Where did I suggest the Laws of Physics didn't apply ? Nowhere.

"An extra three to six minutes riding time over 100km". And really, how many e-bikers ride 100km with their dynamo on ?

So, should I be dissuaded from choosing a dynamo as a back-up lighting system = NO !

 

[vfr400]

From the article you quoted:

"Given the leverage of a wheel and the flywheel effect of the rotating mass, dynamo hub drag only has a small effect on your speed.

The result for most people is likely to be an extra three to six minutes riding time over 100km, all while getting a good charge to your electronics (or while running lights). "

Where did I suggest the Laws of Physics didn't apply ? Nowhere.

"An extra three to six minutes riding time over 100km". And really, how many e-bikers ride 100km with their dynamo on ?

So, should I be dissuaded from choosing a dynamo as a back-up lighting system = NO !

Did you see the bit about the 12 ohm load?

 

[Gringo]

Here’s a thought for the permanently fixed lighting brigade,
What happens when you are cycling in the dark on an unlit road and you get a puncture or anything else that requires your attention (chain or gear issues etc) and that’s just as likely to happen as a flat battery.
I always have at least one removable independently powered light source at night.

 

[Bad Machine]

Yes. Did you understand why they included it >

 

[vfr400]

Yes. Did you understand why they included it >

Yes, but I guess you didn't, so let me explain. It'so that they could put that 7W of extra input power in perspective. 12ohms is 2W of supply power for lights. I can't think of any lights that I'd want to use with a combined input power of 2 watts.

 

[Bad Machine]

Here’s a thought for the permanently fixed lighting brigade,
What happens when you are cycling in the dark on an unlit road and you get a puncture or anything else that requires your attention (chain or gear issues etc) and that’s just as likely to happen as a flat battery.
I always have at least one removable independently powered light source at night.

TBH, I think those in the "brigade" who have had the foresight to spend time making a permanently fixed lighting system, they will have had that covered. For such eventualities, there's a long-life single AA torch in my tool kit.

 

[Bad Machine]

Yes, so that they could put that 7W of extra input power in perspective. 12ohms is 2W of supply power for lights. I can't think of any lights that I' d want to use with a combined output power of 1.5 watts.

Once again, we differ in the amount of light we'd choose for our own lights. Dynamo-powered systems are perfectly able to light my way.

Back to your reference article:

"Does Dynamo Hub Drag Really Matter?

Only a little."

 

[danielrlee]

Here’s a thought for the permanently fixed lighting brigade,
What happens when you are cycling in the dark on an unlit road and you get a puncture or anything else that requires your attention (chain or gear issues etc) and that’s just as likely to happen as a flat battery.
I always have at least one removable independently powered light source at night.

The LED on my phone would be sufficient in that scenario. Another option would be simply reflecting the light off a nearby object. Otherwise, it only takes the loosening of a single screw to allow me to reposition one of my main lights to wherever the light is needed.

 

[Bad Machine]

Yes, but I guess you didn't, so let me explain. It'so that they could put that 7W of extra input power in perspective. 12ohms is 2W of supply power for lights. I can't think of any lights that I'd want to use with a combined input power of 2 watts.

Your guess was wrong.

BTW, it's poor form to edit your posts after someone has responded to the point your trying to make.

 

[niggle]

Philips Saferide 60 beam shot (the Spanninga Axendo is a direct copy of it, as they bought the design off Philips when Philips stopped making bike lights, and bear in mind that mine is the 80 Lux ebike version so a tad brighter still):

From this website: https://swhs.home.xs4all.nl/fiets/tests/verlichting/index_en.html Hardly useless IMO

I have commuted around 5000 miles with a Shimano DH-3D32 hub dynamo and Axa Luxx 70 front light, and similar with a DH-3N80 with a Herrmans H-one S, in neither case could I feel any noticeable drag or tell the difference between lights on or off and the lighting was good enough for doing up to 30mph downhill on twisty Cornish country lanes. So thanks vfr400 but I have already "tried it" extensively and I bet you could not tell whether a bike has a hub dynamo or if lights were on or off in a blind test.

To put it in perspective the impact of having a decent dynamo hub is equivalent to going up an extra foot per mile when off and an extra 6 feet per mile when on and is significantly less than choosing sluggish tyres, or massively less than sitting upright on the bike instead of getting aero, particularly into a headwind (source: http://mccraw.co.uk/hub-dynamo-friction/ ) . I have noticed that the majority of riders on here are on MTBs or hybrids with straight bars and favour higher rolling resistance robust puncture resistant tyres over faster lighter weight ones, whereas I use drop bars (and get down on the drops when riding into headwinds or descending fast) and very low rolling resistance Vittoria Voyager Hyper 120tpi folding tyres.

Then with an ebike you get the assistance from the motor so even the small extra power required can be left to that if you choose, either resulting in a tiny drop of speed or a tiny loss of battery range.

OTOH thanks to those who have pointed out that when you lose traction power on an ebike you still have enough juice for lights, this is good to know and shows the benefit of sharing experience and pooling knowledge.

 

[anotherkiwi]

Out of interest, has anybody who actually does run their lighting from their bike battery, ever been left without sufficient energy to do so?

[multiple power cuts are making editing this "complicated"]

No. Controller LVC at 30v and BMS minimum of 27v-28v for a 36v battery means you have plenty of Wh for lights before everything switches off - at a minimum about 20 Wh.

 

[vfr400]

Philips Saferide 60 beam shot (the Spanninga Axendo is a direct copy of it, as they bought the design off Philips when Philips stopped making bike lights, and bear in mind that mine is the 80 Lux ebike version so a tad brighter still): View attachment 32843

From this website: https://swhs.home.xs4all.nl/fiets/tests/verlichting/index_en.html Hardly useless IMO

I have commuted around 5000 miles with a Shimano DH-3D32 hub dynamo and Axa Luxx 70 front light, and similar with a DH-3N80 with a Herrmans H-one S, in neither case could I feel any noticeable drag or tell the difference between lights on or off and the lighting was good enough for doing up to 30mph downhill on twisty Cornish country lanes. So thanks vfr400 but I have already "tried it" extensively and I bet you could not tell whether a bike has a hub dynamo or if lights were on or off in a blind test.

To put it in perspective the impact of having a decent dynamo hub is equivalent to going up an extra foot per mile when off and an extra 6 feet per mile when on and is significantly less than choosing sluggish tyres, or massively less than sitting upright on the bike instead of getting aero, particularly into a headwind (source: http://mccraw.co.uk/hub-dynamo-friction/ ) . I have noticed that the majority of riders on here are on MTBs or hybrids with straight bars and favour higher rolling resistance robust puncture resistant tyres over faster lighter weight ones, whereas I use drop bars (and get down on the drops when riding into headwinds or descending fast) and very low rolling resistance Vittoria Voyager Hyper 120tpi folding tyres.

Then with an ebike you get the assistance from the motor so even the small extra power required can be left to that if you choose, either resulting in a tiny drop of speed or a tiny loss of battery range.

OTOH thanks to those who have pointed out that when you lose traction power on an ebike you still have enough juice for lights, this is good to know and shows the benefit of sharing experience and pooling knowledge.

It's still 7w extra input for 2W lights! That's 7% extra pedal power that I'd have to add on a normal ride, compared with zero extra effort for non-dynamo lights. As I said, you can't change physics. Stick to your religion. I'm happy with being an athiest.

 

[Bad Machine]

It's still 7w extra input for 2W lights! That's 7% extra pedal power that I'd have to add on a normal ride, compared with zero extra effort for non-dynamo lights. As I said, you can't change physics. Stick to your religion. I'm happy with being an athiest.

It's not a religion. It's called pragmatism.

 

[niggle]

It's still 7w extra input for 2W lights! That's 7% extra pedal power that I'd have to add on a normal ride, compared with zero extra effort for non-dynamo lights. As I said, you can't change physics. Stick to your religion. I'm happy with being an athiest.

Not really, you really will not go much slower if you don't put any more effort in on a hill, and, assuming you are capable of riding an ebike at 15mph with minimal effort, which I certainly am, then the effect on range on the flat will be negligible.

However I am now quite happy to retract my statement that dynamo hub lighting is best for ebikes, as I have learnt from others that ebike wired in lights will continue to work after the motor has ceased I would say that these are best for all ebikes- see I am not at all religious about this as I can change my view when new evidence presents, however I still say, from experience, that battery/rechargeable lights are mostly unreliable, inconvenient, badly designed for road use and theft prone. They are also heavier than ebike lights and more costly in the long run.

 

[anotherkiwi]

Not really, you really will not go much slower if you don't put any more effort in on a hill, and, assuming you are capable of riding an ebike at 15mph with minimal effort, which I certainly am, then the effect on range on the flat will be negligible.

However I am now quite happy to retract my statement that dynamo hub lighting is best for ebikes, as I have learnt from others that ebike wired in lights will continue to work after the motor has ceased I would say that these are best for all ebikes- see I am not at all religious about this as I can change my view when new evidence presents, however I still say, from experience, that battery/rechargeable lights are mostly unreliable, inconvenient, badly designed for road use and theft prone. They are also heavier than ebike lights and more costly in the long run.

You obviously haven't tried this one:
https://www.bumm.de/de/produkte/akku-scheinwerfer/parent/192/produkt/192qmla.html?
No, I didn't pay that price, about 40€ IIRC. I slip mine off and put it in my pocket where it makes a handy torch on unlit footpaths.

I also have this one:
https://www.bumm.de/de/produkte/akku-scheinwerfer/parent/1922/produkt/1922qmla.html?
It was 70 lux rated when I bought it. And once again it cost me in the 40€ (high end of 40's). It is plenty powerful enough for an upright, not quite enough for a trike.

I have been using these for over 3 years so let's say they have cost less than 2.50€ a month for the two of them or 1.25€ each. They run on supermarket brand rechargeable AA cells and so far I have chucked 4 of those. The same cells are also used in my keyboard and various other devices so there is some rotation between heavy use (lights) and lighter requirements.

My light weight e-bike light broke the first time I took the big bike on the metro, it fell over on the first corner... It still lights up but the LED has moved out of alignment with the reflector and I can't open it to repair it is ultrasound welded plastic.

 

[niggle]

The Spanninga ebike lights including 80 lux front and top rated rear cost £30.14 and £11.64 respectively. Front weighs 120g despite having an alloy casing. rear weight not stated but less than the front:

Headlight Spanninga Axendo 80 XE E-bike Grey,Silver

Buy Spanninga Axendo 80 XE Bicycle Front Light - LED online ✓Fast delivery ✓14-day cooling-off period ✓Trusted Shops certification

www.justathlete.co.uk

Spanninga Bike Rear Light - LED - Elips XE - 80 mm online - Justathlete.co.uk

Buy Spanninga Bike Rear Light - LED - Elips XE - 80 mm online ✓Fast delivery ✓14-day cooling-off period ✓Trusted Shops certification

www.justathlete.co.uk

Add a bit of 2 core wire and a couple of connectors, fit and forget, zero running costs.

This is probably the dogs gonads in ebike lights, 150 lux, 6-60 volts so no worries with 48V batteries: https://www.starbike.com/en/busch-und-mueller-lumotec-iq-x-e-led-e-bike-front-light-150-lux-black/?currency=GBP&keep_params&gclid=EAIaIQobChMIodPTn4_b5QIVFuDtCh3DCwnKEAQYAyABEgL_IPD_BwE but not cheap...