Category: Battery Related

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

Suck, Squish, Boom and Blow

                4-Stroke Golf Cart Engines Explored

Those Darned Slot Machines

                What Makes Them Tick

                By an old Slot Machine Mechanic

In the book that I wrote “Electric Golf Cart Repair 101 (and a half)”, I devoted some time in Chapter 4 to explaining the importance of good clean connections in working with electric golf carts. In this post, below, I have cut and pasted a portion of that chapter to reemphasize the point:

We talked in Chapter 2 about the importance of delivering enough power (P in our Ohm’s Law example) to do its job.  How much resistance the Motor offers to current flow through the golf cart’s circuitry is a fairly complicated discussion.  A Series Motor, like we are discussing right now, consists of 2 windings of wire that make up the armature (the part that rotates and is sometimes called the rotor) and the field (the part that is attached to the case of the Motor, remains stationary and is often called the stator). The fact that the field has also been referred to as the stator for so many years had lead to an intermingling of the terms.  Therefore, when abbreviating these terms on drawings, you may see either F (for field) or S (for stator).  Either is acceptable, so don’t worry about it.  These windings are wired in series in our situation and they are made with quite large diameter wire and represent a very low DC resistance to the circuit.

                When a path for current flow from the batteries is first applied, a large amount of current flows due to this low resistance. However, as soon as the armature starts moving, a strange thing happens.  The Motor actually starts to also act as a generator and creates its own voltage that is referred to as a “counter-electromotive force” (CEMF), which opposes the polarity of the source voltage (battery supply voltage) so the amount of current being drawn from the batteries is drastically reduced.  For this example, we are pretending that all of this stuff that goes on while starting the Motor has all occurred and we just have a running Motor producing 5 HP into a 5 HP load connected to an ample source of current (our Battery Pack). We will look at it like this:

We know that A and F each have some small DC resistance, as well as inductive characteristic. But in this example, we will ignore all of that and the CEMF and just treat the Motor as a pure DC resistance, which we will now calculate as a resistor called Rm.

We know that our Source is 36 volts and our Motor is operating at 5 HP.

                Back to Ohm’s Law, we get:

                P = I x E

                5 HP = I x 36

                5 x 746 = I x 36 (1 HP is defined as 746 watts)

                3730 = I x 36

                I = 3730 / 36 = 104 amps (rounded)

                So, as the Motor spins along producing 5 HP from a 36 volt source, our Battery Pack is supplying 104 amps.  But there is another way to express I and we will use it to calculate Rm, our DC resistive equivalency of the Motor (A and F) as it produces the 5 HP with the 36 volt source.

                I = E / R so 104 amps = 36 volts / Rm

Rm = 36 volts / 104 amps = .35 ohms (rounded)

                So, when we treat the Motor as Rm, the following would be our drawing.

Now, it gets interesting.  Let’s pretend that in wiring our batteries in series and wiring the batteries to the Motor, we have some “less than perfect” connections due to corroded battery posts, frayed wires, corroded battery cable connectors, etc.  Let’s say that all of these additional resistances add up to .35 ohms (the same as Rm).  Believe me, it doesn’t take much corrosion to add up to .35 ohms.  So, let’s call this new accumulation of resistance Ra (a is for accumulated resistance).

Our new diagram would be as follows:

But now, when we calculate the current, we must add Rm and Ra together (they are in series) for what we will call Rt (t is for total of Rm + Ra).

                I = E / R = 36 volts / .7 ohms = 52 amps (rounded)

                So now, our accumulated resistance (Ra) has caused a reduction of 50% in current flow.  Hold on, it gets worse.

                If we now calculated the voltage drop across Rm and Ra, we see that:

                E = I x R

                     So

                Erm = I x Rm = 52 amps x .35 ohms = 18 volts (rounded)

                Era = I x Ra = 52 amps x .35 ohms = 18 volts (rounded)

                So, not only has Ra caused a 50% decrease in current flow through the circuit, but it has dropped half of the supply voltage across itself (Ra) and only left half of the supply voltage for Rm (our Motor).  Going on to see what effect it has had on the power available to the Motor:

                P = I x E

                P = 52 amps x 18 volts = 936 watts

                If 1 HP equals 746 watts, we’ve just reduced our 5 HP of performance down to:

                936 / 746 = 1.25 HP

                That’s one quarter of what it was.  That’s why I called connections not only important but exponentially important.

                Conclusion:  Good connections are extremely important in high current situations, as even a very small amount of resistance added to a high current circuit can drastically affect the performance of the cart.

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

Suck, Squish, Boom and Blow

                4-Stroke Golf Cart Engines Explored

Those Darned Slot Machines

                What Makes Them Tick

                By an old Slot Machine Mechanic

I am often asked about issues regarding battery terminals. On an electric golf cart, the battery connections are made in a little different way than with automotive applications.  Instead of having a connector on the end of the connecting wire that “wraps” around a post or is bolted to a side mount connector, golf cart batteries generally just have a post (terminal) sticking up out of a lead connector on both the + and – terminal locations of the battery.  If you look at this bolt, you will see that it doesn’t come out of the center of the battery’s connector, it comes up out of an “addition” to the connector.  Underneath that “addition” is an indent that matches the square “head” of the bolt and keeps the bolt from turning as you attach a cable or wire to it and tighten a nut on top.  You can’t see the “head” because it is on the underneath side, but is firmly pressed into position and provides a good solid connection into the lead “addition”.

                The bolt is a 5/16th inch diameter with 18 threads per inch.  The nut that goes on top is usually turned with either a half inch or a 9/16th inch wrench.

                If something goes wrong, and the battery connector, bolt, wire connector and nut get overheated, the entire unit (all of the above) can become one over welded mess.

                First off, what goes wrong to cause all of this?  The answer is obviously heat, but what caused the heat?  The answer is ALWAYS resistance.  When a large amount of current flow meets with an obstruction (resistance), a large amount of heat can be produced.  Enough, in fact, that the nut can become “welded” to the bolt and can’t be removed without disturbing the seat in the “addition” and allowing the bolt to turn, break off, or even bend.  Why would this resistance show up?  There can be several reasons, but here are a few.

1 – The nut wasn’t tightened when the cable was last installed.  After installing a new cable, it is best to recheck for tightness after driving the cart a short way. You are tightening the nut down on a cable that is seating itself on a lead connector.  Any slight flattening out of the lead as a cable is vibrated around during normal operation, can relieve pressure on the connecting surface and allow for loosening of the nut.  A good way to test for this is to drive the cart and then “feel” each connector end post (bolt) with your fingers, looking for excessive heat.  Remember, where there is heat, there is resistance.

2 – A battery cable can actually be frayed beneath the rubber jacket (where you can’t see it) and as it is vibrated, it can continue to fray until the shear number of strands left are not sufficient to carry the required current without offering the resistance.  Because the problem (the frayed wire) is right next to the connector, the heat is quickly transferred to the connector and bingo – same problem as above.

3 – Another thing that happens is when a cable is replaced, but the cable end or the bolt or the surface that the cable end will press against on the battery connector aren’t cleaned well enough.  Instead of a good, clean metal to metal and metal to lead connection, any leftover corrosion adds resistance and an opportunity for loosening.

No matter how it happened, you are usually left with a nut that won’t come off of the bolt, and probably a loose bolt from trying to remove the nut.

What I do is to move over from the addition, to the center of the circular part of the connector (the pad), and place a new terminal that acts as a new bolt.  I just chop the old cable connector off, crimp a new one on the end of the cable and connect it to the new terminal.

I discuss this with illustrations in the Book Electric Golf Cart 101 (and a half) that is available through the “Stuff for Sale” link on this Site.  It is in Chapter 4 on page 12.  Here is the jest of it.

The fix for the post is to go over to the round pad next to the post, drill a hole down in it one half inch deep with an “F” lettered drill (0.257) bit, tap the pad with a five sixteenth – eighteen thread per inch tap, then put 3 drips of RED thread locker in the hole and then thread a 1” long five sixteenths – eighteen thread per inch stainless steel socket screw into the hole with a five thirty seconds hex wrench, and voila, you have a new terminal. Depending on the batteries’ location, you will probably need to remove the battery from the cart to perform the operation.

If you have trouble rounding this stuff up, we sell, through this Site (Stuff for Sale), a kit containing 6 of the stainless steel posts, the thread locker, the hex wrench, the tap, the “F” drill bit and a depth gauge to do the job with.  It includes the instructions and the illustrations from the book.

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

Suck, Squish, Boom and Blow

                4-Stroke Golf Cart Engines Explored

Those Darned Slot Machines

                What Makes Them Tick

                By an old Slot Machine Mechanic