Electrically Isolate Voltage Sensor from Circuit
Electrically Isolate Voltage Sensor from Circuit
(OP)
Hello this is my first post.
I am trying to build a voltage sensor for a battery management system. The voltage sensor will simply be a voltage divider across a lithium polymer battery that goes to an ADC on a micro controller. However, I need to isolate the two circuits electrically because it is specified by the rules.
I originally thought to use an optoisolator but I don't think that optoisolators work well with analog voltages.
Please let me know if you have any ideas!
I am trying to build a voltage sensor for a battery management system. The voltage sensor will simply be a voltage divider across a lithium polymer battery that goes to an ADC on a micro controller. However, I need to isolate the two circuits electrically because it is specified by the rules.
I originally thought to use an optoisolator but I don't think that optoisolators work well with analog voltages.
Please let me know if you have any ideas!





RE: Electrically Isolate Voltage Sensor from Circuit
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RE: Electrically Isolate Voltage Sensor from Circuit
RE: Electrically Isolate Voltage Sensor from Circuit
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrically Isolate Voltage Sensor from Circuit
And I'll second Bill. If you're dealing with lithium batteries, you'll probably want to sense the voltage with 25 mV accuracy or better. Charging and state of charge determination is very sensitive to voltage.
RE: Electrically Isolate Voltage Sensor from Circuit
ht
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RE: Electrically Isolate Voltage Sensor from Circuit
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Otherwise do it differently. Use a V/F on the battery side and send only the pulse train across the optos. And! Don't use stinkin optos. Use any of the superior magnetic replacements that have arrived in the last few years, to avoid the many problems optos cause.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrically Isolate Voltage Sensor from Circuit
RE: Electrically Isolate Voltage Sensor from Circuit
RE: Electrically Isolate Voltage Sensor from Circuit
Voltage balancing for Li-Ion is extrememely important for safety as well as battery life. I designed a stack sensor using 0.05% resistors in the Meg-Ohm range with FET input instumentation amps. The worse case errors here were in the range of <10mV. I would suggest doing that.
Otherwise, the suggestions from the other guys to ADC it on the battery side, then transmit the data across with an isolater.