Teardown Mercedes EVCharger to Replace AC Plug and Temperature Sensor
Click Here Teardown Mercedes SCP1T3-DM01713A24  and  Click here for additional photos

The simple answer is YES but you have to follow guidelines and check for heating
The problem with using extension cords with EV Charger is that they can overheat and melt if the wire is too skinny). Then bad things happen, Solution use the proper wire gauge (AWG) and check for heating after charging for 1 hour.  

Warm is Ok, Hot like Coffee is not. 

SUGGESTION - Avoid lighted extension cords. They have very poor plug/receptacles

Here is the Guide - EV Charger vs Extension Cord Length

Generally the pins in the J1772 handle are all the same - 16A to 50A.  It is the wire size (AWG gauge) that makes a difference
Here is a table for a 25' long EV Charging (EVSE) Cord. You will notice that the power loss is very small when compared to the power delivered.  You do have to check the temperature of the cord and connectors after charging for 1 hour.  Warm is Ok, Hot like Coffee is not. 
Table - J1772 Max Load vs Cord AWG

If 2021 were to follow the trend, average pack prices this year should be $125/kWh. But over the past 12 months, the price of the key metals used in lithium-ion batteries have risen relentlessly, putting pressure on battery prices.
Today, the cathode material of a lithium-ion cell accounts for around 50% of the manufactured cost. This includes the cost of going from lumps of rock that you dig out of the ground to the finely tuned composition of lithium, nickel, cobalt and manganese that make EVs possible. If you take away the processing costs, the raw materials in the cathode still account for about a third of the total cell cost. You’ve then got copper, used as a current collector for the anode, which accounts for around another 5% of the total cell cost.

Repair Notes:  Disassembled charger and rewired for bench testing, see photo below. The conformal coating is very thick, used a utility knife to strip it off the contact points of interest.  Trace circuit for DC High Voltage ( See Rectifier +- , not earth referenced),  Coil +V (TP 1 325V DC, Coil Drive (TP 2 connects to Omron SS Relay pin 6), Omron Relay pin 4 is HV DC ground and Coil drive ground (not earth ground). 

Failed relay symptoms.  Does not charge,  On first power up and handle plug in there is a faint click.  This is the relay closing and then failing the AC Out Sense which shuts off the relay.  NOTE: the TESLA charger does not show any symptoms of this failure. The display is green and the pilot signal is 1khz @ 40A
To simplify testing use EVDoctor Go NoGo pocket tester - https://www.amazon.com/dp/B08X19DN21 
RELAY Repair - The relay is relatively easy to repair as long a the coil is OK,  Remove 2 metric screws on the bottom, (This is hard as they have locktight on the threads you may have to drill them out)   The 4 pins with the nuts on them are the actual internal contact, Remove any burrs and polish with scotch bright or extra fine emery cloth,  put some silicone lube on the actuator cylinder.  Make sure the cylinder moves freely. The relay is a Curtis Albright SW82-312 Coil 240V DC  ~$100,    Alternate  https://howlandtechnology.com  HTI#6231  SW82-353 240DC CO DUST (13223993) $80.00/Unit.  More details here Assembly & parts List http://www.albrightinternational.com/wpcms/wp-content/uploads/2015/07/SW82822.pdf spec sheet http://www.albrightinternational.com/wpcms/wp-content/uploads/2017/06/SW82-Catalogue-Sheet.pdf 

Bench Testing Setup-

The Chrysler Pacifica EV Charging Cord (aka EVSE) is challenging to repair because the case is sealed. In addition the J1772 Handle is potted and cannot be repaired. 

We recently received a Pacifica EVSE with a damaged J1772 handle (they drove away with it plugged in).  Upon inspection it looked like the J1772 cable had been pulled out of the case so to be on the safe side we decided to open the case. This EV Charger is manufactured by Lear, the same company that manufactures some Chevy and FIAT chargers. Those charger can be opened by cracking the weld on the edge of the case. That proved to be not the case.

We cut the case with a thin blade saw to just below the ridge at the base and found that one of the wires had pulled off the 1/4" quick connect spade terminal.  We reconnected the wire and viola it worked.  NOTE: Don't let the saw blade enter inside the case as you may hit some components

We glued the case together with high strength epoxy.  This was a little challenging because there was a jagged piece on the end of the case.  See photo with the white line.  Besure to cut straight across both ends.  See photos for completed repair and additional info on the fault codes.  bit.ly/Pacifica-EVSE-FaultCodes

We also installed a new J1772 handle. NOTE: Do Not use the standard dies that come with the 20 ton crimper (solder instead). The proximity switch was connected to 2 short pieces of hook up wire that were added because the wires on the switch were too short

NOTEs:
1.  All repairs include our '5 Point Safety Certifications test' and a 6 month warranty. Click here EVLAB '5 Point Safety Certification'  
2. EV BULLETIN Chrysler Pacifica EV Charger Fault Codes
3.  Here are the identifying #'s of the Chrysler Pacifica EV Charging Cord. P05062107AC, S9065010, V96555BD 

This post applies to most J1772 handles but specifically the LEAF with the YAZAKI 73A-2002 or 73FA-1501 handle

We received the charger the latch lever on the J1772 handle was loose and floppy.  We check the proximity switch between pins 5 and ground and found a constant 480 ohms (switch open). The vehicle will not charge if the switch is open.  Browse this link for details.  http://bit.ly/J1772HandleTest

The Yazaki J1772 Handle case is particularly difficult because it is held shut by internal pins vs. screws.  We used a 1" chisel and a 2lb hammer to gently open the handle.  You need to avoid the small pins next to the chisel. there are a total of 9 pins to avoid plus a little clip that retains the spring on the latch lever.

This model of the Yazaki has a plastic pivot pin on the latch handle.  (the model 73FA-1501 has steel pins).  We epoxied the pins back on and because this plastic is hard to glue we drill out the center and inserted a steel pin.  See the finished latch lever.

We thought we were done until we found that the attachment for micro switch was broken. This would probable be Ok because the switch is constrained in the handle but just to be sure we hot glued it under over and behind.

We cleaned up the edge of the handle that had been damaged during opening and using a vise and hammer we convinced the handle to snap together (and it was tight),  We tested the LEAF charger on our EVDOC Lab simulator and it charges at 12A without error.  We did a 240V upgrade and now with an EVDOUBLER it charges in 1/2 the time!

The SD Auto Show was held Jan 1-5, 2020 at the San Diego Convention Center

I took the opportunity to take public transportation from Carlsbad to the Convention Center.  Very easy. Arrived in less than 45 minutes. Cost round trip $7.50 (for seniors)

We were looking for details on the 2020 models especially the OEM Level 1 chargers.  How many have a built-in Level 2 charger ie are they 120/240V ready?  We did not find a single level 1 charger (guess that is not something to showcase)

Many of the Electric Vehicles were highlighted an area called the 'Ener-G Station'.  See the posters listing the current rebates for EV and PHEV vehicles.

​The Highlight of the show was the Ford Mustang Mache.  

​More to come -  David R Ahlgren,  We love hard questions!