EZ-GO Golf Cart Battery Died in About an Hour

[eflyguy]

Eek - sorry - I have a 42V cart (7, 6V batteries) so 42V at rest is a little under 50% SOC.

I don't seem to be able to edit the original post..
..a

[JohnnieB]

Originally Posted by eflyguy

Eek - sorry - I have a 42V cart (7, 6V batteries) so 42V at rest is a little under 50% SOC.

I don't seem to be able to edit the original post..
..a

Yes, the named voltage (2V, 6V, 8V, 12V, 36V, 42V, 48V, etc.) is below 50% SoC, and some brands of batteries have slightly higher At-Rest voltage than others, but it is still a reasonably good red-flag point to keep in mind, or at least a convenient one.

Also, the voltage you see when you first stop your cart is lower than it will climb to after resting for several minutes. I measured the voltage climb rate on a set of six T-105 batteries and found much of the voltage climb occurred in the first 5 minutes, most occurred in the first 15 minutes and nearly all occurred in the first half hour.

Here is what I found.
2008 TXT PDS with six 3 year old T-105's for 36V
Driven 10.2 Miles in Freedom Mode
Stop =37.05V - 68% SoC
5 Min = 37.37V - 77% SoC
10 Min = 37.43V - 78.5% SoC
15 Min = 37.49V - 80% SoC
20 Min = 37.51V - 81% SoC
30 Min = 37.53V - 81.5% SoC
60 Min = 37.57V - 82% SoC

As you see the apparent SoC changed by 14% over an elapsed time of 60 minutes.
While it did continue to climb after that, I stopped taking measurements after an hour had passed.

When I do battery studies (Run-time - Range - AH per mile and the like), I allow the batteries to rest at least 30 minutes before taking the "After" reading. When I just want to know when it is time to head back to the barn, I just use what my dash mounted DVM reads a few moments after my cart stops. That automatically puts me on the safer side.