How to connect a bare solar panel to a rechargable battery

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About 5 years ago, I bought a solar charger for charging cell phones. It
seemed like a great idea, and worked fine for a year at most. Then it
would charge for a minute or so, and shut itself off. It could also be
charged by hooking it to a USB port on a computer or use a phone
charger. It had 4 blue LEDs that were supposed to indicate the amount of
charge it contained. Even after charging form a USB, it did not charge a
phone anymore.  

It's been sitting in a box ever since. I just connected it to a USB
charger and it would not even take a charge anymore. I took it apart and
was expecting to find some AA or AAA NiCd batteries, similar to the ones
that are inside of those sidewalk solar lights. My plan was to replace
those batteries with NiCd cells, the same way I change them in those
solar lights that quit working.

When I opened it, I was shocked. Instead of AA or AAA batteries, I found
two square "pouches". Sort of like tin foil covered bags that are
labeled as batteries. They are flexible, squishy, and just have two
contacts labeled + and - (there are two of them). I have never seen
batteries like this.

Besides those weird batteries, I found a small circuit board with 6 or 7
very small IC chips. One with 16 pins, and the rest have 6 pins each.
Plus an electrolytic cap, and a small coil which is probably some sort
of choke, and several surface mounted things which I assume are
resistors. Also the USB plugs and those 4 LEDs are connected to that
board. All of this seems very complex for such a small charger, and
those chips are so small I can barely see the leads on them, much less
try to repair this thing. Heck, I need a magnifying glass just to see
the solder joints on this thing.

The plan is to salvage the solar panel, and trash the rest of it. The
solar panel is a lot bigger than the ones on those solar lights, (about
4 x 5 inches). I'm suspecting the solar panel is still good, (I will
have to test it to be sure, by hooking a volt meter to it when it's in
the sun).  

My question is whether I can connect this solar panel directly to a
rechargable battery, or do I need some sort of diode or other components
between it, and the battery(s). (I know those solar lights have very
minimal components). But it seems to me that there probably needs to be
some sort of component (at least a diode) to protect the battery current
from back-flowing into the solar panel. In the end, this will just
become a solar charger for NiCd or NiMh rechargable batteries, or I
might even turn it into a solar light sort of thing.

Anyhow, what is needed to attach this solar panel to a common
rechargable AA or AAA battery?


Thanks!


Re: How to connect a bare solar panel to a rechargable battery
On 7/16/17 3:15 AM, snipped-for-privacy@tubes.com wrote:
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It will need a controller and the batteries will need to be less volts  
than the cells unless a boost circuit is employed.

Re: How to connect a bare solar panel to a rechargable battery
On Saturday, 15 July 2017 21:19:12 UTC+1, snipped-for-privacy@tubes.com  wrote:
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Likely the fault is with the squishy lithium batteries.  

If you want to use just the panel, some allow dark current leakage, some don't. Hook it to a battery, put it in darkness and measure. If it leaks add a diode.

Charge control depends on battery chemistry & size. NiCd & NiMH can be charged by just limiting current delivery to C/16, so measure your panel output current in full sun as well as offload voltage. Lithium is much more fussy, hence some of the circuitry.


NT

Re: How to connect a bare solar panel to a rechargable battery
On Sat, 15 Jul 2017 17:58:46 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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The first step to solving a problem is to blame someone or something.
However, in this case, you're probably right.

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Unless the solar cells (or panel) have built in diodes, most
everything I've seen exhibits dark current (leakage).

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I beg to differ.  You might be able to trickle charge NiCd, but NiMH
is considerably more picky:
<http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride
  "It is difficult, if not impossible, to slow charge a NiMH  
  battery. At a C rate of 0.1C to 0.3C, the voltage and  
  temperature profiles do not exhibit defined characteristics  
  to trigger full-charge detection, and the charger must  
  depend on a timer. Harmful overcharge can occur when  
  charging partially or fully charged batteries, even if the  
  battery remains cold."

In other words, C/16 or 0.06C charge rate for NiMH screws up the NVD
(negative voltage detection) mechanism used to detect EoC
(end-o-charge), which can easily overcharge a NiMH cell or battery.


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: How to connect a bare solar panel to a rechargable battery
On Sunday, 16 July 2017 02:24:07 UTC+1, Jeff Liebermann  wrote:
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If the OP had the skill to fault find I'd think they''d already have tried to

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My cordless phones use NiMH with no charge control. They get charged or discharged all the time. Last set of cheap cells lasted at least 1500 cycles. So you can do it.  


NT

Re: How to connect a bare solar panel to a rechargable battery
On Sun, 16 Jul 2017 02:28:25 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

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Maker and model please.  I want to see if I can find a schematic.

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I hate to admit it but you are probably correct.  

My AT&T EL52210 Dect 6.0 handset  
<https://www.google.com/search?q=at%26t+el52210&tbm=isch
uses two AAA 2.4v 400ma-hr NiMH cells.  The battery label demands that
I charge the battery for 16 hrs prior to use.  Doing the math and
assuming constant current charging, that's a C/16 charge rate.  

I disassembled the charger base and took some photos:
<http://www.11junk.com/jeffl/pics/repair/AT-T%20charger%20base/index.html
Not much inside.  6VAC 300ma wall wart, diode bridge, filter cap, and
some unidentified diodes and transistor.  I'll trace out the circuit
and identify the parts if I have time.  Without an IC to do the NVD
detection, this charger is rather crude and probably does not follow
the recommendations from the Battery University site.  

Incidentally, the phone is 5 to 8 years old and shows no sign of
battery problems.  The handsets spend most of their life in the
charger base and the batteries have never been discharged to the point
where the handset complains.  Open circuit battery voltage is now
2.68V which is very much full charge for NiMH.  

Very strange.


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: How to connect a bare solar panel to a rechargable battery
On Sunday, 16 July 2017 18:36:48 UTC+1, Jeff Liebermann  wrote:
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ide>
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BT graphite 1100 series. I saved you the time & googled, no trace of a circ
uit anywhere. So I could be wrong, but I'd be surprised if there were any c
harge control electronics in such equipment. Such non-ideal battery chargin
g schemes are widespread, more or less universal really, in many types of e
quipment.


NT

Re: How to connect a bare solar panel to a rechargable battery
On Sat, 15 Jul 2017 15:15:03 -0400, snipped-for-privacy@tubes.com wrote:

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Those are LiPo (lithium polymer) batteries, normally used in cell
phones and quadcopters.  Photos:
<https://www.google.com/search?q=lithium+polymer+batteries&tbm=isch

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That's the charge controller.

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You'll also need specialized tools to build and repair those, such as
a hot air desoldering station, reflow oven, solder paste, and various
chip manipulation tools.

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You might also want to measure the short circuit current.  Just put an
ammeter across the solar cell leads and see what you get.  

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No.


Yes, a solar charge controller.  What type and size depend on the
ratings of the solar panel and LiPo battery, neither of which are
currently well defined.

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They also do a great job of killing batteries.  LiPo lasts longer than
most, but few batteries will last very long after being cycled between
full charge and total discharge every day.

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True.  Schottky diode for minimum voltage drop.  It's often inside the
charge controller chip.

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In the end, if you use it as a solar powered garden light, you'll
likely kill the battery.  You need to match the battery, charge
controller, and solar cell to each other.  So far, you're not doing
that.

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Better numbers.

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: How to connect a bare solar panel to a rechargable battery
wrote:

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Yep, that's what they look like. I have never seen these before now...

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Yep, I'm sure they sell all this stuff, but I'm not investing the money
in it. I'd probably spend several hundred dollars to get all this stuff,
then spend a thousand dollars to my eye doctor for eye strain, trying to
see these parts. Then I'd remove parts, which are not labeled, and after
wasting hours trying to understand it, I'd still end up tossing it in
the trash. I think I spent around $25 for this charger, and dont think I
got my money's worth out of it, but I am fully aware it is not meant to
be repaired. Like most stuff these days, it's disposible.  

I'm not even considering repairing it, I just want to salvage the solar
cell and make use of it.

I should also mention that last winter Walmart had some portable
cellphone chargers that are meant to be used when the phone's battery
dies. You charge these power packs by connecting them to any phone
charger or USB port. These battery packs sold for $6. I bought two of
them. If I plan ot use my phone in a place that has no means to recharge
the phone's internal battery, I just carry these power packs in my
pocket.  

I thought the solar charger was better, but since it did not last even a
year. I spent close to $20 to save about 50 cents worth of electricity
to recharge a battery pack.

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So, does this have to be designed by hand with individual components, or
is there a chip available that does it all? -OR- can a ready made board
be purchased that is intended to control solar chargers?
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I have to disagree about these solar lights killing batteries. I have
several of these lights mounted on my house, and several more on my
workshop shed. I paid from $5 to $10 for them. I attach them with 1/2"
conduit straps to the wall. Some of them have lasted 5 years, others
have died after 2 years. But considering they are charged and drained
365 times each year, and operate off of one NiCd battery, I really cant
complain, about their life expectancy. Every so often a local store
sells replacement batteries in a 4 pack, ON SALE for about $6. So, for
$1.50 per light, I just replace the dead batteries, and get another two
or more years from the lights.  

Now, if you buy those solar lights that cost $1, they DO NOT last long.
And I also found that if you stick them in the ground along a sidewalk,
they get broken faster than the batteries die, and if you dont step on
them or chop them up with the lawn mower, they wont survive the snow in
winter. Wall mounted is so much better, and in my case they perform an
inportant task, they light up the stairs by my door, without needing to
operate an AC porch light, which will cost a lot more on the electric
bill.  

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So, would one of these diodes be all that I really need to use this
solar panel?  

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I guess you mean I need to determine the output of the solar panel. I'll
have to see what I can measure.

Re: How to connect a bare solar panel to a rechargable battery
snipped-for-privacy@tubes.com says...
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A couple of years ago I decided I needed to get set up for the small  
stuff.  As this is just a hobby I bought some inexpensive gear.  The 10  
x stereo microscope was the most at $ 200.  The a hot air rework station  
with a small soldering iron was another $ 60. Then about $ 800 for  
solder wick, solder paste, tweezers and a few other things. The most  
expensive was the pound of.015 inch solder that will last me a lifetime.

I agree, many things are not made to be repaired.  The parts cost more  
than a new item.  Like one older battery drill.  The batteries would not  
hold a charge.  For slightly more than one battery, I bought another  
drill of better quality that had 2 batteries.

Re: How to connect a bare solar panel to a rechargable battery
On Sun, 16 Jul 2017 18:46:16 -0400, Ralph Mowery

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This is a hobby for me too, but I dont even want to work on the
extremely small stuff. I'd leave the hobby real fast. I find stuff that
small very nerve wracking to work on, and since my eyesight is not real
good, I cant see the stuff too well. Not to mention that for most of
that stuff, you cant even get parts since they dont ID the parts
anymore, and even if they did, as you said the parts cost more than the
item.  

I enjoy working on tube stuff. I will tackle some early transistor stuff
if it's worth fixing, but I usually only work on stuff that I enjoy
doing.

I only tore this solar charger apart to save the solar cell panel. I
know the unit was trash before I even opened it. None of the chips on it
even have any numbers. Before I even spend an hour on that thing, I'd
sooner buy another solar phone charger for around $25. (not that same
brand though). But I dont really need one anyhow. Those $6 battery packs
work just fine and I can charge them on my computer, with my AC phone
charger, or in my car with my car phone charger. I dont even use my
phone real much, but it always seems to need charging when I do need it.
Those power packs work just fine.  



Re: How to connect a bare solar panel to a rechargable battery
On Monday, 17 July 2017 06:30:39 UTC+1, snipped-for-privacy@tubes.com  wrote:
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Surface mount parts are trivial to get for nothing.  


NT

Re: How to connect a bare solar panel to a rechargable battery
snipped-for-privacy@tubes.com says...
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I did see a typo in my price list.  Put in 800 instead of just 80 like I  
should have.  It will take about $ 350 to get set up for the SMD  
repairs.

Sometimes it is fun or interisting to take broken items apart to see  
what is in them and maybe salvage some parts.

Many of the SMD parts are really very inexpensive.  The older tube parts  
are getting very expensive, and some that were common years ago are  
getting hard to find.  

Re: How to connect a bare solar panel to a rechargable battery
On Sunday, 16 July 2017 21:36:17 UTC+1, snipped-for-privacy@tubes.com  wrote:
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any diode, doesn't need to be schottky. But you've still got to get the numbers right. Start with measuring the panel's offload voltage & short circuit current in full sun.


NT

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