Solar power tests

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Solar power tests

Postby BarryK » Mon 22 Sep, 2014 10:33 am

Hi,
I am a retired electronic engineer, in the late 1970s I even briefly worked in solar energy research.

I don't have access to sophisticated test equipment anymore, however, I have managed to conduct some reasonably accurate tests of some solar power systems that will suit backpackers.

For anyone who might be interested, I have created a web page:

http://bkhome.org/light/solar/index.html

The page will be probably be updated sometime.

One up:
The website will eventually have links to more pages.

Regards,
BarryK
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Re: Solar power tests

Postby icefest » Mon 22 Sep, 2014 9:10 pm

Interesting read, though it sounds like you still haven't found the perfect system. :D
If you're ever in Victoria and want to test a powerfilm r28, you're welcome to borrow mine!
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Re: Solar power tests

Postby highercountry » Tue 23 Sep, 2014 4:58 pm

Thanks BarryK, very interesting.
I really appreciate the amount of work you've put into the testing and write-up.
My interest in the subject comes from a bicycle touring perspective where I recharge various devices from an inbuilt wheel hub dynamo. I didn't realise that charging a battery and then charging a device from the battery was so inefficient, nor how the manufacturers commonly overstate battery capacity and panel output levels. Very informative (for me).
I've been toying with the idea of combining dynamo charging with a small solar setup for some time now. I'll be watching your site with a great deal of interest.
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Re: Solar power tests

Postby icefest » Tue 23 Sep, 2014 5:49 pm

I love my hub dynamo.

A good battery should have a round trip efficiency of greater than 85% (most will be >90%). I've wondered in the past whether charging unregulated 18650 cells might be better than a dedicated battery.

Now I just need to find a safe 12v MPTT solar charger for unprotected 19650 cells.
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Re: Solar power tests

Postby highercountry » Tue 23 Sep, 2014 7:04 pm

icefest wrote:I love my hub dynamo.


Same here.
In a really gadget geeky way I get a kick out of supplying my own power for a GPS, (dumb) phone, 2xAAA rechargeables for the tail light and another single AA for my low powered Silva head torch.
Five or six hours each day on the road and I can keep everything topped up. I can either charge directly to the devise/battery or else keep a 9000mAh lithium battery topping up as I go.
I use a Busch and Mueller EWerk, a purpose built rectifier which also has controllable Voltage and Amperage output.
It's a great system. Over a typical one to two week tour I am completely self-sufficient from a power point of view.
I haven't toured yet with my new camera and iPad Mini but I doubt very much I can pedal-power them as well. That is where the addition of a solar panel is of much interest.
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Re: Solar power tests

Postby icefest » Tue 23 Sep, 2014 10:31 pm

I just bought the EWerk for my mother for her touring bike. :D
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Re: Solar power tests

Postby highercountry » Wed 24 Sep, 2014 7:24 am

Ha, ha, icefest. Combine light(ish) weight camping with cycling and a whole new universe of gear and gadgetry opens up.
Of course all of it it absolutely essential to survival. :D
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Re: Solar power tests

Postby keithy » Thu 30 Oct, 2014 11:22 pm

Barry - There's a good website blog you should check out - http://www.crazyguyonabike.com/doc/?doc_id=9258. He's being doing tests on various panels for a while, and there are good reviews there from other users as well like http://www.crazyguyonabike.com/doc/?doc_id=8860.

I have currently got a few 7W and 13W Goal Zero panels, a 10W Instapark Mercury panel and various USB chargers for AA/AAA batteries. I've also been testing my kit mainly last year before I went to Nepal for a month. I had used a stripped out USB cable conected to a multimeter, then connected to whatever I was charging to test the current output, but have also bought a few of the Charger Doctor usb gizmos that work well.

In the old days (around 2004-5) I had tried I think it was 3W iSun ICP Solar and Sunforce folding solar chargers, but the current output was really low (was 12V output to a cig lighter connector), and then bought a Brunton 3.5W panel, and a flexible Coleman 5w panel but the outputs again were so low charging AA/AAA batteries and USB lithium ion battery packs was painfully slow.

But with my current kit, I pair either the 7W or 10W panels with a 5000mAh lithium ion USB battery pack, and a USB AA/AAA charger - I have both Goal Zero Guide10 Plus AA charger, which when paired with the Goal Zero solar panels can use a dedicated pin socket to provide a higher unregulated current to the charger, so in theory the batteries charge faster. However, the hassle with the Guide 10 plus AA charger is that you HAVE to charge 4 batteries at once, you can't do just 2 at a time. You can still use the USB output to micro USB input on the charger, it will just be slower. I have also bought Fujicell SCH500 AA USB charger (www.youtube.com/watch?v=fTVaeG6QJxE‎) instead of the Goal Zero Guide10 Plus charger, as the Fujicell would let me charge 2 AAs at a time instead of 4. I used it mainly for recharging AA batteries in my UV water filter, GPS handheld as well as headlamp/torches.

I took both a 7W and 10W panel on the month trip to Nepal where they both functioned well on two separate 2 week treks. The 7W panel without charger weighs about 350gms, and the 10W panel adds another panel and is about 450gms but is quicker. Given that I didn't use the Goal Zero AA charger, I will just take the 10W panel.

For reference, my Goal Zero 7w panel charges a 5000mAh battery from empty to full in about 10 hours (over 2 days). Via USB the Goal Zero outputs 5V at about 0.5A (this is for my version bought in 2012 – I think the latest version has upgraded the circuitry and now outputs 5V at up to 1A). My 10w (Instapark Mercury 10) panel cuts that time down to about 5-6 hours as it outputs a higher current, and a 13w panel (Goal Zero 13) brings it down to about 4-5hrs, which can output up to 1A. The 7w panel fully charged a Sony camera battery (1000mAh) directly via USB to the camera in about 2 hours in direct sunlight.

As an aside, I found it interesting with the Charger Doctor to notice the quality and length of USB charging cables and the impact it has on the charging current. So I have used the Charger Doctor to test and separate my various charging cables and keep the ones that let higher currents through to the connected device (these are usually thicker and shorter cables)
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