• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 1221 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25570EVM-206: Solar cell recommendation

David__
Genius 3585 points
Part Number: BQ25570EVM-206
Other Parts Discussed in Thread: CC3220SF-LAUNCHXL, , BQ25570, CC3220SF, BQ25895, TIDA-01556

Hi, I have purchased BQ25570EVM-206, CC3220SF-LAUNCHXL, OPT3001DNPT, and HDC2080DMBT from Digikey.

My team is trying to create an outdoor Wi-Fi ambient tracking application.

This is the battery, which I bought from Adafruit, I'm trying to charge; Lithium Ion Battery Pack - 3.7V 6600mAh (PRODUCT ID: 353)

SHENZHEN PKCELL BATTERY CO, Model：ICR18650 6600mAh 3.7V 1S3P

https://www.adafruit.com/product/353

This is the detailed specification

I wish to charge this with a solar cell. I'm trying to create a prototype.

Q0. Is the EVM has a fixed voltage output of 1.8V due to R9 and R10 (or ROut1 and ROut2)?

If so, what part should I change to get 3.3V output, also supporting peak output current up to 110 mA? I'm creating a demo that draws 90mA from the 3.3V output.

If this IC cannot support this current, I hope to get an alternative solar charger + buck converter which supports higher output current.

Q1. For this battery, what solar should I connect at VIN (J1 & J2)? I'm new with the solar cell so I need your advice, please.

This prototype will be installed on a highway located in Tyler Texas, so we are trying to do solar charging during the day time.

https://www.turbinegenerator.org/solar/texas/tyler/

In Tyler TX, fixed Tilt Sunlight Hours: 4.9 hours per day

It would be best if the recommended solar cell (or cells) can reach the max Charge current, which is 0.1A.

If not, I wish to achieve 25mA as a minimum charging current.

Q2. Since I'm using the CC3220SF-LAUNCHXL, I thought 3.3V supply was necessary to use all the Wi-Fi features.

If I can use all Wi-Fi features with 1.8V supply, will connecting every ICs (BQ25570, CC3220SF, OPT3001DNPT, and HDC2080DMBT) extend the battery life compared to using 3.3V supply?

Q3. Does the BQ25570 have a feature that shows the remaining battery?

Or do I have to use a voltage divider or an IC from TI to get this?

Q4. Lastly, if I connect an external power supply instead of a battery at VBAT pin

(when the battery is not ready/want to test the system quickly),

will the power supply get affected when BQ25570 tries to charge it? I'm currently using RIGOL DP831

https://www.sicamax.ch/downloads/dp800_userguide_en.pdf

and I want to make sure I don't want to damage the external power supply.

Is there a VOUT disable/charge disable pin for BQ25570?

  • 0
    TI__Mastermind 19480 points

    Q0. The output voltage on EVM is fixed. You can use the below tool or equation in the datasheet to calculate the resistor divider value.

    The EVM can support ~110mA peak current.

    Q1: The maximum input voltage on BQ25570 is 0.1 to 5.5V. So any panel output is from 0.1 to 5.5V is capable. However, the charge current is ~110mA on BQ25570 and your battery is >6000mAh. Therefore, the charge time will very long.

    Please consider the reference design below which is for higher current charging.

    http://www.ti.com/lit/ug/tidudj2/tidudj2.pdf

    Q2: I am assuming you are referring to extend battery run time. Connect every thing to 1.8V rail on BQ25570 will not extend battery run time. When there is no enough input power, the 1.8V rail will get the power from the battery.

    Q3: No. 

    Q4: A regular one directional power supply cannot be used to simulate battery as it cannot sink current. You will need a Keithly source meter or a Kepco bypolar power supply to simulate battery. 

  • 0 in reply to Jing Zou
    Genius 3585 points

    Thanks, Jing.

    Jing Zou said:

    However, the charge current is ~110mA on BQ25570 and your battery is >6000mAh. Therefore, the charge time will very long.

    Please consider the reference design below which is for higher current charging.

    I see. Thanks for the recommendation. Although I don't have to charge my battery quickly, the size of the panel was another issue.

    My maximum size of the panel can be 8 inch x 4.5 inch (203.2mm x 114.3mm).

    Whereas this demo used a big solar panel.

    Q0. Just like BQ25570, the BQ25895 also generates 3.3V or 3.5V output to MCUs, right?

    Q1. I noticed the max charge current of BQ25895 is 5A. Then what's the max output current at 3.3V? It seems that this is not specified in the datasheet.

    Q2. Compared to BQ25570, the BQ25895 doesn't have internal MPPT( Maximum Power Point Tracking) controller?

    Since I'm new with this solution, adding a firmware or an extra MCU for MPPT seems a hassle to me.

    Q3. Also, in the above picture from TIDA-01556, what is the solar panel used for the design? I cannot find any BOM at all.

    Q4. Back to the original question for solar panel recommendation, may I ask my requirements;

    - BQ series that has buck converter (3.3~3.5V output supporting 110mA or above)

    + solar charging solution for single cell 6600mAh Li-ion

    + charge current 100mA or above

    + charge current

    + MPPT controller included (or if I can ignore MPPT  and still charge it, it can be an option for me)

    - solar panel size or 8 inch x 4.5 inch (203.2mm x 114.3mm) smaller to achieve specified charge current

    + Integrated Reverse Blocking FET for Solar Input Protection

    + Input High-Impedance Mode for Open Circuit Voltage

    + the panel that works with the BQ series

  • 0 in reply to David__
    TI__Mastermind 19480 points

    Hello David,

    The app note just shows an example of the panel we used in the test. It doe snot necessary to be the exact same. 

    What you need to watch out is the solar panel output needs to be within the input operating range of the BQ25895 or any devices you connect at the output of the solar panel.

    Q2. BQ25895 does not have a regulated output like BQ25570 but do have a similar path called SYS. Please start a new thread regarding on BQ25895. 

    Q3. The solar panel used in the application note is the one in the link below. Please start a new thread on questions regarding TIDA-01556. 

    http://webosolar.com/store/en/12v-24v-solar-panels/901-solarland-5watt-6volt-polycrystalline-solar-module-slp005-06u.html

    Q4: Regarding on solar panel options, we do not make recommendation of solar panels. As it varies from applications to applications. Typically you can go to digikey and search for the panels that can meet your power budget and size requirement.