new tests with NiMh solar charging

Skyko · March 2010

I have been tinkering with a few items in preparation for possibly designing my own smart solar NiMh charger (maybe charge LiFePo too). I made a couple of interesting purchases I would like to share.

The first is a two cell AA NiMh car charger on clearance at Radio Shack for $1.47 It claims on the package to be a fast smart charger with overcharge protection. It has an input range of 12 to 24 volts at 300mA and an output of 1.5V 800mA x 2 (on the package). I took it apart immediately (actually in the parking lot of the Rat Shack) and noticed it uses the same 34063 DC-DC converter IC that some of my other cell phone chargers use (a good part). It also has a 16 pin surface mount dip labled Samya L5568 which must be a proprietary microcontroller designed (or just relabeled) by Samya. I didn't notice any thermister or low ohm high wattage current sense resistor so I am unsure how they are measuring when to shut off (DV drop maybe?). I found the website of the manufacturer here: http://www.samyatech.com.tw/eportal/modules/shop/index.php?main_page=product_info&products_id=27 and they still seem to make a version of this charger.

I have it plugged in right now and charging two 2300mA batteries using a 12V bench supply (no sun out today). It is drawing about 0.24 amps at 12V but in a rather funky pulse fashion (it draws 0.24 amps for about 1/2 second then drops down to about 0.14 amps for a fraction of a second then back up to 0.24 amps). I bought two of these chargers (big spender!) and both do the same thing so it must be some function of the charge cycle.

The second and perhaps more interesting item I bought is a Brunton Inspire USB rechargable 11 watt-hour LiPo battery module. It has a built in USB input charger for the internal LiPo and can also charge other USB devices at up to 1 amp at 5V. It claims to be made for solar charging also (and Brunton does make a lot of the portable solar panels). It came somewhat charged and I was impressed how much it charged up my Nexus One android phone (from 50% to 100% in about an hour). It also looks like it might be a good candidate for solar charging. I hooked it up to my bench supply simulating a very cloudy day (5V at 200mA coming out of the DC-DC converter which would be about 1 watt out of my 14 watt panel). It actually was able to use this tiny bit of power over about 3 hours to bring the LiPo up from 50% to 75% charge. This is a good sign as I want to get whatever sun is available when hiking with the panel draped across my backpack. I then set the bench supply to simulate full sun and the 5V 1amp DC-DC cig lighter charger the Inspire came with charged the LiPo from 75% to 100% in under 1 hour. At first I was unsure if it would actually shut off but I am just now seeing the current draw from the bench supply drop from about 12V at 500mA down to under 100mA now. It must do some sort of topping off charge after it is indicating 100% capacity by the crude 4 led indicator. Anyway, this $40 4 ounce module is looking quite promissing.

here are some pics of the two items:

niel · March 2010

Re: new tests with NiMh solar charging

it's nice you are delving into this aspect and some have popped onto the forum in search of the same answers and options as you are. i may need to see if i can get any of those discounted chargers for myself.:D:cool: trouble is, it requires 2 cells in series and i love those that charge the cells individually. 2 cells may also be too limited as many devices require more than 2 cells, but for the price it's nice.
i look forward to reading more on your investigations and trials.

Skyko · March 2010

Re: new tests with NiMh solar charging

I did a little more testing on the Brunton Inspire USB charger/battery module. At a very low voltage input (around 3.5V) the four blue leds come on but the charging lightning bolt indicator does not flash. The current draw at 3.5V is negligable (under 1mA). If you crank the voltage up to about 5V the charging indicator starts flashing and the Inspire starts absorbing current (the current jumps to about 90mA at 5V into the DC-DC cig lighter adapter that is hooked via usb to the Inspire. I haven't measured the voltage and current between the Inspire and the DC-DC adapter but I would take a guess at about 4V 80mA or thereabouts. So the Inspire will charge off as little as 1/2 a watt from a solar panel, which is good. Instead of directly charging my Nexus One, which probably wouldn't even activate the charging cycle at only 5V 90mA, I can charge this battery during an overcast day, still gathering 3 to 5 watts then dump it into my Nexus One at night.

If I went with the 14 watt roll up panel at 14 ounces and this battery module at 4 ounces that would be 18 ounces, or about 18 AA batteries. I would need to gain about 36 watt hours from the setup to offset the extra weight over just bringing a lot of charged batteries. Definately a setup that would pay for itself (in weight) on a 2 week hike, but debatable if it is a bit much to carry for 1 week or less. Perhaps the 6 watt 7 ounce panel would be better for shorter hikes...

RWB · March 2010

Re: new tests with NiMh solar charging

I have played around with Solar Charging these small devices alot. And it seems there are tons of combinations that simply just do not work very good.

The Powerfilm Solar USB AA Charger simply does not reliably fully recharge your batteries, it says they are fully charged way before they actually are charged, its very frustrating but it simply did not work well enough for me. Plus you can only get power out of the USB Port if the Batteries are Charged. No Direct Solar to USB Output Which sucks if all you need is to charge your phone.

Learned alot about these small systems.

What you need to look out for and test is how the battery reacts with the Solar Panel you plug into it. I think the Black New Trent Labeled Battery was the best I had found for $30 and it had a 5400mah 3.7v Battery in it which would give you 3.5Ah at 5v once the battery voltage was upped to 5v. The only thing I didn't like about it was that when the sun went down the unit would stay powered on until somebody hit the power button to turn it off. It was draining power while it was on. So if you left it out to charge all day its going to stay on until you shut it off and I didn't like that. I wanted it to just charge while the panel put out enough power to do that and then shut off when there was no input power. I wonder how that Brunton battery you have handles the solar input as the panels output fluctuates through out the day.

All the other batteries simply did not store enough energy for me to think it was really useful. The Powerfilm AA charger would give you .75Amp Hours at 5v on a fully charged set of AA Batteries.

I found that a Powerfilm 10W panel with the Cigarette Lighter Adapter was perfect for plugging in all your Cigarette Lighter Chargable Devices that pulled less than 1Amp. The panel is super small and lightweight, durable, and is easy to tilt towads the sun for max output which is critical if you are really wanting the most charging current.

I consider this the BEST USB Charger Available, well its about to be released soon. Hell it even has MPPT Built for the 1 solar cell for maximum charging current. Check it out http://www.solarjoos.com/

Here is some pictures of some of the smaller systems and panels I played around with last summer. Figured you might enjoy them.

http://picasaweb.google.com/RWBRWB/20090809?feat=directlink

Skyko · March 2010

Re: new tests with NiMh solar charging

Hmm that new Orange device looks cute but at the basics it is still a 2.6 watt solar cell unit that weighs 24 ounces! Cool that it works underwater...I wonder how they get the mini usb connector waterproof.

I like your pics! I have some similar panels to yours, a Brunton 6 watt foldable, a Brunton 26 watt foldable, and a Powerfilm 14 watt rollable. Both of the Brunton panels are CIGS technology, which I believe has a better efficiency than the Powerfilm rollable, but the rollable is much more durable. All three are about 1 ounce per watt.

The new Brunton Inspire battery/usb voltage output/charger does shut off automatically when fully charged and also shuts off when the device it is attached to stops drawing power. It really seems to have been designed around solar charging since it will charge at such a low power input. I think pairing it with the 14 watt Powerfilm will create a charging solution just over 1 pound that can keep all my lights and electronics charged on an extended hike. I am glad I never went with the Powerfilm USB/AA charger (was tempted at one point) since you seem to have found it weak.

Thanks

RWB · March 2010

Re: new tests with NiMh solar charging

The Joos Orange looks to be awesome! Its more than a 2.6W Solar Cell, Actually they say that the max panel amperage output at 3-4V is 2.6 Amps which means it should fully recharge the replaceable Battery in 2-3 hours when put in direct sunlight.

Its a Solar Cell, Solar Charge Controller with MPPT, 5400mah 3.7V battery which will probably end up giving you 3.5Ah at 5v after its converted from 3.7 to 5V. I've tested other 5400mAh 3.7V batteries that do the same up conversion to 5v and I consistently ended up with 3-3.5 Amp Hours at 5V out of the USB Port. I do not understand why these companies do not just publish real world USB 5v Output Ratings instead of the larger numbers after its converted. I guess 99% of people do not understand how to check it anyways. Oh and that Orange also has Software so you can actually read the solar input in Watts live, it will log the solar input over time and display it, it will also show you your batteries State of Charge via software that you can plug into your Iphone or PC which is really cool, especially since its only going to be $100. It Sounds Perfect to me. Can't wait to get my hands on one. Tried to get one for a Early Review but no dice, only a few for press to review and write about only.

Yea the Brunton panels use Global Solar CIGS Solar Cells that are 7% Efficient. Powerfilm is 5-6% Efficient. I would prefer a 10 or 20W PF Foldable Panel over their rollable panels simply because the foldable panel fold up to super small sizes are they are very durable. I have a 10W panel I have had strapped to the back of a lawn chair outside pointing towards the sun and its been out side for 6-7 months now because I'm testing how well they hold up over time. After a full winter the 10w foldable panel still looks like new, I see no signs of wear so far.

Your 14W Power Film Panel should be perfect to charge your Brunton USB Battery Pack via the panel to Cigarette Lighter Adapter PF sells or gives with their panels.

Let me know how the Brunton Battery pack works out. How many Amp hours is it?

The automatic shut off is nice sometimes and a real pain in the ass when your powering devices that have low current draw like my Sony WideBand Radio that pulls such low current the Mini Gorilla would automatically shut off in 1 or 2 mins and then I'd have to turn it back on over and over gain basically making it unusable.

Anyways I love portable solar power systems, the smaller the better.

Let us know how it goes after testing it out for awhile.

mike95490 · March 2010

Re: new tests with NiMh solar charging

in the photo, it looks like a single .5V, 4A PV cell, maybe it powers a DC-Dc converter, or maybe it's just a mock-up. Just 2 watts any way you slice it.

RWB · March 2010

Re: new tests with NiMh solar charging

Yea I'll put it to the test as soon as I can get my hands on one.

maybe it is a Mock up and there just testing out the market.

I want one that's all I can say.

Skyko · March 2010

Re: new tests with NiMh solar charging

Well yesterday was the first day of (albeit hazy) sunshine and so I did a complete cycle test of a fully drained Brunton Inspire LiPo USB module charged through the included DC-DC car adapter (up to 5V 1amp out) powered by a Powerfilm 14 watt rollable panel. At 10 am I started charging the 11WH LiPo and noted about 2.5 watts going into the car adapter from the panel. This climbed to about 5 watts at 1pm and the Inspire was fully charged at around 1pm although it did a slowly decreasing topping charge until around 3pm when it shut off and would take no more current. I had the Brunton Solaris 26 watt foldable CIGS panel outside at the same time dumping into a 13 ohm resistor and saw a bit less than double the power of the 14 watt panel so both were performing similar in the hazy sun.

I then hooked the fully charged Brunton Inspire up to my Nexus One smartphone which was at 18% capacity and in a little less than 2 hours it was at 100%. The Inspire still shows 3 leds lit which indicates somewhere between 50% and 75% capacity left. Thus fully charged it should give about 2 full charges to the N1.

The total weight of the 14 watt panel, adapter, LiPo module and Nexus One smartphone is under 2 pounds.

I want to add a final bit of kit to my setup, this Sanyo AA/AAA usb two cell NiMh charger. It uses an Atmel microcontroller to do smart charging of 1 or 2 cells off of USB 5V at up to 500mA. It charges 1 cell at 850mA or 2 cells at 450mA, so does DC-DC conversion inside. I found it for $14 and it weighs just a bit over 1 ounce.

http://us.sanyo.com/dynamic/product/Downloads/USB_Instruction_Manual-27295019.pdf

RWB · March 2010

Re: new tests with NiMh solar charging

Glad you found a small battery that correctly solar charges.

Here is a 6.8 Amp Hour/100 Watt Hour Battery that has 5v USB, 3v, 5V, 9V, 12V, 16V, 19V, 21V, and 24V outputs.

I am charging with a 30W Solar panel that has a Voc of 26V, I would perfer to charge with a Powerfilm Panel but they do not put out high enough voltage to properly charge the internal battery. The PowerFilm panels will only charge 1/2 to 3/4 of the way full.

So far this is the most powerful and universal super small portable solar rechargeable system available that I can find. It can provide power for just about any small electronic device you could find. What I like most about it is that it will simply just blow away all the other smaller battery systems out there capacity wise.

BB. · March 2010

Re: new tests with NiMh solar charging

By the way, in the photos from RWB--the AA Eneloop battery pack just powers the DC Amp*Hour / Watt*Hour meter (keeps its readings if the sun/charging batter pack "go away").

-Bill

Skyko · March 2010

Re: new tests with NiMh solar charging

Ya the powerfilm 14 watt panel open circuit voltage is only 21.5 volts or so. But I guess you could use a boost converter or hook two in series...

My 26 watt Brunton Solaris foldable panel looks similar to yours but it also is only about 22 volts open circuit.

A 100 watt hour battery is nice but it would be crazy to hike for two weeks carrying that kit (plus tent, food, clothes, bear spray). I am already wincing at the 1.5 pounds my 14 watt panel + LiPo battery is. I am going to play around with the 6 watt foldable today but I don't think it has the uhmpf to reliably charge the Inspire LiPo in one day unless I hike out in the open in Arizona.

Skyko · March 2010

Re: new tests with NiMh solar charging

Did some side by side testing yesterday and today with the Brunton 26 watt CIGS panel and the Powerfilm 14 rollable amorphous panel.

Watt for watt the Brunton seems to be outperforming the Powerfilm, at least in the very overcast condtions.

For example, I am charging the Brunton Inspire LiPo battery through a dc car adapter and in extreme clouds at 10am I am getting 3.92V at 100mA into the adapter from the Powerfilm 14 (about 390mW) and 4.18Vat 230mA into the adapter from the Brunton 26 (about 960mW). Aside from the claims on the Powerfilm site that amorphous works better in low light I would have expected around 500mW out of the Powerfilm 14 if the Brunton 26 was doing almost a watt.

When the sun came out a bit I saw a similar scaling...around 4 watts out of the Brunton 26 vs 1.8 watts out of the Powerfilm.

Interesting.

RWB · March 2010

Re: new tests with NiMh solar charging

You should see the rated output from the panels only on idea sunny days when the panels are pointed directly towards the sun.

The Brunton CIGS panel should produce more power under cloudy weather than the Powerfilm Panels but not too much considering the CIGS is only 1 to 2% more efficient than the PowerFilm Panels.

Its hard to compare 2 different sized panels accurately but its fun trying.

Which panel do you plan on taking with you?

Skyko · March 2010

Re: new tests with NiMh solar charging

I do not understand this concept of ideal sunny day...I live in Seattle.

Actually we have some pretty nice weather June through Sept.

2% efficiency difference is huge if the Powerfilm is 5%. that is a 40% increase in efficiency of the CIGS panel vs the Powerfilm.

The Powerfilm 14 rollable advantage is that it can be left outside during a nuclear blast and you just wipe it down afterward. The Brunton 26 looks fairly durable but I worry about the interconnections between the panels on the fold lines...I hope they used a very flexible resilant conductor.

The Powerfilm foldable models look interesting too. They use amorphous instead of CIGS technology, but they are very very light. I think the 10 watt model is 9 ounces, where-as my 14 watt rollable is 17 ounces. Their website recommends the foldable for dry environment though.

I think I will take both the 26 and 14 on short trips where wieght is not a factor to compare which one performs best for it's size. It will probably be that I take the 14 watt when I am hiking in summer or sunny climates, and the 26 watt when hiking in winter or northern climates.

niel · March 2010

Re: new tests with NiMh solar charging

pvs are generally rated at 1000w/m^2 and is a strong solar intensity. when it's overcast you certainly are not getting that intensity, but even if the sun is out you may not be getting that intensity as it varies per location and time of year. seattle isn't noted for its abundant sunshine, but don't feel bad as neither is pittsburgh. solar still works, but just at a reduced overall level.

RWB · March 2010

Re: new tests with NiMh solar charging

Skyko wrote: »

I do not understand this concept of ideal sunny day...I live in Seattle.

Actually we have some pretty nice weather June through Sept.

2% efficiency difference is huge if the Powerfilm is 5%. that is a 40% increase in efficiency of the CIGS panel vs the Powerfilm.

The Powerfilm 14 rollable advantage is that it can be left outside during a nuclear blast and you just wipe it down afterward. The Brunton 26 looks fairly durable but I worry about the interconnections between the panels on the fold lines...I hope they used a very flexible resilant conductor.

The Powerfilm foldable models look interesting too. They use amorphous instead of CIGS technology, but they are very very light. I think the 10 watt model is 9 ounces, where-as my 14 watt rollable is 17 ounces. Their website recommends the foldable for dry environment though.

I think I will take both the 26 and 14 on short trips where wieght is not a factor to compare which one performs best for it's size. It will probably be that I take the 14 watt when I am hiking in summer or sunny climates, and the 26 watt when hiking in winter or northern climates.

The Foldable Powerfilm Panels are plenty durable for everyday use in my experience, I have has a 10W PF panel strapped up to a chair for the last 6 months during the whole winter and the panel still looks like new.

The 10W PF Panel is super light and small, if it would provide all the power you need then I would get one of those as the ideal super light weight panel. Same with the 20W PF Foldable Panel, both are super light weight. I have both panels.

The Global Solar panel should be fine over the long haul as far as the wires go. They are Mil Spec Approved.

Check this out: http://www.youtube.com/watch?v=Blwwq6M0JG4

http://www.youtube.com/profile?user=joosorange#p/u/1/rPkVUkePmPI

new tests with NiMh solar charging

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