Old 3 wheel ezgo won't charge long

toystuff

I have an old 3 wheel ezgo that has a EZGO Textron Total Charge charger. When I plug it up to charge it goes to full charge then within 10 mins it shuts it self off. I have replaced all the batteries and some cables but it still won't charge it up to a full charge. My question is What controls the the rate and length of charge? Any help will be appreciated.

BGW

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JohnnieB

Welcome to BGW.

The charge rate is controlled by the transformer and capacitor combination in the charger.
The charge time is determined by a control board that senses battery voltage, or a timer that times out.

With properly broken in, moderately discharged batteries, the charge current jumps up to about 25A initially, stays there about 15-20 minutes and then tapers off to about 2-6A until the battery voltage raises into the 44-46V range (for a 36V battery pack) and the control board automatically shuts off the charger.

New batteries will take longer to charge.
The charger shuts off quickly when batteries are at or near full charge.

What is your battery voltage? (New batteries will read over 38.22V at full charge - Readings taken 6-12 hours after charger shuts off)

Here is a chart showing State of Charge vs. Battery voltage.

Attached Images

StateofChargeChart.jpg (53.8 KB, 3 views)

toystuff

Thanks JohnnyB I checked the amps on the battery and they were Fully charged at around 39 volts, The motor was only getting 11volts running so checked back to the speed controller and it was only putting out 36 volts on the bottom post with 5,6 and 10 volts on the rest of the post on the speed controller. Should the speed controll not have constance power on each post ?

JohnnieB

Sounds like the charger and batteries are doing okay.

I'm guessing here, but I think you've got a resistor cart. Is what you are calling a speed control a louvered metal box with four cables attached to it and three coils of bare wire inside?

If so, the coils are selectively placed in series with the motor by the accelerator pedal and you have 4 speeds. 1st has all three coils in series, 2nd has two, 3rd has one and 4th connects battery directly to motor.

On the Bottom post, you ought to get the same as you get going directly across the battery. If not, you've got some serious cable and/or connector problems.

If you don't have a schematic for your cart, go to the Sticky:s on the opening page of Electric EZGO and download the one for a Resistor Cart. I think it is for a Marathon, but the drive system is similar if not the same.

toystuff

From the pedal switch going to the resistors how much voltage should you get on each cable?

JohnnieB

Zero Volts.

There are four cables going from pedal switch to resistor box. Unless the connectors are corroded or the cable is frayed, you are measuring across a piece of 6ga copper wire.

Most voltage measurements are made from the most negative terminal of the battery pack (B-) to some other point.

From B- to the four cables between the pedal switch and the resistor box, you should get the same voltage reading at each end of each cable.
The only one I know for sure is the one that bypasses the resistors completely (Bottom one one your cart) and that should be the same as your total pack voltage (From B- to B+)

The voltages given in your second post tells me you don't have any open resistors, but other than that, I have no idea what those voltages should be.

toystuff

I do have voltage the same as the batteries on the bottom but the rest of the cables are really low in voltage. I ordered a wiper switch and will go from there. This may be a good learning experience but I really appreaciate the help.

JohnnieB

Let's try this again.

Attach the Neg. test lead of your DVM to B- (Negative post on Left Rear battery.)
Find the cable that connects Accelerator Switch to the F/R Switch and connect the Pos. test lead to the F/R Switch end of it.
Your DVM will now measure the voltage across your motor (Stator + Armature windings) and F/R Switch.

Hang your DVM so you can read it while cart is moving or get a passenger to hold it and take readings.

With accelerator pushed down slightly, you should get approximately 25% of your battery pack voltage.
Push down a little further and it you should get roughly 50%.
Push a little further and it should go to about 75%.
All the way down and it should read full battery pack voltage.

The first three readings are very - very approximate because the resistors change value as they age.
(Technically, they get red hot or hotter during use and the the surface vaporizes, so the heater wire they are made from grows smaller in diameter over time and they increase in resistance.)

The last reading is the key reading. If you are not getting the full battery voltage with the accelerator all the way down, you have a cable or connector with high resistance someplace between B- and the F/R switch.
Any cable, component or connection getting too hot to touch, other than the resistor box and the posts on it, are bad.

The top speed for a stock Resistor cart is typically in the 10-12 MPH range.

toystuff

I have checked the current on the four cables coming from the wiper switch to the resister. I had 36 on one then 5 then 7 and with the pedal wide open I was only getting about 10 volts on the last cable so I ordered a new wiper switch. I believe the wire from selonoid to the wiper switch is burn up.