Sunny Buddy Inductor Saturation at 2A

Components & Accessories Power
1

Hello forum,

From the V13 hookup guide:

Charge current = 1/(R1*Rsen)

Also given, Rsen = 1ohm will give 550mA charging current.

This implies=> R1 = 1/0.55 ohm

So to get 2A charging current(max limit of IC) => R1*Rsen = 1/2

So Rsen = 1/(2R1)=1/(2(1/0.55)) = 0.275 ohm = 275mOhm

Is this doable.?

Also, can the inductor withstand this output.? Because a saturation issue is found mentioned in some articles.

Thanks,

mahesh

2

Hi mahesh,

Unfortunately, you will not be able to set the charge current for the Sunny Buddy to 2A without switching inductors. The inductor on the Sunny Buddy has a max spec of 1.05A and the inductor will probably start to saturate above ~850mA. The engineer who designed this board replied to a similar question in the [comments on the product page.](https://www.sparkfun.com/products/12885#comment-55117659ce395f5d4d8b4567)

3

Hi TS-Mark,

So how efficiently someone can charge a 6000mAh battery using a 6W/8.8V panel connected to sunnybuddy.?

850mA would be small enough for it. Is there a recommended fix (or change inductor) here.?

Thanks

4

A short answer is not very efficiently. The peak power output of this [6W Solar Panel is 6V/1025mA in full sun and optimal conditions. Even with the Sunny Buddy configured to output at ~850mA it will most likely take over a day to charge a fully-discharged 6Ah battery since you will most likely not have 7 hours of optimal conditions in a single day. That is also assuming there is no load on the battery discharging it.

You could try adding a custom resistor to the R SEN pads on the Sunny Buddy to adjust the charge current. That is covered in the “Battery Output” section of the [Sunny Buddy Hookup Guide. We cannot help with adding a custom inductor to try and further boost the output of the Sunny Buddy.](Sunny Buddy Solar Charger V13 Hookup Guide - SparkFun Learn)](Solar Panel - 6W - PRT-13783 - SparkFun Electronics)