High volt EV battery reading ADC on arduino

hi team, i wanna read the ADC of an Arduino of high volt EV battery 72 v (can go up to 88v on charging), I'm trying to use a differential amplifier & below is my schematic, I need to make it work, could someone please help me to get safe ADC value with such high volt reading though LM324. ic.

please favour me to check & what i should modify to get it proper working as ADC to read 80+v DC though my arduino pro mini..

Check the use of a voltage divider using resistors.

The op amp doesn't do anything useful.

You could use a 20:1 voltage divider for a 5V Arduino ADC input. Make sure the lower resistor is 10K or less. For example, a 180K/10K will give you a voltage reduction ratio of 19:1, so 88V would result in 4.6V input to the ADC.

Voltage Divider

Calculate your voltage divider for the maximum (88V) and/or add an over-voltage protection diode and maybe a reverse-voltage protection diode also.

Choose high-enough value resistors that you don't draw excess current or overheat & burn-out the resistors.

You don't need a differential amplifier if the battery and Arduino have a common ground.

And you obviously don't need an amplifier and with the "extra" resistors on the input you actually have a differential attenuator (good) but not enough of an attenuator for 80V. :wink:

An LM324 isn't a "rail-to-rail op-amp so you'll need a positive power supply of maybe 7V or more if you want the output to go to 5V, and a negative supply so the output can go all the way to ground.

Anything greater than 50V is considered "dangerous" so be careful and make sure everything is eventually enclosed & insulated so nobody can get shocked.

Yes, sir, actually battery & Arduino don't have common ground, that's the main issue as we are using flyback topology for isolated ground, & isolated 5v output of our flyback supply will power opam ,

Sir my main doubt is , do we directly need to feed battery volt to opam to use this differential circuit , can opam handle it, as i read, lm324 can handle 32 volt only.

if not, then after voltage devider only , i need to feed devider volt to this opam circuit.

sir, we were suggested to use differential amplifier by our senior mentor sir to safely give this 88v to ADC of arduino mini. (please see gain formula i was suggested to use, now i need help to calculate gain & hence to get safe ADC to read this high voltage)

can you please help to give some reference of calculating gain.

Don't see that in your diagram.

I don't see why you have to use an opamp.
Can't you just charge a capacitor with a voltage divider to a voltage that the Arduino can handle,
and present that voltage periodically to the Arduino with a DPDT relay.
Leo..

Here is my 5v output supply circuit, which I got from Car-usb charge circuit, due to the high volt & noisy ground of the EV battery, we were suggested to use Flyback topology.

Please comment on this too, if any issue with this circuit too.

If you cannot have a common connection between DC Input GND and Output GND then you will need some kind od analog isolation circuit.
Have a look at this.

Ahh, you mean the principe of the 5volt supply.
I thought you meant "Flying capacitor", which is what I drew.

A flying capacitor, with a small signal relay, is an easy and cheap way to measure isolated voltages.
To power your Arduino from that 80volt battery..,
why not use a mains powered cellphone charger with USB socket.
They should run on 80volt DC.

With that Gravity board you must also have a second 5volt supply on the battery side.
Leo..

Thanks sir for flying cap method for isolated ADC.
&
can you please put a bit more light on this, " mains powered cellphone charger with USB socket ",

I'm not getting anything, such as local, I was looking similar readymade circuit, that I can use or with some modification, can be used.
can you some reference links., if I can get such a flyback circuit somewhere?

& about Opam ADC, Actually, I've already submitted this opam circuit to the paper, so I was planning, if I can use the same opam based circuit as ADC with my isolated power supply circuit.

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