i got a navin minihomer a couple of months ago for the purpose of logging GPS data so i could geotag my photos...it works great, it's IPX6 waterproof, and it gets about 10 hours of battery life in real-world (mixed open/strong-signal and obstructed/weak-signal) use...one of the best $50 i've spent in recent time

the problem is that 10 hours isn't enough...i would like 12 hours of real-world use at the very least and 14-15 would be perfect

since it's almost always in use outside during the day and it uses a standard mini-B USB interface, i would like to attach it to a small solar charger that will trickle charge it during use...it doesn't need to be strong enough to actually charge it; i'll settle for slowing the drain enough to give the extra 4 hours of operation (i'd be thrilled if it even just maintained the battery)

obviously, they already make devices that do this, and they're not that expensive...take your pick for less than $10 after shipping:

http://shop.ebay.com/?_nkw=solar+usb+charger&_sacat=See-All-Categories

and you can make your own easily enough (though probably not for much less than $10 to make it worth the trouble...i do have some solar garden lights lying around that i'm not using):

http://www.instructables.com/id/How-to-make-a-Solar-USB-charger-simple/
http://www.wonderhowto.com/how-to-build-solar-powered-usb-charger-78846/

okay, so why make this thread at all? because i'm paranoid about getting some cheap POS that will, in short order, trash whatever device i use it with...while i am only looking at this for the purpose of my datalogger, i'll probably use it to trickle charge my cell phone or mp3 player or whatever else i have that's USB and i'd prefer to get y'all's advice about what to look out for before wasting time and money on something that either won't work or will somehow damage my electronics

should i get something that has built-in li-ion batteries for voltage regulation or will just a panel work? most seem to be 5.5v...is that safe for USB (i thought spec was 5v)?

600mAh battery, 300-500mAh output, $7.31: http://cgi.ebay.com/400158662897
1350mAh battery, 1000mAh output, $10: http://cgi.ebay.com/280567908626
2600mAh battery, 400-800mAh output, voltage selection?, $13: http://cgi.ebay.com/160486316957

9/28/2010 8:45:44 AM

I would think you'll definitely want one with a battery pack.

Solar chargers are all but a joke in terms of power generation unless you're plumping out cash for some high grade silicon. You'll notice stuff on eBay takes 2 days of full sunlight to charge it's internal 1500mAh internal battery. So roughly your cell phone, and it needs 2 days of nominal output.

And at that point all you're doing is carrying a backup battery. Of course there's always the possibility some cheap chinese crap will bake your equipment - but you only paid $50, so I'd say go for it. I was considering a solar solution for my mifi - but recently discovered a 'hack' that allows it to charge and keep broadcasting. No worries yet.

9/28/2010 9:54:00 AM

http://www.solio.com/charger/solio-charger-comparison-chart.html

I like those. The classic supposedly charges a 1650mAh battery in 9+ hours.

9/28/2010 10:01:38 AM

^ unfortunately, the cheapest is $60

like i said, i'm not looking for a charging solution...just something that will give me an extra 20-50% battery life on an extremely low-power device

it'd be cool to have around if i needed to charge my cell phone or mp3 player and i had time to wait, i guess

wouldn't a diode keep the devices from being toasted (assuming the diode is working)? and since diodes (in my extremely limited understanding) come at a cost of ~.5v AND since USB spec calls for 5v±5% (so 4.75-5.25v), the 5.5v power output of the panel should be okay...yes?

9/28/2010 10:10:40 AM

Sounds like you could use a Minty Boost. Not solar, but compact and will extend the device's life.
http://www.ladyada.net/make/mintyboost/

9/28/2010 10:47:52 AM

okay, perhaps someone who has even a basic knowledge of electrical matters can explain this to me

if the solar panel itself is rated for 5.5v at 80mA, that's the max it can deliver via direct light, yes? so if a battery has a capacity of 800mAh, that means it will take roughly 10 hours to charge, yes?

using these same nice, even numbers, let's say that the unit lasts 10 hours and has an 800mAh battery...does that mean that i could, in theory, use the unit and the battery would never drain (assuming direct sunlight and consistent energy usage by the device)? if it lasted 10 hours and had a 1600mAh battery, then it would receive a 50% better battery life if plugged into the panel during use (so it would last 15 hours before running out of power)?

now, most of these solar units have the ability to plug them into the wall to charge the internal battery...so when the solar unit (not just the panel) says it has an output of 1000mA, i assume that it's referring to charging a device attached to the unit while it's plugged into the wall (so now it's 1000mA instead of 80mA)? if this is true, the USB 2.0 spec calls for a max of 500mA and that's a little scary for the charging port of the unit to allow for twice that

and where does the voltage come in?

[Edited on September 28, 2010 at 11:04 AM. Reason : ^ aha, that's pretty cool! still $20, though ]

9/28/2010 11:00:23 AM

VERIFICATION OF ABOVE STILL REQUESTED

debating between these two:

http://cgi.ebay.com/180528629097 ($9.89)
- cheaper
- built-in 1350mA li-ion battery (smaller, lighter)
- comes with plethora of adapters
- scares me that it says it outputs 1000mA when USB specs calls for no more than 500mA (but only when plugged into the wall, i think)

http://cgi.ebay.com/290480909515 ($13.49)
- "name brand"
- US seller (more expensive, though)
- uses AA batteries instead of li-ion battery (can also be used to charge them)
- power outputs seems more realistic, safer
- bulkier, heavier, fewer adapters

9/29/2010 8:32:42 AM

sounds like you should just get another battery.

9/29/2010 10:36:59 AM

^ two problems with that:

1.) the unit is sealed to be waterproof...yes, i probably COULD cram a screwdriver in there and try to pry it open, but why would i?

2.) the goal is to extend battery life without interrupting operation

9/29/2010 11:06:35 AM

in that case, don't they make usb external batteries/power modules?

9/29/2010 11:19:13 AM

of course they do...but i doubt these are any more expensive and they have additional functionality

9/29/2010 11:28:40 AM

bump!

8/9/2011 10:39:17 AM

i got the $10 one, in case anyone cares...haven't used it

also got a AA energizer power pod (or whatever it's called) with mini and micro USB tips...haven't used it, either, but it was only $3 and the 2 included li-ion AA batteries were probably worth that

8/9/2011 10:44:32 AM

^^ thanks!

I'm in the market for something similar. I'd like something to take camping/fishing/etc that can charge my phone. I've done some googling and this seems to be the best one. It's the adventure 10 from http://www.goalzero.com/

I like the portability and the connection options plus it can also charge AA/AAA for use in other devices or to charge at night.

Thoughts?

8/9/2011 10:51:09 AM

Bttt

1/22/2012 2:32:46 PM