Questions about Solar LiPo charger

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danwow
 
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Questions about Solar LiPo charger

Post by danwow »

I was wondering if the following was possible...

We have a small device, with average power consumption of ~20mA when active, and has a 150mA battery. I was hoping to use a large solar panel (actually the ID:1525) to trickle charge the battery. The location it is going to placed has rather poor daylight access, but is lit by a combination of MH or Fluorescent lights that are quite bright. We replaced the 2.2K SMD resistor with a 10k to drop the amperage (to 100mA) coming from the charger, as we don't need anything close to 500mA, to charge our 150mAh battery. Under the worst case situation the red power and amber charge lights flash once per second now, and I assume that its pulses are the large capacitor discharging. Is this sufficient to actually keep the LiPo charged if it is fully charged using USB before hand? Does decreasing the current, by increasing the resistance, mean that it will actually provide more frenquent pulses and actually charge quicker?

Thanks!

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adafruit_support_bill
 
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Re: Questions about Solar LiPo charger

Post by adafruit_support_bill »

Under the worst case situation the red power and amber charge lights flash once per second now, and I assume that its pulses are the large capacitor discharging.
The pulses do indicate that it is charging in short bursts as sufficient charge is built up in the capacitor. You mention 'worst case'; what do the indicator leds do under better lighting conditions?

danwow
 
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Re: Questions about Solar LiPo charger

Post by danwow »

Oh, under incandescent or sun light the LEDs are near solid or solid. I am not concerned about the functionality of the board, rather whether reducing the mA output using a higher resistance would increase the pulse rate.

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adafruit_support_bill
 
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Re: Questions about Solar LiPo charger

Post by adafruit_support_bill »

I don't think it would make much difference. The total power transferred to the battery would be the same.

As far as keeping it charged, the question is whether the average charge rate is equal or greater than the 25mA (assuming 80% charge efficiency and a 20mA discharge rate) If it were always pulsing, at a 100mA charge rate you would want to see at least a 25% duty cycle. If it is alternating between solid-on and pulsing, you need to be concerned with the overall average charge time.

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