INA219 14V 10A

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JaBa
 
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INA219 14V 10A

Post by JaBa »

Hello,
my project calls for monitoring a 12V battery which can be charged with up to 100W and a discharge not to exceed 150W. In other words, around 10A. In accordance with what I've researched so far, I could use a 0.01 Ohm 1% 5W resistor instead of the onboard 0.1 Ohm resistor.
I just don't believe that I can push 150 W across the leads in that board. I'm also not sure I want to risk damaging the board by trying to replace the resistor.
So, my thought is that I add the 0.01 Ohm resistor across the terminal jack... Leaving the 0.1 Ohm resistor in place. That way, most of the current is not on the board at all. Ok, so the parallel resistance is not 0.01 Ohm, but at 0.0091 Ohm it's pretty close. If necessary, I can adjust the calculated V/A values in code.
So, my two questions are:
1) Does that resistor of 0.01 Ohm, 1%, 5W seem reasonable?
2) Does my thought of adding the resistor across the connector and possibly adjusting the calculated values in code seem reasonable?
I really don't care about an accuracy of 8mA... I'll be rounding to tenth of an Amp/Volt anyway.
Thanks.

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adafruit_support_mike
 
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Re: INA219 14V 10A

Post by adafruit_support_mike »

Using an external resistor in parallel with the onboard .1 ohm is a good idea. About 90% of the power will pass through the 0.01 resistor, and only 10% will pass through the 0.1

At your upper limit for power (150W) the current will be about 12.5A, and about 11.4A will flow through the 0.01 resistor. The power dissipation through the resistor will be around 1.14W, so a 5W resistor is a good choice. It leaves you plenty of headroom.

Adjusting for the parallel voltage in software is easy, and you'll want to do it. A 10% error is big enough that you'll mentally adjust for it anyway, so add a couple lines of code to do it automatically.

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