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I am trying to read an array of batteries up to 60V with a PIC. I have made a potential divider to scale down to 5V.

I am worried because my system share the GND from battery system which delivery up to 500KWh and so i think this path of current can damage my micocontroller. Anyone knows a better circuit ? or how can i protect my uC

Also I have seen from another post add a buffer on the Vout voltage divider, anyone knows why? is it for decrease the current on the micocontroller pin?

Thanks Antonio

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  • \$\begingroup\$ Rate your resistors and creepage in your divider accordinly! \$\endgroup\$
    – winny
    Mar 1, 2017 at 18:55
  • \$\begingroup\$ An Opto-isolator. \$\endgroup\$ Mar 1, 2017 at 19:11
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    \$\begingroup\$ I'm pretty sure you need to look again at your battery specifications. 500 kWh at 60 volts suggests a battery capacity of 8333 amp-hours, and that is an enormous array. Are you sure you don't mean 500 kW? And even then, that implies battery currents of over 8000 amps. If you have to ask about how to drop 60 volts to 5 volts, I fear you'll kill yourself messing around with power levels that high. At the least you're going to start vaporizing cables. \$\endgroup\$ Mar 1, 2017 at 20:08

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As long as the voltage divider is correctly calculated, your µC is safe.

What you must watch out for is ground loops, make sure your digital ground and power ground are connected together only in one point.

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As long as your ground from the digital end is connected directly to the negative battery terminal and NOT through the main negative cable from the battery to whatever you are powering, isolation should not be an issue as long as there are no other ground connections elsewhere in the system.. e.g. to the utility supply line. Everything needs to be grounded in the one spot on that last battery NEGATIVE terminal.

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But please be careful messing with 60V, 500KWh of battery power.

If you don't know what your doing... stay away...

Any yes, you need to drop that 60V if you want to read it with the PIC or you will let the smoke out.

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  • \$\begingroup\$ Dear, Thank you for your message, what do you mean for "directly to the negative battery terminal and NOT through the main negative cable from the battery" ? My idea is to bring the cable from the last negative terminal and connect to my GND device. IS it a problem ? \$\endgroup\$ Mar 2, 2017 at 9:09
  • \$\begingroup\$ See when you ask question s like that it tells us all "YOU SHOULD NOT BE PLAYING WITH THIS STUFF...." I'll show you in the answer. \$\endgroup\$
    – Trevor_G
    Mar 2, 2017 at 16:04
  • \$\begingroup\$ Good luck Make sure your insurance policies, Life, and Fire, are up to date. \$\endgroup\$
    – Trevor_G
    Mar 2, 2017 at 16:09
  • \$\begingroup\$ Tk Very much Mr Trevor. \$\endgroup\$ Mar 2, 2017 at 18:32

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