Solar harvesting into Li-ion battery

AEMLION R2 has the two LDOs configured to a fixed 3.3V and 1.8V. This works fine for most people. However some people wanted to further reduce power consumption of their application by lowering the output voltage to resp. 2.5V and 1.8V. Below is the table with Battery and LDO configuration pins of the AEM10941 chip. CFG0[1) can be changed from 1 to 0. With this setting the battery can be used down to 3.01V in stead of 3.60V in R2. 

This change will greatly extend battery life of the application. People asked me how to change the pin. I had to tell them that the CFG[1] is set by a copper trace UNDER the chip, this makes it almost impossible to modify the AEMLION R2 board. 

So no I have redesigned the PCB. In AEMLION R3 the LDO voltages can be set using a 0R jumper resistor.

This board is not for sale yet because I still have large stock of R2, I think in few months I will order a new batch of 100 which has the new design.  

I compared AEM10941 to BQ25570 and it shows that AEM10941 is the best for solar. 

For thermal I would choose BQ25570 

For the HackadayPrize 2018 I designed a Tiny Solar Energy Module. It is cool because it can harvest enough energy from indoor light to power simple BLE or LoRa applications. I am selling two boards on Tinde for $24.90. One stores it's energy into a Li-ion battery, EAMLION, and the other stores it into a pair of supercapacitors, AEMSUCA. This is really cool because now you can make applications that runs forever from indoor light without a battery!

Tiny Solar Energy Module project on Hackaday.io
https://hackaday.io/project/159139-tiny-solar-energy-module-tsem

AEMLION project on Hackaday.io
https://hackaday.io/project/160376-solar-harvesting-into-li-ion-battery

AEMSUCA project on Hackaday.io 
https://hackaday.io/project/160470-solar-harvesting-into-supercapacitors

AEMLION is sold on Tindie  for $24.90
https://www.tindie.com/products/jaspersikken/solar-harvesting-into-li-ion-battery/

AEMSUCA is sold on Tndie for $24.90
https://www.tindie.com/products/jaspersikken/solar-harvesting-into-supercapacitors/

Yesterday I have received 50 assembled boards from Elecrow. I tested them with simple test rig and they all work well. I am very happy with the quality delivered by Elecrow. I started selling on Tindie.

https://www.tindie.com/products/jaspersikken/solar-harvesting-into-li-ion-battery/

50 PCB assemblies were finished by Elecrow and shipped to the Netherlands. They arrive tomorrow, but I have no time to test and fulfill Tindie orders soon because few days ago my wife gave birth to a baby boy!

I have created a simple test rig to test the oncoming batch of 50 AEMLIONs. It applies 1.5V to the solar input and it has LEDs connected to the 3.3V and 1.8V. This basically tests the circuit. It does not have a bed of needles but it simply two 5 pins rows of vertical male headers that are under 15 degree angle. When you push the board between the pins they make contact with the castellated vias.

The package with the 50 AEM10941 ICs shipped with PostNL on 6 Sept still has not arrived at assembler Elecrow. It is stuck since Sept 18th at customs. After a short Chinese holiday Elecrow is working with customs again and try to release the package. I expect It wont take long. 

I have shipped AEM01941 ICs using PostNL to the assembler Elecrow in China for assembly of 50x AEMLION. I have prepared the Tindie webshop were I will be selling them. However the parcel has not arrived at Elecrow. PostNL track and trace shows on Sept 18th the package was released by customs in China, after that no more updates :-(. Elecrow now is working with customs to get the package. PostNL will not try resolve the problem before Oct 2nd, so that sucks. The package is just sitting there until then... To try out my own webshop I have sold 1 prototype to someone in California and received a lot of interest, at this time there is a waitlist for 14 pieces. 

In May/June I have designed the 1x1 inch Tiny Solar Energy Module to take part in the HackadayPrize2018 Power Harvesting challenge and won! And then I received a lot of interested in selling it. However since most projects have different power demands and people want to choose their own solar panel, I decided to remove the onboard solar cells and make two even tinier designs derived from the TSEM. They are both 0.8x0.6 inch small. The first is the AEMLION which is charging a Li-ion battery and the second is the AEMSUCA which charges a pair of supercapacitors. 

I will be selling the AEMLION and AEMSUCA on Tindie for $24.90. At the moment ELecrow is working on 50 assemblies of each.

I have measured AEMLION battery charge current using three different solar panels in indoor light (500 lux), outdoors in the shadow, and in full sun (~500W/m^2). 

Indoors (~500 lux) and with the smallest solar cell the battery is charged at 50uA for 10 hours. Then the application must have an average current of (50uA*10hrs/24hrs) 20uA or less. That's enough for a simple Bluetooth Low Energy beacon or a very simple LoRa application. If that is not enough you need to select a larger solar panel. 

Outdoors in shadow current is 10-20 times larger. And in sun 100 times larger. 

As you can see the AEM10941 can charge a battery from indoor light but indoor light is really only suitable for very low power applications.

Recently I ordered 50x PCB assemblies from Elecrow that i want to sell on tindie,  but I need a testrig for it. I quickly made one with prototype board, 0.1" headers, a battery, a capacitor, some leds and resistors.

I just press the board-under-test between the two rows of angled male headers, and then the solar input gets 1.5V from the battery and the LEDs indicate the 3.3 and 1.8V outputs work. Basic functionality checked!