1999 ezgo Series ???

[JohnnieB]

The typical voltage drop for a 36V - 225AH battery pack is 1V per 100A of draw, your stock series controller maxes out at 275A and you batteries are dropping a total of 5.83V. or a bit over twice what a broken in set of new 6V-225AH batteries drop when they are at 80°F. Don't know how many amps were actually being drawn, but with 23" tall low pressure I suspect the amp draw was pretty close to maxing out the controller.

All six batteries are within 0.1V at rest and under load, so their only problem appears to be reduced capacity due to old age and maybe cool/cold temperatures. However, capacity loss due to aging is a slow progression and you said the problem developed overnight.

I suspect bad connections, contacts or cables. Is anything getting hot?
Cables shouldn't get more than about 10°F above air temperature.

Check the voltage between the controller's B- and B+ terminals at rest (after solenoid clicks, but cart not moving) and under load the same as you did on the batteries.

If the under load voltage is significantly lower than the 35.0V sum of the individual battery volts under load, than there is something amiss in the amp deliver system (cables, solenoid and connections)

[busman9]

No wires hot. Solenoid not hot
Pack V—38.4
B+ B- after solenoid click. 37.9
B+ B- under a load 34.3 until you get moving and then 35.9 while cruising full throttle

[orangeman6]

Originally Posted by busman9

No wires hot. Solenoid not hot
Pack V—38.4
B+ B- after solenoid click. 37.9
B+ B- under a load 34.3 until you get moving and then 35.9 while cruising full throttle

We’ll see what johnnieb says, but is that 34.3 just from a dead stop on flat pavement or uphill?
I didn’t catch it initially but johnnieb noticed you said the performance dropped overnight. Is that correct?

[busman9]

34.3 is hard accel from a dead stop
I need to take it to a hill and try it but will wait to see what Johnnie thinks

[handtools]

I know there is good technical information in this thread but here is my 2 cents, if your cart is doing what you want/need it to do don't get hung up on the numbers. When the cart stops performing up to your needs then start looking for problems. I've had batteries last 7-8 years and still do everything I needed them to do. Again just my 2 cents worth.

[busman9]

I agree but I am trying to figure out is the issue batteries or something else (controller)

[JohnnieB]

Looks like there is a little undesired resistance somewhere in the cables, connections and contacts, but not all that much.

Connect your DVM between the solenoid's battery side large terminal and controller side large terminal and see how much voltage is dropped during hard acceleration after the solenoid clicks.

Should be up to about 5V before solenoid clicks (Voltage drop of the pre-charge resistor) and 0.01V/100A, or less, after it clicks (contacts close).

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If not for the sudden onset mentioned, I'd suspect low battery storage capacity due to age and cool temperatures. Your location is about 0.3° of Latitude south of mine and it has been getting mighty chilly overnight here.

Typical battery life is about 4 years in your location (see attached map) and your batteries are 3 years old, so they probably only have about 50% of the rated storage capacity and if the overnight temperatures were in the 40's like they have been here, they are at about 75% of that capacity.

So if the were 225AH new, they are now about 112.5AH at 80°F and about 84.38AH at 40°F.

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Bottom line: Upgrade to 48V.