Freenove 4WD car with Raspberry 4 won’t boot up from batteries but will when plugged in

Question

We have been building the 4WD Freenove car with a Raspberry Pi 4. We purchased two Samsung 18650 batteries.

When we try boot up from battery power the red LED turns on the Pi. However the green ACT LED doesn’t or barely lights up and we get no action!

If we plug the Pi in (while mounted and connected to the Freenove car) it boots up no problem.

What could cause this? The SD card works (evidenced by booting when plugged in), and we have red LED power light when powered via battery but it won’t boot!

Thoughts? Are my batteries dead? They are brand new!!

How are your samsung batteries wired to the freenove car and Pi? Post a photo. — CoderMike, Jan 31 '22 at 16:43
Ya, we would need to see how these are wired, and if you have a regulator in use, how that is wired. Nominal voltage for those are 3.6V so if you are using them in parallel, I doubt there is enough voltage to boot. If the batteries are in series with no regulator, you would have 7.2 Nominal which is a little high, and those cells can be as high as 4.2 each, so 8.4 which is too high for the Pi. So you really should be running these in series with a good 5v regulator to bring the voltage down to the right range. — Chad G, Jan 31 '22 at 17:47
Ok I will it is built into the actual car so it is a full kit. Trying to figure out how to add a pic — Saul, Jan 31 '22 at 18:16
I have added an image of the back of the car. The battery system is on the actual car. As mentioned the Pi shows a red led when we switch it on just won’t boot up! (Unless we plug it in!) — Saul, Jan 31 '22 at 18:26
The car comes directly from the freenove 4wd smart car kit we didn’t do any of the battery wiring and the pi is getting some power because of the red light — Saul, Jan 31 '22 at 18:38

score 2 · Answer 1 · answered Jan 31 '22 at 20:38

2

Based on the information in your question, the likely suspect is the input voltage to the RPi is below 4.63V. Yeah - 4.63V is an odd number, but it's based on the value of the PMIC's internal reference - explained here.

For battery-powered projects, the RPi4 would ordinarily be a questionable choice - because it consumes the most power. See this table in the "official" documentation that lists the Typical Power Requirements for all RPi models.

But if you need the RPi4 performance, you need more stored energy. If you've not developed an energy budget, you should; here's a start. If you have other questions, we'll try to help, but suggest you provide more details in your question.

answered Jan 31 '22 at 20:38

Seamus

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thanks. The kit was purchased as a gift by my father to my son! I agree that the pi4 may be too power hungry ultimately for this application. However we purchased two 3.7v 18650 batteries so we should have sufficient voltage! I will review the other docs you link to to see what more I can learn and will share more later. Thanks again!! – Saul Feb 01 '22 at 20:01
@Saul: Good luck - there are lots of Q&A here on power-related issues, but let us know if we can help. – Seamus Feb 02 '22 at 21:46

tlfong01 · Answer 2 · 2022-02-02T07:31:07.373

Answer

Your pink batteries might be fake.

I googled the FreeNove 4WD datasheet which says the following about their LiPo batteries requiring discharging current > 10A:

1. 4WD Smart Car Kit for Raspberry Pi
... Both flat and button top 3.7V 18650 batteries with discharge current >10A.
... For 18650 capacity, it should be 2000~3500 mAh. A bigger capacity may be fake.

References

(1) Freenove 4WD Car Kit for Raspberry Pi [Overview] 27,622 viewsOct 18, 2019

(2) Freenove 4WD Tutorial for 4WD Car Kit FNK0041 4,957 viewsMar 9, 2021

(3) Freenove 4WD Chapter2 Assembly & Chapter3 Test Freenove 4WD Pi Car 6,545 viewsAug 20, 2021

(4) Freenove 4WD Smart Car Kit for Raspberry Pi 4 B 3 B+ B A+, Face Tracking, Line Tracking, Light Tracing, Obstacle Avoidance, Colorful Light, Ultrasonic Camera Servo Wireless RC - Amazon us$70

(5) Freenove 4WD fnk0043 Tutorial pdf - FreeNove

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