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More Solar testing
By Psycogeek, Section Solar Posted on Thu May 12, 2005 at 07:19:38 PM MST
Still apart, and i can test things.

Thanks to the people here, i am in the final stages of the assembley of a bunch of broken reject silicoln.
and i have done the tests that I needed to do, and i can do some simple test on it if you would like.
most of this you already know.
There is NO LID on this yet, so the heat is not a factor in the tests.
the sun is a blazing california no clouds.
SHADING, the percentage of the cell that is shaded, even ONE cell in a group, drops the amperage of the group the relative ammount of the shading. but even if you can get sun to a section of every cell, you can still get 1/6 the power out of it.
CHIPPING , when 1/16th of the cell is chipped off, the cell can still operate at near 100%. ex: 3.40A from totally unbroken , unchipped 3.36 from ones with corner chips as large as 1/2" x 1/2" although the chipped ones i extended the back plate with a silver contact pen.
DISCOLORATION, no difference. very light blue, to almost black, there is no difference in the output. cept the black ones are certannly hotter, so i expect this to effect it more after the pannel has a lid on it.
Big HOLES in the back plating. minimal difference, but i ran the contact pen across all holes to fill them in, now no difference.
DUST, it had collected quite a bit of dust, sitting here parked while i was working on the other 150 projects, and there was no output reduction from the dust that had collected. the dust particals probably covered less than 10% in this test.
and finally, the one i wished to know for battery charging
VOLTAGE POTENTIAL DIFFERENTIALS: there is a vast output reduction from voltage differentials.
EX:
a 3V section of the pannel 3.40A shorted
with a 1.2V battery charging 2.75A
with 2x1.2v batteries 2.4v .98A
soooo, a greater voltage potential would charge these particular batteries MUCH faster.
(disclaimer) ALTHOUGH there is a need to stop the charging or end up overcharging the battery. its very important to taper or stop charging of most batteries.
so although you can gain more amperage output from a higher voltage differential, there is a need to taper off charging with most charging stuff anyways.
so i will definatly set this pannel up to go series parellel, with some switches.
so i can get 6Vx3 or 12v or 18v.
If you want me to do some tests, that i can do easily and cheaply, now is the time, while its opened up.

More Solar testing | 16 comments (16 topical)

Re: More Solar testing (3.00 / 0) (#1)
by ghurd on Thu May 12, 2005 at 01:38:14 PM MST

Kind of sound like not enough cells in the string.
Usually, there should be a little more than 2 cells per volt.
Then about another cell for the diode.
So for 3 volts, thats 8 solar cells.

The 1.2v cells, are those AAs?
The voltage will climb very fast if they are fed 1 amp.
It could be the cell voltage is rising so fast, it is limiting the amps,
as you are connecting the meters, etc.

G-
Ghurd.info

Re: More Solar testing (3.00 / 0) (#2)
by Psycogeek on Thu May 12, 2005 at 02:10:27 PM MST

they are Ni-CD D cells.

and me thinks your 100% correct, that to charge 2 of them at higher rates, i would need more cells.
i have not applied the diode yet, almost forgot :) thanks for reminding me.
another voltage drop :-( with the diode.

if there are mosfets with extreemly low voltage drops, where is the diode of say 4-5A value that has minimal voltage drop?

i will probably be voltage regulating the voltage on the output, with a L338 thing, will i need a diode TOO?

[ Parent ]

Re: More Solar testing (3.00 / 0) (#3)
by ghurd on Thu May 12, 2005 at 02:20:51 PM MST

Avoid charging Ni-Cd's at faster than the C/10 rate.
It kind of 'boils' them, for lack of a better word right now.
The junk that gets boiled is gone or ruined.
Then the battery can't hold as much.
"Memory" means it remembers half the important stuff is gone.

I don't think you will need a diode with a 338, but can't say for sure.

Eveready website, then energiser, then tech documents has some great info on charging.
Seems that for voltage controled charging of NiCd's it was 1.46 or 1.48V per cell?

I hate to be a bummer, but check the milliamp hours of the Ds.
AA Ni-Mh may hold more at up to 2500mah.
Most of the Ni-Cd Ds I see are only about 1200mah. :(

G-
Ghurd.info
[ Parent ]

Re: More Solar testing (3.00 / 0) (#4)
by Psycogeek on Thu May 12, 2005 at 03:11:03 PM MST

these are sanyo 4400ma. they are a bit old, compared to the 9000-11000ma Ni-mhys they have now, but they at least arent sub-Cs in a plastic D case :-)
they can be hit hard for a charge or discharge, AS LONG AS, they arent hit hard after they are charged.
meaning they only Overcharge at C/10 440ma, but you can charge the first 80% up at 2-3AMPS, AS LONG AS you know that actually is the first 80% :-)

meaning the specs they have for charging are actually the overcharge rate, if you charge at thier speced rates , you will never destroy the cell.

of course addd in that i am pulse charging too, to improve capacity and life of the cells.

[ Parent ]

Re: More Solar testing (3.00 / 0) (#6)
by ghurd on Fri May 13, 2005 at 07:12:10 AM MST

Sub C in a D case?
Thats not SOOO bad.
Saw what looked like a 2/3AA in a D case once.

Keep an eye on the heat.

Not sure if I buy into the pulse charge for Ni-Cd or Ni-Mh.
Most of what I have seen seems like the regulation is just better with all the fancy pulse circuits, compared to the other circuits.

I am sure I do not buy into the 'discharge before and during charging' circuits.

All the ones I made have regulate the voltage mostly, with a "current limiting device" (AKA resistor), so as the battery gets higher, the amps go down. The initial current is also limited.
The charts show how the V peaks then drops to the final V. I stop charging at the final V, but before the peak. Then just let it charge longer at maybe C/20~25.
No heat, no ruined batteries.
Some said it looks like the battery is only 95% full. But you lose the top 10% in 24 hours anyway. And it does not ruin the batteries!

G-
Ghurd.info
[ Parent ]

Re: More Solar testing (3.00 / 0) (#8)
by Psycogeek on Fri May 13, 2005 at 07:39:51 PM MST

its in the book. every study of Pulse non-pulse, for metal electrolyte batteries has shown a better longevity with pulse charging.
i think there is good reasons why it works.
even li-ion cells had a much greater longevity when pulsed, and in that test, the pulse pounded the cells , compared to the non-pulsed method. after 500 cycles the non-pulsed had 80% life, the pulsed 90% life.
Gotta get stuff outa the electrolyte, and back on the plates, without heating the cell.
i dont understand it all, but it falls along the logic of every REALLY GOOD battery charging cuircut i have used, be it li-ion, ni-mhy, wet Lead acid , or (and especially) Ni-Cads.

[ Parent ]

Re: More Solar testing (3.00 / 0) (#10)
by ghurd on Sat May 14, 2005 at 06:48:57 AM MST

Sound like you are up on the rechargables.

Off track, but...

Did you hear anything about the batteries with built in charging circuits?
They were to be on the market by now. Good idea.
I guess you could connect them to 6V, 12V, or whateverV,
and the circuit in the battery itself took care of everything.

What do you think of the rechargable alkalines?

G-
Ghurd.info
[ Parent ]

Re: More Solar testing (3.00 / 0) (#11)
by jimjjnn on Sat May 14, 2005 at 07:28:07 AM MST

I am somewhat familiar with chrging circuits built into batteries. Former employer decided to manufacture batteries with charging circuits in the battery packs for their equipment. They had to give the idea up as the charging circuits always failed due to a lack of cooling of the circuits.
This recently came back to haunt me as my laptop computer had the charging circuits in the battery pack. Used the batt pack twice and the pack failed to charge after that. Pack under warrantee so no charge replacement. 2nd pack failed after 3 months and used about 6-7 times. I tore both packs apart and found the cells inside were in good shape. I then used the batts in another project with a 317 volt reg and was able to charge the batts and use them. I still am using them in a way that both packs are paralleled(Sp). They are still working after 3 years. Starting to show age tho as they don't have the capacity that they originally had.
Denver,CO
[ Parent ]

Re: More Solar testing (3.00 / 0) (#12)
by Psycogeek on Sat May 14, 2005 at 02:02:54 PM MST

rechargable alkalines
Much better sealed , so they are very unlikely to leak.
only handle 25 fair deep discharges
if they go 100% flat 0V they do not recharge
great for topping off and using in stuff that needs to work (low self discharge)
totally useless for stuff that gets used hard and used often.

i think they would be usable in things like remotes, cause they wont get leaked, and they could potentially last years if they were topped off regularly.
i think they are useless, in eveything that sucks batteries down so fast, that self discharge is not an issue.

i am converting everything i can to li-ion now, because self discharge just sucks, and alkalines are weak, and lithium primary cells are a waste of good money.

i just got in a li-ion D size cell, that is 4.6A at 3.6V , its light, and potent.

[ Parent ]

Re: More Solar testing (3.00 / 0) (#13)
by ghurd on Sat May 14, 2005 at 07:42:03 PM MST

Rechargable alkalines.
What about 10ma 10 hours a day every day?
Current drops as voltage drops.
They stop discharging at 0.680V per cell. LED nightlights.
Any good?
The regular alkalines can go a year. No BS.
G-
Ghurd.info
[ Parent ]

Re: More Solar testing (3.00 / 0) (#14)
by Psycogeek on Sun May 15, 2005 at 06:41:46 PM MST

they should love that.
leds are great for having thier own shutoff curcuit :-) when the gate no longer triggers, there is no more flow.

[ Parent ]

Re: More Solar testing (3.00 / 0) (#5)
by Ungrounded Lightning Rod on Thu May 12, 2005 at 05:37:51 PM MST

CHIPPING , when 1/16th of the cell is chipped off, the cell can still operate at near 100%. ex: 3.40A from totally unbroken , unchipped 3.36 from ones with corner chips as large as 1/2" x 1/2" although the chipped ones i extended the back plate with a silver contact pen.

When building with chipped cells you might want to build a series/parallel array where each "cell" is several individual chipped cells in parallel. The limit on the current of the panel is the limit of the current of the weakest "cell", so making each "cell" the parallel combo of several physical cells lets you average out the variations and have all the "cells" about the same current capacity.

Re: More Solar testing (3.00 / 0) (#7)
by Psycogeek on Fri May 13, 2005 at 07:29:23 PM MST

Last test.
sombody was asking about CAR WAX.
so i had some leftover plastic, and waxed it with a silicoln type of high gloss wax.
both pieces of plastic were first cleaned with windex.
the wax (specifically) was RX "Gold Glass"
BOTH the top and the bottom were waxed.

there was not a mesuarable difference between the waxed and the unwaxed.
which is Kinda weird, because the wax did increase the reflectivity of the plastic.

i got it wired up so it will change between 6V at 9A , and 18V at 3A.
i will do some pictures of the motly thing later.

Re: More Solar testing (3.00 / 0) (#9)
by Ungrounded Lightning Rod on Fri May 13, 2005 at 08:38:52 PM MST

there was not a mesuarable difference between the waxed and the unwaxed.
which is Kinda weird, because the wax did increase the reflectivity of the plastic.

The wax will tend to change the reflection from scattering (cloudy/fuzzy) to specular (mirror-like) without making much change in the amount of reflection.

Main advantage of waxing a panel, IMHO, is to help it shed water and snow before it freezes onto the surface or causes mud to stick to the surface.

[ Parent ]

Re: More Solar testing (3.00 / 0) (#15)
by Psycogeek on Thu May 26, 2005 at 06:29:23 AM MST

one more test.
the totally stupid reverse it and send like 10AMPS of juice back to your 9Amp solar cells.
i was charging off the AC wall plug charger, to get the batteries toped off, so i could test my cutoff, and when i finished i hooked the cell up backwards.
as you might know i dont use or have a diode on the solar cell itself.

When i woke up, i see the voltage dropped, the small test leads are goopy hot, and the meter is running backwards OOPS.
SO
i managed to test totally slamming the cells with reverse voltage, WHILE they were trying to pump it back the other way.

it survived, the pannel heated up hotter than it had ever been, i could tell by how far the platic had domed up.
dont know why the stupid fuses didnt blow, guess i could lower them down a bit :-)

talk about durable hunks of silicoln, swithed them back, they started recharging everything i lost, like nothing happened.

Re: More Solar testing (3.00 / 0) (#16)
by Psycogeek on Wed Jun 01, 2005 at 06:52:50 PM MST

Angles, or solar tracking.
here in cal we have a LOAD of available sun.
(all values are approximate)
at the latter part of the day the angle of the sun can be 45*
a mere 20* tilt tward the sun, when the sun is at such an angle
achieved me a 2X output of amperage.

my unscientific tests, shows that there is indeed a large amerage loss, from not having a capacity for the solar cells to track the sun.
i would have thought with there being so MUCH of it, and it being summer (almost straight up) that this would be of little issue or consequence.

if i could Easily build a strong capable tracking unit for a reasonable price, that would hold up under HIGH wind and other exterior conditions, without flopping around, or breaking it, or the gearing or whatever that is used to track it, then it would be a valuable assett to the fullest capacity of output.

More Solar testing | 16 comments (16 topical)

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