Thanks Gents
I’m relatively new to WA so am enjoying the wonderful new places of which I have no previous knowledge or experience. Very lucky to have the privilege.
As per Jim’s experimental results/suggestion, to give the sunflower half a chance I’ve now added a 18650 rechargeable (2600 mAh) with overcharge protection. Let’s see what happens after a day in the sun tomorrow.
The Phone was at 5% charge and the 18650 at 3.5V when connected just now. Have only about an hour of sun left in the day here.
Cheers
Michael
Edit: comment. one problem with the intermittent solar charge without battery bank is that every time the phone detects charge it turns screen on for about 20 seconds. Because this is so intermittent with solar power the screen coming on and off constantly burns any power gains resulting in negative charge. Better to have bank between panel and phone. But not sure if the 2600mAh 3.7 attached to the sunflower will adequately play that role?
With the Cygnett i never noticed the screen coming on and off whilst powering it just trickled it up at 100% constantly without turning screen on and off all the time…
Results today matched Jim’s first experiment. The 3.7 helps a bit initially, but over time the solar cannot keep up with demand and it fizzes out.
I found a smartphones app which is meant to help things (designed for use with a solar charger) stops the screen coming on and off constantly it may help I’ll try it tomorrow.
Otherwise fingers crossed one of the other regulators on order will arrive and I’ll try that too
Excellent spot Robert, we’ll likely need to increase the number of panels used, or use a boost converter to get the appropriate output. The other option (which is not advised as described by Jim below) would be to modify the Sunflower if possible, by either replacing a resistor or regulator so that it doesn’t cutoff until a lower voltage if possible, but that wouldn’t be covered by warranty and could destroy the board.
Advise against modifying the Sunflower board.
(see previous post about how much manufactures and designers put into a device to ensure it works, from Robert)
The data sheet for the CD3065 charger says input of 4.4V to 6V. LiPo’s charge to 4.2V or there about.
To adequately charge a phone or power bank via the Sunflower USB out port, I estimate a 3W panel is needed, at least. My Power bank wont charge if less than 200mA and my phone charges at 430mA (doesn’t have a fast charge mode).
If the Sunflower is used to provide USB 5V to some other device, has an attached LiPo and Solar Panel it should work very well. That is what it is designed to do. Recharge battery in sun, provide battery power when no sun.
Recently got my solar charge of phone and power bank working using a 20W Powertech panel from Jaycar and a 5V 2.5A regulator from Pololu. The 5W panel I tried did not provide enough current. Maybe the 10W would have been enough. The 20W panel is more than capable of providing enough current. I was able to get 1.3A out of the regulator on a resistive load and still maintain 4.93V. The Powertech panel outputs around 22V which works well with the regulator (6 to 35V in) but would fry the Sunflower.
I would have liked a smaller panel, the 20W is rather large. But I wanted to use the sun to charge my devices. Happy with that setup. The LiPo’s I have will use the Sunflower to charge.
Yes Yes Yes. The only way you are going to get more POWER out is put more POWER in.
You can use a boost or buck converter to get whatever output turns you on but YOU CANNOT GET MORE POWER. In fact you will lose some. It’s called “efficiency”. Remember that word? I have been flogging it to death. You will NEVER get 100% and every time you use something like this a bit (sometimes about 15%) is lost and more POWER has to be input to make up for these losses.
The nature of this project requires battery back up but using a power bank (such as my Cygnett) you straight away lose nearly 30% of the input (Solar) power and every time you introduce another device like this or some sort of converter you lose another quite large chunk and your required solar panel is getting bigger and bigger.
I really think the simplest solution here would be to have a solar panel charging a gel or lithium battery via an MPPT controller as a stand alone unit. This of sufficient capacity to do the job. Convert (up or down) to 5V to keep the phone charged. One conversion, minimum losses. Do something to deter the cockatoos or live with it. Whatever you do, if a larger capacity panel is needed is going to be larger physically. At the moment there is no way around this.
Or change a battery periodically as previously suggested.
Cheers Bob
Thanks Gents.
Yes agreed the efficiency (70% or less) of the sunflower is too low, to keep the phone alive and run this simple little app. It works okay if you turn the phone off to charge which is useless for my purpose.
The little step up converter has arrived in the mail today, it ‘claims’ >93% so I’ll give that a try in the next day or two.
Okay thanks all, completely agree efficiency is a problem.
I managed to squeeze in an extra little 0.25W panel (okay not much but everything helps) and ditched the sunflower, instead installing a little boost converter which claims 93% efficiency.
This setup is able to directly power the powerbank (which the sunflower could not). I will now attach phone and see how it goes.
Hi all
A good thing to come out of this project is that all this measuring and testing is invaluable experience. I have found that things you find out for yourself are rarely forgotten. Especially if you dig a hole due to a particular problem then climb your own way out of it.
Please keep us posted on progress and final decisions.
Cheers Bob.
Exactly, we’ll need to up the number of cells either way, or switch them out to those which have a higher power output (if they don’t match the required voltage only then will we need the converter, they’re fairly efficient devices, but sadly still have losses due to physics ) make sure to let us know how you solve it Michael, I’m curious to see how you got around it.
Thanks Gents
Watching it this morning the panel started charging power bank from 7am once fully lit by sun. Lights flashing one bar full (out of 4), let’s see what happens over next few days.
Phone is happier with power bank. App working correctly and phone not getting too hot (not constantly struggling to charge like it was when directly hooked up through the sunflower).
If this doesn’t work I noticed Bunnings have a little “Tactix 9” clear waterproof case (IP68) for less than $20 which will nicely fit something like Kathmandu’s little 5W panel. Quality is low compared to the Pelican case, but it might do the job.
Cheers
Michael
Update: After 4 days it’s running fine. I had to put some silver reflective tape on the Pelican box as I feared the phone was getting too hot (it’s okay on standby mode to about 60 degrees but not beyond).
The power bank is holding it’s own (but not going up) still at two bars(same position in which it started 4 days ago) phone is at a constant 100%. This is in about 50% sun (morning) and 50% shade (afternoon).
I discovered an App which allows you to automatically turn off phone (and back on again) at scheduled intervals. That will save us at least 50% power as I only need morning shots (4.30am - 9am). The photo capture App allows an auto-turn on at power start up. I’ll have a play with that over this weekend, it could be a game changer.
That’s excellent! I’m wondering whether there’s anything else that can be done on the phone (such as only connecting to a network at certain periods to check for notifications rather than staying on the whole time) in order to save even more of the limited power in this setup. Make sure to send through some pictures of the finished product and to submit to the create a project link from earlier if you’re interested. We’re excited to see it.
Good progress. I think everyone who has contributed to this thread is interested in the final outcome and the configuration used to achieve result. Please keep us posted.
Cheers Bob
Very good points made in this thread! Most notably testing with real world applications, and finding products best suited for the solution!
I’ll pass this through to Graham, showing all the excellent work you have all done!
For Michael,
As Bryce has stated; we are more than happy to publish your work on our site under the ‘Learn> Projects’ tab, follow the process on that page and on completion, we will be able to generate a store credit for your hard work!
The heat the Phone and Lithium batteries in general get to when being charged by a solar panel was the highest concern to me in my project. It is not the charge current but being outside in semi shade. I now have a long cable, so the solar panels are in the sun and the batteries are inside the house.
Not possible with your project, but heat should be considered, Given the stories of phones catching fire when left in the sun inside a locked car. Information I have read says to keep the Lithium battery below 50 degrees Celsius in general.
If you just want pics at a particular time of day I can think of other options that might work. Maybe they would not suit you though. ie Arduino and RTC to trigger a DSLR camera. Raspberry Pi and Camera, but resolution might not be good enough and the Pi cannot be shutdown as efficiently as the Arduino.
Anyway, your project helped me solve my own which I had shelved. It now does what I want.
Could possibly use a phone with a removable battery and hard wire it to power bank. Having said that it’s coping okay so far with the heat with reflective tape on box. We have hundreds of 18650s in trail cameras up in the hot sun and they go okay.
The reason why I chose a phone is because for the price ($150) you can’t beat the image quality, it’s just as good as a $1200 trail camera (which are not even floodproof). I can’t afford to use DSLR cameras. Raspberry Pi cameras have questionable image quality no autofocus and no inbuilt storage.
Phone (with time-lapse App) is the best solution.
This is not relevant to your project but is to phones, power banks and solar panels.
The plug pack charger provided with the phone has a communications protocol with the phone to determine the charge current. I always wondered how they could charge at a higher rate. Didn’t know that before, call me dumb, LOL
It explains why my solar panel will only charge the phone at 430mA not the 1.9A it is capable of providing. The plug pack charge provides around 1.7A to the phone. I would have to build a charger that provided the correct communications with the phone and it may vary between phones and devices. My plan to use the sun to charge my devices has suffered a set back.
Anyway just putting that out there as something I have wondered about but never researched till now.
Excellent, very excited to see how this one turns out. And it is quite interesting how fast charging works, it turns out that there are some data that gets communicated between the two devices to determine the maximum current and voltage that the connection and the charging rig can handle then switch up to it for the duration of the charging cycle (usually both the current limit and the voltage changes, although this depends on the standard) AndroidAuthority has an interesting article on it.
That’s brilliant! and exactly what this forum is designed for, glad to hear everyone has benefit from this. Have a great day!
) make sure to let us know how you solve it Michael, I’m curious to see how you got around it.
