88 Marathon Charger

[dczysz]

I recently bought my first golf cart, 1988 Ezgo Marathon. I've had it for 8 months. The batteries are about 1 year old. First question, how or when should it be charged? Second, should the charger run for 12 hours (complete cycle around the charger dial) or will it turn off once the batteries are fully charged?

Up until 2 weeks ago, when I put it on charging, I'd set the dial to the start position and it would charge the full 12 hours and end at the off position. The past couple of weeks, I can put it on charging and it will stop at the 3 hour mark. Any advice will be very much appreciated.

[JohnnieB]

Welcome to BGW!

First question is easy: If you use your cart that day, put it on charge that night.
Second question cannot be answered as clearly and concisely.

There are a lot of other variables, but basically, how long it takes to charge a battery depends on how far down it was discharged, the Amp Hour capacity of the battery and how much charging current the charger puts out.

Since you are charging the same batteries on the same charger, it more or less depends on how much they were discharged.

Brand new batteries may take 12 hours and more to charge fully, but after they've been broken in and if they aren't discharged lower than 70% State of Charge, 4-6 hours is reasonable.

I can only speculate why your charger was running 12 hours until a few weeks ago, but lets find out if it is fully charging your batteries now.

Spray the charger plug and receptacle with some contact cleaner and plug/unplug a few time before cleaner evaporates.
Also, clean connections were the wires from charger receptacle connects to batter pack.
Charge batteries until charger turns off. (Hopefully, it turns off before timer times out)
Let batteries "Rest" for about 12 hours and measure both battery pack voltage and individual battery voltages.

Pack voltage should be around 38.2V and individual batteries should be about
6.37V
Also voltage spread between highest/lowest battery should be <0.1V or so.

Here is a chart show Voltage vs State of charge.

[JohnnieB]

Oops, I didn't answer the second part of your second question.

The charger you are describing automatically shuts off when the battery pack's on-charge voltage reaches 44-46 volts.
If the pack doesn't reach the cut-off voltage within 12 hours, the safety timer shuts it off.

Here's a picture of what I think you are describing.
If so, it is built like a tank and is 100% repairable.

[simple man]

Two other things you can check are to make sure you have water in each cell, just covering over the plates. Also remove and clean ( one by one, so you don't get them mixed up ) all of your connecting cables for the batteries, and the two charging cables that connect to each end of your battery pack. Any poor connection at these points will let the charge voltage increase, possibly causing the charger to turn off sooner. Follow " JohnnieB's " steps for your voltage checks, as this may pinpoint a bad battery.