I mounted R-Divider breakout board, time to get some code working, but ready to measure from any 3.3V CPU with I2C and no descent Analog input, ohh, did I say ESP8266 ?
Solar Voltage Panel
Battery Voltage
On Board Voltage
Here are picture, as you can see, seems PCBs.io silk is much better now, really close to OSHPark
Assembled
I’ve just put 1% 1M+1M Resistors and 100nF filtering, so we divide input voltage by 2 (so up to 6.6V input)
@BoRRoZ
It’s just a R-Divider (if you already have Analog input on device) and if not (like ESP8266) you can stack it with ADS1115 board (I2C 4 ADC inputs) like below. You can see github readme for more information
You can find this ADS1115 board (new version smaller) on ebay for less than $3
yes , I have 2 possibillities, the Maynuo M9812 electronic load and the Turnigy Accucell 6
The Maynuo have a special battery testfunction and can, when connected to PC spit out information/graphs
You set the end voltage (normal between 2.75 and 3.2 V depends on the buildin protection circuit/datasheet)
and you set the discharge current (between 0.2 and 1 C)
then push start and go do the dishes/do some shopping and when reached the end voltage it stops discharging and give you the mAh.
what I really need is a logging power tool… like Ladyada have been busy finding a diy solution
I have a clone I think, anyway, if you connect them with an old PC powersupply you can do many things.
a very nice menu option is ‘storage mode’, the charger checks the lipo and if its full it start discharging to 70%, if its empty it starts charging to 70%.
one thing you must watch:
If you set it to LiPo discharge, it stops (preprogrammed) @ 3.2 V
What I do, i discharge LiPo with NimH selected , there I can set amps and voltage, so I set that to 2.8 V, then I know its really empty.
Then I set it back to LiPo and charge (it stops preprogrammed @ 4.2 v and when the current is < 0.01 A
Now you can read on the display the real capacity.
To spare your battery’s discharge @ 0.2 C and wait 10 minutes between discharging and charging.
I’m experimenting with a solar panel & supercaps.
The start looks promissing, but the main challenge is the power consumption of the LoraWan communication with the 3.3V RN2483.
The delay of the gateways is a problem for me because I live in the center of large white spot on the map in the Netherlands without existing coverage from TTN gateways. But better to wait and receive a solid product.
In case you want to check or add some suggestions, the URL is:
Still no sun today
I’m also curious how it is going to perform.
In case I need more current it is also possible to use multiple series banks in parallel but then it becomes more complex with balancing resistors in the supercap bank.
Today I tested a RN2483 for connectivity to ensure that is works, and it did! Still had to use the KPN LoraWAN network because there is no TTN gateway in range of my house. I used a terminal session and AT commands to insert the necessary config settings and saved in to the EEPROM of the RN2483. This simplifies the sketch on the Atmega328P.
Three challenges that I’m struggling with:
my 3.3V 8MHz breadboard Atmega328P can only be programmed with ArduinoISP programmer on 3.3V, I don’t have a working serial interface with my computer, think it’s the reset pin that is blocking
Autobaud of the RN2483 isn’t working and 57K speed is too high for soft serial of 8MHz MCU
I thought my situation would be simple and easy because my board is already 3.3V so no level shifter needed to the RN2483 and ISP programmer use had benefit that UART is unused so available for the communication with the RN2483 but Serial.print didn’t work or is this logical?
And don’t know the person you mentioned but every help is welcome.
Looks impressive!
It should be could to first really fully charge them and leave them for a day.
With your 5.5V caps in parallel you don’t need such a balancing system if I correctly understood.
I have similar caps like you ordered but one small disadvantage is that they are not breadboard friendly to experiment with. That is way I now use other ones.
for those of you with more electrical engineering experience, would a goldcap or a super capacitor be a good choice to power a LoPy in the field, if it gets additionally supported by a solar cell?
Just thinking about what is better in terms of long live…
The LoPy is only an example. It’s more about the type or class of device (low power device) and the powering options for really long periods without having to worry about charging cycles of a normal rechargeable battery.