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By eddymart
#199276
Hi, i have buy a SparkFun Sunny Buddy, connected a 3.7v 1800mah lipo, and some solar panels (or dc, same things).
The battery never charge more than 4v. With an external lipo charger, same battery, no problem to go to 4.2v - full charge.

I have increase current with R_SENSE = 0.05ohm but no change, only 4v in battery.

Any idea?

Many thanks in advance.
By jremington
#199296
Solar panels: 6v in series, 18v in parallel
That cannot be correct.

If you want help, please provide a meaningful answer to this question: what is the voltage and the current provided by the power source used as input to the Sunny Buddy?
By Angel.zir
#200393
Hi,
It seems i have the same problem. My LiPo batery charges only up to 4.0V
It is a 1s 4000Mah LiPo.
My solar panel is:

Material polycrystalline silicon
Body dimensions 290 x 330 x 25mm
Voltage at max power 17.49V
Current at max. power 0.58A
Short circuit current 610mA
Maximum power 10W

The load on the buddy is a 5v step up converter --> Arduino Nano, a ultrasonic sensor hc sr04 and a HC-12 Radio.
I live in Greece, and believe me, its bright outside...

I added a 0.1 Ohm resistor in parallel on R_SEN, so 0.1/0.07=1,428 A
I turned the poti on the buddy to 3v with the panel pointing to the sun and no load and battery connected.

If you need any other information, please ask.
By Valen
#200716
4 volt battery voltage is as it is designed for. In the LT3652 datasheet on page 9 it is explained that charge function operates to achieve a final float voltage of 3.3 volt on the Vfb pin. If you look in the schematic you'll see that the voltage Vfb is made from the output (battery) voltage with a 220k/47k resistor voltage divider (R2 and R3). If you feed 4 volts into such a resistor pair then 3.3 volt comes out between them. I'm sure Sparkfun chose those values to cover most lithium-based battery chemistry.