Key Switch Wiring for Lights and Reducer

[agpfl]

I am about to start working on getting some lights wired in. There will be 48v to 12v reducer. I am going to replace the standard key switch that only has off and on with a unique 3 position key switch that will have off, on, and lights.

I have a couple options I came up with

1) Should I wire the reducer to the light position and not use a relay (option 1)

2) Should I wire the reducer to the on position and wire a relay to the light position (option 2)

[yurtle]

A good reducer has a low amperage "on" wire, which can easily be fed by a standard 3 position key switch.

I did the same by purchasing a 3 position uniquely keyed switch. Was expensive, but still a "stock" EZGO switch.

By "the same" I meant my 3 way key switch did off, on, on with accessories.

[agpfl]

Originally Posted by yurtle

A good reducer has a low amperage "on" wire, which can easily be fed by a standard 3 position key switch.

I did the same by purchasing a 3 position uniquely keyed switch. Was expensive, but still a "stock" EZGO switch.

What about a bad reducer? I had already bought a cheap chinese piece of junk, one that only has 48+, 48-, 12+, and 12-.

Which option would you chose?

[yurtle]

It's not a "bad" reducer. How many amps is it? I don't know the rating of the key switch, but you probably don't need a relay. A pair of 55 watt headlights at 12 volts is close to 10 amps. Add tail lights, and I would think the key switch could easily handle 10 amps. I know I've pushed that through mine for years, before converting to LED headlights.

Ignoring losses, 12 volts at 30 amps would be less than 10 amps on the 48 volt supply. I'd simply switch the 48 volt input to the reducer.

[agpfl]

I only plan to run a 50w led light bar up from (4.2 amps) and led tail lights (.5 amps).

I am thinking option 1 is the easiest and least complex. I was just unsure if that was the best route to go.

[orangeman6]

Hope I'm not hijacking the thread, and it looks like these guys have this particular instance sorted out, but I was looking for some clarification on this topic in general.

1. When we're trying to figure out what an electrical device will handle, it's amps that we should be focused on, correct?

2. Amps= watts/volts?

3. Isn't there also an "arc" (not sure of the correct term) that occurs when a switch operates, and isn't that a potential issue, as far as damaging, or wearing, a switch?

4. Isn't most everything in our vehicle's 12v system ran through a relay?

5. The relays job is to "pass the current" and protect the switch?

I ran separate switches to my reducer, lights, stereo, and dome light. I ran each one through a relay as well. After finishing everything, I came across a post that talked about a diode being installed as well (to handle the relay "arcing" I believe) so I went back and put those in too. My switches were expensive, and I really didn't know what I was doing, so I figured I'd take the safest route. It didn't add much to the wiring time, and I'm not a fan of short cutting things, so it was worth it to me. However, I'm not into wasting time/money either so would appreciate what the experts have to say, so that I know better in the future.

Again, hope this isn't messing up Impaper's thread and thought it may be applicable for those dealing with similar issues.

[yurtle]

A relay is simply a switch, and will be subject to any arcing that a toggle switch would. The main use for a relay is to allow a toggle switch to see one voltage and only enough current to energize the coil, and control a different voltage and/or higher current.

[orangeman6]

Originally Posted by yurtle

A relay is simply a switch, and will be subject to any arcing that a toggle switch would. The main use for a relay is to allow a toggle switch to see one voltage and only enough current to energize the coil, and control a different voltage and/or higher current.

Yurtle, thanks for the reply, and that was my point and/or question. That was why I used relays and installed a diode with each one. There have been a decent number of threads lately related to key switch controlling accessories, including reducers. I figured what I did was probably overkill and that's what I'm trying to get clarification on now. The automotive relays were cheap and not difficult to install, even for me Is my formula above correct to use for comparison with the switch rating to know when a relay isn't needed? And, why push the limit (if we sometimes are) when relays are easy, cheap, and so widely used in automotive applications?

Thanks again for the reply, just trying to make myself a little less stupid

[yurtle]

For the voltages we're dealing with - 12 through 48 - all the switch cares about is amperage.

[cgtech]

A "perfect" reducer would work like this example- 12v light bulb drawing 4 amps at 12v (48w) could be converted from a 48v pack at a load of only 1a from the 48v pack (48/12 = 4:1 ratio). Typical halogen cart headlights vary from 36 watts to 55 watts each. In real life, nothing is perfect (and perpetual motion does also not exist as far as I have seen). Some energy will always be lost to heat in the conversion process. I have measured a dc converter supplying headlights & brake lights supplied by below 5 amps at 48v (some converters are better, some worse). Actually only reasonable efficiency by the law when heat losses are taken into account (see below), but still better than hurting 2 batteries by making their life slow hell.