[Solved] Solar Charging a LoPy

[roadfox]

Hi
I have a LoPy on the pycom expansion board with a LiPo attached to the battery plug.
Now i would like to charge the LiPo with a solar module. But it's unclear to me where to attach. Is the +5V on the pycom expansion board a suitable input? or do i have to cut a usb cable and attach the solar module to the USB port?

Thanks to all the Replies

Summary:

• The 5V VIN on the pycom expansion board is NOT usable for charging a battery on the battery connector
• a powerfull 5V charging source can be connected to the USB connector and the LiPo or NiMH on the battery connector get's charged
• for a "weak" source like a small solar panel you have to build your own "charger"

Solar Charging:

• a very good hint form @jmarcelino is to use a TI BQ25570 energy harvester chip to connect a solar pannel to different kinds of batteries/accumulators

[livius]

@roadfox
look here https://forum.pycom.io/post/6639

[roadfox]

I cannot find an answer to my question on this thread. To me it's still unclear if a can feed the 5V for charging the LiPo trough the VIN pin on the expansion board or if the charging Voltage HAS to be fedd over the USB connector.

[livius]

@roadfox
First - you cannot attache solar panel direcly - you must use some regulator
and i link it for you in below post -there is solutoion for 3V3 pin. You can use VIN but max 5.5V if i remember corecly.
Without regulator you can have e.g. 7V on your solar panel and this damage your Lopy.

But someone can correct my answer if i am wrong here.

[jmarcelino]

@roadfox
No, feeding 5V through the 5V pin on the expansion board will not charge the battery because that comes after the autoswitching power mux (which does reverse voltage blocking)

[roadfox]

@livius said in Solar Charging a LoPy:

@roadfox
First - you cannot attache solar panel direcly - you must use some regulator
and i link it for you in below post -there is solutoion for 3V3 pin. You can use VIN but max 5.5V if i remember corecly.

To Charge a LiPo you need a higher Voltag than the Cell so i doubt that i can charge my 3.7V ratet LiPo with 3.3V

Without regulator you can have e.g. 7V on your solar panel and this damage your Lopy.

My "regulator" consist of a 5V Z-Diode, that protects the expansion board from overvoltage

[livius]

@roadfox

i would like to charge the LiPo

somehow i omit that you mean charge LiPo not power Lopy throught.

[roadfox]

@jmarcelino Many thanks for clarification, so let's cut that USB cable then :-)

[maamar]

I do the test with Lipo batterie 1200mAh and solar panal 5V , 450ma, and it works the whole day, but I have some trouble sometimes to swap directly to lipo, and I may be lipo was discharging !

[jmarcelino]

I've been running the SiPy from a $7 solar panel into a TI BQ25570 energy harvester chip and supercap bank.

Hope to get some time to write about it soon.

I don't have data to back this so take it as is , but using the expansion board for this seems very inefficient to me.

[gcapilot]

@livius I think you're right about the damage - my solar panel produced 7v and fried my expansion board.