How much does battery voltage tell you about battery health?

[scottek]

I just picked up my first electric cart, it's a 1993 EZGO XI500/XT500 Turf Truck. I'll take some pictures tonight and start an introduction thread.

I had to replace one battery to get it running, the old battery had a terminal that cracked from corrosion. The night I replaced the single battery it seemed like it had more torque. Now I'm wondering if I should replace the rest of the batteries. I've already conducted all the proper maintenance checks, but I'm still confused if the batteries need to be replaced.

Can you tell if a battery needs to be replaced by it's voltage?

1. 2012 Trojan T105 6.28v
2. 2012 Trojan T105 6.29v
3. 2012 Trojan T105 6.26v
4. 2013 Energizer 6.33v
5. 2015 Duracell 6.40v (new)
6. 2012 Trojan T105 6.30v

[scottyb]

Battery voltage can be a good indication of battery health when read with the cart under load. Take a reading 12 hours after charge. and a reading when the cart is going up hill with pedal to the floor. These 2 numbers will us some indication.

[JohnnieB]

The batteries are connected in series, so they should all be the same make, same AH capacity and same age.

A new battery added to a group of used batteries will quickly acquire the same age related characteristics as the older batteries.

Battery voltage is a diagnostic tool and can give you some insight to the battery's health when certain preconditions are met. For example, if the voltages listed were taken about 12 hours after the charger shut off, than the five older batteries are only charging from about 82% to 94% of their full capacity.

The true measure of battery health is load testing. Ideally, a load test starts with a battery charged as much as it will accept and then measure the time it takes to be discharged to 1.75VPC (Volts per Cell) at a constant discharge rate of 75A, but that takes specialized test equipment. (Car battery load testers don't work for deep cycle batteries)

[scottyb]

Originally Posted by JohnnieB;..... ([COLOR="Red"

Car battery load testers don't work for deep cycle batteries[/COLOR])

But a steep hill does. do not put the cart up against an im-movable object for load test. Permanent damage can result to batteries and drive components.

[scottek]

Updated steep hill load testing results...

What do new batteries help the most - Torque, Speed, Distance?

1. 2012 Trojan T105 6.28v -> 5.73v
2. 2012 Trojan T105 6.29v -> 5.73v
3. 2012 Trojan T105 6.26v -> 5.70v
4. 2013 Energizer 6.33v -> 5.77v
5. 2015 Duracell 6.40v (new) -> 5.90v
6. 2012 Trojan T105 6.30v -> 5.73v

[JohnnieB]

Originally Posted by JohnnieB

(Car battery load testers don't work for deep cycle batteries)

I need to clarify that statement.
The meter on a car battery type load tested is not calibrated for deep cycle batteries and they typically only apply the load for a few seconds.

If you happen to have one, if used in conjunction with a DVM, it can be useful for comparing batteries. However, you can get the same information just using a DVM and climbing the same hill while monitoring each battery separately.

[JohnnieB]

Originally Posted by scottek

Updated steep hill load testing results...

What do new batteries help the most - Torque, Speed, Distance?

1. 2012 Trojan T105 6.28v -> 5.73v (0.55V drop)
2. 2012 Trojan T105 6.29v -> 5.73v (0.56V drop)
3. 2012 Trojan T105 6.26v -> 5.70v (0.56V drop)
4. 2013 Energizer 6.33v -> 5.77v (0.56V drop)
5. 2015 Duracell 6.40v (new) -> 5.90v (0.50V drop)
6. 2012 Trojan T105 6.30v -> 5.73v (0.57V drop)

Which of the three improves the most, depends on how bad the batteries are.
Compared to the new Duracell, the other five batteries don't look all that bad and appear to be fairly well matched.

With all new Duracell batteries, my guess is that you'd get more distance most of all and maybe a little more speed, as well as a bit more torque, but torque is hard to quantify unless you have something other than the seat of the pants type dynamometer.

If you can lay your hands on a 6V charger, I'd charge the living daylights out of the five older batteries and see if they will charge to a higher SoC (State of Charge).

------------
Unless you replace the rest of the batteries in the very near future, the new Duracell will have to be considered a sacrificial battery and replaced at the same time the older five are.