Black Lives Matter - Action and Equality. ... Adafruit is open and shipping.
0

USB, DC & Solar Lipoly charger
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Re: USB, DC & Solar Lipoly charger

by kje on Mon May 07, 2012 5:47 pm

john444 wrote:KJE,

Since you are on a different topic, let me suggest that you start a new thread or contact me directly.
If your new project is not using Adafruit products then off forum might be better.


I sent you a PM. :)
kje
 
Posts: 18
Joined: Sat Apr 07, 2012 8:02 pm

Re: USB, DC & Solar Lipoly charger

by maxima on Tue Jul 31, 2012 12:14 pm

john444 wrote:Hi KJE,

Solar panels are expensive so I understand your desire to use what you have.
These two suggestions presume that your panel is fairly small, say ½-A or less.
And they are wasteful since you will be throwing away 1/3 of the power of your panel.

Simplest is to series 5, or more likely 4 diodes. Could use any of the 1N4000 series. They are inexpensive.
The next possibility is to use a 6-V regulator. It would just go between the 9-V panel and the charger.
Either suggestion will allow you to use your 9-V panel with the Solar charger.

If your panel is in the neighborhood of 100-mA then a 6-V zener diode would work.
No need for a series resistor since the panel limits the current.
Panel mfg are generous with their ratings.
Try these suggestions but, if the diodes get hot resort to the regulator.

Good Luck


I actually did this for some 12V Panels. I also added a LED (+ 50ohm resistor, in case) to let me know when the circuit was kicking-in. You have to add-up all the voltage drops to get ABOVE the level used by the charger which is around 4.5V (at Vin). I used a 3.3V Zener+LED+Resistor which adds-up to 3.3+2+1=6.3V (Max is 7 at Vin). So when charging, the current at full sun is ~75mA at 4.5V (instead of ~12V, so not terribly efficient, but useable in a pinch) and the LED is OFF, when the charge is complete (or you unplug the battery) the LED comes on and saves the charger from being blown if your load doesn't draw enough to bring the panels below 7V (in my case it idles at 3mA with bursts of 200mA).
maxima
 
Posts: 1
Joined: Tue Jul 31, 2012 11:55 am

Re: USB, DC & Solar Lipoly charger

by chimo on Wed Aug 01, 2012 8:33 pm

I see that this product has an in stock time estimate of 15-20 business days. It seems to have been sitting at that time estimate for a while. I signed up for the notification email, however, is there a better estimate for availability? Thanks,

Paul

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Re: USB, DC & Solar Lipoly charger

by john444 on Wed Aug 01, 2012 9:54 pm

Hi Maxima & Chimo,

Although it is 'possible' to operate the solar LiPo charger on a panel rated over 6-V,
if you review the previous posts you will see where it is not really advisable.

The power output of a solar panel is not great anyway.
When you throw away major percentages of the available power,
(IMHO) it becomes not worth the trouble. It takes way too long to charge.

However, there are those who want to try things for the experience
or to use the parts they have on hand and I encourage them.
But, if you are going for effect - use the proper panel.

Good luck with your projects, John

john444
 
Posts: 443
Joined: Sun Mar 04, 2012 2:42 pm
Location: Claremore, Ok

Re: USB, DC & Solar Lipoly charger

by chimo on Wed Aug 01, 2012 10:40 pm

I have a Nomad 7 solar panel from Goal Zero that I picked up before a recent camping trip. It has three outputs:

1. Standard USB @500mA
2. ~12V @ ~200mA
3. 6.5V at ~1000mA (basically direct output from the solar cells - intended for their Guide 10 Battery Charger)

As you can see, outputs 1 & 2 take some serious efficiency hits (50%+).

There are 13 segments in the cells rather than 12 in each panel for the 6.5V rather than 6V.

I also picked up an iSound Portable Power (brag sheet says 16,000mAh battery), it's kind of flakey for charging off of the Nomad 7's 12V output unless the sun is strong. Charging for the iSound is 12V @1A. It will charge on less and will will continue to charge until current drops to around 150-160mA.

Rather than rip apart the Nomad 7, my intent is to draw off the Guide 10 output and feed a homemade battery pack w/ USB output. I ordered some cheap USB boards from DealExtreme (DX) that say they will supply 1000mA but I am very skeptical of most of the specs put on DX products. (I will test them to see if they come anywhere close to their specs.)

Mostly, just doing it for fun. :)

Cheers,

Paul

john444 wrote:Hi Maxima & Chimo,

Although it is 'possible' to operate the solar LiPo charger on a panel rated over 6-V,
if you review the previous posts you will see where it is not really advisable.

The power output of a solar panel is not great anyway.
When you throw away major percentages of the available power,
(IMHO) it becomes not worth the trouble. It takes way too long to charge.

However, there are those who want to try things for the experience
or to use the parts they have on hand and I encourage them.
But, if you are going for effect - use the proper panel.

Good luck with your projects, John

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Re: USB, DC & Solar Lipoly charger

by chimo on Wed Aug 08, 2012 9:36 am

A used board I picked up off a member here arrived yesterday and I gave it a quick try last night.

I threw on a 17670 Li-ion and used the solar output from the Nomad 7 panel. I wasn't expecting much in the way of charging current as I tried it after dark and lit the panels with only a couple of low wattage bulbs. I got about 75mA charging current. Shading one panel dropped the curent to around 30mA. I will try it in full sun when I get a chance. I have yet to profile the panel's output.

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Re: USB, DC & Solar Lipoly charger

by chimo on Tue Aug 21, 2012 1:51 pm

Back in stock! 48 left (now).

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Re: USB, DC & Solar Lipoly charger

by john444 on Tue Aug 21, 2012 7:26 pm

Hi Chimo,

The Nomad 7 panel is pretty nice. At 7-w, the $100 price puts me off somewhat but reviewers say the found it for $60.
IMHO $10/watt seems to be about the going rate for packaged solar panels. $5/watt would be a bargain.
Just for comparison, the Adafruit 1-w is $10, 2-w is $25, 3.4-w is $35 and the 3.7-w is $30.
But, note: the 1-w & 3.7-w are unmounted panels while the 2-w & 3.4-w have a rigid alum back w/ mounting studs.
I am kind of cheep, ah, - I mean frugal. I use the 2-w panel and leave it in the sun until the 'done' LED comes on.
I seem to go through spells where I charge the dozen or so LiPos I have over a weekend, changing them when I think of it.

To deal with the 6.5-v to 7.0-v rating of the Nomad 7, I would add a series diode between the panel & the LiPoly charger.

chimo wrote:I have yet to profile the panel's output.
I really like your idea.
How can we do this so that my results will be comparable to yours?

John

john444
 
Posts: 443
Joined: Sun Mar 04, 2012 2:42 pm
Location: Claremore, Ok

Re: USB, DC & Solar Lipoly charger

by chimo on Mon Aug 27, 2012 10:02 pm

john444 wrote:Hi Chimo,

The Nomad 7 panel is pretty nice. At 7-w, the $100 price puts me off somewhat but reviewers say the found it for $60.
IMHO $10/watt seems to be about the going rate for packaged solar panels. $5/watt would be a bargain.
Just for comparison, the Adafruit 1-w is $10, 2-w is $25, 3.4-w is $35 and the 3.7-w is $30.
But, note: the 1-w & 3.7-w are unmounted panels while the 2-w & 3.4-w have a rigid alum back w/ mounting studs.
I am kind of cheep, ah, - I mean frugal. I use the 2-w panel and leave it in the sun until the 'done' LED comes on.
I seem to go through spells where I charge the dozen or so LiPos I have over a weekend, changing them when I think of it.

To deal with the 6.5-v to 7.0-v rating of the Nomad 7, I would add a series diode between the panel & the LiPoly charger.

chimo wrote:I have yet to profile the panel's output.
I really like your idea.
How can we do this so that my results will be comparable to yours?

John


John,

I will probably do a simple test as indicated at this web-site. http://www.ehow.com/how_8708794_measure-solar-cell-iv-curve.html

I'll try to do it on a clear, sunny day and will likely try another curve or two with artificial light.

Paul

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Profiling Solar Panels

by john444 on Tue Aug 28, 2012 2:26 pm

Chimo,

Measuring the open-circuit voltage (Voc) and short-circuit current (Asc) will set a panels limits.
However, Voc & Asc are a long way from useable power output.
The maximum-power-point (Vmpp & Ampp) values are more useful but rather difficult to measure.
Lady Ada showed that we can approximate the mpp by using a fixed voltage load.
It may be practical to use the solar-charger as a load for small 6-v panels.

I propose we try to achieve 1% accuracy. 1% should be good enough for most applications.
Also, while measuring the Voc is pretty easy, it is more difficult to get good Asc readings.
And, I am not sure how to measure solar intensity within 1%.

Any Ideas?
John

john444
 
Posts: 443
Joined: Sun Mar 04, 2012 2:42 pm
Location: Claremore, Ok

Re: USB, DC & Solar Lipoly charger

by chimo on Tue Aug 28, 2012 7:24 pm

John, it will be pretty difficult to do a real comparison between the panels unless we have the same calibrated light source.

The Nomad 7's USB out does a pretty good job of charging an iPhone even with mediocre light, however, I am not impressed with the loss of half the raw output of the panel - the USB out is limited to 500mA (2.5W). If I can get 75-80% of the PV panel output (~5W peak) to some Lithium-based cells, I will be happy.

I have not torn apart the Nomad 7 (yet) to see what they are using to drive the USB and 12V outputs, however, the documentation states that more than one output can be used at once. The panel assembly is water resistant so it may be coated or potted. I will likely wait until that "new panel smell" wears off.

Paul

chimo
 
Posts: 10
Joined: Wed Aug 01, 2012 7:44 pm
Location: Ottawa, ON

Re: USB, DC & Solar Lipoly charger

by john444 on Tue Aug 28, 2012 9:32 pm

Paul,

Let's start a new thread.
This one is getting very long and we are actually off topic.
I have some other ideas i would like to bounce off you.
How about "Profile Solar Panel output"?
See you over there.

John

john444
 
Posts: 443
Joined: Sun Mar 04, 2012 2:42 pm
Location: Claremore, Ok

Please be positive and constructive with your questions and comments.