Yaw Know About Solar Chargers?

[mjr]

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.

It's not been stated and the power input the devices require doesn't vary with the charge method.

[Jdsk]

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.

I'm surprised by that, and it isn't my experience with the hub dynamo powering a Garmin Edge 1000, 2 iPhones, a Bluetooth headband and 2 Kindles. No tablet and no lantern, which might explain the difference.

Jonathan

[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.

So that's (18.5 + 4.4/3) * 2 = 40 W hr/ day?

Thanks

Jonathan

[rjb]

40 watts x 24 hrs. That's a huge power drain. Almost 1Kwhr ie 1 unit of electric. My 4kw pv array on the roof is generating only 3 Kwhrs over the course of the day on average at this time of year.

[Biospace]

I would appreciate pointers please.

This coming summer, if I wanted to charge a USB block/battery, to then use to charge phone every day, what solar panel would be suited for the job? (either the a specific set up, or the specs on one)
...
...is it not possible to position it on bike to charge while riding ? Is it not practical ?

My experiences of this:

Pre-touring testing is the only sure way of being sure that what works on paper will work in reality, ime. Folding PV panels mounted over panniers will often result in very poor performance with one section in the shade. Two individual panels each connected to a battery bank worked much better for me than one folding five-panel solar panel, watt for watt.

A battery bank with quoted capacity four times that of your phone battery may struggle to fully recharge the phone more than twice. Temperatures, age and condition of batteries all play their part in the losses, losses which can be higher than anticipated when charging batteries from batteries.

If completely off-grid for over a week or so, a dynohub makes a lot of sense even if in the saddle for only 3 or 4 hours a day. Every little bit counts when you're battery-reliant with no access to mains charging. However, I've always found cafes and restaurants more than happy to allow you to charge devices and small batteries, which at times has been extremely useful.

One final point, it's worth spending a little time finding/working out how to minimise unnecessary phone battery consumption. Reducing consumption, as always, is a virtuous circle, but especially noticeable when carrying your own power generation.



k, for example

[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.

So that's (18.5 + 4.4/3) * 2 = 40 W hr/ day?

Obviously not. 18.5 + ( ( 4.4 / 3 ) * 2 ) = about 21Wh / day. That's worst case, like touring somewhere without good bike route signs so nav is on most of the day. It can be much less somewhere like BE or NL where having a few navigation notes and following signs is easy.

[mjr]

40 watts x 24 hrs. That's a huge power drain. Almost 1Kwhr ie 1 unit of electric. My 4kw pv array on the roof is generating only 3 Kwhrs over the course of the day on average at this time of year.

You seem to have just dropped the h/day from the 40Wh/day! It would be 1.67W x 24h if it were constant. It would be 0.04kWh of electric per day. But it's not because misplaced brackets made it almost double.

[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.

So that's (18.5 + 4.4/3) * 2 = 40 W hr/ day?

Obviously not. 18.5 + ( ( 4.4 / 3 ) * 2 ) = about 21Wh / day. That's worst case, like touring somewhere without good bike route signs so nav is on most of the day. It can be much less somewhere like BE or NL where having a few navigation notes and following signs is easy.

Thanks

It wasn't clear what needed to be doubled for the "same again".

Jonathan

[Galactic]

Folding PV panels mounted over panniers will often result in very poor performance with one section in the shade. Two individual panels each connected to a battery bank worked much better for me than one folding five-panel solar panel, watt for watt.

It certainly used to be the case (and I presume it still is) that PVs in series would only deliver as much power as the weakest unit. So if you had a series of panels, 4 in full sunshine, one in the shade, each of the 4 would only pump out as much as the one in the shade. So it makes perfect sense to me what Biospace says about having separate panels on each side rather than a long one or two that are part of one thingy.

[mjr]

It wasn't clear what needed to be doubled for the "same again".

Really? Would you expect Rachel on Countdown to pull four letters if asked for "vowel, consonant, and the same again"?

[Cowsham]

Well I've just took delivery of a BigBlue fold up 28w solar panel -- will let yous know how it turns out -- our low grey skies won't be ideal but hopefully it'll be good in the summer.

[Valbrona]

My new three panel solar charger seems to be saying to me 'Connect a power bank and not a mobile phone', or at least the instructions for it does. It appears you can get problems on a dull/overcast day with a mobile phone attached. Of course I am now worried about damaging my phone.

Helpful comments appreciated. Thanks.

[Jdsk]

Yes, there's recent discussion of devices not liking intermittent power supply, but unfortunately it's spread across several threads.:
viewtopic.php?t=159957
viewtopic.php?t=159858
viewtopic.php?t=149863

And the bottom line seems to be to use a USB battery pack, as you suggest. As you'll see in those threads for some patterns of use that brings into question whether the solar panel or charging dynamo is needed.

Jonathan

PS: I wouldn't expect it to damage the 'phone.

[Valbrona]

PS: I wouldn't expect it to damage the 'phone.

No more than it's going to damage a portable power pack, one suspects.

It's output is given a 5v/2.4A. But not sure what that means in terms of a cloudy day. Do you get fewer volts or fewer amps, or both? But then again I don't know what a volt or an amp is.

[st599_uk]

Modern USB devices negotiate power levels with the charger. If that doesn't happen they go to the slowest charge level available.

You then have 2 problems - if the panel is producing more, where does the excess power go? (Heat) And if not producing the minimal level, the phone will stop charging (and the excess power turns to heat)