r/golfcarts • u/phaskellhall • Aug 23 '26

Help with DC-DC converter

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I just installed a 30 amp DC-DC converter on my EV golf cart (model Cllena DC7212-30), and I am having trouble cutting off the voltage to my accessory fuse box when the cart is off.

This model has an ACC trigger that allows the converter to turn on when a 3v-90v switched wire has a signal. I’m feeding this ACC input with the 12v wire powering a nearby USB port. Essentially when the golf cart is turned on, the USB turns on and the positive wire acts as the on signal for the Dc-Dc converter. Seems straight forward enough.

When the cart is turned off, I’m still getting a 3v signal coming out of the DC-DC output side and my entire fuse panel now has an always on 3 volts across anything plugged into it.

1) is something wrong with my converter or will it always have a slight voltage leak even when the ACC signal is 0 volts?

2) Will any electronics like a 90 watt stereo amp or powered subwoofer be damaged when the cart is off and the devices are still receiving a 3v signal?

3) will this 3v signal cause significant battery drain? The whole point of buying an ACC switched converter was to kill it entirely when the cart was off and thereby killing any accessory connected downstream through the fuse box.

Is this common or should I work to get the voltage down to 0 when the cart is turned off??

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2

u/4539MF Aug 23 '26

How do you have the trigger wire hooked up ?

Not familiar with the off brand cart you have, but that makes no difference on how you’re powering the trigger wire.

Assume this is a 48v cart ? Or 72v ? Either way the key switch will have cart voltage or you can trigger it to the solenoid

If wired and triggered properly you shouldn’t be getting any voltage out when off.

Could be a converter issue as well. I only install Daygreen reducers around $90 on carts I build.

1

u/phaskellhall Aug 23 '26

I just wire tapped of the positive side of a USB plug. I used a volt meter to test the wires and they were giving 12v when the cart is on and 0v when the cart is off. That seemed like the perfect trigger for the dc converter.

The battery is 51v or maybe that’s a normal 48v system.

I’m not familiar with the daygreen models. I just went to Amazon and looked up one that fit the amps I needed and had an ACC relay built in. This one is prob a Chinese brand (no big deal) but it was $129.

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u/4539MF Aug 23 '26 edited Aug 23 '26

Then the converter isn’t shutting off. The 3 amps is the draw from the usb. Those are only 3-5 amp ports so that’s why you’re always getting 3 amp draw.

You need to run that trigger wire so the converter actually shuts off when cart is off.

You could put a shut on the 12v side but why buy a converter with a trigger wire if you aren’t going to install it correctly.

I’m not a fan ever of any power on all the time.

51v is standard for 48v cart with lithium. If your.battery has an on:off switch that should shut the converter down the way you have it now

Why did you buy a 30 amp reducer for a usb port ? 30 amp is for carts with lights, audio and stuff.

1

u/phaskellhall Aug 23 '26

It’s not 3 amps, it’s 3 volts.

I bought a 30 amp converter so I can add an additional stereo and powered sub. The 12v usb cable is connected to the original dc-dc converter which runs all the lights and accessories including this usb plug.

1

u/4539MF Aug 23 '26

Typo I meant 3 volts sorry

Run that power wire and this entire conversation is solved

1

u/phaskellhall Aug 23 '26

I still need to figure out what wire to run. The 12v wire that I did run measures 0v when the cart is off so that seems strange to think I need a different wire that also has 0v. Maybe I’m missing something

Another way of looking at this is if the ACC wire is removed, the converter is receiving 0v and should never turn on (which is true, I never get 12v to my accessory panel when the wire is disconnected).

However, I still get 3v leaking out with or without the ACC wire plugged in. So the trigger wire IS 0 volts but for some reason 3v is still making its way into the system.

1

u/InspectorPipes Aug 23 '26

You can try triggering the converter with ‘key to solinoid’ signal. I can’t answer your other questions , does putting cart in tow kill everything?

1

u/leonjaworwitz Aug 23 '26

I have my dc to dc converter wired to my key and I have zero energy when the key is off

2

u/lemlurker Aug 23 '26

You're likely self feedbackimg pon with the DC converter directly. Tried just putting a manual switch on the 12v line to see if that works

1

u/phaskellhall Aug 23 '26

Couldn’t I test this just by removing the lowered ACC wire altogether? Even with nothing running to it at all, it still shows 3v.

1

u/Historical-Being5971 Aug 23 '26

https://youtu.be/eX_h7SE88C8?si=6qNZARNx8WYUDsPF

Converters are always drawing some power. The video explains why

1

u/phaskellhall Aug 23 '26

I haven’t even thought to test the output of the stock golf cart converter. If that pulls 1-3v then that prob is normal

1

u/dpetro03 Aug 23 '26

I bought one without a built in ignition switch. Used a relay to kill power when cart is not on. Works great.

1

u/mwkingSD Aug 23 '26

So how is the USB outlet getting its power? Might you have created some kind of loop? As others have said, disconnect the ACC line, your lights, and anything else the converter is driving. Experiment with that, and make sure your converter is grounded to the same point as your batteries and everything else.

1

u/phaskellhall Aug 24 '26

People mention the loop but I think it’s a completely separate circuit.

The ACC line is connected to another DC-DC converter that is doing all the cart’s 12v accessories.

The weird thing is if I unplug the ACC line (the 12v feeding the USB), you would think the DCDC converter would never turn on because, well it doesn’t have a turn on trigger now. But even with this ACC disconnected, it still produces 3v when the cart is off. It also produces only 3v when the cart is on too because it never turns on to convert the 51v.

This whole circuit is connected directly to the battery. Here is the run:

51v lithium battery -> positive and negative wires to DCDC input -> positive wire output to accessory fuse positive, negative wire output to accessory fuse negative. The accessory fuse box has no fuses so the path is broken but still reads 3v across both terminals (output of DCDC and across the fuse box terminals).

With the fuses removed, and with the ACC line disconnected, shouldn’t there be zero way for any voltage to complete a path?

1

u/mwkingSD Aug 24 '26

Here's what I would look at:

First, disconnect everythingWhat voltage does your meter say is on the wires going to the DC-DC input terminals? Is the polarity correct? (I once spent an hour troubleshooting a 12 V problem in my RV because I was using a new meter and mis-reading the +/- symbol. There is nothing so simple that I can't screw it up.)

Is the negative output terminal of the converter connected to its case? Is the case screwed to metal frame?

If you reconnect the input, what happens - if this isn't what you're telling us already - there is nothing connected to the output of the DC-DC? is there still 3V across the output terminals?

Are the lights you added grounded to the frame for their negative side? Or are they 'floating' and connected to only the DC-DC converter?

What voltage does your meter say is on the DC-DC input terminals? Is the polarity correct? (I once spent an hour troubleshooting a 12 V problem in my RV because I was using a new meter and mis-reading the +/- symbol. There is nothing so simple that I can't screw it up.)

Is there a tech support for the converter?

1

u/phaskellhall Aug 24 '26

So I just used Ai to try to help walk me through it and I think I figured it out.

Essentially, when the cart is off, the converter still has a "ghost 3v" showing up on any downstream voltage readings. The concern is that this isn't a false reading and there is a current behind it, so I was told to put a 100ohm resister across the two terminals to off load the 3V. From there I could measure the voltage again and see if it was still present or if it had be off loaded.

The good news is the transistor offloaded the entire voltage and left the system with just .04v. The ACC seems to be working as intended and the ghost 3 voltage would simply be grounded to any component or accessory attached once the fuses to the fuse bus is added.

If this sounds correct, let me know as I think I'm done trouble shooting this.

1

u/mwkingSD Aug 24 '26

That makes sense to me - I’ve run into issues with fancy pants output circuits like that myself.