Hi,

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

On 11/4/2009 2:09 PM D Yuniskis spake thus:

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

I found this one at Harbor Freight:
http://www.harborfreight.com/cpi/cta...emnumber=96728
A little big for your stated purpose (7 amps).

I thought I had seen smaller ones there, but didn't find them. Perhaps a
more careful search might turn them up. They do sell some very small
solar battery charging kits, including panels, for cheap, so they
probably have smaller controllers.


--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?

- harvested from Usenet

On Wed, 04 Nov 2009 15:09:47 -0700, D Yuniskis
put finger to keyboard and composed:

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

If the battery capacity is big enough, and the PV panel voltage is not
too much higher than battery voltage, then you won't need a regulator,
only a 1N5817 Schottky diode to prevent the battery from discharging
into the panel.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:
On Wed, 04 Nov 2009 15:09:47 -0700, D Yuniskis
put finger to keyboard and composed:

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

If the battery capacity is big enough, and the PV panel voltage is not
too much higher than battery voltage, then you won't need a regulator,
only a 1N5817 Schottky diode to prevent the battery from discharging
into the panel.

This is inefficient. You want to find the "sweet spot"
where you get the most power from the panel. I.e.,
at no load you get no power and at short circuit the
same applies.

Ideally, you want to coax the most from the panel by
operating it where it "wants" to be operated. Then,
move this into the battery incurring the least losses
possible in the process...

D Yuniskis wrote:
Hi,

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

What is the power requirement of the "irrigation pump"? The pumps I've used
wouldn't run long off of a couple wheelchair batteries.

Bob F wrote:
D Yuniskis wrote:
Hi,

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

What is the power requirement of the "irrigation pump"? The pumps I've used
wouldn't run long off of a couple wheelchair batteries.

I'm harvesting rainwater. So, I only need to move a few hundred
gallons at a time (i.e., I'm not watering an orchard! : ).
I'm more concerned with restoring the level of charge in the
batteries quickly enough with these tiny little PV's...

On 11/5/2009 8:48 AM D Yuniskis spake thus:

Bob F wrote:

D Yuniskis wrote:

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

What is the power requirement of the "irrigation pump"? The pumps I've used
wouldn't run long off of a couple wheelchair batteries.

I'm harvesting rainwater. So, I only need to move a few hundred
gallons at a time (i.e., I'm not watering an orchard! : ).
I'm more concerned with restoring the level of charge in the
batteries quickly enough with these tiny little PV's...

Did you check out that Harbor Freight link I gave earlier? Hell, for as
cheap as they are, you could get one of their smaller solar battery
charger kits, with controller, and just add your panels to theirs for
more power.


--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?

- harvested from Usenet

On Wed, 04 Nov 2009 18:17:34 -0700, D Yuniskis
wrote:

Franc Zabkar wrote:
On Wed, 04 Nov 2009 15:09:47 -0700, D Yuniskis
put finger to keyboard and composed:

I've rescued several small PV panels along with a pair
of gel-cels from an electric wheelchair that still have
useful life. I'd like to put together a charge controller
to run the irrigation pump "for free".

Any pointers to suitable designs? The PVs are small
so Isc is on the order of 100-200mA (though I may
double that)

If the battery capacity is big enough, and the PV panel voltage is not
too much higher than battery voltage, then you won't need a regulator,
only a 1N5817 Schottky diode to prevent the battery from discharging
into the panel.

This is inefficient. You want to find the "sweet spot"
where you get the most power from the panel. I.e.,
at no load you get no power and at short circuit the
same applies.

Ideally, you want to coax the most from the panel by
operating it where it "wants" to be operated. Then,
move this into the battery incurring the least losses
possible in the process...

aka Maximum Power Point Tracker. Google MPPT