Diode melting

[Gratz71]

Thanks….maybe I just had one backwards. I’ll get another and try again.

Everything I read for Alltrax controller I though I did need two.

[Volt_Ampere]

There should be only ONE diode! No diode goes on the big terminals. I don't think you need the precharge resistor with the Alltrax controller. Read up on the Alltrax install and look at the wiring diagram.

[Gratz71]

The wiring diagram I am looking at shows 2 diodes for the Alltrax

[JohnnieB]

Originally Posted by Volt_Ampere

There should be only ONE diode! No diode goes on the big terminals. I don't think you need the precharge resistor with the Alltrax controller. Read up on the Alltrax install and look at the wiring diagram.

Good advise for everyone, including the quoted poster.

All currently sold Alltrax sepex controllers (XCT) have a diode between the large terminals as well as one between the small terminals.

The diode between the large terminals is called the "Regen" diode. Its only purpose is to protect the controller from over-voltage if the solenoid de-energizes during regen braking.

Apparently if the battery pack is disconnected (solenoid contacts open) while the motor is operating as a generator (Regen braking mode), the generated voltage skyrockets and can take out the controller. The 6A-660V diode might explode if this happens since regen braking can cause more then 100A to flow towards the battery pack, but replacing a $5 diodes is a lot better than replacing a $500 controller.

The banded end of the regen diode faces the battery side large terminal.

FYI: The pictures posted earlier showed a pre-charge resistor. XCT controllers do not use pre-charge resistor.

Also the stacking order is wrong. The highest amp connectors go onto the studs first, followed the progressively few amp connectors.

[Volt_Ampere]

My Alltrax wiring diagrams do not have a Regen Diode or Precharge Resistor.

Live and learn. I have two Alltrax controllers and neither called for a "regen diode". It does make sense as a protection for the controller in the unlikely event that power gets interrupted during Regen.

As JohnnieB said, you should always put the high current conductors on a terminal first so that they have minimum resistance to the post. This is true on the solenoid as well as on the batteries.

My guess is that Alltrax added this diode because many of us are using Lithium batteries that have a BMS that can and will interrupt battery power under certain conditions. My BMS does not do this but most do. A normal FLA battery setup won't disconnect and it would be unlikely that the solenoid would open during Regen. (but anything is possible)

[Gratz71]

Thanks for the responses…this is my first cart so I’m still learning!! Thanks for all the info though!!

[Volt_Ampere]

We're all learning! All the time. This forum is a great way to learn more quickly. :-)

[JohnnieB]

I screwed up.

Not all XCT applications have a regen diode. Yamaha's and EZGO with Curtis 1264/1268 do not - the rest do.

Or at least that is what the schematics in the XCT ops manual that is now on the Alltrax website indicate.

[Volt_Ampere]

Seems to me that a much higher current diode would be required to protect things if the circuit opened during a 50 amp plus regen. Initially, all of that current would have to flow through the only path left - the diode.

[JohnnieB]

Originally Posted by Volt_Ampere

Seems to me that a much higher current diode would be required to protect things if the circuit opened during a 50 amp plus regen. Initially, all of that current would have to flow through the only path left - the diode.

Same here, so I looked up the specs on the 6A6 diode they use. (6A6 datasheet attached.)

Looks like it'll pass in the neighborhood of 400A for 8.3mS, about 180A for 83mS and about 90A for 830mS.

A quick look at some of the data logs from my XCT indicates a max regen amps (Negative numbers in battery amps column) is just under 100A with the duration of regen braking episodes is up to about 10 seconds, but only a few of those seconds are over 50A.

I'm not sure if it will or it won't.