Charging 3.7V 2800mAh CR123A using BQ25570 w/ 2V 160mA Solar Cell for Boron


I grabbed this BQ25570 breakout board from Aliexpress BQ25570 to use for charging CR123A 3.7V 2800mA CR123A battery using a 2V 160mA Solar Cell solar cell for BoronLTE project deployment.

The board didn’t come with any documentation, @Rftop I think you mentioned you had some experience with this board in a previous post that locked so I couldn’t follow up there. Any help on how to configure the GND, EN, V_EN, V_OK pins on the breakout board would be appriciated :slight_smile:

@babsndeep , I can’t find the box with most of my reference designs for indoor solar harvesting.

But going off of my memory, it seems like Grounding the EN pin was all that was required that wasn’t obvious. I think V-EN is only used to activate the buck regulator when needed.

Have you checked that your module will charge the onboard SuperCap (without any of your load attached) ?

I did just find these notes :

EN: IC enable pin is active low
V_EN: Buck regulator output mode enable pin is active high
V_OK: battery normal output flag ( 0V or VBAT), “Supercap is Charged”
VOUT is regulated to 2.6V when V_EN is tied to VBAT.

For this Module, I didn’t use the low voltage regulator output, since I connected my loads along with the Battery pins (but no Low Voltage Protection for Li-On chemistry going that route). I was using Large SuperCaps connected to the BAT Pins, not lithium.

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The module is charging the SuperCap without any load attached.

I have the following configuration:
BQ25570 EN connected to GND to enable IC.
CR123A connected to BQ25570 BAT + / -
Solar Cell OUT + / - connected to BQ25570 NPUT + / -
CRA123A also connected to Boron JST connector.

The boron is in deep sleep 98% of the time, the idea is to top off the CR123A using the Solar Cell / BQ25570 (which I think should be easy enough outside given just few hours of direct sunlight on the Solar Cell).

What do you think?
Appreciate the you digging into boxes to help :slight_smile:

What you have described should work.

Maybe it's possible that the CR123A is indeed charging but not easily noticeable due to the typical "flat" charging/voltage curve (considering these charge pumps are such a small source) ?
Especially since you've confirmed the module is charging the SuperCap as expected.

You might want to watch out for any change in the Battery Temperature between Voltage Measurements. A Li-On battery's Voltage changes with the battery temperature, more than I would've expected when you're trying to quantify the performance of a Low-Powered Project.

I assume that you are required to use this particular 2V Panel in this project.
Can you temporarily operate (2) Panels in series just to speed up the bench testing ?

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