Agree. The Sunflower, while good, would not suit for what Michael wants. I hope my testing today showed that to be correct. For my purpose it is perfect and I have it now setup to work as I originally wanted it to. Thanks to this post.
With respect to your previous post, Bob, agree, all valid concerns I had too. Careful considered of available current levels is needed.
Cheers
Jim
Thanks guys
Im not sure but I think you are ivercomplicating the maths.
The Phone is using 420mA over 24 hours. So we need input of about 17.5 mA / hour average to maintain.
If we get 200mA out of the solar panel (tested by Jim at 280mA in full sun) for 2.5 hours a day, we are good yes?
Cheers
Michael
Hi Michael,
The specifications for the 2W Solar Panel 80x180 (Seeed Studio) is 360mA at 5V. My measurements showed 4.4V, 267ma to 313mA from the solar panel when the LiPo was charging. The 4.4V remained pretty consistent.
The voltage regulator you linked above is a DC to DC buck converter. The datasheet for the chip shows it to convert a higher voltage to a lower voltage; the level determined by components external to the chip. 5.5V to 20V in producing 5V out for a USB port. Any solar panel you use would need to be rated at higher than 5V for the regulator to work. Two of the Seeed panels in series might work. But I am predicting just one would not. (btw the chip data sheet does not mention solar usage)
Something to consider.
As to the maths. My testing showed the Power bank needed 200mA at least to start charging. If phone connected to power bank draws 17.5mA then 280mA should be enough to replace the charge over a few hours as long as there is direct sun. Cloudy rainy conditions would mean longer charge time but if the available current dropped below 200mA, the power bank might not charge at all.
I am unsure how a power bank would behave if it was being charged and also powering a device. I don’t know if the internal charge circuit can handle that situation. I think there are power banks that can be used that way. The solar panels and power banks from Katmandu could be connected like that, I was told by the sales person.
Cheers
Jim
EDIT: Tested the power bank I used yesterday. When on charge, the USB out port is disconnected.
Thanks Jim
All good the power bank I have charges and powers simultaneously (Cygnett).
The buck converter agreed could be an issue. One way to find out, when parts arrive I’ll give it a run. According to the core electronics site the typical voltage 2W solar panel 80x180 is 5.5v ( up to 10v in full sun) which is theoretically perfect. Strange that you saw consistent 4.4V. Was that going into or coming out of the Sunflower?
The proposed site (NWesyern Australia) is VERY sunny.
Cheers
Michael
Hi Michael
Yes in the dry season and probably pretty damn wet in the other season (depends on how far north I suppose).
If I had known where you are I would not have suggested ducking into Jaycar to discuss the product I suggested. Probably not very practical to do that.
When working out your power bank back up time have you actually checked the mA/hr capacity of yours. I think some of the documented claims are pretty optimistic. For instance I have one claimed 50000mA/hr but could not possibly contain more than 5 X 18650 batteries. Equates to 8000 - 10000 max. Did not work anyway so got a refund.
Michael if you are assuming everything is 100% efficient then I think you maybe looking through the proverbial rose tinted glasses. I don’t think 200mA will be anywhere near enough and I personally would look at something closer to 1A. But that is me.
Well that is pretty much all I have to offer and I wish you all the best of luck. Please keep us informed how you get on. Particularly long term .
Cheers Bob
Thanks Bob
Appreciate your and Jim’s help and advice, you may be right, let’s run the prototype and see how it goes.
I’m in Perth so no problems to chat with in store staff if needed. I FIFO up north half a dozen times a year.
I’m just hoping I can use a smaller panel because it will fit inside a waterproof box and I won’t lose it at field site in Kimberly when the big floods come. The trail cameras previously used are not doing the job (not floodproof, expensive and poor image quality).
But let’s see if any prototype works prior to deployment agreed. It’s fun trying : )
Cheers
Michael
Correction to above. 5 x 18650 batteries might be up to 13000mA/hr 9but not 50000).
I too have a Cygnet rated at 15000mA/hr, would hold 6 batteries so probably real. I will charge up and see what the capacity really is. I do know I tried to use it as a power supply once and found you have to have a load of 300 - 500mA to get a “clean” 5V.
You also have Altronics, used to be in Roe St. Don’t know where now.
Cheers Bob
Hi Michael,
With respect to the solar panel output voltage.
The 10V they talk about is the open circuit voltage, nothing connected to the panel.
Previous testing last year. (today cannot test due to rain, no direct sunlight)
Measured with multimeter, open circuit voltage 6.31V.
Connect to a charging device, no battery, drops to around 5V.
Connect a battery, drops to 4.5V approx.
All voltages measured at the Sunflower solar input.
Regards
Jim
Sunny day today, did some more testing on the Sunflower, more for my own interest.
There were some flaws in what I did the other day so I wish to correct them.
The Sunflower will work without a Battery, up to a certain level.
150mA from the 2W solar panel (231mA input).
2W solar panel not connected to anything. 6.78V.
6.78V dropped to 6.3V over 10 minutes.
The drop slowed from 0.2v for first minute to 0.03V last minute.
If it was in shade and then placed in the sun most likely the volts would be a lot higher, up to the 10V mentioned by the manufacturer.
Solar panel 5.04V when charging LiPo not 4.4V as previously stated.
The current out of the solar panel is very much determined by the angle of panel and position of sun in the sky, as you would expect.
Cheers
Jim
Thanks Jim
The Sunflower has now arrived and I’ve got 2 other voltage regulators still in transit:
Once all the regulators and panel arrive (early next week hopefully) I’ll give them a run.
Cheers
Michael
Hi All
While things have been a bit quiet the last few days I carried out an experiment with my power bank
This may be of interest to followers of the current topic so I share.
I point out that I only carried this out once. Maybe should be done over several cycles.
Measurement device: Ruidig AT34 USB Tester. This device displays instantaneous Volts , Amps, load Resistance also a running total of mAh and equally importantly mWhr.
Power Bank: Cygnet / 15000mAhr. Cygnet state in their blurb that this is the BATTERY capacity (at 3.7V).
Also printed on the device is capacity as 55.5Whr (55500mWhr)
Firstly discharged at 490mA until shut down.
Charged until shut off: About 9hrs. 12560mAhr. 64283mWhr.
Discharged at 490mA until shut off. About 19 - 20hrs. 9336mAhr. 46760mWhr.
This tells me that I need to put 64283mWhr into the power bank to get 46760mWhr out.
This equates to approx 73% efficiency.
By making a couple of assumptions this can be disected into charge efficiency and discharge efficiency.
The end user will be interested in how much power needs to be put in to replace the power discharged at the output end. As the re-charging or replenishing voltage will probably be different to the output voltage the power figure would be the unit to use in estimating. As I pointed out earlier the efficiency of some devices can be significant and need to be considered. This is actually a bit of a surprise as I would have expected something like 85%. You will never get any where near 100%. Might be why this figure seems to never be published.
Cheers Bob
Thanks Bob, most interesting!
Still waiting on voltage regulators to turn up so I can test them. The core electronics 2W panel has arrived.
Cheers
Michael
Hi Bob,
Thanks for the info.
I have come to the conclusion some specs are taken in the most ideal of situations, like a laboratory or such. The solar panels I tested are a good example. This is why testing done by people like us is important, it gives a real world perspective.
cheers
Jim
You can get a “real world” take on things. If not in the public domain a reputable manufacturer will or should provide this sort of info if required. I recall the last project I helped look after for AWA required that de-rating to be applied for an ambient temperature of 50 Deg C. Try getting that number publicly published. Philosophy here is if the info not forthcoming you can’t or won’t buy it. The contract specs demand you have this info. Swtchmode power supplies were surprising. Where normally a 100 Watt supply would be required this quickly became 150 or even 200 Watts. If you want something to work properly you just cannot disregard some of these things and hope the problem will go away.
Cheers Bob
Hi Jim
Am a bit disappointed to see you make a statement like that.
Firstly specs are usually written/negotiated before any design/lab work takes place. After all the design team has to have an end goal otherwise they could be designing a product that will not meet any customer requirements. Could be massaged/fine tuned during design/lab phase due to circumstances arising during this period. May or may not have a small manufacturing pilot run to prove design/manufacturing process. The whole thing then turned over to manufacturing/test room control.
A good design lab and test room will have access to test equipment the “average” hobbyist or enthusiast can only dream about. What’s more and very important is that this equipment is CALIBRATED periodically. Used to be “active” equipment every 12 months and “passive” (wattmeters etc) every 5 years. Don’t know what to-day’s requirement is.
A quick example. When I worked full time we had occasion to demonstrate the importance of unwanted stray inductance. A fitter had left bypass capacitor leads full length instead of cutting short. We were able to measure the inductance of a 50mm straight piece of tinned copper wire. Namely the capacitor lead. It was only picoHenrys I think from memory. The point I am making the equipment was available and we were able to measure it. Not really the sort of thing you could expect to do in a home workshop.
I will not comment on this again as we are digressing from the original problem but I must say in closing. If I were given a piece of equipment with 2 sets of test results with differing entries, 1 from a recognised test facility and another from a well intentioned unknown enthusiast/hobbyist with unknown facilities and unknown test eqpt calibration status I am afraid I know which one I would have to believe.
If anyone would like more examples and would like to start a new thread I would be happy to oblige.
Cheers Bob
Hi Bob,
Thanks for your reply.
Fully understand how specs are measured and accept the manufacturer information.
My point is, when deciding to buy a Product, a review from someone else that has bought it, helps. It gives a practical real world experience. Sometimes these reviews can be biased and incorrect I understand that too.
Absolutely agree, I would take the Manufacturer specs any day over what I could produce myself.
regards
Jim
On a field trip to Southern Cross for a week. No progress unfortunately. Will update when possible.
Rain delayed field trip so home to play with electronics : )
Hooked up 2W panel to the sunflower regulator (solar in Port) and connected phone to out port (via USB port supplied). Solar panel is behind clear Pelican case lid.
Phone immediately recognised charge and indicated charging (displayed lightning bolt). There was no requirement to add a separate 3.7 battery to the sunflower (it works without it).
Phone charging very slowly going up 1-2% an hour. Slightly disappointing but at least it’s not going backwards!
When alternative regulator arrives I’ll give that a go too (Australia Post is snail like slow…).
Cheers
Michael
Hi Michael,
I found the Sunflower would work without a separate battery, but the current is less than ideal.
2W panel about 150mA, 1W panel around 90mA.
The power bank I used would not charge on these levels.
My phone operated but charge is very slow as per your experience.
I assume the phone only charges when the available current is more that it needs to operate.
Cheers
Jim
Hi Michael
I purchased one of these “Sunflower” devices but have not had a play with it yet.
If you look up the relevant page in Core’s website and go to the bottom of the blurb you will see 2 links in blue. Select one of these (they both end up at the same web page) and you will have some more specs. DFRobot very kindly publish efficiency figures which will go a long way towards explaining your disappointment at the low charging rates. Have not delved into this area at all but I was quite surprised at the charger efficiency (73%). I thought MPPT controllers were better than that.
I know I have been harping on this “efficiency” thing for a while but please don’t fall into the trap of ignoring it and wonder why things don’t work as expected.
When measuring things like this because of the different voltages involved I find it easier to use power units (Watts, Milliwatts) down through the system then convert to Volts, milliamps (Amps) or whatever you need at the end. Like adding and subtracting decibels to get to an end result. So much easier. When you use the one unit you can more easily see where any energy may be lost.
Looked up where Southern Cross is. You seem to get to some interesting places. Back in mid 80"s I assisted with a tender for a project which involved 103 earth satellite stations. One was Warburton (about 700k from Leonora towards Alice Springs, one was Balgo Hills (a couple of hundred ks south of Fitzroy Crossing) and another (forget the actual name) 190k west of Wyndham, nearest phone Gibbs River . I suspect you could be familiar with these places. We (AWA) did not win that tender.
Cheers Bob
Just found it. That place was Doongan
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