EZGO 36Volt Textron Charger problem

[ezgofast]

I have an older EZGO with a 36 V Textron Total charge III charger. When I begin charging the batteries, all is fine, charger starts, initially at high amp as it is suppose to. It use to slowly go down on Ampmeter until batteries fully charged and then shut off. Now, it starts high on Amps, then drops just a little, then shuts off. I checked battery voltage and they seem charged, but I know after running it for 45 minutes that the charger should be running for more than 3 minutes. It used to run for a couple of hours after a similar run in the golf cart. Any suggestions?

Thanks.

[WW]

[JohnnieB]

Check for loose/corroded connections.

Put DVM across main battery terminals (Might be marked BL+ and BL-) What is the total battery pack voltage? (38.20 is fully charged)
Plug in charger while monitoring battery pack voltage. It should increase when charger clicks on and increase to about 44-46V before the charger shuts off automatically.

Let us know what you measure and we'll go from there.

[ezgofast]

Thanks for the suggestions JohnnieB. First checked connector on cart at 37.3 V. Across BL+ and BL- was also 37.3 V. Then put on charger. It came on for a minute at about 18 A, then shut off. While charging, across BL+ and BL- was 39.2 V. After it shut off, Voltage was 40. Waited a few minutes. Checked Voltage across cart plug and BL+/BL-. Both read 38.2 V. All connections on batts and electrical are tight. Tried one more time. plugged in charger, came on for about 30 seconds at 18 Amp. and shut off. Looks like total voltage is sitting at 38 V. Checked across each Battery and they are all 6.3 to 6.4 V. I saw in one of the other issues that there are 3 stages of charge. I used to have a gradual decrease in charging. Now only "High". Is there something in the charger control board that might not be letting it slow down rather than just shutting off. I guess next step is to look inside charger unless you have any other suggestions. It is very puzzling that it is still at 38 Volts (very near a full charge) after all I have run it. Maybe it makes sense that if it does not go into "trickle state", I will get 90% of the charge at the 18 Amps and very little at lower charging Amps. Ideas? Thanks very much!

[JohnnieB]

Attached is a State of Charge chart, showing voltage at various States of Charge. New batteries will be slightly higher, older slightly lower.

If the battery pack is close to fully charged (38.2V), the charger isn't going to stay on more than a few minutes.
If it is down to 75% (37.3V), it ought to take about 4-6 hours to charge.

The amount of current the charger puts out depends on how much higher the voltage of the secondary of the charger's transformer is to the voltage of the battery pack (It's actually a bit more complicated, but that will suffice for now). All the control board does is energize a relay that applies AC power to the transformer's primary windings when it senses voltage above about 27-30V for a 36V charger and de-energize that relay when the sensed voltage reaches 44-46V. The control board also has a safety timer that de-energizes the relay if the sensed voltage does reach 44-46V within about 12-16 hours.

Sounds like your charger has a sick control board.

If you want some good info on the care and feeding of Batteries, go to ScottyB's website and read everything on the top left menu that has "Battery" in its title.
http://www.cartsunlimited.net/