Deleting primary contactor when using a reversing contactor

[SEHunter]

In another thread i was discussing how I’ve had problems with the MZJ-400 solenoid failing on a CC DS. This thread is not to discuss that any further but it led me to this topic. As the title suggests, I’m considering deleting the primary solenoid completely since I’m running a reversing contactor.

I know some will bring up safety but can anyone describe in detail any realistic scenario where this could be dangerous? If the controller were to have an internal short, is it even guaranteed that it would always be able to cut power to the contactor coils so it would open? I have no intention to start arguments or downplay safety, on the contrary I just would like input from others on this board before i do this. Thanks.

[Volt_Ampere]

There is a very good reason why all electric vehicles have a main contactor!

[CP241]

Originally Posted by Volt_Ampere

There is a very good reason why all electric vehicles have a main contactor!

Our vehicles have multiple inside the battery pack itself, depending on the model. Add more with a split pack

For safety of people as well as the electronics in the vehicle. I would leave it alone. The forward and reversing contractor is to replace a manual FNR switch. Not cut voltage to the system. 2 different purposes.

About the same as removing the drivers seatbelt because you’ve got straps to hold cargo in the back. I’d figure out WHY you’re burning up the mzj400 and fix that instead of delete it and cause bigger problems.


Edit:just read your other post. I’d put it back the way it’s supposed to be, those solenoids aren’t meant to be energized like that. I’d Let the controller do it’s job.

[SEHunter]

Understood but can either of you provide a realistic or likely scenario of how the absence of a primary solenoid on a CC DS would be unsafe? For example, an airplane can have an electrical or mechanical failure and everyone dies when it crashes but it doesn’t keep thousands of people from flying every day because that scenario is not likely. Possible, but not likely.

[WalterM6]

Here is an example you might understand. I bet that your house hasn't tripped a circuit breaker in years and your house will work perfectly well if you were to remove the circuit breakers. Would you ever consider removing the circuit breakers? I hope not.

[SEHunter]

By realistic, I meant an actual realistic scenario pertaining to DC powered golf carts, not an unrelated scenario about an AC powered structure. But thanks (i guess) for your unrelated and useless comment.

[Volt_Ampere]

I think WalterM6 was right on with his example. Let's say a MOSFET fails in your controller and throws full battery voltage on the motor. The only to kill the current is the contactor. Controllers are designed to kill the contactor if they sense a failure.

[SEHunter]

What’s the odds of that? Has that happened to your cart or someones cart you know?

[CP241]

Originally Posted by SEHunter

What’s the odds of that? Has that happened to your cart or someones cart you know?

Agree with VA and Walter.

It’s there to kill power to the high amperage system. If something goes bad in the controller and shorts, the motor could go to full throttle with no way to control or kill it. Since turning off the key, releasing the pedal, and the run/tow switch are all necessary to make the controller tell the contactor to close. You’re effectively bypassing all safety. And since this is a hunting cart you frequently travel off road meaning sticks, rocks, etc could damage the harness and short wires together “permanently” turning the key switch or pedal switch on. There’s a lot of potential failure modes that could go very very wrong by bypassing the main contactor.

What are the chances? Honestly, probably relatively low. But not zero. Not worth it in my personal and professional opinion. But clearly judging by your attitude and responses, nobody is going to convince you otherwise. Go ahead and bypass it, we’ll hope for your sake nothing happens.

[Volt_Ampere]

Originally Posted by SEHunter

What’s the odds of that? Has that happened to your cart or someones cart you know?

$hit happens - electronics fail. Fuses blow. Has it happened to me? No. I have had controller failures that would not energize the solenoid. I don't know what would have happened if the thing was bypassed.