12 VOLT SOLAR CELLS, AND DYNAMO CHARGER ??????????????

[Dr. Slick]

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, that uses
3.6 volt NiMH, but i think there are Zener diodes that
limit the voltage coming from the generator to 7-8
volts, so i think i can remove these to get more
voltage (closer to 13-14 volts?).

I believe i could just use a regular 13.8 volt
DC power supply, and have a 3-way switch to go from
the solar cell, to the dynamo, or to the AC power
supply, directly to the charge controller above.

I other words, the charge controller (made for
photovoltaics) would be used for any of the three
sources of DC power.

Does this sound like a good idea? Or should
i get a separate charger for the DC power supply?

Is there a cheap, simple LED circuit that can
indicate the charging function and the state of the
battery?

Thanks for your help,

Slick

 

[CWatters]

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

Best check that charge controller is designed to work with NiMH cells. They
behave differently to Lead Acid cells.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, that uses
3.6 volt NiMH, but i think there are Zener diodes that
limit the voltage coming from the generator to 7-8
volts, so i think i can remove these to get more
voltage (closer to 13-14 volts?).

Might work but I suspect you may have to turn the dynamo 3 or 4 times faster
(12/3.6 = 3.333 times). This might not be possible without changing the
gearing? At that voltage/rpm the dynamo may not be very efficient.

I other words, the charge controller (made for
photovoltaics) would be used for any of the three
sources of DC power.

You need to find out more info. Ask the makers if it's possible to power the
charge controller fro a DC source and what input voltage range is required
to charge 10 NiMH cells.

 

[James Meyer]

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains.

Slick

You don't need a charge controller for the solar cell source. Its
output is 1/10th of the battery's capacity and that amount of charge current
will be fine with no controller in the system.

You don't need a charge controller with the dynamo either.

If you use a "normal" commercial battery charger for the 120 volt AC
source, you won't need a seperate controller either.

A simple voltmeter will give you all the information you need to
determine the health of the battery.

Jim

 

[CWatters]

You don't need a charge controller for the solar cell source. Its
output is 1/10th of the battery's capacity and that amount of charge current
will be fine with no controller in the system.

The 1/10th overcharge rate is usually ok (in that the battery won't over
heat or explode) but it might shorten the life of the battery if used long
term. Manufacturers recommend a lower rate if you are planning to leave the
battery on float for very long periods.

A simple voltmeter will give you all the information you need to
determine the health of the battery.

eg cells that exhibit a higher than normal "on charge" voltage are less
healthy.... or did you mean you can use a volt meter as a charge state
indicator? That's only possible if you calibrate it carefully

 

[Joerg]

Hi Dr. Slick,

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, ...

Look into real alternators for motorcycles or cars. These are usually
much better quality and longer lasting. And cheap. Better bearings, too.

Regards, Joerg

 

[Tom Seim]

Good Evening,

I'm building a 12 volt recharging system with
a 12 volt, 0.375A (12"x12") solar cell, and this charge
controller:


http://store.dependablesolarproducts.com/etaen12vo5am.html


The battery is a 12 volt NiMH, 3AH.

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, that uses
3.6 volt NiMH, but i think there are Zener diodes that
limit the voltage coming from the generator to 7-8
volts, so i think i can remove these to get more
voltage (closer to 13-14 volts?).

I believe i could just use a regular 13.8 volt
DC power supply, and have a 3-way switch to go from
the solar cell, to the dynamo, or to the AC power
supply, directly to the charge controller above.

I other words, the charge controller (made for
photovoltaics) would be used for any of the three
sources of DC power.

Does this sound like a good idea? Or should
i get a separate charger for the DC power supply?

Is there a cheap, simple LED circuit that can
indicate the charging function and the state of the
battery?

Thanks for your help,

Slick

The charger you are going to use is not designed for a NiMH (they dont
say, but I am sure it is a lead-acid type). Refer to a NiMH manual
before you go ahead with this. Otherwise be aware that the battey
might catch fire.

 

[James Meyer]

The 1/10th overcharge rate is usually ok (in that the battery won't over
heat or explode) but it might shorten the life of the battery if used long
term. Manufacturers recommend a lower rate if you are planning to leave the
battery on float for very long periods.

Solar cells will only provide current when the sun's shining. That
reduces the total current available over the long term to a value that should be
safe. Not to mention that most solar cell manufacturers rate their cells for a
perfectly clear day on top of Mt. Everest during a solar flare.

eg cells that exhibit a higher than normal "on charge" voltage are less
healthy.... or did you mean you can use a volt meter as a charge state
indicator? That's only possible if you calibrate it carefully

I meant that if one weren't going to automate the process or attempt to
provide legally binding measurements, that a quick look at the voltmeter would
provide all the information one should need to determine the condition of the
battery. Of course the voltage would be different depending on the load and the
temperature and whether the current was going into or out of the battery.

Jim

 

[m II]

Not to mention that most solar cell manufacturers rate their cells for a
perfectly clear day on top of Mt. Everest during a solar flare.

and when the planet is closest to the sun




mike

 

[Dr. Slick]

The charger you are going to use is not designed for a NiMH (they dont
say, but I am sure it is a lead-acid type). Refer to a NiMH manual
before you go ahead with this. Otherwise be aware that the battey
might catch fire.

You may be right, as the batteries they sell seem to be lead
acid.

I was also looking at this charge controller:

http://www.solorb.com/elect/solarcirc/spc2/index.html

It seems a bit simple, but it may be good enough
for what we need. It says it can take NiMH too.


Slick

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hi Dr. Slick,

Look into real alternators for motorcycles or cars. These are usually
much better quality and longer lasting. And cheap. Better bearings,

too.

An alternator for an automobile, and probably a motorcycle also, are way
too much for a charger that needs only a half amp. Cars use a hundred
times that current.

I've used a hard disk spindle motor to drive some LEDs. Try it
sometime.
It depends on the motor, obviously it has to have permanent magnets.

 

[Joerg]

Hi Watson A.Name,

An alternator for an automobile, and probably a motorcycle also, are way
too much for a charger that needs only a half amp. Cars use a hundred
times that current.

The one I saw in a friend's scooter was just the size of a fist. After
all, you need some mass and size if you want to operate it with a hand.
Either the other hand needs to grab it or it would have to be mounted on
something. There should also be suitable versions for riding lawn mowers
and stuff like that.

I've used a hard disk spindle motor to drive some LEDs. Try it
sometime.
It depends on the motor, obviously it has to have permanent magnets.

I have to try that. Wish I had kept the last HD that had croaked.

Regards, Joerg

 

[Tom Seim]

You may be right, as the batteries they sell seem to be lead
acid.

I was also looking at this charge controller:

http://www.solorb.com/elect/solarcirc/spc2/index.html

It seems a bit simple, but it may be good enough
for what we need. It says it can take NiMH too.


Slick

To safely charge NiMH you must sense & terminate charging on either:
1. dV/dt drop
2. dT/dt drop
This circuit doesn't seem to do either. Check out:
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1037,C1078,C1088,P7601,D5235

Tom

 

[Dave VanHorn]

Newer NIMH's, like the C type cells from Sanyo, can take long term
overcharge without problems. Check your data sheets.

 

[Dr. Slick]

Newer NIMH's, like the C type cells from Sanyo, can take long term
overcharge without problems. Check your data sheets.

Do you have to worry about Low Voltage disconnect with
NiMH? With lead-acid, you obviously do...


S.

 

[Dr. Slick]

It notes that Lead-acid cells are best suited to the natural power curve of
solar cells.

I get the feeling they are more robust against overcharging and overvoltage
than other chemistries. They certainly seem okay with the simple charging
circuits in most cars and chargers.

The British Antarctic Survey use lead-acid in their polar instrumentation.
Now there's an extreme application.
Like Dr. Slick's app, they use turbines and solar cells, but of course they
have to work for several years unattended. Cells have to harvest sun over a
six month summer, as there is none during the winter.

Dr. Slick, what is your application?
i.e. what is the power to be used for?

This will power two 40-60 watt lights, with a
motion detector attached.

Are lead-acid batteries really the way to go?
Some charge regulators don't have a low voltage disconnect
circuits, so the battery can be drained if you aren't
careful. If i'm not mistaken, NiMH don't have this
problem, right?


Slick

 

[Tom Seim]

Newer NIMH's, like the C type cells from Sanyo, can take long term
overcharge without problems. Check your data sheets.

Well, I did that. From Sanyo's manual
(http://www.sanyo.com/batteries/pdfs/twicellT_E.pdf):

"Also, to obtain a long service life from the Twicell, over-charging
must be avoided as much as possible."

This assertion that over-charging is ok comes up time and again. Yeah,
it's ok if you don't care about battery life.

Tom

 

[Ken Smith]

IIRC no cells like being drained as flat

IIRC the Silver Chloride (or something like that) battery loved being
discharged. You had to discharge it for storage. You could charge it up,
use it for a day and then run it flat. Discharged it would last for
years.

The down sides were: Charged it went bad in a month and they cost a *LOT*
to replace. The only Silver Chloride batteries still in use that I know
of are the ones for testing blasting caps.

 

[Dr. Slick]

NiCD cells DO like to be drained completely flat.

Otherwise you get the old memory effect if you
try to recharge them when they are only partially
discharged, and the cells will then not hold a full
charge.


Slick

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Hi Watson A.Name,

The one I saw in a friend's scooter was just the size of a fist. After
all, you need some mass and size if you want to operate it with a hand.
Either the other hand needs to grab it or it would have to be mounted on
something. There should also be suitable versions for riding lawn mowers
and stuff like that.

I have to try that. Wish I had kept the last HD that had croaked.

The scooter size still takes too much power to operate by hand. And the
smaller engines on lawn mowers that I've seen use the coil for the
ignition to generate power for the lights, etc. This is a part of the
flywheel, and can't be removed and used as a unit.

 

[N. Thornton]

I would also like to be able to use a hank-cranked
dynamo charger, and also a way to recharge the battery
using regular 120 AC mains. The dynamo that i wish to
use comes from a very cheap survival radio, that uses
3.6 volt NiMH, but i think there are Zener diodes that
limit the voltage coming from the generator to 7-8
volts, so i think i can remove these to get more
voltage (closer to 13-14 volts?).

Yup. Youll need more speed for more V though.