Hello!
I want to measure up to 200A bidirectional current (for a solar system battery, charging and discharging), and the voltage goes up to 30V. I want to use a 200A 75mV shunt. I can't use the INA219 because the battery voltage is over 26V, and the INA226 which seems good for my application isn't easily available in my country. I wanted to use an ADS1115 for reading the shunt, but I'm not sure if it can work bidirectionally. I can isolate the Arduino from the battery DC system using an AC adapter powered from the inverter, but I also would like to separately read the battery's voltage.
The voltages on the ADS1115 inputs must be between 0V and the ADS1115 supply voltage at all times, or it will be instantly destroyed. So no bidirectional measurements, and no high side measurements.
Watch out for counterfeit or fake ADS1115 modules, as well. Buy them only from reputable suppliers.
If I've got the right fugures INA219 measures up to 4.2 Amps. not 200.......
It can be used with an external shunt (not the one already soldered on the board) , so with a 75mV 200A one it should be able to do that, but my battery has higher voltage than the maximum of INA219.
That means I can't use it, because I need bidirectional measurements. Any other suggestions?
Just use the INA226, or the INA260: Adafruit INA260 High or Low Side Voltage, Current, Power Sensor : ID 4226 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits.
What does "not easily available" mean?
By "not easily available" I mean that it isn't in stock at local retailers and I would have to order it from a foreign store and mess with customs.
I can get the INA260, but can it work with an external shunt? Tha INA219 board has a separate onboard shunt that can be desoldered, but the INA260 has an integrated shunt in the IC, so I can't remove it.
Your very best source of information is the device data sheet. What does it say about external shunts?
Measuring the current from the solar panels and measuring current from the battery will give the difference blah, blah, blah.
I put a blocking diode between my solar panels and the charge controller to prevent the battery from discharging through the solar panel at night. Battery current through the individual solar cells can damage the cells and reduce solar panels output.
How is you solar panel and battery set up ? I presume that you have got an charge controller to charge the batteries already ?
If that's the case I would say you would need 2 shunts one to monitor the charge going into the battery and one to measure the current going out the battery. This way you would not need to measure it bidirectional.
The problem I see with only using one shunt is what happens when the sun is out and charging the battery but also at the same time what if you was drawing current from battery how could you monitor what's going in and out at the same time ?
Probably just as well to delete that. 
Can you get the INA 169 or the INA196.
Two of them, and an ADS1115 in differential mode could also solve your problem.
Leo..
Yes, I have a charge controller and inverter.
That's good then 
, What type of controller is it ?
The one I've got gives Modbus output and I just read the Modbus to keep check on the battery. I also built an battery monitor that monitors the current going in and out of the battery and using Peukurts factor even predicts state of charge and runtime left on the battery depending on the current draw
You will also have a problem in measuring voltage as you need a common ground .
200A is serious current have a look at isolated DC current transducers and they will allow you to make a sensible rugged installation. You can’t afford to have bits of wires running around with connections to a panel or battery
Hi,
Why not use two shunts, one on the PV array lead to the battery, and one on the lead from the battery to the load?
That way you can be always measuring your PV current and your load.
If you want to, you do some maths and calculate the battery charge current.
You don't have to worry about bidirectional current shunt systems.
Tom.... 
I have an inverter that is also charge controller in the same box, so measuring the current on the PV wires will result in reading the current used for both battery charging and AC loads.
Luckily, it seems that I found a local retailer that has the INA226 that supports bidirectional shunts up to 36V.
It's a combo charger+inverter unit. It can report data via serial, but its internal measurements are not too precise or accurate, so I would like to do my own measurements.
Like to see how you would wire that up without 0v issues ….
How accurate is it and what accuracy are you hoping from the Arduino ?