Wiring 12V Switches

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Old 05-17-17, 09:39 AM
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Wiring 12V Switches

Hi all,

I'm in the process of building a battery box for my 12v leisure battery so we have a powerpoint for the LED lighting, phone chargers etc.

I was thinking of adding 5 or 6 sockets (2 cigarette and 3 USB and 1 voltage meter) and was using the below as my inspiration

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I'm going to run all of the swtiches via a mini blade fuse box which has a common live connection point.

However, I'm wondering what to do with the negative wires from the switches.

In the example i'm using as a reference, all of the negative connections from the switches have been daisy chained together with just one connection to the batteries netavie terminal

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Whilst this is very neat, is it safe to do?

I'm assuming that doing it this way will mean that the wire you use to connect the netagive connections up needs to be of a sufficient gauge to deal with the potential current from all of the sockets...?

Cheers

Macca
 
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Old 05-17-17, 10:20 AM
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First, I would not bother with switches. They add expense, complexity, take up space and are one more component that can fail. With sockets (cigarette and USB) the most reliable way to turn something off is to simply unplug it.

With or without switches I would simply tie all the negatives together. You can do that with a terminal strip, buss bar or even wire nuts.
 
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Old 05-17-17, 01:42 PM
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Hi there,

Thanks for the suggestions.

Just to clarify, when you say tie all of the negatives together - they will need a connection to the negative on the battery as well (a connection from the terminal strip to the battery)?

Cheers

Paul
 
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Old 05-17-17, 02:55 PM
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I agree with Pilot that the switches serve no useful purpose.

However, if you choose to use the switches understand that the "negative" terminal on the switch is ONLY for the light bulb contained inside the switch. Unless you WANT the switch illuminated when on you do not need to connect anything to the negative switch terminal. Using the switch indicator lamps WILL drain the battery faster.
 
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Old 05-17-17, 03:04 PM
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Ah, I'd not realised that the negative connector on the switches was just for the leds. Very useful information

Your right in threat they serve no real purpose though, they just look cool
 
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Old 05-17-17, 03:12 PM
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My age is showing, my experience with the lighted switches was back when they had incandescent bulbs.

If you really do have LED indicator switches the additional drain of the LEDs will be minuscule. Yes, all the negative terminals would be connected together and also to the negative battery terminal. One more thing to be aware of, the switches will probably be rated at 12 volts and if your battery is anything but 12 volts the LEDs may not light (low voltage) or they may prematurely fail from high voltage.
 
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Old 05-17-17, 03:24 PM
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and if your battery is anything but 12 volts the LEDs may not light (low voltage) or they may prematurely fail from high voltage.
Switches rated for 12VDC are made with automotive use in mind - which is 13.8V nominal, and can be as high as 14.2V while the engine is running. They won't fail.
 
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Old 05-17-17, 05:54 PM
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Thanks for all the replies, they have been most useful.

Whilst I've got your attention, can I run the wiring past you?

I'm planning to use 21 amp wire for the sockets / switches (if I use them) and run 15 amp fuses for the cigarette sockets and 5 amp fuses for the USB sockets.
Any issues with this?

Also, for the mini blade fuse box - are there any pros / cons to using a fuse box with a single live connection to the battery over one that has separate live battery connections (other than less wires)

Cheers

Macca
 
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Old 05-17-17, 06:18 PM
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What kind of battery and where did you get the box from?
I have been wanting to build something like this since I was given an extra group U1 (AKA Power wheel chair battery) 39AH 12V battery.
 
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Old 05-17-17, 06:19 PM
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A multiple fuse fuseholder with one power line to the battery is fine. You may find the standard size (ATC) plastic fuseholders easier to find locally than the minis.

ATC-&-ATO-Ganged-Fuse-Block-6way

#14 automotive wire should be heavy enough for your internal wiring.
15A for the lighter plugs is ok.
5A should be ok for the USB adapter ports. That would depend on what the adapter called for too.
 
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Old 05-17-17, 06:19 PM
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Do the USB sockets have a built in DC-to-DC voltage converter?
 
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Old 05-18-17, 03:53 AM
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What kind of battery and where did you get the box from?
I have been wanting to build something like this since I was given an extra group U1 (AKA Power wheel chair battery) 39AH 12V battery.
Hi there,

I made the battery box out of left over kitchen cabinet panels I've had in the garage for the last 10 years

The battery is a 110ah Numax leisure battery.

Cheers

Macca
 
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Old 05-18-17, 04:00 AM
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A multiple fuse fuseholder with one power line to the battery is fine. You may find the standard size (ATC) plastic fuseholders easier to find locally than the minis.

ATC-&-ATO-Ganged-Fuse-Block-6way

#14 automotive wire should be heavy enough for your internal wiring.
15A for the lighter plugs is ok.
5A should be ok for the USB adapter ports. That would depend on what the adapter called for too.
Thanks for the info,

The USB sockets are 4.2A so 5A should cover it nicely.

For the fuse box connection to the battery, I was going to stick an inline fuse in the wire as well with a fuse rated to cover the max output of the fuse block (which will be 60A if I have 3 x 15A sockets and 3 x 5A sockets).

Good idea or overkill?

Cheers

Macca
 
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Old 05-18-17, 04:03 AM
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Do the USB sockets have a built in DC-to-DC voltage converter?
Err, I don't think so.

I'm looking at this kind of thing;

https://www.amazon.co.uk/Amazingdeal...usb+socket+4.2
 
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Old 05-18-17, 06:04 AM
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The last picture in the Amazon listing states 12 volt input and 5 volt output so it looks like the sockets has a voltage converter built in.
 
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Old 05-18-17, 06:57 AM
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And from the specs:
Input voltage: 12V
Fits: 20mm to 30mm Diameter Handlebars
Output voltage: 5V
Output Current: 2.1A
So that should work.
 
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Old 05-19-17, 03:28 AM
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Thanks for all of the input everyone, it's been really helpfull

I'm off on holiday tonight for two weeks, but I'll be ordering all the bits in so they are waiting for me when I get back.

I'll post some pictures up when I get it all put together.

Cheers

Macca
 
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