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Question about Solar Lithium Ion/Polymer charger - v1.0
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Question about Solar Lithium Ion/Polymer charger - v1.0

by tablet on Wed Jan 09, 2013 1:45 pm

Hello,
I have the charger Solar Lithium Ion/Polymer charger - v1.0, and I wonder if I can charge this battery:
https://www.adafruit.com/products/353
The battery has 3 balanced 2200mAh cells. The charger, MCP73871, can only charge batteries with a cell. Then, how can I charge this battery? I need to charge the battery with a solar panel.
Thanks,
Regards.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tastewar on Wed Jan 09, 2013 2:06 pm

I have those very components, along with the large (3.4W) solar panel (product id 500). I put everything together a few days back, and when I remember, I put them by a window where the sun will hit the panel. All indications (LEDs) are that it's charging just fine, but I haven't filled the battery yet! (note that I don't always remember to move the panel where it will get sun, it's inside getting sun thru new efficient windows which probably block some sun, it's been somewhat cloudy, etc.)

I'm not sure what the phrase "can only charge batteries with a cell" means...
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by adafruit_support_bill on Wed Jan 09, 2013 2:19 pm

The charger, MCP73871, can only charge batteries with a cell

What that means is that the charger is designed to charge a 3.7v cell - not two or more in series.
The 6600mAh pack is 3 wired in parallel, so they appear as a single cell to the charger. The cells are carefully balanced, so that they will charge & discharge evenly. So it is safe to charge this pack with your charger.

Charging a high capacity pack like this can take a while. To speed things up, you can increase the charge rate by soldering in a programming resistor. For details, see "Adjusting the Max Charge Current" here: http://learn.adafruit.com/usb-dc-and-so ... he-charger
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tablet on Wed Jan 09, 2013 4:31 pm

Hello, thanks for reply. I have a question. I am using this product:
https://www.adafruit.com/products/500
output 6V at 530 mA, 3.4W.
The output voltage for this panel with cloudy days is less than 5V, then the charger not work.
Datasheet of charger:Use any 6V solar panel (6V seems to work best, 5.5V may work, 5V does not work)
I'm thinking to use a more big solar panel,12V 10W, for I get more voltage in cloudy days and regulate the output voltage of solar panel to connect the charger.
What do you think?
I use the resistor for increase the charge rate, I solde two resistors of 1K in paralell with the resistor of 2K.

Regards.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by adafruit_support_bill on Wed Jan 09, 2013 5:37 pm

Regulating 12v down to 6v to run the charger would not be very efficient. A larger 6v panel would be a better choice.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tablet on Thu Jan 10, 2013 5:04 pm

Hello, You think the battery will charge if i have a continuos consumption of 50mA with 6 hours sunlight each day.
Thanks,
Regards.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by adafruit_support_bill on Thu Jan 10, 2013 5:15 pm

50mA for 24 hours is 1200mAh. To get 1200mAh of charge at 80% charge efficiency, you will need about 1500 mAh of charging power. Divided over 6 hours that would be a charge rate of 250mA. To get 250mA at 6v, your solar panel would need to average 1.5W over the 6 hours.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tastewar on Fri Jan 11, 2013 2:57 pm

adafruit_support wrote:
Charging a high capacity pack like this can take a while. To speed things up, you can increase the charge rate by soldering in a programming resistor...


I'm trying to make mine as flexible as possible. Does this resistor affect the charge rate across all input sources, or is the USB port separately limited to 500 mA? (If not, I think that would make a nice enhancement for a rev b board...)

Semi-related question: For charging USB devices, I've seen you use the MintyBoost along with, so I've got (another) one on my WishList. It appears that you don't sell it without the battery holder, is that true? Finally, I must be overlooking something, but I don't see the output voltage (LOAD port) mentioned anywhere. What is it?
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by adafruit_support_bill on Fri Jan 11, 2013 3:45 pm

Does this resistor affect the charge rate across all input sources, or is the USB port separately limited to 500 mA?

The chip itself doesn't know what the input source is. The programming resistor just limits the maximum charge rate allowed for the battery.

you don't sell it without the battery holder, is that true?

True.

I don't see the output voltage (LOAD port) mentioned anywhere. What is it?

The connector labeled "LOAD" is where you connect your load (in this case the MintyBoost) to the charger.

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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tastewar on Fri Jan 11, 2013 4:30 pm

Ha! That's funny :-)

No, I understand what it is, just wondering what voltage is supplied. Sounds like it will use Solar (or whatever input) if sufficient, and battery if not. Solar panel could be 6V, USB -- 5ish, DC input -- whatever(!), and battery, 3.7. What should I expect for voltage across those two pins?
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by adafruit_support_bill on Sat Jan 12, 2013 6:59 am

The "load sharing" function of the chip will switch between the input source and the battery, depending on available power and battery charge state. So the voltage at the LOAD terminals can vary a bit.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by john444 on Sat Jan 12, 2013 3:22 pm

Hi Tastewar,

tastewar wrote:just wondering what voltage is supplied.

The voltage on the 'LOAD' terminal seems to be roughly the same
as the battery voltage. Varies from about 3.3 to 4.2-V.

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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tastewar on Sat Jan 12, 2013 6:14 pm

Thanks. Seems like the MintyBoost is a good addition.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tablet on Mon Jan 14, 2013 4:34 pm

Hello, thanks for the information. I have a new question. The maximun output current of solar panel is about 530 mA, then, the output current of charger will never be 1A, or I am wrong.
Thanks,
Regards.
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Re: Question about Solar Lithium Ion/Polymer charger - v1.0

by tastewar on Mon Jan 14, 2013 4:44 pm

The battery discharge rate should be independent of the solar panel's output. *If* you have been able to charge the battery, it should be able to discharge at its own rate. So the output at the LOAD terminal can be greater. But yes, if the solar panel is the only input, you can't charge the battery faster than the solar panel's output.
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