DC-DC Converter

[yawood]

My cart is a 2012 Club Car Precedent with 6x8VDC. I have drawn up a simple circuit for installing a 48VDC-12VDC converter outputting up to 30A. Click here for a .pdf of the specs. The circuit uses a 24VDC relay capable of easily switching the converter at a full current draw. Initially I will have very small loads (USB connectors, LED flashing indicators and maybe a horn) but I may add lights etc later so I'll put in a good sized unit to start with.

I plan to wire it through a separate switch so that the circuit is active only when I want it to be and not every time I use the cart (for example the indicators will only be used on my short drive to the golf course - I live on a golf course estate). I will connect the 48V directly to the batteries rather than through the existing wiring loom so that I can use larger cable to carry any current that is required. As shown in my diagram I plan on using 25 amp wire for that connection. I reasoned that as the reducer is rated to output 12V at a max of 30A (i.e 360W) an input of 48V would need 7.5A for 360W so a 25A cable is more than sufficient (please let me know if anyone can see a flaw in that logic as I am only an amateur at this). There will also be a 30A fuse on the 12V side which I haven't shown.

Because it is a 24VDC relay it will run off three of the batteries. This means that three of the six will have a slightly greater current draw but it is minimal (about 80mA max, I figure). If I find it is a problem I'll move it to the other three periodically, however, as a more permanent solution I intend to build Sergio's excellent passive voltage bypass zeners so the batteries will automatically rebalance each time they are charged. Again, if people see a problem with this approach, please let me know.

[scottyb]

It should be noted that nothing grounds to the golf cart frame. Earth ground is an automotive practice that does not work well with an electric cart. All "ground" connections must be brought back to the battery pack main negative. I hope this helps.

[Roxyflash]

I wired a voltage reducer the same way using a 24 volt relay its just for lights.I may get a 48 volt relay to use the whole pack for trigger wire but probably not needed.The 8 volt batteries dont give you many options.

[Sergio]

As Scottyb mentioned, in US there is a safety code where no vehicle system over 24v can use the chassis for common ground.

My only suggestion would be to use a 48v relay, You can still use a manual ON/OFF switch, but get the +48v from the Cold side of the cart key switch.

http://www.mouser.com/Search/Product...55-T9AP1D52-48

That way you can still only turn it ON as needed, but everything goes OFF with the key switch even if you forgot to turn the manual switch OFF.

[yawood]

Thanks for the replies.

Yes Scottyb I was going to return to batteries or pick up an earth on the existing loom as appropriate - just didn't draw it that way but thanks for pointing it out as it's an important point.

I've taken your advice on the relay Sergio and have ordered the 48V relay.

Are you happy that the 25A wire is big enough for the 48V side of the converter?

[Sergio]

Yes, 12ga wire would be plenty for the 48v side.

As You mentioned, an ideal 48v->12v converter would have 25% of the load on the 48v side, but I like to use 50% to compensate for efficiency and operating temperatures.

[yawood]

Thanks Sergio.

Can you explain your cold side wiring or point me to a thread where you have already done that?

When you say fused as close to the battery as possible, do you have a preferred method, e.g a battery post fuse (like a midi fuse)?

[Sergio]

The "Cold Side" is a reference to the side of the Key switch that only has power when the switch is ON.

The side that always has power is considered the "Hot Side".

The OEM location for a voltage reducer on a Precedent is up front:

http://www.buggiesgonewild.com/attac...r_location.jpg

You can just cut the wires on the 12-pin connector harness on a Precedent and tap the wires You need.

Look at the diagram below on the bottom right for the wires that need to be cut to add a voltage reducer.

http://www.buggiesgonewild.com/attac...ont_wiring.jpg

Fuses are designed to protect the wires from catching fire in case of a short so the should always be located as close to the power source as possible.

You can use any kind of "weather-proof" inline fuse enclosure right at the battery terminal, use whatever type fuse is readily available in your region, example:

https://www.amazon.com/Support-Holde.../dp/B017BAF7GS

If You purchased a "bucket harness" for your Precedent (rear lights and brake pedal), it should already have a "blue" wire to connect to the pack positive.

The "negative" side has to come off the Controller B- or from the black wire with a Yellow "bullet connector" that is already provided on the OEM harness for accessories.

[Patela2oh]

A) If it's only for light stuff use the stock reducer that is plug and play with the wiring harness. Easy, clean, cheap and key switch driven

B) our plans make sense but some reducers have a remote switch lead. I.e. Connect it to the output (on) of the key and it will only be active after key is turned on. This way no extra switches / relays or if you wanted you could put a switch that interrupts the signal so you have a "on / off" only when key turned option.

You can mount lots of easy places like stock shock towers or I put mine in the arches on the plates with standoffs for circulation.

Also some ball park things I learned:
1) common buss bar for negative side / ground as you DONoT ground to chassis
2) fuse before the reducer and a fuse block before each item / switch.
3) spread the load across the entire pack not just 3 or 4 batteries.
4) have fun and ask lots of questions, a lot easier than a garage / golf course fire






Sent from my iPhone using Tapatalk

[theboss20]

Nice job! Good info...should go into the sticky file...