Can a small photocell panel be connected to a flashlight type rechargable battery?

Started by October 11, 2018
I acquired a dead solar cellphone charger unit. I did minimal testing of
it, and it was totally dead. It has the surface mount components, so I
did not go any further. I salvaged the 2.5" X 4" solar cell panel, and
tossed the rest of it. In a lighted room, (lights turned on) it puts out
just under one volt DC. I imagine it will put out more voltage in
sunlight, but I have not tried it, since we have not seen the sun in
days.

Anyhow, can I connect that panel directly to a common AA rechargable
battery? (or maybe I should charge two batrteries at once, in series)?

If not, is there a simple circuit I can build, or should I just steal a
circuit board from one of them solar yard lights, (which have a much
smaller solar panel).

oldschool wrote

>I acquired a dead solar cellphone charger unit. I did minimal testing of >it, and it was totally dead. It has the surface mount components, so I >did not go any further. I salvaged the 2.5" X 4" solar cell panel, and >tossed the rest of it. In a lighted room, (lights turned on) it puts out >just under one volt DC. I imagine it will put out more voltage in >sunlight, but I have not tried it, since we have not seen the sun in >days. > >Anyhow, can I connect that panel directly to a common AA rechargable >battery? (or maybe I should charge two batrteries at once, in series)? > >If not, is there a simple circuit I can build, or should I just steal a >circuit board from one of them solar yard lights, (which have a much >smaller solar panel).
Some charge controller chip would be in place. Do not use AA, use lipos. What is the short circuit current that panel gives in direct bright sunlight? And the open voltage? Your controller needs to be able to handle that. That also determines if you need a switcher or not to go the battery voltage level.
On Thursday, 11 October 2018 06:38:23 UTC+1, olds...@tubes.com  wrote:
> I acquired a dead solar cellphone charger unit. I did minimal testing of > it, and it was totally dead. It has the surface mount components, so I > did not go any further. I salvaged the 2.5" X 4" solar cell panel, and > tossed the rest of it. In a lighted room, (lights turned on) it puts out > just under one volt DC. I imagine it will put out more voltage in > sunlight, but I have not tried it, since we have not seen the sun in > days. > > Anyhow, can I connect that panel directly to a common AA rechargable > battery? (or maybe I should charge two batrteries at once, in series)? > > If not, is there a simple circuit I can build, or should I just steal a > circuit board from one of them solar yard lights, (which have a much > smaller solar panel).
See how much current the panel puts out in bright sun. Also check its voltage unloaded. Then we'll know how runnable this is. NT
On Thursday, October 11, 2018 at 1:38:23 AM UTC-4, olds...@tubes.com wrote:
> I acquired a dead solar cellphone charger unit. I did minimal testing of > it, and it was totally dead. It has the surface mount components, so I > did not go any further. I salvaged the 2.5" X 4" solar cell panel, and > tossed the rest of it. In a lighted room, (lights turned on) it puts out > just under one volt DC. I imagine it will put out more voltage in > sunlight, but I have not tried it, since we have not seen the sun in > days.
Nope in more sunlight it will put out more current. The voltage is mostly fixed. You can put panels in series for more voltage. George H.
> > Anyhow, can I connect that panel directly to a common AA rechargable > battery? (or maybe I should charge two batrteries at once, in series)? > > If not, is there a simple circuit I can build, or should I just steal a > circuit board from one of them solar yard lights, (which have a much > smaller solar panel).
In article <fhntrd1aq3c9jkfp3haigrk512mdfc5aj8@4ax.com>,
 <oldschool@tubes.com> wrote:
>I acquired a dead solar cellphone charger unit. I did minimal testing of >it, and it was totally dead. It has the surface mount components, so I >did not go any further. I salvaged the 2.5" X 4" solar cell panel, and >tossed the rest of it. In a lighted room, (lights turned on) it puts out >just under one volt DC. I imagine it will put out more voltage in >sunlight, but I have not tried it, since we have not seen the sun in >days.
If it's showing 1 volt "open circuit" in room light, when measured with a high-impedance voltmeter, then I think it's unlikely to put out much more voltage under direct sunlight. More current, yes; more voltage, no.
>Anyhow, can I connect that panel directly to a common AA rechargable >battery? (or maybe I should charge two batrteries at once, in series)?
You _can_ connect it directly to one or two batteries in series. It is unlikely to charge them at all, based on what you've written.
>If not, is there a simple circuit I can build, or should I just steal a >circuit board from one of them solar yard lights, (which have a much >smaller solar panel).
Ideally, what you would have is a voltage-boost circuit which is capable of raising the voltage enough to charge the batteries, _and_ to do so in a way which operates the panel at its point of maximum power delivery. Professional solar charge-control circuits do this (although they usually _drop_ a higher panel voltage via a buck regulator). You might want to look into the simple "joule thief" circuit. This is a simple blocking oscillator voltage booster, which is often used in small LED flashlights to boost a single AA cell (1.5 volts nominal) to a high enough voltage to turn on a white LED (roughly 5 volts I believe). You might be able to build one which can boost a 1-volt panel's output up above 1.4 volts (enough to charge a NiCd or NiMH).
On Thu, 11 Oct 2018 00:32:34 -0500, oldschool@tubes.com wrote:

>I acquired a dead solar cellphone charger unit.
Most cheap cell phones use 5.0V DC to the charger connector. My guess(tm) is that it's either an amorphous silicon or thin film panel delivering about 6V DC. Amorphous are nice because they're cheap and produce usable power in fairly dim lighting, while polycrystalline cells are more expensive and don't work well in dim lighting. The problem with amorphous cells is that the efficiency sucks. <https://en.wikipedia.org/wiki/Solar_cell_efficiency> <https://en.wikipedia.org/wiki/Solar_cell_efficiency#/media/File:PVeff(rev180813)a.jpg> Approximately: Amorphous 9% Thin film 16% Polycrystalline 18% Lots of guesswork. Are you sure it's a cell phone charger? Perhaps it's solar powered garden light? Duz the panel look something like this polycrystalline panel? <https://www.ebay.com/itm/3254-6V-0-6W-Solar-Panel-Poly-Module-DIY-Cell-Charger-For-Light-Battery-Phone/202427427685>
>I did minimal testing of >it, and it was totally dead.
Wrong. You didn't have enough light to properly determine if the circuitry was functional. A minimum light level will be needed before the electronics will delivery any output. Indoor room testing isn't bright enough, unless you put the panel under a desk lamp. Put the device back together and try again outside in sunlight or with a desk lamp.
>It has the surface mount components, so I did not go any further. >I salvaged the 2.5" X 4" solar cell panel, and >tossed the rest of it. In a lighted room, (lights turned on) it puts out >just under one volt DC. I imagine it will put out more voltage in >sunlight, but I have not tried it, since we have not seen the sun in >days.
Well, try it. You should measure the open circuit voltage and the short circuit current. Don't leave the ammeter across the panel for very long or the panel might overheat.
>Anyhow, can I connect that panel directly to a common AA rechargable >battery? (or maybe I should charge two batrteries at once, in series)?
I know about NiCd, NiMH, lead acid, LiIon, and other chemistries, but somehow, I've never seen a "common rechargeable" AA cell. Is that a brand name of something?
>If not, is there a simple circuit I can build, or should I just steal a >circuit board from one of them solar yard lights, (which have a much >smaller solar panel).
Buy a small 3.6V LiPo cell. You can buy charge controllers that will charge it if your solar panel can deliver enough power. I'm not going to try and find one until you supply some numbers. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Thu, 11 Oct 2018 22:34:37 -0000 (UTC), Jasen Betts
<jasen@xnet.co.nz> wrote:

>On 2018-10-11, Jeff Liebermann <jeffl@cruzio.com> wrote: > >> Well, try it. You should measure the open circuit voltage and the >> short circuit current. Don't leave the ammeter across the panel for >> very long or the panel might overheat.
>They don't change colour in response to a load, open-circuit and short >circuit produce almost exactly the same self-heating
Change color? No, I didn't say that. I use a short circuit test to check for defective cells in a panel. Short the panel, full sunlight, and use an IR camera or IR thermometer to measure the temperature rise of each cell. A defective cell will usually be warmer than the other normal cells: <https://www.novuslight.com/testing-solar-panels-with-thermal-imaging-cameras_N7799.html> <https://solarprofessional.com/sites/default/files/articles/images/10_NEW_SP7_2_pg24_Mehalic-7.jpg> "Hotspots Detection in Photovoltaic Modules Using Infrared Thermography" <https://www.matec-conferences.org/articles/matecconf/pdf/2016/33/matecconf_icmit2016_10015.pdf> For example, when someone shorts a 300 watt panel, that generated power has to be dissipated somewhere, which means dissipated in the solar cells. With 60 cells, that's 5 watts per cell at the MPP (maximum power point), which is not a trivial amount. The instructions for such tests often include some manner of warning not to leave the panels shorted for too long or they might overheat. Sometimes, they show a hot cell with an open circuit condition (usually when the shading protection diode goes open circuit). The tiny panel the OP is using will probably do nothing dangerous if the panel is shorted, but I consider it good practice to add the overheating warning since there's no clear boundary between what size panel is safe and unsafe to short. In other words, if he burns his house down shorting a power source, I would want to at least claim that I warned him. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On 10/11/2018 01:39 PM, Dave Platt wrote:
> In article <fhntrd1aq3c9jkfp3haigrk512mdfc5aj8@4ax.com>, > <oldschool@tubes.com> wrote: >> I acquired a dead solar cellphone charger unit. I did minimal testing of >> it, and it was totally dead. It has the surface mount components, so I >> did not go any further. I salvaged the 2.5" X 4" solar cell panel, and >> tossed the rest of it. In a lighted room, (lights turned on) it puts out >> just under one volt DC. I imagine it will put out more voltage in >> sunlight, but I have not tried it, since we have not seen the sun in >> days. > > If it's showing 1 volt "open circuit" in room light, when measured > with a high-impedance voltmeter, then I think it's unlikely to put out > much more voltage under direct sunlight. More current, yes; more > voltage, no. > >> Anyhow, can I connect that panel directly to a common AA rechargable >> battery? (or maybe I should charge two batrteries at once, in series)? > > You _can_ connect it directly to one or two batteries in series. > > It is unlikely to charge them at all, based on what you've written. > >> If not, is there a simple circuit I can build, or should I just steal a >> circuit board from one of them solar yard lights, (which have a much >> smaller solar panel). > > Ideally, what you would have is a voltage-boost circuit which is > capable of raising the voltage enough to charge the batteries, _and_ > to do so in a way which operates the panel at its point of maximum > power delivery. Professional solar charge-control circuits do this > (although they usually _drop_ a higher panel voltage via a buck > regulator). > > You might want to look into the simple "joule thief" circuit. This is > a simple blocking oscillator voltage booster, which is often used in > small LED flashlights to boost a single AA cell (1.5 volts nominal) to > a high enough voltage to turn on a white LED (roughly 5 volts I > believe). You might be able to build one which can boost a 1-volt > panel's output up above 1.4 volts (enough to charge a NiCd or NiMH). >
You can make a crude maximum power point tracker out of one of those and an 8 pin AVR uP. The uP power pin gets hooked up to the boost output and its ADC can be used to measure its own supply voltage, which should vary with light intensity. The battery can be charged with a PWM output from a pin and output current into the charging battery can be sensed indirectly via sensing die temperature with the on-chip temperature sensor
On 2018-10-12, Jeff Liebermann <jeffl@cruzio.com> wrote:
> On Thu, 11 Oct 2018 22:34:37 -0000 (UTC), Jasen Betts ><jasen@xnet.co.nz> wrote: > >>On 2018-10-11, Jeff Liebermann <jeffl@cruzio.com> wrote: >> >>> Well, try it. You should measure the open circuit voltage and the >>> short circuit current. Don't leave the ammeter across the panel for >>> very long or the panel might overheat. > >>They don't change colour in response to a load, open-circuit and short >>circuit produce almost exactly the same self-heating > > Change color? No, I didn't say that.
No, but assuming that conservation of energy is a law of the universe you implied it. A shorted panel produces no power on the terminals. An open circuit panel receives the same amout of energy from the sun as a shorted one (otherwise it would change colour), so same temperature. -- Notsodium is mined on the banks of denial.
On Friday, October 12, 2018 at 1:31:04 AM UTC-4, Jasen Betts wrote:
> On 2018-10-12, Jeff Liebermann <jeffl@cruzio.com> wrote: > > On Thu, 11 Oct 2018 22:34:37 -0000 (UTC), Jasen Betts > ><jasen@xnet.co.nz> wrote: > > > >>On 2018-10-11, Jeff Liebermann <jeffl@cruzio.com> wrote: > >> > >>> Well, try it. You should measure the open circuit voltage and the > >>> short circuit current. Don't leave the ammeter across the panel for > >>> very long or the panel might overheat. > > > >>They don't change colour in response to a load, open-circuit and short > >>circuit produce almost exactly the same self-heating > > > > Change color? No, I didn't say that. > > No, but assuming that conservation of energy is a law of the universe you > implied it. > > A shorted panel produces no power on the terminals. An open circuit panel > receives the same amout of energy from the sun as a shorted one (otherwise > it would change colour), so same temperature.
Sitting on the side line listening to this the space between what you said and what he said became apparent. You are both right. You are talking about the panel and he is talking about individual cells. Since the panel does not have to be uniform unless it is a single cell, the problem cells can be hotter than the fully functioning cells because they are passing the full current when the output is shorted. Functioning cells are generating electrical power which leaves the cells so they can be cooler. So there should also be a difference in voltage across the cells when some are bad. The bad cells will have a lower voltage (since this is power leaving the cell) or even reversed. Rick C.