Batteries get weak faster lately

[jonequest]

I have a 36volt EZGO TXT with a 48 volt conversion and ~16 month old GC8V US Batteries running a 72400 Alltrax Controller and EMP motor upgrade. I have no lift kit or big tires. When fully charged overnight if I am by myself I can get maybe 28 mph max which I guess is OK for my setup but I notice that performance degrades much more quickly lately. Yesterday I drove it about 2 miles and after even the first mile I seemed to max out at about 24 mph. The other day while riding my kids around the neighborhood with a total of me and 5 kids on the cart I used to be able to drive just fine all day. (I DON'T do full speed with kids) But I notice now its getting much weaker after the first 1-2 miles as well. I have always used a LVS charger that is suppossed to help desulfate batteries. Any ideas? P.S. I also always plug in the charger after riding and let it automatically kick off and on as needed to keep the batteries charged.

[DaveTM]

Have you checked the water levels in the batteries? Also, have you checked the battery charge about an hour or so after the charger has shut down, and then the next morning to see how the batteries are holding a charge overnight?

[jonequest]

I do have a voltmeter hooked up to the key so I can see if there is a drop. I usually just have the batteries on constant with the charger. I am also good about keeping water in them after hearing the horror stories. What sort of drop is alowable after 1 hr, 12 hours, etc.?

P.S. When I am at idle fully charged I am at about 50-51 volts, when I am under load it drops to about 45 volts lately if i remember right.

[JohnnieB]

Originally Posted by jonequest

1.What sort of drop is alowable after 1 hr, 12 hours, etc.?

2. When I am at idle fully charged I am at about 50-51 volts, when I am under load it drops to about 45 volts lately if i remember right.

1. That isn't quite how it works.
Lead-acid batteries acquire a "Surface Charge" when they are charged and to get a reasonably accurate State of Charge (SoC) from the battery voltage, you have to allow the surface charge to deplete.

This can be done by letting the battery "Rest" for about 12hrs, or by driving the cart for about half a mile and letting the batteries rest for about 15 minutes.

FWIW: Lead-acid batteries self discharge at about 1% of SoC per day, but due to construction and materials used, this rate varies.
Also, batteries recover from being under load, much faster than they self discharge.

A fully charged 48V battery pack made up from mature batteries in good condition, should read about 50.93V at-rest.

2. You have 170AH batteries and a 400A controller, so the Under-load voltage will drop some.
To get an accurate SoC voltage reading, let the batteries rest about 15 minutes after they have been under load.

When accelerating or climbing hills, or other heavy load conditions, try not to allow the under-load voltage to drop below 42V (1.75VPC) for a 48V battery pack and never go below 36V (1.5VPC) unless in a dire emergency.

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Which 48V LSV charger are you using?

What is the shut-off voltage? US battery is looking for 62V (2.583VPC), so there is a possibility you have been undercharging your batteries.

To check the charger's shut-off voltage, charge the batteries until the charger shuts off automatically, then unplug charger from cart and then plug it back in, initiating a new charge cycle.

Watch the DVM battery meter. The highest voltage it reaches is the shut-off voltage.

If you don't catch the voltage the first time, restart the charge again, it won't hurt the batteries. (Might even help them)

---------------
To determine your battery pack's health.
Measure SoC 12 hours after the charger shut-off.
Should be about 51V for the 48V pack. Each 8V battery should read about 8.5V and all six should be within 0.1V of each other.

Drive cart for several miles or until performance is noticeably diminished, wait 15 minutes and measure the voltages again.

You can determine the SoC from attached chart.
If a baseline for run-time had been established, you could tell how much they have deteriorated, but without it you can only guess.

However, all six batteries should still be within 0.1V of each other

[jonequest]

I have the LVS-4825A. My charger was on green light with the batteries at ~52 volts. I unplugged and replugged the changer plug to reinitiate it and it slowly climbed to 62.6v max, then settled into 62.3-62.5v. The yellow chanrging light was still on but it you can see it stopped climbing. The good news is that I could smell the batteries gassing and hear a little bubbling so the charger seems to be doing well. I have upgraded all but 5 of my battery wires to 2 gauge welding cable. The remaining wires are 4 gauge but older and may not have the cleanest ends on them. Could that be significant?

[JohnnieB]

The charger appears to be doing its job.

4Ga cable should be adequate for a 400A controller, but if they are old and/or have dirty connections, they might be the problem, or at least a contributing factor.

However, the symptoms you are describing, indicate a battery pack with reduced capacity.

Might be just one battery dragging the whole pack down, so do the before and after test I described in my previous post, and post the before and alter numbers.

[jonequest]

Originally Posted by JohnnieB

The charger appears to be doing its job.

4Ga cable should be adequate for a 400A controller, but if they are old and/or have dirty connections, they might be the problem, or at least a contributing factor.

However, the symptoms you are describing, indicate a battery pack with reduced capacity.

Might be just one battery dragging the whole pack down, so do the before and after test I described in my previous post, and post the before and alter numbers.

OK will do.

[DaveTM]

Ya know....I was gonna tell you everything JonnieB told you....but I couldn't find my darn foil hat!! I think my wife hid it 'cause I think she's an alien.

Well.....JonnieB's not a alien 'cause my tin hat told me that.

Carry on.

Dave

[pernellj954]

Yeah, JonnieB is fart smeller; I meant Smart Feller! :)