USB / DC / Solar Lithium Ion/Polymer charger

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tyn
 
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USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Hi, I had a question about the charger, I'm designing a project where the charger's charge rate can be 3A, can I do that with the "USB / DC / Solar Lithium Ion/Polymer charger"?
If not, then how can I change the charge rate to 1A by soldering a resistor? I'm a newbie to electronics, so please explain in plain. :)

http://www.adafruit.com/products/390#Description

Thanks in advance.

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_rick »

The schematic is here
To get a 1A charge rate, change R11 from 2K to 1K

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Thanks, but is that possible to charge with an 2.5~3A input solar panel? This project requires faster charge rate.

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_bill »

The charge rate is limited by the charger to 1A max. It doesn't matter how much your panel is capable of providing.

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Thanks.

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Is it possible to increase the charge rate to 3A by modifying the board? Or the limitation is from the MCP chip?

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_bill »

It is a limitation of the chip. Being a linear regulator, any excess voltage has to be dissipated as heat in proportion to the current being drawn. There is only so much heat you can dissipate from such a tiny package.

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Do you have any suggestions on a better chip that can charge with as large as 3A and has smart load sharing at the same time?
Have you ever heard of "R2A20057BM" chip? What do you think about this chip comparing the MCP one.
Here's the data sheet:
http://www.datasheetarchive.com/dl/Data ... 114801.pdf

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_bill »

That chip looks like it could do what you want. Just be sure to stay within the charge rate recommendations for the cells you are charging.

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Cool! Thanks,
But I saw that R2A20057BM only supports one lithium cell, does that means I cannot use it to charge a 3 cell li-ion battery that is listed on Adafruit website?

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_bill »

The 3-cell 6600 mAh is three matched cells in parallel with a balancing circuit. It appears as a single cell to the charger.

tyn
 
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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by tyn »

Thank you very much!

But does the R2A20057BM has over voltage and over current protection if I charge from a solar panel?
And does MCP has such functionality too? If the solar panel pushes more current than what the chip can afford, what would happen?

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Re: USB / DC / Solar Lithium Ion/Polymer charger

Post by adafruit_support_bill »

If the solar panel pushes more current than what the chip can afford, what would happen?
The chip in our solar charger does not limit the input current and if the voltage goes too high it will overheat. The R2A datasheet does mention something about input current limiting - although i have zero experience with the chip myself.

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