USB / DC / Solar Lithium Ion/Polymer charger

by tyn on Sun Oct 27, 2013 11:06 pm

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

by adafruit_support_rick on Mon Oct 28, 2013 2:29 am

The schematic is here
To get a 1A charge rate, change R11 from 2K to 1K
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Re: USB / DC / Solar Lithium Ion/Polymer charger

by tyn on Mon Oct 28, 2013 9:35 am

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

by adafruit_support_bill on Mon Oct 28, 2013 10:02 am

The charge rate is limited by the charger to 1A max. It doesn't matter how much your panel is capable of providing.
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Re: USB / DC / Solar Lithium Ion/Polymer charger

by tyn on Mon Oct 28, 2013 10:24 am

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

by tyn on Thu Oct 31, 2013 9:54 am

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

by adafruit_support_bill on Thu Oct 31, 2013 10:02 am

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

by tyn on Thu Oct 31, 2013 10:24 am

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

by adafruit_support_bill on Thu Oct 31, 2013 10:57 am

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

by tyn on Thu Oct 31, 2013 11:23 am

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

by adafruit_support_bill on Thu Oct 31, 2013 11:31 am

The 3-cell 6600 mAh is three matched cells in parallel with a balancing circuit. It appears as a single cell to the charger.
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Re: USB / DC / Solar Lithium Ion/Polymer charger

by tyn on Thu Oct 31, 2013 2:28 pm

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

by adafruit_support_bill on Fri Nov 01, 2013 4:55 am

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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