Sw202 question

[Dadkins]

I currently have the 36v sw202 NR7094 contactor installed. I just upgraded to 48v lithium. Do I have the get the 48v sw202 now? My current one is getting hot

[ThreeCW]

The following information is based on the Albright / Curtis Albright SW202 Reverse Contactor ... if you have an "SW202 Style Reversing Contactor" then it is a likely a Chinese knockoff of the Curtis Albright and you would have to confirm these specs elsewhere.

The voltage rating (V = 36 volts in this example) of a SW202 reverse contactor is based on the two operating coils which open and close the contacts (one each for forward and reverse). According to Curtis Albright, the pull in voltage (to activate the coil) is approximately 60% to 66% of the rated voltage for intermittent and continuously rated coil types respectively. This means that the coil will activate (pull in) at 60% x 36 volts = 22 volts for an intermittent rated coil or 66% x 36 volts = 24 volts for a continuous rated coil.

Curtis Albright also rates the drop out voltage (when the coil will release) at 10% to 20% of V or 4 to 8 volts for a 36 volt coil.

Considering you are now running a 48 volt system, you are likely subjecting the coils to a higher voltage than they have been designed for. This may result in a shorter coil life and possibly additional heat generation in the coil.

These same Curtis Albright Reverse Contactors (regardless of the coil activation voltage) are rated for 48 volt DC operation if not equipped with magnetic blowouts and for 96 volt DC operation if equipped with magnetic blowouts. So the point here is the Reverse Contractor high amperage circuits should be able to certainly handle the 48 volts (nominal) that you are now using ... at least for a Curtis Albright contactor.

You mention the "current one is getting hot". Is it the coils that are getting hot or is the high amperage circuitry of the reverse contactor that is getting hot?

Do your have the reverse contactor mounted in a location that allows cooling of any heat that is generated in the contactor?

I am not sure what type of the controller you are running, but if it is a modern one, you might be able to set the "coil pull in" voltage according to what you need for your 36 volt coil. Note that shock loading (from driving in rough terrain) may mean that you need to have a somewhat higher "coil hold" voltage.

Note also that the Albright / Curtis Albright SW202 Reverse Contactor is rated for 250 continuous amps ... any chance you are exceeding that amperage ... which could explain why your "current one is getting hot".

See attached spec sheet for more information.

[Dadkins]

Wow thank you for all of that info! The one I currently have is an Albright 36v one. It is getting hot at the bottom and pretty quickly. The max amps I’m pulling is 320. So the one with the magnetic blowouts can handle 72v as well? That may be in plans for the future. I am currently using a navitas 440amp controller. I believe there is somewhere that says coil put in but I’m not sure if it can be adjusted. I’ve made sure all the lugs on the contactor are tight. Here is a pic if that helps. Thanks so much for the help!

[Dadkins]

I also installed a Mjz400 solenoid. Could it possibly be that things aren’t wired properly?

[Dadkins]

The stripe on diode is facing the red key wires

[ThreeCW]

What is the model number of your 440 amp Navitas?

Can you post a link to or a copy of the controller manual?

If the bottom of your SW202 is heating up fast, I suspect your 36 volt coils are not able to handle the 48 v input.

Check the voltage going into the coil(s) when the coil has been activated. That should help you in troubleshooting the problem … hopefully before you burn a coil out.

Also see if you can turn down the voltage used to activate the coil from your Navitas controller.

I also attached a parts diagram in my last post. You might get lucky and be able to replace the coils with 48 volt versions.

[Dadkins]

It is the top diagram. What bolt would I use to check the voltage once activated?

[Dadkins]

My reversing contactor is getting the full voltage even with the controller off. Is this normal?

[Dadkins]

And the small post on solenoid don’t seem to be getting voltage with or without the key on

[ThreeCW]

I had a look at the the Navitas wiring diagram (a clearer diagram is attached below for reference) and it appears that you have removed the factory Direction Selector Switch and replaced it with the 36 volt Albright SW202 Forward Reverse Contactor. Under conventional circumstances, the controller is used to drive or operate the forward and reverse coils of your SW202 Contactor.

It is unclear how you wired the SW202 Contactor, but based on one of your other threads, I suspect that it has been wired directly and the SW202 is not powered (or controlled) by the controller. This is certainly an option, but if wired directly, it does not allow you to adjust the Pull In Voltage and Hold Voltage going to the forward and reverse coils of the SW202. If that is the case, you would be providing 48 volts to a 36 volt coil, creating excessive heat and most likely (almost certainly?) shortening the life of your 36 volt SW202 coils.

You might want to contact Navitas directly to see if they can offer you a wiring diagram that allows you to control the SW202 from your controller and adjust your Pull In and Hold voltages to suit your 36 volt SW202 coils.

Either that or replace the SW202 36 volt coils with 48 volt coils ... or switch to a 48 volts Forward - Reverse Contactor.

Originally Posted by Dadkins

It is the top diagram. What bolt would I use to check the voltage once activated?

To check the activation voltage of your SW202 coils, you would use the 6 mm spade connectors on the SW202 ... voltage should be measure across what would normally be a red and black wire.

Originally Posted by Dadkins

My reversing contactor is getting the full voltage even with the controller off. Is this normal?

Not sure how you have wired in your SW202, but under normal circumstances, with the controller off, the solenoid should also be in the open position and no voltage should be seen at your SW202. Could be a solenoid issue or wiring issue.

Originally Posted by Dadkins

And the small post on solenoid don’t seem to be getting voltage with or without the key on

Depending on how your have your solenoid wired, it may take the Rocker Switch to be in the FWD or REV position plus the key switch in the ON position plus the Foot Switch activated in order to have voltage across the two small posts of the solenoid.

Hope this assists with your troubleshooting