@arthurlutz I'm using a Max17043 to read the State of Charge of a LiPo Battery, It sits between the battery and the charger or the wipy. (https://datasheets.maximintegrated.com/en/ds/MAX17043-MAX17044.pdf) sparkfun has a nice board for it (https://www.sparkfun.com/products/10617) It uses I2C to get the state. Even wrote a library for it (https://github.com/andrethemac/max17043.py). André

I am using the expansion board 2.0. I have no deep sleep shield yet (Pycom forgot to send the deep sleep shield with the order of the lopy 2 weeks ago. They told me a deep sleep shield is on its way now) We deinit the WLAN from start because we don't use it. We charge just using the micro-usb cable. It is configured with the jumpers at 450mA charge current. In the battery test we did, we intentionally drained the battery fully to see how long it would last. We expected the LoPy to stop working eventually, but expected we would be able to recharge it using the USB connection at that point. Can the deep sleep shield -if used on the LoPy 1- recharge a drained battery by just plugging the USB-cable in after the battery was exhausted and shut off by the deep sleep shield?

@martinnn said in Pysense charging current: @peterb If you look at the PCB, from pin 2 (ISET) of the charger a trace goes directly to a 0402 resistor (which is connected to GND), measuring 1.2 kOhm. Looks pretty obvious to me. Probably difficult to see without microscope though. Thanks! I will find a mircroscope.

Many thanks!

When working with unprotected cells, a circuit like this should work fine, right? [image: 20170825235011-yimzrv24.png] With a MAX6430EGUS+T, the ~LBOH output turns low when battery voltage is <3.3V, while ~LBOL turns low when battery voltage is <3.0V. That should trigger the left MOSFET and turn off the entire circuit.

@jmarcelino Was the battery type (Li-Ion) anywhere documented regarding the charger chip? That all should be by the vendor. I would probably combine the expansion board electronics with the LiPo Rider Pro. But I don't like to put too much unnesecary chips onto the board. I am not yet aware of charger and protection circuits (as discussed in my other thread https://forum.pycom.io/topic/1671/expansion-board-lipo-save-power-down-function-so-save-lipo-undervoltage) Assembling these two boards and connecting them with another USB cable is ok for prototyping, but nit ok for a end product - so to say :-) What about a KiCad project on github? Collecting circuits for various aspects? And documenting application notes for combining them into new ones? Btw, I have ordered three ADS1115 4 channel 16 Bit converters to monitor these voltages. It get's an interesting project... What is not yet clear to me is the fact that batteries probably have their own undervolt protection, that could nock out the remaining circuit so that it stops recharging in an undervolt situation, if not properly designed. So for my experiment, could I put the Seeed Studio Lipo Rider Pro battery connector in parallel to the expansion board battery connector and put there then the battery? If that is possible, I could keep switched off the step up converter for the USB port on the Lipo Rider and save me a USB cable :-)

My suggestion? Don't bother with ADC measurement. Get a "gas gauge" breakout, like the one from SparkFun: https://www.sparkfun.com/products/10617 I've created a thread with feature suggestions for the various expansion boards. One thing I'd like to see is the gas gauge IC integrated to all boards; preferably the MAX17048 (which is a newer, more power-efficient version of the IC on the previously-mentioned breakout). Forum thread here: https://forum.pycom.io/topic/2476/expansion-board-suggestions

@scg94 Even if a solar cell is mostly a current source, I would limit the voltage to about 5V, to be compliant with the regulators and the interface you are using. About the charge current look at the documentation here : https://docs.pycom.io/pycom_esp32/_downloads/exp_v03_pinout_v13.pdf It's 450 mA (with jumper) or 100 mA (without jumper).