# Using the INA226 to measure current up to 80A from 42V battery

Hello,

I'd like to use the INA226:

datasheet:

along with a 10 milli Ohm shunt resistor and a current of upto 80A in order to monitor the high current off from my battery now in the data sheet it says "Senses Bus Voltages From 0 V to 36 V"

what is the meaning of that? Can I measure the high current from the 10mOhm Shunt resistor with that ic (max 0.8V voltage drop on the shunt)?

or that would mean that I could measure a current of upto 3600A with that 10mOhm resistor?

MikeLemon:
Hello,

I’d like to use the INA226:

datasheet:

along with a 10 milli Ohm shunt resistor and a current of upto 80A in order to monitor the high current off from my battery now in the data sheet it says “Senses Bus Voltages From 0 V to 36 V”

what is the meaning of that?
Can I measure the high current from the 10mOhm Shunt resistor with that ic (max 0.8V voltage drop on the shunt)?

or that would mean that I could measure a current of upto 3600A with that 10mOhm resistor?

Another question that comes with that after a little bit of research. Is it necessary to connect V-Bus say of the battery to the INA226?

MikeLemon: in the data sheet it says "Senses Bus Voltages From 0 V to 36 V" what is the meaning of that?

If your shunt is "high-side" (in the + line), then the INA226 can measure voltage and current. In that case battery voltage is limited to 36volt.

If the shunt is used "low side" (in the ground line), only current can be measured. Leo..

Wawa: If your shunt is "high-side" (in the + line), then the INA226 can measure voltage and current. In that case battery voltage is limited to 36volt.

If the shunt is used "low side" (in the ground line), only current can be measured. Leo..

So If already have a component that measures voltage I can put it in the low side and measure what ever currents I want with this setup?

If so then where I connect the VBus pin?

Datasheet: "The device can also measure the power supply bus voltage by connecting this voltage to the VBUS pin." I assume you don't connect VBUS if you're not going to use it. Leo..

Wawa: Datasheet: "The device can also measure the power supply bus voltage by connecting this voltage to the VBUS pin." I assume you don't connect VBUS if you're not going to use it. Leo..

Aight thank you very much that was very helpful

OP: Please aware aware that the surface mount shunt resistor that is provided on the typical INA226 breakout board is unsuitable for your 80 amp application. It will vaporize/explode at 80 amps. It's a one watt resistor so at 12 volts, it's good for maybe 60-75 milliamps continuous dissipation. You need a typical 50mv shunt rated at 100 amps. EBay is probably the cheapest source.

If your desoldering abilities aren't up to the task, you can leave the existing 10 milliohm shunt in place and connect the output (the smaller screws on the shunt) to the terminals on the breakout board. Parallelling the two devices will result in lowering the voltage to 47.1mv at 100 amps.

The 100 amp shunt is a good idea, but a 1 Watt, 10 milliOhm resistor is rated for a maximum current given by I2R = 1, or I = 10 A, independent of the supply voltage.

avr_fred: OP: Please aware aware that the surface mount shunt resistor that is provided on the typical INA226 breakout board is unsuitable for your 80 amp application. It will vaporize/explode at 80 amps. It's a one watt resistor so at 12 volts, it's good for maybe 60-75 milliamps continuous dissipation. You need a typical 50mv shunt rated at 100 amps. EBay is probably the cheapest source.

If your desoldering abilities aren't up to the task, you can leave the existing 10 milliohm shunt in place and connect the output (the smaller screws on the shunt) to the terminals on the breakout board. Parallelling the two devices will result in lowering the voltage to 47.1mv at 100 amps.

I'm going to use this shunt:

https://www.digikey.co.il/product-detail/en/vishay-dale/WSLP39211L000FEB/WSLPC-.001CT-ND/2695283

That is a 1 milliOhm shunt, not 10.

I'm going to use this shunt: https://www.digikey.co.il/product-detail/en/vishay-dale/WSLP39211L000FEB/WSLPC-.001CT-ND/2695283

Are you planning on replacing the existing resistor with that device? If so, I'd rethink your plan. Ignoring the fact that the INA226 input will drop to 6.4 millivolts, the traces and terminal block on the breakout board are unsuitable for 80 amps.

Assuming the trace width to the shunt connections are about 75 mils wide with 1 oz copper, the traces will fuse in under a second at 80 amps.

What existing resistor are we all talking about. Yes, common INA219 boards (Adafruit, ebay) have an onboard 0.1ohm shunt. But OP is talking about an INA226. There are AFAIK no breakout boards available with this chip.

Why use a 0.01 shunt anyway. Battery/supply connections are made with wires. They have resistance (that you can calculate). Just use a length of that existing wire as shunt. Leo..

There are AFAIK no breakout boards with this chip

eBay search for Chinese INA226 breakout

avr_fred: Are you planning on replacing the existing resistor with that device? If so, I'd rethink your plan. Ignoring the fact that the INA226 input will drop to 6.4 millivolts, the traces and terminal block on the breakout board are unsuitable for 80 amps.

Assuming the trace width to the shunt connections are about 75 mils wide with 1 oz copper, the traces will fuse in under a second at 80 amps.

Who cares I'm designing my own PCB. but thanks for the worry.

avr_fred: Are you planning on replacing the existing resistor with that device? If so, I'd rethink your plan. Ignoring the fact that the INA226 input will drop to 6.4 millivolts, the traces and terminal block on the breakout board are unsuitable for 80 amps.

Assuming the trace width to the shunt connections are about 75 mils wide with 1 oz copper, the traces will fuse in under a second at 80 amps.

Hum, I'm not a pro, but I have read the TI manuals on the INA series, and I think the shunt resistor (typically R100) on the INA219 is on board, while the INA226 uses an external shut. And as you stated putting an appropriate shunt resistor on the break outboard might not be the best arrangement.

I am wondering if this would be an acceptable shunt

http://www.mouser.com/ds/2/281/dpm_shunts-25677.pdf

I am wondering if this would be an acceptable shunt