Boron solar charging questions

Hardware
1

I have a solar powered boron on the bench today and was noticing a few things as it switches in and out of different light levels, was hoping someone might be able to enlighten me to what it’s doing under the hood:

  • Device has mesh/cell/etc turned off, but is awake with no light on the panel: draws 2.5mA from the lipo
  • Device gets low, partial sun, I can see 1-10mA coming from the solar toward the boron. Device actually increases amount drawn from the lip0 to 4-6mA
  • Device breaks some threshold on solar north of 12-15mA coming from the panel and switches over to ((solar mA)-3mA) going back in to the lipo.

The switch-over is really less predictable, sometimes I see it happen as high as 30mA being fed in. Scoped the input and the solar is providing a fuzzy-but-solid 5v any time there’s even remotely light on the panel.

If the light is at just the right level I’ll see the same 2.5mA coming from the lipo, a pretty consistant 1mA being drawn from the solar, and the solar voltage dips ~1-.5v briefely at a rate of 4hz. (edited to get measured rate)

Setup perimeters:

  • One DMM interrupting the positive line of the lip heading toward the boron
  • Another DMM interrupting the positive line coming from the solar panel
  • solar panel is small, roughly 3x4" area. good day puts out ~350mW
  • Somewhere in investigating I unsoldered the charge LED, figuring that might contribute to the increased current (IE charge light comes on, but isn’t really enough power to function). No meaningful difference in the above.

Code looks about like this:

detachInterrupt(LOW_BAT_UC);
delay(2000);
pmic.setInputVoltageLimit(5080);
pmic.setInputCurrentLimit(100) ; 
pmic.setChargeVoltage(4208); 
pmic.setChargeCurrent(0,0,1,0,0,0); 
pmic.enableDPDM(); 
pmic.enableBuck();

Seems like on a cloudy day where the solar panel is feeding a little bit in I’m actually using up more power than I would be without anything?

2

Bump in case anyone has any insight or advice at all on this…

3

I would get rid of this line:

pmic.setInputCurrentLimit(100) ;

And what does this setting set the charging current at?

pmic.setChargeCurrent(0,0,1,0,0,0);

4

Can do- I though that was required to keep the device from pulling too much current and collapsing the solar voltage?

Second one- based on this (lines 588 and on):


I (at leas think) this is setting the max current that can be applied to the battery to 512mA.

5

You don't need to limit incoming charging current if your using the code below along with DPDM because it will limit the charging current to keep the solar panels battery voltage from dropping below 5v.

pmic.setInputVoltageLimit(5080);

The 512mA charging current is just fine.

If your seeing discharging during the day when the solar panel is charging then you may need a bigger higher wattage panel.