88 Marathon wiring question

[Babyboomerboy]

I have checked the battery pack while it was sitting still. The reading was 37 DCV. I have a PDF of the service parts manual for the 1988 Ez Go Marathon. The picture of the power wiring on page BB1 doesn’t show any connections with the labels B+ and M- or M1. The only labels are CL+, CR-, BL+, BL-, BR+, BR-, A1, A2, S1, S2 and 1,2,3,4. As I first posted I am a new first time owner of a golf cart so if I seem to be stupid about this it is because I am. I am still trying to figure out how to test the battery pack while driving it is down the road. Any help would be appreciated.

[JohnnieB]

I suspect you have a Resistor drive cart rather than a controller drive cart, and the missing labels are on a cart with an electronic speed controller.

I'm guessing, but this may be an easier to read schematic for your cart.

As for battery voltage, 37V at rest is low for a 36V battery pack, a bit less than a 70% State of Charge. (Fully charged is 38.2V)
Here is a chart showing Pack voltage vs State of Charge (Note: Voltages given are taken 12 hours after charger shuts off automatically.)

Apparently you found someplace to measure the pack voltage while cart wasn't moving, so fasten the DVM test leads with alligator clips or something similar, to where ever that was and have someone hold the meter and monitor DVM while driving.

Also, connecting the DVM leads to the two terminals in the cart's charger port will read battery pack voltage.

However, battery voltage drops while under load, so the voltages while driving doesn't mean much to most people.
What is usually done is to stop, wait about 10-15 minutes for batteries to recover and then measure the pack voltage sitting still.

[Babyboomerboy]

Here are some pictures of my set-up.

[Babyboomerboy]

Does these pictures help explain what I have?

[JohnnieB]

You have a Resistor Drive.
In the second picture, the box with 4 posts on top is the resistor bank.

The schematic I posted is for a resistor cart.

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Since you were trying to figure out how to measure the battery pack voltage while driving cart, may I presume the cart is very slow and won't run very far or long?

I'm mot sure, but I think the top speed of a stock resistor cart is about 10MPH.

As for run-time and range, the cart uses about the same energy from the battery pack whether it is running at its fastest speed or one of the three slower ones.
Like mentioned in my previous post, the battery pack wasn't fully charged, which could mean charger or charging issues.
The pictures tell me that two of the six batteries have been replaced. That typically means that the batteries replaced had failed, which in turn means the four batteries that were not replaced were the same age as the two that did.
Also, the two Exide replacements are very likely to be the economy grade, which are 186AH and the standard battery is 225AH.

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To check the health of the battery pack, do this:

Check water level in batteries.
If plates are exposed, add only enough distilled water to raise level to about 1/4" above top of plates and fill to proper level after they are charged.

Fully charge batteries. Either let the charger shut of automatically or run it 12 hours if it is a manual charger.

Let the batteries rest at least six hours after charging. (12 preferred)

Measure bot pack voltage and individual battery voltages
Pack voltage should be about 38.2V, each 6V battery should read 6.37V and the difference between the highest and lowest should be 0.1V or less.

Drive cart for a few miles, let the batteries rest and measure the voltages again.

This chart will tell you what the batteries discharged to and the individual battery voltages should still be within 0.1V of each other.