23 replies to this topic

[Morgan]

Hi there

 

I'm wiring some stuff up in my brother in law's van at the moment and need some assistance to see if what I want to do is actually possible!

 

He has two batteries and a voltmeter.

 

Basically, I want to wire it up so that using the one voltmeter, I can switch between the batteries to check their voltage.

 

Like this:

 

 

 

 

Is that possible?

 

I bought this switch today but it doesn't seem to have enough terminals to wire up? It seems you can flick it either direction and whatever you wire up will turn on, rather than wiring up two devices to switch between?

 

 

 

 

 

The packet said:

 

Pin 1 - Acc 1

Middle pic - Power

Pin 2 - Acc 2

[SAV84C]

http://www.exploroz...._batteries.aspx

 

[Morgan]

Yep. That's exactly what I've drawn up above

 

That switch looks like it only has three pins on the back too? I can't see how that would work?

 

Might need one like this

 

 

 

...which I can't seem to find without having to buy 1000 units!

[SAV84C]

You didnt look very hard

 

http://www.jaycar.co...&SUBCATID=978#1

[Morgan]

Haha. Awesome.

 

Google failed me this time!

[SAV84C]

Haha. Awesome.

 

Google failed me this time!

 

 

Jaycar was the first place i looked before google

[Adam]

Middle pin to volt meter, either side to one or the other battery?

Test with test lamps? I'm only guessing

[Tim.]

Yep like your drawing but the voltmeter -ve also has to connect to Battery 1 -ve.

 

I'm sure you knew this though.

[Morgan]

As long as it has a negative, it would work wouldn't it?

[Tim.]

Yeah if both batteries share the same earth (-ve), that's fine.

[Morgan]

Well they don't share an earth per say. They're batteries ...so they have their own negative terminal.

[Tim.]

i.e. are both batteries are connected to the chassis of the vehicle? if so, that's fine.

[Morgan]

Hmmm...

 

I'm guessing the main battery will be chassis-fied through the standard grounding process but the second battery isn't. It's easy enough to do, I'm sure.

[Tim.]

Yep, just ground the second battery somewhere nearby and you'll be right. How are you charging the second battery?

[Morgan]

Solar panel bolted to the roof

[CodeBurn3r]

The Second Battery wouldnt be much use if it isnt grounded anywhere :S what is it used for?

Just ground both batteries and then your set. as above, middle to volt meter, 2 outer pins to battery

[Morgan]

Maybe that's why it was sparking at me...

 

Haha.

[CodeBurn3r]

Remember.. in cars.. the Negative ( - ) Terminal runs to ground / chassis,

most circuits are completed by having their active/positive connection on all the time to the battery in some way (via a fused link) and then the negative/ground is switched

 

you will find 90% of automotive circuits are ground switched.
there are arguments both ways why each is better but i have almost always found things to be ground switched in cars.

 

Queue Jase for the guru talk... 

[RX25SE]

 

 

 

 

 

 

 

 

THIS

IS

AWESOME!

 

Queue Jase for the guru talk... 

 

Bah.

 

You guys have it sorted.

[Adam]

No one invited you, Jase.