Do solar battery chargers work?

 

I have a project that would have a small embeded computer running about
1 hour a day.  It takes about 15 watts to run.  I was thinking about
powering it with one of those "battery saver" solar chargers.

Would a 5 watt or 11 watt battery trickle charger work for this?

Here are two I am looking at:
http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeIdi70&productId  0306865&R 0306865
http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?storeIdi70&productId  0315904&R 0315904

thanks
chad

 

chad@chadphillips.org wrote:

Well, one hour a day drawing 15 watts would be 15 watt-hours/day.
Figure 20% off the top for panel heating and advertising effects,
another 20% (to be on the safe side) for battery inefficiency in
charging/discharging. That gives us (15/.80/.80=) about 24 wh/day.
Figure you'll get an average of at least 3 'sun-hours' at your
location even in the middle of winter (most of the USA) and your
panel will need to be (24/3) 8 watts.

You might squeak by on a 5 watt panel except during winter but I
would error on the side of caution and use the 11 watt panel.

You'll need a battery too, of course. If you want to run the
thing 5 days without sunlight you would need (5 * 15W) 75 Wh.
If this is a 12V battery that would be (75Wh/12V) 7 amp-hours.

Anthony

 

On Fri, 23 Sep 2005 22:13:16 -0700, Anthony Matonak


...advertising effects?

Qu'est-ce que c'est ?

-=s

 

Scott Willing wrote:

Advertising typically uses numbers that, while technically
accurate, do not reflect real world conditions. This is why
few people get the mileage shown on their cars window sticker
and nobody considers a single can of coke two servings.

This applies to solar PV panels in two forms. The first is the
STC (standard test conditions) using a temperature lower than
the panels will usually experience and, if I recall correctly,
illumination slightly more than typically found at ground level.
The second is that the warranties are usually only for 80% of
that figure. Technically, they can ship panels with slightly
less output than advertised and stay this side of the law.

You'll see this in the case of wind turbines also. The Air-X
is advertised as a 400W wind turbine but it only generates
this in hurricane force winds. It's really more of a 100-200W
wind turbine in day to day service.

You see this in generators also. That 3kW generator may only
be able to do 3kW for a very short time and it's continuous
rating may only be half that.

Advertising effects are simply the tendency of advert writers
to stretch the truth as much as they can without going to
jail. In the case of PV, some companies are better than others
in this regard.

Anthony

 

My BP panels produce much more than they are rated at and their guarantee
point, after one year is 95%.  I believe the rating power is at 25 degree C.
My Sharp panels are guaranteed at a little less and haven't been through a
winter yet to know about this factor.  Last winter my BP3160s produced over
200W each for 160W rated panels. They were purchased used. I do not know
their age. Oh yeah. They were hung vertical on my deck from a rafter on my
deck.

From the excepts I have read the Air X will never produce much over 200watts
because it furls before it's rated output. Most articles doing testing have
revealed it as a rip-off and a hoax.

Scott Willing wrote:

Advertising typically uses numbers that, while technically
accurate, do not reflect real world conditions. This is why
few people get the mileage shown on their cars window sticker
and nobody considers a single can of coke two servings.

This applies to solar PV panels in two forms. The first is the
STC (standard test conditions) using a temperature lower than
the panels will usually experience and, if I recall correctly,
illumination slightly more than typically found at ground level.
The second is that the warranties are usually only for 80% of
that figure. Technically, they can ship panels with slightly
less output than advertised and stay this side of the law.

You'll see this in the case of wind turbines also. The Air-X
is advertised as a 400W wind turbine but it only generates
this in hurricane force winds. It's really more of a 100-200W
wind turbine in day to day service.

You see this in generators also. That 3kW generator may only
be able to do 3kW for a very short time and it's continuous
rating may only be half that.

Advertising effects are simply the tendency of advert writers
to stretch the truth as much as they can without going to
jail. In the case of PV, some companies are better than others
in this regard.

Anthony