For this post, I would like to re-emphasize the importance of being sure that the problem that you are troubleshooting ISN’T being caused by a battery issue. I can’t tell you how many times I’ve been called in to help someone with a cart that has been extensively “diagnosed” by at least six neighbors as everything from a bad motor to a bad transaxle to a bad solenoid, only to discover the REAL problem was a battery or two (or six).
To begin with, as I have mentioned over and over again in the book “Electric Golf Cart Repair 101 (and a half)”, and other blogs on this site, I highly recommend that you get the back wheels off of the ground before you start troubleshooting. In order to load and test the battery pack, you’re going to have to depress the accelerator to put the cart in a “Normal Operation” (like it was being driven). If the problem (no matter what it is) goes away while you are doing that, away goes the cart (see the posts in the “Whoops” category for a laugh or two and a reality check on how dangerous these things can be to work on).
There are times when you might need to drive the cart while troubleshooting, because there are problems that will only show up when the system is loaded down. When you jack the rear wheels off the ground and run the Motor in troubleshooting, the Motor isn’t loaded (required to provide the normal energy to spin the wheels) as much as it would be under Normal Operation Mode. But these problems are unusual and most troubleshooting can be done with the wheels off the ground.
The next step is to verify that the Battery Pack isn’t the problem. Once the wheels are up and the seat is off, place the negative probe of the meter on B- and take a look at B+ with your positive probe. It needs to reflect a reasonably charged Battery Pack. For a 36 volt cart, it should show at least 37 volts. IF it is a 48 volt cart, it should read at least 49 volts. If it reads something much lower, stop right there, get the charger out and let it charge a few hours before starting. Chapter 4 offers more information about batteries.
So, now that you have a reasonable B+, we want to make sure it stays that way when we try to load it down. So, turn on the Key Switch (KS), put the F/R Switch in Forward and depress the accelerator enough to activate the Accelerator Micro Switch (Acc MS) and, therefore, energize the solenoid. Of course, if the cart has some other problem (other than battery related), then the cart won’t try to run. But if the solenoid does energize (go “clunk”), watch the B+ to see what happens. If the reading drops down more than a volt, you might still have a battery problem.
At this point, because we have the wheels off the ground, we aren’t putting the normal load on the Battery Pack, but any significant drop in B+ must be investigated.
If the solenoid does energize and the B+ barely changes at all, you are probably ready to continue to the chapter that best matches your cart and start troubleshooting.
A common scenario that I see a lot, is one where when the accelerator is depressed, the cart makes a rapidly clicking, rumbling or growling noise, but the wheels don’t move, or at least not for any appreciable distance. What usually is happening in this case is that there is a battery or two that is (are) “falling” out when the pack is loaded. It is actually the solenoid (what I call the Main Contactor) that is making the noise.
Often interpreted as a slipping or grinding noise, the solenoid is probably engaging when you first depress the accelerator to try to get the cart to move, but just as soon as it engages, the Battery Pack is then loaded so the solenoid drops out. The Battery Pack can’t maintain enough voltage to hold the solenoid in. Then, just as the solenoid drops out (less load to the Battery Pack) the voltage jumps up just enough to try to energize the solenoid again and the cycle starts over. The solenoid makes a growling noise as it energizes, then lets go , then energizes and so on. I’d go back to the Battery Pack voltage. Put a meter across the whole pack (B+ to B-) and then observe the voltage as you try to make the cart move. I think you have at least 2 of the batteries “falling out”. Remember that the batteries are in series, so all of the current has to flow through all of the batteries. Even one of them will kill the whole process, and drop the pack’s potential down to where it can’t hold the solenoid in. If so, you must now isolate which battery (batteries) is (are) the culprit(s). In order to do so, just connect your meter to each battery individually (one at a time), and watch the meter as you depress the accelerator. When you see the meter voltage drop drastically across any one of them, you’ve got the rascal. Of course, it could be that all of the batteries are shot and won’t maintain an adequate supply to keep the solenoid engaged under a load.
Let’s take the worst case scenario and say that the voltage only drops a little and spins the tires, but when trying to drive the cart under normal circumstances, it only “chugs” (acts like it’s trying go but can’t or does run but erratically). This is a more difficult scenario because we are going to have to load the cart down to see exactly what is happening.
To do this, I would take the cart off of the jack, alligator clip the meter’s probes to B- and B+ and put the seat back on, but use a little block of wood under the back edge of the seat to keep the seat from pinching the meter leads and then set the meter on top of the seat, so that you can drive the cart normally while reading the meter.
If the cart indeed “chugs” and the B+ drops way down, you probably have a battery “dropping” out. To identify the culprit (or culprits), leave the negative probe of the meter on B- and move the positive probe to the positive terminal of the first battery in the series strung Battery Pack (this is discussed and diagrammed in Chapter 2). This will be the same battery that the negative probe is on (B-). So now your meter will be looking at the first battery’s voltage only. Now we put the seat back on and drive the cart again. If the cart still “chugs” but the voltage of the first battery stays within a volt or two of its unloaded value, the first battery is not the problem. The next stop would be to move the probes of the meter to the second battery and repeat the process, then the third and so on.
If the “chugging” is, indeed, a battery problem, one or more of the batteries will show a large change in its reading when loaded. It also could be caused by a battery cable that is barely making contact and starts arcing when loaded. If so, it will generate heat at the point where the problem is. Let it “chug” a couple of times, then feel around carefully with your hand for a hot spot. That could be your culprit. As mentioned before, it could be that all of the batteries are shot and won’t maintain an adequate supply to keep the solenoid engaged under a load.
Anyway, I can’t overemphasize the importance of eliminating any Battery Pack issues before any troubleshooting is done.
Ron Staley has published the following books, and you can get more information about them by just clicking on each title below:
Electric Golf Cart Repair 101 (and a half)
Techniques, Tips, Tools and Tales
Gas Golf Cart Repair 101 (and a half)
Techniques, Tips, Tools and Tales
4-Stroke Golf Cart Engines Explored
What Makes Them Tick
By an old Slot Machine Mechanic
One reply on “Start with the Batteries”
I found my “culprit” with the help off your post.