Club car DS IQ slow

[ampedforay]

Hello all,

I inherited a 2003 48V Club Car DS IQ. The cart worked fine, but now has a couple of issues. I list all of them I have noticed because I don’t know if they are related.
The main problem is slow top speed. It only goes about 7 mph and slows on even a small hill. The battery bank reads 50V and maintains around 48V under load (driving the cart). The individual batteries all hold around 8V under load. The speed sensor test results in braking and buzzing when put into neutral or reverse, but coasts to a stop with no braking or buzzing in forward. Would a bad speed sensor only not work in one of the three F/N/R switch positions? It’s the GE style flat press in sensor.

The other issue is that the headlights don’t work anymore. The cart has a factory(?) 12V converter. It shows part# 15950. It has 50V across B- and B+. There is nothing across 12- and 12+. It reads the full 50V across 12- and B-, and across 12+ and B-. From other systems with a +/- supply, I would expect a ground in between so that it would supply either the +12 or the -12 voltage with 24V between the two. I have only been able to located one diagram which included the converter, but it shows the converter as wired except for an enable tied to B+ that I assume is internal as there are no other connections on the converter.

The other thing is that there is a B- lug which has two heavy wires (one going to OBC, one going to speed controller), and a smaller (maybe 12ga) wire connected. The smaller wire runs underneath forward but is not connected to anything. This wire looks like it has broken off, but I can’t find from where.

Thanks for any insight.

[Sergio]

Unless You have a specialty dc-dc converter, the typical 48v->12v converter does not have a differential output, there is only one negative that is common to both the +48v and the +12v side.

What do you mean by B-, the pack negative battery post?

The terminology B- is typically used for the Controller B- terminal.

There can only be one cable from pack negative to Controller B- and that cable must pass through the OBC.

Do You still have the OEM black Controller, if not sure just post the model number?

[ampedforay]

Thanks for the reply Sergio,

The B- does go through the OBC. The B- Lug is an insulated standoff mounted on the same plate as the speed controller and OBC.
B-lug_edited.jpg
The controller has three wires to B-. One from Battery, One to voltage converter, and one to the B- lug.
The controller is black Curtis PMC model 1510-5201.

I’m assuming the converter is toast. Good B+ and B- but nothing across +12 -12 terminals.

Converter.jpg

[Sergio]

Hard to see the small pictures, but from your description the pack negative cable is not wired correctly (or You used the terminology B- to mean more than one thing).

The pack negative cable needs to go from from the battery post through the OBC and directly to the Controller B-.

That is a high current connection.

There should be another 10ga wire from Controller B- that goes to that stand-off for the OBC charger output and accessories negatives/converter.


Here is a wiring diagram for your cart for reference:

It appears the dc-dc converter is bad from your description.

Make sure all high current cables are tight and have no signs of corrosion, meaning they do not feel "crunchy" inside when you flex the cable near the ends from side to side.

A stuck solenoid can also cause problems with high speed operation if it is sticking closed and lack of power if the contacts are damaged.

Do You see signs of overheating on the pre-charge resistor installed on top of the Solenoid?