1995 Medalist 36 volt controller question

[cgtech]

Spm600, there. Its gonna require a bit of work to get it to fit, but, power will be superb.

[scottyb]

Originally Posted by cgtech

Spm600, there. Its gonna require a bit of work to get it to fit, but, power will be superb.

The cabinet is 16 inches long on the SPM600 and although it has an awesome output of 690 peak amps the size of the unit deters most people away from it. Additionally some engineers say that a wet cell battery pack has no more than 500a to give up at a time and that any more is a waste like putting a 2 inch gate valve on a 1 inch pipe.

Most people use the SPM48500 on this cart. Use with HD F&R switch and 2g cables throughout for best performance. This control and 400 solenoid (pkg#485 at carts unlimited) can be used on 36v now and 48v later which makes a popular choice. 48v will give you 33% more torque and speed.

[cgtech]

Originally Posted by scottyb

The cabinet is 16 inches long on the SPM600 and although it has an awesome output of 690 peak amps the size of the unit deters most people away from it. Additionally some engineers say that a wet cell battery pack has no more than 500a to give up at a time and that any more is a waste like putting a 2 inch gate valve on a 1 inch pipe.

Most people use the SPM48500 on this cart. Use with HD F&R switch and 2g cables throughout for best performance. This control and 400 solenoid (pkg#485 at carts unlimited) can be used on 36v now and 48v later which makes a popular choice. 48v will give you 33% more torque and speed.

I agree the available controllers are reaching the point of diminishing returns for lead acid batteries. But, on the other hand, i can say from experience that a YDRE converted to series pulls harder with a Spm800 than it does with a Spm500. An Spm500 would be a great choice.

[JohnnieB]

A series motor's impedance (dynamic resistance) increases as the motor's RPM increases, so at some RPM the motor, in and of itself, will be incapable of drawing all the amps a FLA battery pack can produce and/or all the amps the controller can pass.

Therefore, with the same motor and battery pack, the difference in performance between controllers with different amp ratings is limited to below the RPM at which the motor's impedance allows it to draw the max amps that can be passed by the lower ampacity controller.

For example: If a specific series motor will only draw 400A when 36V is applied to it and it is loaded down to 1,000 RPM on a dynamometer, it will produce the same amount of torque at all RPMs above 1,000 RPM whether it is fed by a 400A, 500A, 600A or 1,000A controller. However, there will be more torque produced with controllers that will pass more than 400A below 1,000 RPM because the motor is capable of drawing more Amps at RPMs below 1,000 RPM.

Of course, the "Magic" RPM depends on the motor's Torque vs RPM curve and the voltage applied. IE: For the same specific motor with 48V applied, it would draw 400A at about 1,250 RPM.

FWIW: 1,000 RPM is roughly 4.5 MPH with stock height tires and gears, while 1,250 RPM is roughly 5.5 MPH. Taller tires and higher speed gears will up the speed for a given motor RPM, so the increased low end performance would be felt over a broader speed range.

[scottyb]

And there u have it .

[Q2arrowhunter]

Thank you all. What All do I need to convert from 36 to 48? It looks like Im in need of new batteries also now so depending on the cost difference.

[JohnnieB]

Originally Posted by scottyb

And there u have it .

That is "it" for series motors. It gets far more complex for sepex motors and AC motors, but their impedance also increases with RPM, so the same basic concept holds true.

I tried to keep it out of the Tin Hat stratosphere.

[JohnnieB]

Originally Posted by Q2arrowhunter

Thank you all. What All do I need to convert from 36 to 48? It looks like Im in need of new batteries also now so depending on the cost difference.

Battery pack, Charger, Solenoid and Controller all have to operate at the same voltage.

The SPM controllers mentioned operates from 36V to 48V, and the kits Scotty sells come with a solenoid.
The 400A version comes with a 200A/800A solenoid that is voltage specific, the 500A (& larger) comes with a 400A/1000A solenoid that works from 36V to 48V. The 400A/1000A solenoid is optional with the 400A kit.

[Q2arrowhunter]

Think I will stay with 36 volts. And for the record - I only pulled against the 4-wheeler once - That is all it took - and it was at least 4 years prior to me having my issues.