Got my 3-position switch, but now...

[BradKW]

...I just realized that I don't know what to do with the neutrals. This is the back of the switch:

[img=300x300]https://dh778tpvmt77t.cloudfront.net/images/products/11001_back.jpg[/img]

Since the purpose of the switch is to allow me to swap the power feed to 'fridge between 12v and 24v battery banks, I don't know what to do about the neutrals. I have a couple guesses, but can't Goggle anything that applies directly enough that I feel confident with it.

I'm hoping maybe the 24v neutral would work for both 24v and 12v..?

Also, can't find something showing what those two little screws are bottom left...probably ground?

TIA

 

[highdesertranger]

you don't have a neutral in DC. you switch the positive the grounds should be common. aren't your grounds common, as in chassis grounds. highdesertranger

 

[Matlock]

I'll give it a shot but I'm limited without adding a diagram.
Positive from 12v battery goes to input 1,
Positive from 24v battery goes to input 2,
A positive wire goes from Output to positive on frige.
You are only switching from 12v to 24v with this switch.

Ground fridge to frame or negative bus bar, (black wire).
Make sure you fuse to wire size.

 

[BradKW]

My understanding of DC is that it always needs a complete +/- pathway, and that there isn't really any actual "grounds" in a vehicle...that a "chassis ground" is actually a common neutral.

So far, all of my circuits on both 24v and 12v form a complete +/- loop to battery terminals with wires...I guess I am also calling negative "neutral", perhaps that isn't correct.

I actually have two neg. bus bars, one 24v and one 12v.

 

[John61CT]

Yes it's not a true ground.

Better to use "negative" than "neutral" though.

There was a long thread discussing this 24/12 switching, where it seems a good idea to ensure the fridge is fully off for "a while" before moving over to the other voltage.

Does your switch have an OFF position between 1 and 2?

I hope it doesn't have a "1+2" aka Both position!

 

[DannyB1954]

Two different battery systems can share the same vehicle grounds. If the switch you bought has a both setting, and you have a 12 volt and 24 volt battery attached, it may cause you problems. In the both position, the power from the 24 volt will want to go into the 12 volt battery. Could be a lot of amperage.

There are only 2 wires in a battery system Positive and Negative. Some people refer the negative as being a neutral, but this makes things a bit confusing.

 

[BradKW]

yes, it has an Off position...the older thread you're referring to was actually my initial questions that ended up with choosing this switch.

[img=300x300]https://dh778tpvmt77t.cloudfront.net/images/products/11001.jpg[/img]


Danny: so far I haven't "grounded" either 12v or 24v systems because I'm still not clear on what happens if I basically connect a 12v battery bank to a 24v bank by tying both to the chassis. I shut everything down when I'm not there working on it, but it is something I need to figure out. 

It sounds like you have some thoughts on this, but I'm afraid I need you to break it down more til I can get my head around it...

 

[highdesertranger]

you won't have a problem grounding both the 12v and 24v system to chassis ground. just don't combine the positives anywhere. the switch you have will work fine. 12v one input, 24v the other input. highdesertranger

 

[John61CT]

Yes all DC negatives not only can, but **should** be tied together, including to the chassis and engine block.

But don't rely on the chassis, make round trips, same heavy cable gauge & length, back to the power source.

 

[SternWake]

The smaller terminals on the bottom left are for disconnecting the  alternator field wire when turning switch to OFF.  Perhaps you can utilize them for something else.

 

[DannyB1954]

That switch will be fine. Some have a "both" position which would not work well, (couldn't tell from the first pic).

What I am not understanding is if you have 12 volt devices attached to the output of the switch, how do you prevent them from getting over voltage when you select the 24 volt position? Vice Versa if you have 24 volt devices connected to the output, how do they get proper voltage if the switch is set to 12V?

It may be best to not connect 24 volts to that switch, but use a separate switch to turn it on and off. That way the 12 volt stuff can only get 12 volts and the 24 volt stuff can only get 24 volts. The cost of another switch would be less that the hoops you would have to jump through to make it work with one switch.

 

[NeedAnEscape]

His fridge can handle 12v and 24v. He's just using it for the fridge.