# Solar Powered Li-Ion Battery Charger

R

#### Ray D.

Jan 1, 1970
0
Hey all,

I'm going to be building a solar powered Li-Ion battery charger for a
class project, and I just wanted to ask a few questions that I hope
some of you may be able to help me out with.

First off, here are the specs for the battery:
Camera: Minolta DiIMAGE G500
Battery: Lithium Ion NP-500, 3.7V, 820 mAh

I think I found a good match for a solar cell and IC - the links are
below:
http://www.sparkfun.com/commerce/product_info.php?products_id=7840#

Unfortunately the only specs given for the solar cell are Voc = 8V,
Isc = 310 mA. I also estimated the power dissipated in the IC (as per
the equation in the datasheet) and it is nearly negligible - about 50
mW.

Some assumptions that can be made are the device will be used only
during peak sun hours and will be angled perpendicular to the sun for
maximum insolation on the cell. I don't necessarily need the battery
to fully charge in one shot, but merely keep the battery from dying
over the course of a week or so.

So with that said, is there a way to determine (or estimate) the
operating point of the solar cell without an IV curve? Obviously the
output of the chip will be around 4V (battery voltage), so does that
imply the solar cell will be operating at that voltage? The pulse
charger requires a current limited source (which a solar cell is
inherently), so will that mean the solar cell operating point will be
the lowest Vcc at which the IC will operate, in order to maintain the
highest current? I'm just confused as to how determine the operating
point of a device that uses a pulsed current, where the high current
value is basically the maximum the solar cell can provide.

I'd also like to do a load analysis. What do you think would be the
best way to do this? I know most are simply a static voltage and
current value multiplied to give you the power (and also time the
device will be used to yield an energy figure). Again, though, the IC
is a pulse charger and has two main sections in the charge cycle -
constant current and constant voltage (where the current pulses
decrease until it reaches full charge). Should the load analysis
follow the complexity of the device, or would a simple estimate of
output voltage and charging current suffice?

just use a car battery adapter for power', or 'you can buy a solar
powered charger at this website'. I'm doing this project and want
some helpful input! Any suggestions or help in understanding the
solar cell operation with this chip and battery are greatly
appreciated! Thanks so much.

P

#### Phil Allison

Jan 1, 1970
0
"Ray D."
I'm going to be building a solar powered Li-Ion battery charger for a
class project, and I just wanted to ask a few questions that I hope
some of you may be able to help me out with.

First off, here are the specs for the battery:
Camera: Minolta DiIMAGE G500
Battery: Lithium Ion NP-500, 3.7V, 820 mAh

I think I found a good match for a solar cell and IC - the links are
below:

http://www.sparkfun.com/commerce/product_info.php?products_id=7840#

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,P9551

** That charger IC is probably *quite unsuitable* for use with a small
solar panel - due to the total unpredictability of available voltage and
current.

Quote:

" I don't necessarily need the battery to fully charge in one shot, but
merely keep the battery from dying over the course of a week or so. "

Since you only require to perform top ups on the battery - simple, direct
connection is all you need. That solar panel will likely never deliver
more than 200 mA anyhow.

Rest of your tortured, over-analysing deleted.

...... Phil

R

#### Ray D.

Jan 1, 1970
0

Sorry about that - the chip I was looking at was the LTC4052-4.2. The
link you have there is for the LTC4062 which is a linear charger - not
suitable since the power dissipation is much greater.

** That charger IC is probably *quite unsuitable* for use with a small
solar panel - due to the total unpredictability of available voltage and
current.

Are you referring to the unpredictable operating point of the cell, or
the unpredictability of the sun? If it's the latter, I already said I
would only use it on a perfectly clear day where the solar insolation
is relatively constant for the time the battery is charging (anywhere
from 1 -3 hrs at around 12PM). If conditions were hazy or cloudy, I
wouldn't be using the charger. Also, the IC accepts a voltage range
from 4.5V-10V, so as long as the current is somewhat constant (which
it is over a wide range of voltages on the IV curve, and I think it
would be as long as the insolation does not greatly vary) I don't
think the voltage changes would affect the system too much, right?

Quote:

" I don't necessarily need the battery to fully charge in one shot, but
merely keep the battery from dying over the course of a week or so. "

Since you only require to perform top ups on the battery - simple, direct
connection is all you need. That solar panel will likely never deliver
more than 200 mA anyhow.

I don't think directly connecting it would be a good idea because
there would be no means for over-charge protection. Also, a Li-Ion
battery needs to charge in two steps where the second step does not
demand a constant current like the solar cell would most likely
provide (and does require constant voltage of ~4.2 volts which I doubt
the solar cell would provide). And for a battery with a capacity of
820 mAh, 200 mA does not seem insignificant. Obviously it would take
a few hours to fully charge, but like I said, if I built this and the
solar cell provided 200 mA for an hour or two I think that would
suffice to keep the battery from dying. I really want to know, with
this setup, what would determine the operating point of the solar cell
(more specifically the voltage). As long as the voltage isn't close
to Voc (where the current on the IV curve severely drops off), I think
the current would be high enough to provide sufficient charging.

P

#### Phil Allison

Jan 1, 1970
0
"Ray Dope"
"Phil Allison"
Sorry about that - the chip I was looking at was the LTC4052-4.2. The
link you have there is for the LTC4062 which is a linear charger - not
suitable since the power dissipation is much greater.

** Yaaawnnnn .....

Are you referring to the unpredictable operating point of the cell, or
the unpredictability of the sun?

** The sun is quite predictable - been that way for ages....

Shame about the weather, sun angle and assorted light obstructions etc.

If it's the latter, I already said I
would only use it on a perfectly clear day where the solar insolation
is relatively constant for the time the battery is charging ....

** I will puke if you post this utter TRIPE again.

Tip:

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something.

** Snip more spew inducing drivel....

I don't think directly connecting it would be a good idea because
there would be no means for over-charge protection.

** Your pathetic, wimpy panel is all the protection you need.

Snip more spew inducing drivel ....

....... Phil

R

#### Ray D.

Jan 1, 1970
0
** Yaaawnnnn .....

** The sun is quite predictable - been that way for ages....

Shame about the weather, sun angle and assorted light obstructions etc.

** I will puke if you post this utter TRIPE again.

Tip:

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something.

** Snip more spew inducing drivel....

** Your pathetic, wimpy panel is all the protection you need.

Snip more spew inducing drivel ....

...... Phil

You know, I'd really prefer if you didn't reply - if I was looking for
a pompous jackass I wouldn't have posted this on an electronics forum.

P

#### Phil Allison

Jan 1, 1970
0
"Ray the ASD fucked Dope"
Are you referring to the unpredictable operating point of the cell, or
the unpredictability of the sun?

** The sun is quite predictable - been that way for ages....

Shame about the weather, sun angle and assorted light obstructions etc.

If it's the latter, I already said I
would only use it on a perfectly clear day where the solar insolation
is relatively constant for the time the battery is charging ....

** I will puke if you post this utter TRIPE again.

Tip:

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something.

** Snip more spew inducing drivel....

I don't think directly connecting it would be a good idea because
there would be no means for over-charge protection.

** Your pathetic, wimpy panel is all the protection you need.

Snip more spew inducing drivel ....

GO DROP DEAD - you fucking autistic asshole.

....... Phil

M

#### Mark

Jan 1, 1970
0
I really want to know, with
this setup, what would determine the operating point of the solar cell
(more specifically the voltage).  As long as the voltage isn't close
to Voc (where the current on the IV curve severely drops off), I think
the current would be high enough to provide sufficient charging.-

the easiest way may be graphically..

draw an IV curve of the solar cell at some illumiunation...

see where they intersect...

the usual object is to operate near the peak power point of the solar
cell.

Mark

R

#### Ray D.

Jan 1, 1970
0
"Ray the ASD fucked Dope"

** The sun is quite predictable - been that way for ages....

Shame about the weather, sun angle and assorted light obstructions etc.

** I will puke if you post this utter TRIPE again.

Tip:

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something.

** Snip more spew inducing drivel....

** Your pathetic, wimpy panel is all the protection you need.

Snip more spew inducing drivel ....

GO DROP DEAD - you fucking autistic asshole.

...... Phil

You're a sad little man, Phil. I really feel sorry for you.

R

#### Richard Henry

Jan 1, 1970
0
You know, I'd really prefer if you didn't reply - if I was looking for
a pompous jackass I wouldn't have posted this on an electronics forum.

I see you've met Phil.

R

#### Ray D.

Jan 1, 1970
0
I see you've met Phil.

lol, yea.... after snooping around I'm noticing that this type of
behavior is not all that unusual for him. I think it's funny how
people like him are arrogant and ignorant behind the comfort of the
internet. I bet he's really some socially inept nerd who is pissed
off at the world. Luckily that's not my problem so he can be as
demeaning as he wants, I'm just going to ignore him.

P

#### Phil Allison

Jan 1, 1970
0

** Go **** your mother - again -

you posturing, autistic pile of sub-human garbage.

...... Phil

P

#### Phil Allison

Jan 1, 1970
0
"Ray the ASD fucked Dope"

** I will puke if you post this utter TRIPE again.

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something - you dumb as dog shit cunthead !!!

- you autistic fucking asshole.

...... Phil

R

#### Ray D.

Jan 1, 1970
0
"Ray the ASD fucked Dope"

** I will puke if you post this utter TRIPE again.

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something - you dumb as dog shit cunthead !!!

- you autistic fucking asshole.

...... Phil

"Autism - A psychiatric disorder of childhood characterized by marked
deficits in communication and social interaction, preoccupation with
fantasy, language impairment, and abnormal behavior, such as
repetitive acts"

That sounds like you, Phil! Perhaps Tourettes? Hmm...

P

#### Phil Allison

Jan 1, 1970
0
"Ray the ASD fucked Dope"

** I will puke if you post this utter TRIPE again.

Load it with a 5.1 volt, 5W zener and insert a current meter is series.

Learn something - you dumb as dog shit cunthead !!!

- you autistic fucking asshole.

"Autism - A psychiatric disorder of childhood....

** Totally false - it is neither " psychiatric " nor limited to children.

ASD is a life long, mental disability characterised by many things -
including obsession with hypotheses and irrelevant detail while completely
failing to comprehend the wider picture.

That you have repeatedly ignored the idea of buying a panel and testing its
behaviour in preference to holing a pointless mid-air debate proves the
point.

...... Phil

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