Charging current and SOC estimation on Thingy52

[Aleksandar Lazarevic]

Hello,

I was examining the power supply part of the Thingy and I noticed that the charging current is set to 0.5 C, wich is 720 mA (checking XR6804's datasheet it seems that actually it has been set to 784 mA). Given that there a USB port (max current is 500 mA) is used to charge the device, isn't the required current set too high?

I also checked the way the SOC is estimated and I found out that a "Battery voltage - SOC" look-up table is used. How has been that table filled, are those OCV measurements? If not, I guess a constant discharge current has been used and I'd like to know what is the value of that current.

Thank you in advace!

Aleksandar

[Bjørn Kvaale]

Hi Aleksandar,

I will get back to you on the first question. Update: If the USB cable can only provide 500 mA, then it will charge with 500 mA. If however you theoretically had a USB that can charge with 720 mA (or 784 mA), then this max current could be provided. 

For the second question, a constant discharge current was used & voltage of the battery was measured along the way. The Thingy:52 was fully charged & then constantly discharged until the battery was depleted. The discharge current used was 73 mA. The Thingy:52 battery capacity is 1440 mAh.

Kind Regards,

Bjørn