Yaw Know About Solar Chargers?

[pjclinch]

Put all that together and it's way heavier than the 200g extra of a dyno hub!

But they also have very different functionality. eg Dynamo hub not much use at night where a power pack is. Dynamo hub not much use whilst you're sitting beside your tent drinking coffee but a solar panel is. Does not make either better or worse, just different.

And, one of the downsides of dynohubs for this avowed dynohub fan, they're down at Liz Truss levels of usefulness when you need to fix a puncture after dark, particularly a front one!

Pete.

[hamster]

Too true, you always need a small battery light.

However I disagree with your metaphor. To have Liz Truss levels of usefulness they would have to be actively bad for you rather than merely not improving the situation.

[mjr]

If I'd known then what I know now I wouldn't have bought the B+M headlights with built-in USB charging.

Why not? What knowledge would have changed your decision? What would you buy instead?

I recommend as a first question in the decision tree: "Can I manage with one or two USB battery packs?".

I often manage with a 6600mAh (at 3.7V) dual-port passthrough-possible USB pack, and a 2200mAh one which can have its 18650 battery changed. I've not yet wired the USB charger sat in my drawer into a dynamo circuit.

[Jdsk]

If I'd known then what I know now I wouldn't have bought the B+M headlights with built-in USB charging.

Why not? What knowledge would have changed your decision? What would you buy instead?

That when touring we could keep all of our devices charged with a small cheap USB battery pack.

This would have been cheaper and probably avoided the repeated failure of the headlamps.

I'd have bought the same SP hub dynamo but a cheaper simpler B+M headlamp as on the other tourers. And the same 22,000 mA hr USB battery pack.

Jonathan

[mjr]

Just out of interest:
# what do users believe that their daily power usage / demand (in electrical watt hours) is?

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

# what percentage of the rated output of their panels do they think that they normally achieve?
# and why do they think that that’s the percentage that they achieve?

About 40% in summer, measured with a USB doctor, and I suspect that's probably because of imperfect alignment while the panel's spread on the rack top if riding or a table if not. So it's a useful contribution but doesn't avoid the need for mains top-ups unless power consumption is reduced.

[Jdsk]

Just out of interest:
# what do users believe that their daily power usage / demand (in electrical watt hours) is?

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

Why 3.7 V, please? (Nominal USB charging is 5 V.)

And then you have to add the inefficiency of the supply somewhere to get the total energy.

Jonathan

[Jdsk]

...
So it's a useful contribution but doesn't avoid the need for mains top-ups unless power consumption is reduced.

I think that's the crucial information in determining the overall approach.

Of course lengthening that interval between the need for mains power may be important for some trips. How it pans out for us and the related capacity of the battery pack is what I didn't know and wish that I had.

Jonathan

[mjr]

Just out of interest:
# what do users believe that their daily power usage / demand (in electrical watt hours) is?

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

Why 3.7 V, please? (Nominal USB charging is 5 V.)

I suspect the makers quote the mAh at the battery voltage rather than USB voltage to make it look more.

And then you have to add the inefficiency of the supply somewhere to get the total energy.

I've allowed for 20% loss getting the power into the devices in the above figures.

[Carlton green]

Just out of interest:
# what do users believe that their daily power usage / demand (in electrical watt hours) is?

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

# what percentage of the rated output of their panels do they think that they normally achieve?
# and why do they think that that’s the percentage that they achieve?

About 40% in summer, measured with a USB doctor, and I suspect that's probably because of imperfect alignment while the panel's spread on the rack top if riding or a table if not. So it's a useful contribution but doesn't avoid the need for mains top-ups unless power consumption is reduced.

Thank you, a useful answer. As a Dynamo would normally have a rated output of 3 Watts then your consumption seems to me to be in the range that a dynamo by itself might not be sufficient to power your devices.

[Jdsk]

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

Why 3.7 V, please? (Nominal USB charging is 5 V.)

I suspect the makers quote the mAh at the battery voltage rather than USB voltage to make it look more.

Thanks, but I'm not sure what you're describing here. Is it a USB battery pack charging each device through a USB-A connector?

Jonathan

[Jdsk]

And then you have to add the inefficiency of the supply somewhere to get the total energy.

I've allowed for 20% loss getting the power into the devices in the above figures.

Thanks

Jonathan

[mjr]

As a Dynamo would normally have a rated output of 3 Watts then your consumption seems to me to be in the range that a dynamo by itself might not be sufficient to power your devices.

I agree. A 3W dynamo and a 20W (so 8W average in sun in reality IME) solar panel together might avoid the need for mains charging, but either alone would see a gradual decrease of charge levels over the trip.

[mjr]

Why 3.7 V, please? (Nominal USB charging is 5 V.)

I suspect the makers quote the mAh at the battery voltage rather than USB voltage to make it look more.

Thanks, but I'm not sure what you're describing here. Is it a USB battery pack charging each device through a USB-A connector?

No. It's 80% of the battery capacity of the device (which is stated by its maker in mAh at 3.7v), plus 25% (to allow for 20% loss). Some of the devices have USB micro-B sockets. Some have USB C.

[Jdsk]

Just out of interest:
# what do users believe that their daily power usage / demand (in electrical watt hours) is?

About 5000mAh at 3.7V (so 18.5Wh?) for the phone/navigation/comms, 1200mAh (so 4.4Wh?) for charging the Fire every 3 days and maybe the same again spread across the lantern, earpiece, speaker and other small devices.

# what percentage of the rated output of their panels do they think that they normally achieve?
# and why do they think that that’s the percentage that they achieve?

About 40% in summer, measured with a USB doctor, and I suspect that's probably because of imperfect alignment while the panel's spread on the rack top if riding or a table if not. So it's a useful contribution but doesn't avoid the need for mains top-ups unless power consumption is reduced.

Thank you, a useful answer. As a Dynamo would normally have a rated output of 3 Watts then your consumption seems to me to be in the range that a dynamo by itself might not be sufficient to power your devices.

How many hours pedalling a day are you assuming in coming to that conclusion?

Thanks

Jonathan

PS: I can easily generate enough power for all of our devices from the dynamo hub.

[Jdsk]

I suspect the makers quote the mAh at the battery voltage rather than USB voltage to make it look more.

Thanks, but I'm not sure what you're describing here. Is it a USB battery pack charging each device through a USB-A connector?

No. It's 80% of the battery capacity of the device (which is stated by its maker in mAh at 3.7v), plus 25% (to allow for 20% loss).

Thanks. But I don't understand how you are charging the end devices.

Jonathan