[villagetinker]

While this is specific to Yamaha golf carts, it MAY be applicable to other makes.

A another poster contacted me about an observed high voltage on their (2017) cart battery, over 16 VDC with the cart running. I have the same cart, and checked mine, I saw over 18 volts DC with the cart running. NOTE: in both cases the voltage regulator is working correctly. There appears to be a design flaw in the wiring, and the voltage regulator is seeing the voltage drop in the main power circuit. To confirm this, I watched the voltage go UP when I turned on the headlights.

Now a cart repair service was over at the neighbors and the neighbor and I were talking and I mentioned the high voltage concerns. The repairman overheard us, mentioned he has seen this on many BUT NOT ALL Yamahas. I mentioned a possible fix, new wiring, fuse, and a relay, and he mentioned he knew of a quick fix, BUT DID NOT TELL ME....

So if any one else has come across this let me know of the "quick fix".

Here are the gory details, the sense wire from the voltage regulator is run all the way to the dash after the ignition switch. It therefore sees all of the voltage drop due to the connected equipment after this switch, EFI system, headlights, turn signals, accent lighting, possible radio, fans, etc. The fix we have found was to relocate the sense wire to be connected direct to the battery (+) terminal via the relay and fuse, which results in the correct 14.5 to 15 VDC charging voltage.

I am getting ready to implement our fix, but if there is an easier one, I am really interested.

[Altavia]

Agree In theory the sense wire should be connected close to the battery.

[KennyP]

Im going to say, if it fixes the over voltage situation and doesnt cause any other issues then its fixed right?

This is a known issue with yamaha carts and I think there are a variety of ways that it is fixed. Some more expensive than others.

[Dave951]

I replaced the battery on my yamaha gas cart and checked the charging voltage at the battery and it was fluctuating between 16.7 and 15.4 but never any higher I don't know the charging amps since I don't have a Amp attachment for my Fluke meter

[KennyP]

So that is how yamaha charges there gas cart. I could tell you the reason why, but it doesnt really matter.
Club Car and EZGO both charge there carts like a normal car battery 14.1 to 15 volts, but steady.

Yamahas do have an issue like the OP stated where they will over charge, club cars and ezgos will also. Its the yamahas that are weird when they do overcharge in the 17 plus volt rate and that needs to be fixed.

[metoo21]

Just checked mine and with the gas pedal to the floor, I get 18v. Less rpms produce a lower voltage. Did not test with headlights on but the LED side marker lights were on.

Battery is about 22 months old. It is sealed so I can't check the water level. What is the quick, cheap fix?

[villagetinker]

All, the fix my friend suggested and I came up with also is on my short list of items to do. This will involve the installation of an automotive relay, a fuse and holder, some wiring, and cutting one wire. I really wish someone knew what the "quick fix" is. I will try to include a sketch of the original wiring and the revised wiring in a future post.

[metoo21]

Thanks. Looking forward to the wiring diagram.

[metoo21]

Originally Posted by villagetinker

All, the fix my friend suggested and I came up with also is on my short list of items to do. This will involve the installation of an automotive relay, a fuse and holder, some wiring, and cutting one wire. I really wish someone knew what the "quick fix" is. I will try to include a sketch of the original wiring and the revised wiring in a future post.

Got the wiring diagram yet?

[villagetinker]

Originally Posted by metoo21

Got the wiring diagram yet?

Here is the wiring diagram, I just finished the modification to my cart and verified the voltage readings.

I used compression fittings to cut and extend the red/white wire, and spade lugs for connections to the relay, ring terminals for the battery connections. The fuse holder had leads long enough to get to associated equipment.

Hope this helps.

VT

[metoo21]

Originally Posted by villagetinker

Here is the wiring diagram, I just finished the modification to my cart and verified the voltage readings.

I used compression fittings to cut and extend the red/white wire, and spade lugs for connections to the relay, ring terminals for the battery connections. The fuse holder had leads long enough to get to associated equipment.

Hope this helps.

VT

Thanks

[Velvet]

I’m just wondering if this could be why my battery ran down completely even after everyday use on a 2022 Yamaha QT put together by TV Golf carts? I think even after the engine is shut off there is drain on the battery.

[villagetinker]

Originally Posted by Velvet

I’m just wondering if this could be why my battery ran down completely even after everyday use on a 2022 Yamaha QT put together by TV Golf carts? I think even after the engine is shut off there is drain on the battery.

The drain on the battery is easily checked with a digital multimeter, set it to the DC CURRENT position and initially a 2 amp scale, then remove either the lead on the battery, and connect the meter in series with the battery and the disconnected lead, you should get a reading of 0 amps (or milliamps). If you get a reading, then yes you have something draining the battery. The problem I was solving related to over charging the battery which can also shorten the life of a battery.

[villagetinker]

Here is the revised wiring diagram, I added the "standard" wiring color codes if you buy a relay with a socket

Do NOT use the attached document, the color codes for the relay wiring may be wrong, see later post for rev 3 document.

[villagetinker]

OOPS I made a mistake, it turns out the color codes for the wires on the relay sockets are NOT standardized, please use the revised document.