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Topic: Electronics wired into car battery circuit (Read 126 times) previous topic - next topic

feynman137

Jan 14, 2021, 05:30 am
Hello,

I am trying to wire up the circuit below.  But am a little worried that as things are when the engine connected to the 12V battery starts-up it will suck power from the 5V battery or damage my circuit in some way.  

I plan to use a simple buck converter to take the 12V down to 5V.  Will this protect me from current flowing from the 5V battery bank back to the 12V battery during motor start-up?  Or should I add some sort of diode?

I apologize if this question seems overly basic.

CrossRoads

#1
Jan 14, 2021, 05:43 am
Diode would be a good choice to keep the battery from back driving the converter.

You should have a battery charge control circuit as well so the battery doesn't get overcharged.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

PerryBebbington

#2
Jan 14, 2021, 07:22 am
To take power from your 5V battery the vehicle battery would have to drop below 5V. If that happens then your vehicle battery is dead anyway.

Btw, there is no such thing as a 5V battery, no battery chemistry gives 5V.

johnerrington

#3
Jan 14, 2021, 08:44 am
What exactly are you trying to achieve?
I'm trying to help. If I find your question interesting I'll give you karma. If you find my input useful please give me karma (I need it)

feynman137

#4
Jan 14, 2021, 02:41 pm
Quote from: CrossRoads on Jan 14, 2021, 05:43 am
Diode would be a good choice to keep the battery from back driving the converter.

You should have a battery charge control circuit as well so the battery doesn't get overcharged.
Alright great I'll look into getting a diode.  Thanks for the suggestion about the battery charger too.  I wasn't sure if it would be necessary.

Quote from: johnerrington on Jan 14, 2021, 08:44 am
What exactly are you trying to achieve?
Several things.  Trying to monitor performance of a few motors and send to database.  On top of that there is a real problem with theft of these motors or the 12V battery, so need to be able to power the circuit if the 12V battery is disconnected and get GPS info.

Idahowalker

#5
Jan 14, 2021, 03:00 pm
The circuit applies and removes power from the RPi. If power is just removed from a RPi without shutting down the RPi OS first, their will be problems.

I use a 5V switching regulator designed for the auto environment to run a RPi in my car.
1/18/2018, got my first Arduino Uno.

feynman137

#6
Jan 14, 2021, 05:47 pm
Quote from: Idahowalker on Jan 14, 2021, 03:00 pm
The circuit applies and removes power from the RPi. If power is just removed from a RPi without shutting down the RPi OS first, their will be problems.

I use a 5V switching regulator designed for the auto environment to run a RPi in my car.
You are absolutely right.  I only want power to flow into the RPi.  Guess I need to add diode here.
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