EZ GO TXT Speed versus Battery Life

griffey

Hi Folks.

I have a 2002 EZ GO 36v Electric golf cart that I purchased about 9 months ago. All year I have been able to play golf all day (sometimes more than 27 holes) and drive back and forth to the course (about three blocks away) on a single charge, with no noticeable slow-down or sluggishness by the end of the day.

A month or so ago I installed the "speed chip" into the controller. As promised, the cart goes much faster now.

I did that at the end of the summer and didn't play much golf after that, and when I did it was only a few holes or so. Well, the last two times I played golf I was only able to make it through about 9 holes and then inched my way down the street home.

The water level in some of the cells of some of the batteries was low, so I added distilled water as instructed and put the cart on the charger.

And after that I was still only able to play about 9 holes.

My question is this: does the "speed chip" really reduce driving time by that much, or is it likely that something else is in play here? (Like I drove for too long with battery water slightly low and now my batteries are jacked up?)

Thanks in advance for any help and/or advice!

G.--

BGW

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scottyb

Sounds like something else is at play, maybe a weak battery?

JohnnieB

Welcome to BGW!

Technically, it takes more amps to run at 18MPH than it does at 13MPH, but you travel further in the same amount of time, so the difference more or less nulls out.

It also takes more amps to accelerate from 0 to 18MPH than it does from 0 to 13MPH, but there more things going on than just that.

It is cooler now than is was, so your batteries won't be delivering as much energy or at as fast of rate. (IE: At 0°F cart batteries only have about half the capacity they do at 80°F)

What PDS Mode were you running in before installing the speed chip?
If it was no chip or the All Terrain chip, the only difference is speed, but if it was either of the Hill modes, you had regen braking, which puts some energy back into the battery.

How far have you been discharging your batteries before recharging?
If you don't know, that is part of the problem.
They should never be discharged more than 50% State of Charge.
They should also be charged after each use, no matter how slight.

Were the plates exposed, or was the electrolyte level just low?

To determine the condition your batteries are in:
Charge them until the charger automatically shuts off.
Wait 12 hours.
Measure the pack voltage and the individual battery voltages.
The 36V pack should read 38.2V and the individual batteries should be 6.37V each, and the individual battery voltages should be within 0.1V of each other.

Let us know the voltages and we will go from there.

griffey

Thanks for the replies!

I was running with no chip previously (I even got to take off the "you're going to void the warranty" sticker!!).

I do not know how far I was discharging the batteries. Typically I'd drive down the street, play however much golf, drive home, and put the cart on the charger.

Yes, I had exposed plates--which is why I feared that this might be a bigger problem than just the speed mode..

I don't have a voltage tester--I suppose I ought to get one...

Thanks again. My wife and daughter headed "to town" (we live in a rural area) so I'll send them a text and have them pick up a voltmeter thingy.

Thanks!

G.--

JohnnieB

You'll need a DMM (Digital Multi-Meter) if you plan on any DIY cart maintenance.
An inexpensive one in a blister pack from a big box store or the local auto parts store is adequate.

You also need and on-board battery level meter to tell what the State of Charge is while you are out and about.
The most accurate is something like is: http://www.cartsunlimited.net/Digita...ry_Meters.html

Or an analog type will do the job.
Personally, I'd steer clear of the LED bar-graph types because some of them have a nasty habit of telling lies about the battery level.

griffey

Thanks JohnnieB. I had my wife grab me a multimeter while she was at WalFart. Assuming I'm using this thing correctly, each of the six batteries is hitting right on 6 volts, and when I touch the two terminals that connect to the cart, it reads 35 or so.

I was expecting readings much lower than that (even though you said they should ideally be slightly higher).

The meter I have is an analog one with a needle, not one with a digital readout, but on the 2, 4, 6, 8, 10 scale, the needle was hitting right on the 6 for each battery.

Thanks again for your help.

G.--

JohnnieB

I'm not sure what your expectations are based on, but they need to be reconsidered.
A 36V battery pack at 36V is less than 50% charged and you should never discharge your batteries more than 50%.

Here is a Voltage vs State of Charge chart.



Unfortunately, I may have misled you when I said an analog meter will do the job. I was referring to a dash mounted battery level meter, which is akin to a fuel gauge in a car. With some practice reading it, an analog battery level meter mounted on the dash is accurate enough to tell you when to head back home and put the batteries on charge.

However, for troubleshooting a cart and/or or checking battery voltages, an analog meter does not define the voltages closely enough to be meaningful.

Please note on the attached chart that the difference between a 90% charged 6V battery (6.31V) and a 100% charged 6V battery (6.37V) is only 0.06V, which is impossible to read on an analog meter.

For meaningful readings, the meter must define voltages under 10V down to 0.01V and voltages under 100V down to 0.1V.


Unlike NiCad batteries, Lead-Acid wet cell batteries have no memory and should be charged after each use, no matter how slight the use is.

Here is a battery tutorial that will provide some factual information about golf cart batteries. http://www.cartsunlimited.net/How_Batteries_Work.html

While on the website, reading everything with "Battery" in the title, will provide a lot of useful information.

Attached Images

StateofChargeChart.jpg (53.8 KB, 0 views)

griffey

Thanks JohnnieB. I'll get a digital meter next week after work. I didn't realize how these things worked--I assumed half-charged would be 3 volts each. :)

This afternoon I cleaned battery terminals and such and took the cart for a spin. As expected, after driving around the course for a short time it became very hard to go up slight inclines and barely got back to the clubhouse. I went inside and had a drink and watched some football and a couple of hours later when I went home the cart was as fast as it was to start the day and zoomed home with no problems.

So the question now becomes: am I in for a new set of batteries next Spring?

Thanks again!

G.--

JohnnieB

I suspect your batteries have been overly discharged a few times, so they might be pretty sick, but you never know for sure until you do a few tests.

Between now and the time you get a DVM (Digital Volt Meter) next week, charge and recharge the batteries repeatedly.

Plug the charger in and after the charger shuts off automatically, unplug it from cart and then plug it back into cart to initiate another charge cycle.
Do that two or three times a day if possible.

Check the fluid levels in the batteries because they are going to be gassing a lot.
Use distilled water only. Do not overfill.

After you get a DVM, let the batteries rest about 12 hours after the charger shuts of automatically and then measure the pack voltages and the individual pack voltages. (Record the voltages)

That will tell us if they are taking a charge.

To tell if they are holding a charge, play 9 or 18 and let batteries rest for 10-15 minutes after you get back home.
Then measure the voltages again.

Post both sets of voltages and we should be able to make an educated guess about the batteries' health.

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Your experience with the cart barely making it to the 19th hole and running fine later is consistent with the way batteries work.

When a battery discharges the electrolyte stratifies, meaning the electrolyte closest to the plates is more used, so the battery voltage is lowered. Let the battery rest for a few minutes and the electrolyte concentration equalizes throughout the cell and the voltage recovers.

Roughly the same thing happens when a battery is charged, but in the opposite direction.

That is why you have to wait about 12 hours after a battery has been charging and about 15 minutes after it has been discharging to get meaningful voltage readings.

------------------

Don't worry, the fog soon clears.

I had been repairing electrical and electronic device for several decades before I got a cart, so I already knew a bit about electric motors, speed controls and batteries, but I still had some learning to do.

griffey

I have not driven the cart, but Sunday, Monday, and Tuesday I initiated the charging cycle 2 or 3 times each day.

I got the digital meter last night and measured each battery today.

Those numbers are as follows: 6.19, 6.20, 6.32, 6.11, 6.17, 6.20, and the total for the whole system read 37.1. Not even close to each other, and according to your chart, 37.1 is around 60%. Yikes.