Dc energy monitoring system

Good afternoon everyone.

Going build dc monitoring system for my camper running 12v lifepo4 setup.

The gear I was looking at.

shunts 100A 75mv (high side) x5
Ina3221 (triple CH, 26v max, fridge & lights output)
Ina169 (single CH, 60v max, solar input)
Arduino uno (powered off same source)
Haven't decided on bidirectional chip for battery charger. (Don't think ina1221 supports bi)
12v step down to power gear

Be great get your thoughts and any problems I might run into.

Thanks Luke

INA169: https://www.ti.com/product/INA169.
INA3221: https://www.ti.com/product/INA3221

Why a analog INA169 ? Is that because the distance is too far for the I2C bus or is there no 60V I2C version ?

You can step down to 5V and power a Arduino via its 5V pin. There is a risk that current can flow into the USB port of a computer.

A problem could be the GND.
With high currents through ground wires, a good common ground is hard to make. If you do something wrong than many amps might try to go through the Arduino board.

When the ground current can take two routes, the ground current can decide to use a smaller wire and ignore a strong thick wire. For example when the small wire is inductive coupled with the positive power wire. For higher frequencies it is often worse. Current spikes are higher frequencies. You have indeed high frequencies in your 12V DC system.

I would add a few good old fuses, so a shortcut near the Arduino will not damage the rest.

How do you display the numbers ? A LCD display is not durable in a camper (sun, heat, vibrations).

Hey, thanks for quick response.

Ina169 I haven't found replacement for i2c, I know they have over chips like 80v with i2c but no one sells modules.

So with GND problem put 3amp fuse on both sides (+,- wire) between power source to 12-9vdc buck converter I was looking at.

The dc system is in closed area but was going run no screen, looking at wifi setup for easy access, data logging in future.

I hope answered your questions.


Alright, that sounds okay. As long as you don't use the I2C bus to go somewhere else in the camper. Keep the Arduino next to a I2C device.

Cheers, plan is build hole lot nside pvc box

Do you know of ina chip that dose bi-directional 16v min.


Search for: high side current sensing bidirectional i2c

INA226 ?
INA219 ?
Does the INA209 output signed data ?

I never looked into bidirectional current sensors.

Can you draw a block diagram of all your major components and wiring and where you will be measuring current and voltage please?

A picture is worth a thousand words.

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

INA226 is 36volt/16-bit bidirectional.
Breakout boards available.
INA219 is it's predecessor. 26volt/12-bit bidirectional.
INA3221 is three INA219 in one chip.

INA169 is high voltage, but uni. And needs the (10-bit) Arduino A/D.
You need two of them back2back for bidirectional.

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Tom here's block diagram hope it helps

Leo, thanks for info.
Solar panel doesn't need bi-D
Is there chip dose i2c be easyer, solar panel use 45ocv

Thanks Luke.

The solar controller might not have a common ground with the rest of the system.

Sorry didn't add line, negative line runs between mppt unit and battery, is that you mean, sorry if I miss understanding you.

Why not just use 2 shunts one coming from battery to your load monitor everything and then one from your solar panel so you can monitor the charge going in

Have a look here this will give you some idea

I’ve built one and made some changes and used an 16bit adc all credit goes to the author

Edit ignore the 2 shunt I’ve just looked at your picture more as I was looking on phone but the link still would give you some ideas, it uses The Peukert equation where you take more than 1 ampere out of the battery

There is likely not a straight connection between solar panel negative and battery negative.

Measuring between MPPT unit and battery can be done high-side and low-side.

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