Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: How do you charge a laptop battery with
a solar panel ? Posted: Thu Jul 16, 2009 1:33 am
Joined: Tue Dec 30, 2008 1:53 pm
I'm thinking of
trying to charge my Lenovo Thinkpad x60s battery with an R-14 Powerfilm
flexible solar panel.
I hope this question is not too elementary
for this august forum.
Anyway, the idea is to charge the battery
with it in the laptop, but with the laptop turned off. I think having
it turned On will most likely not work (as follows.)
told me that since the wattage of the solar panel is much less than
the draw of the Thinkpad, it won't work. I'm not an electrical engineer,
although I did quite well in physics. The only problem is, it's been
quite a few years (of disuse.)
Here are the numbers :
The Powerfilm is rated at 15.4V and .9A ( ~14 watts)
Lenovo Thinkpad X60s Laptop
The battery is 14.4v / ~5200 mAh
I measured the current draw of the Thinkpad - when OFF (battery charging
only) - at .25A and 115v (= 29watts ).
When On, it's something over
I measured this straight out of the wall, before the inline
transformer that converts the 110v to ~20v (?). (I'm not sure what the
charging voltage is, but the charger says 20v / 3.5A = 70watts - probably
what's need to actually power a running computer)
I had thought
that the battery charging would charge at a much lower current, like
a trickle current, .1C or so, but this is not necessarily the case with
Lithion batteries it seems. See Lithium Ion Battery Charging Basics
It's more like .2 to .7C actually.
One idea, if this is not going
to work, is to pull the battery off and charge it outside the laptop,
but this looks complicated as there are about 8 or 9 contacts on the
battery, and I have no idea what is what. It sounds a little risky anyway.
If anyone could be of help that'd be great.
Post subject: Re: How do
you charge a laptop battery with a solar panel ?Posted: Thu Jul 16,
2009 3:41 pm
Joined: Sun Aug 03, 2003
Location: Erie, PA
If you don't mind spending a few bucks, you might get away with
buying one of the chargers made to plug into a car cigarette lighter
and interfacing it with your solar panel. The voltage specs seem to
agree well. Should be a simple 2-wire connection between the two devices.
This one is made for the ThinkPad
- Kirt Blattenberger
RF Cafe Progenitor &
Post subject: Re: How do
you charge a laptop battery with a solar panel ?Posted: Fri Jul 17,
2009 1:29 am
Joined: Tue Dec 30, 2008 1:53
Yes, I have one of those bookmarked actually.
In fact a few months ago I bought an inverter to plug into the cigarette
lighter, and now I'm thinking I should have just used one of those.
But this time I'm powering off the solar panel.
And it still
seems to me that the laptop will try to draw more than the panel will
That's what I'm trying to figure out actually, if someone
can fill me in.
But thanks, nevertheless.