PSDM potential failure

I upgraded to lithium batteries on my 2009 GEM e2 and all was well until I proceeded to replace the charger. Instead of disconnecting the discharge cable I decided to cut it to save time. Whoops, I forgot to open the disconnect switch. Wham, the cable shorted out and now I no longer have power to the motor/controller. All the accessories are still working fine. I assumed that one of the main fuses blew out but they all checked out. Is there an electronic device/mechanism in the PSDM that could have failed and is it repairable? Any evaluations/recommendations would be appreciated.

Describe again exactly what wire and where it was that you cut that made it go * POW *!!

What lithium batteries did you put in? My first thought was the BMS should have tripped. Since you say all the accessories are working I’m guessing your pack has output power.

You say you checked the fuses. Did you include the round one in the barrel holder on the right side? It’s called F13.

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I installed (6) 72v Allied lithium batteries wired in parallel for a total of 108Ah. They have worked fine for the past year. I had an issue with a loose connection on the A2 terminal of the controller and had it rebuilt. In the meantime, I decided to remove the old charger for the “wet” batteries. Instead of disconnecting the discharge side of the charger from the PSDM, I cut the cable with my pliers and shorted it out. Now I no longer have power to the controller. I checked all the fuses on the fuse board which you attached and they all proved out. The F13 fuse is not visible so I used a multi-meter to check continuity and it is OK. All the accessories work which come through the 72v to 12v converter. I have 72v entering the PSDM but no discharge current.

So it sounds like you might have managed to get the old charger out of the car by now? Can you show me a pic of this charger?

Also a pic of the cable you cut?

If you look at the dash display- do you see anything on it at all? (Possibly a yellow light shaped like a power cord?)
Or is it completely dark?
What happens when you turn on the key?

Have you power cycled the Main Power switch at the bottom of the fuse panel? (flip it to OFF for 60 seconds, then back ON. Does the display still remain dark and lifeless?

Your statement:

I have 72v entering the PSDM but no discharge current.

Is a bit puzzling, How are you observing this?
What points are you probing?

You could pull them out of the cart, cover them with ABC dry chem, then file an insurance claim citing “miracle” as to why no fire damage to your gem.

I think you may be on to something. Attached are pics of the charger with cable cut. The output cable has four (4) wires, B,R,W & G. The B & R are 72v out to the PSDM. The attached diagram shows the W & G wires going to the charger interlock in the PSDM through the key switch. When I turn the key on, the power cord symbol shows up on the display indicating the charger is plugged in. However, the charger is obviously not plugged in. Since the PSDM thinks the old charger is plugged in, the current is prevented from going to the controller.

The display photo shows the “plugged in” icon with the key “on” and an additional monitor that I installed for the lithium batteries because the display no longer showed the charge. It will register to 100% @ 80v when fully charged. It just isn’t fully charged at the moment.

If I closed the white/green circuit to the charger interlock do you think that would allow the interlock to permit voltage to the controller? Or does it need a current?

I would appreciate your thoughts.

cut cable from charger
charger cut cable

Ha ha. I’m glad I didn’t damage the batteries.

Here is the electrical diagram that I was referring to. I had to convert it to an image.

This shows the importance in how you need to be fairly accurate in describing your conditions and exactly why I have been asking so many questions.

That leftover green wire in that bundle that went to your charger is your interlock wire. It keeps the car from driving away when the charge power cord is still attached to the car. With the Charger now missing your car thinks it is charging.

Take your meter, check and see if you still have 72v still on the Black and Red wires in that bundle. If yes, then connect the Green and Red wires together and switch on the key again. Your dash should light up as normal and your car should run. If you need to find another source of B+, just run that green wire over to the Pos on top of the controller.

I suggest you take your cutters with the torch mark from the original cut and permanently wire them to the wall above your workbench as a reminder not to cut things willy-nilly without knowing EXACTLY what they do.

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OMFG, one SMALL detail missing on this step by step is to throw the master disconnect BEFORE you go and start stripping wires and connecting them together with who knows what method.

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Wow. I forget one TINY little step and the world comes unglued.

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You do have a good point, the OP is obviously already experienced with cutting into energized wires.

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Thanks for your feedback. I actually now have two pairs of pliers with spark marks on them. I guess I am a slow learner. That’s why they put insulated grips on the pliers. I will follow your suggestions later this morning and let you know the outcome. I may still have a speed problem with the controller but I will get back to you if that occurs. Again, thanks for your help.

So I closed the green wire with the positive connection. The “plugged in” icon disappeared when I turned the key on. Now I have a temperature icon with a wrench blinking in the display. I still don’t have any power to the controller. It sounds like the W wire may need to be terminated as well. What are your thoughts?


Instead of throwing it to the garbage I’ll send you a label and you throw it in the mail🙂

Leave that white wire alone. That is your Batt temp wire. It is no longer needed.

That temp light is probably your motor temp sensor. Have you been doing any other work down in the motor area? Locate the double set of wires in their own plug down by the motor speed sensor(speed sensor is a three wire plug). The two wire plug should be connected together to bypass the motor temp sensor function(open = motor hot).

Normally, The thermometer will not keep the car from moving. Overheated motor usually speed hobbles the car just to get you home.

There may be more than one issue going on.

As you indicated the two wire harness at the motor is wired and taped together. The three wire tachometer is connected to the end of the motor.

Just to review, this entire problem started when I cut the wires on the charger going to the PSDM. We have resolved one problem with the green wire which removed the “plugged in” interlock.

There are 76v going to the PSDM but zero going out with the key switch on.

There is also the temperature icon and wrench icon showing up on the display which could be preventing output voltage.

Is this taken with the KeyOn? or OFF?

There are 76v going to the PSDM but zero going out with the key switch on.

How are you measuring this “Zero going out”? What points exactly are you probing?

You also notice there is a little turtle head peeking out from behind your Batt monitor? That is another clue.

What else is going on under there? Do you see the DH, DL, and REV indicators? Is there a box around the Drive mode currently selected?

With KeyON and drive selector switch in REV do you get the beeper?

Do you have the dash plastic removed at this time? (upper and lower) We might need to look at some of the wiring at the PSDM.

The display pic is with the key “on”. Key “off” it goes black.

With the key “on” I am measuring zero volts on my multi-meter going out to the controller terminals.

That turtle head has been there since I replaced the batteries over a year ago. This agrees with the one red bar shown on the charge level. That’s why I added a lithium battery monitor on the display as shown in the photo. Not sure why the lithium batteries don’t register on the display.

The R, DL, and DH are all blinking with the box around them independent of the switch position.

There is no beeper in the reverse position.

Both dash enclosures are removed. All wiring is exposed.

PSDM inside cab