Voltage drop when charging.

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jeffand

Well-known member
Joined
Jan 31, 2013
Messages
441
Location
WI
Is the FFE monitoring AC line voltage while charging? The Tesla Model S does monitor the AC power line voltage. If it see's a significant voltage drop from no load to full load. The car will back off on the current to bring the voltage back up to normal levels. The causes for this are poor wire connections, and long wire runs to the charging stations. Have any of you seen low voltage issues while charging?
 
No, the car doesn't "back off" like the Model S will, thankfully. The implementation of that "safety feature" leaves many owners with a totally checked and to spec setup but with limited charging. Tesla blames the electrical infrastructure, electricians and power company blame Tesla being over sensitive.
 
It would be nice if the FFE had a screen that showed line voltage, and current. This way you could tell right away if thier is an issue with a charging station.
 
Some people (including me) have installed inexpensive combo meters either inline or within their charging stations for just this purpose. And, of course, some EVSE units have this built in. I can look at mine and see that normal full current is about 28 amps and there is a 3 volt drop under full load.

The problem with having it in the car is that the car cannot tell what is normal for a particular circuit. A long run may have 5% voltage drop under load and this may be just fine. On the other hand, if a very short run suddenly develops a 3% drop due to a bad connection or broken wire strands, this is not OK!
 
I was thinking this could be usefull when using a public charging station. Since the install qualty can very widely.
:arrow: A charging station at a distance of 318 feet, of 8 ga copper wire, and 30 amps of current the vehicle will see a drop of 12 volts (5%).
 
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