Two voltmeters and connection problems?

Status
Not open for further replies.
T

Tony K

Member
Hello all,

I'm getting close to the connections stage for electrics in my boat. Most things are straight forward enough but because I have two batteries I have included two voltmeters in the dash panel.

Normally as I understand it, a single voltmeter would be connected to the ignition switch, but I can't do this because it will give me the same reading on both gauges from the battery used for the ignition circuit. I can run a fused connection to each battery respectively but this will be live all the time and the gauges will be on all the time, unless the master switches are off. Is it possible for me to make them work and give accurate readings from each battery while activating them with the other gauges on the ignition circuit?

I think I've created a problem for myself?

Cheers Tony K
 
Thanks cowboybob,

But I have two volmeters in the dashpanel with the other gauges ready to go. I think your plan is with one voltmeter and a switch to each 12v source? Am I being dumb?
 

You could substitute a SPST switch for the relay. The relay just makes it all easier and more elegant (one less switch on the console...).
 
Thanks great work, I would never have figured it out. However, if I had two 12v SPST relays activated by the ignition switch would both voltmeters work at the same time?
 
Tony K said:
Thanks great work, I would never have figured it out. However, if I had two 12v SPST relays activated by the ignition switch would both voltmeters work at the same time? ...
Click to expand...
Yes.
Tony K said:
... Sorry also, what amperage make and break relay(s) would you recommend?
Click to expand...
Well, the voltmeters will pull very little current (μAs), but for convenience sake, a standard automotive SPST Relay (or equivalent) would be suitable.

Since I don't know your location, look for something that looks like these below:
Relay:

and Connector harness:

Most automotive parts stores carry these items. A SPDT relay would be fine also: just use the NO (normally Open) pin. Be sure to get the correct connector for the relay you buy.
 
I don't have a boat so I think about my car.
Doesn't your boat have an engine that drives an alternator and a charger? If so then why do you need a voltmeter? My car does not have a voltmeter and sometimes I have the radio playing for hours without the engine running. The battery has never been dead.
Maybe you use the batteries for running high power heating devices without the engine and its charger running?
Oh, is your boat propelled with a high power electric motor and the voltage drops quickly?
 
Exactly AG, you don't have a boat.
The guy is building his boat with an all singing all dancing electrical system, his hobby let him get on with it. All good fun I say.

So your battery has never been dead, aren't you the lucky one.
If you do have a flat battery at an awkward moment, you can always push start the car or get a jump start from a passing vehicle.
It would be an interesting exercise to push start a boat out at sea!
May be that is why he wants two batteries and two voltmeters.

JimB
 
Thanks everyone, especially Cowboybob. I was getting a bit worried about it. I am still not sure what will happen when the Blue Sea automaticc charging relay is charging both batteries, what the voltmeter readings will show, but the connections will be fine now.

Cheers Tony K
 
Just thought cowboybob, Is there any reason I can't wire the relays into the circuit before the voltmeters then they would not be sitting with a live supply to them?
 
Tony K said:
Just thought cowboybob, Is there any reason I can't wire the relays into the circuit before the voltmeters then they would not be sitting with a live supply to them?
Click to expand...
You could.

But if you put the 1/4A fuses close to the batteries (as I tried to show in the schematic), any electrical issues "upstream" would not pose any problems (that I can think of) since the fuses would blow with the slightest load provocation. Two relays at the batteries would also require two additional wires from the console selection switch, further complicating the issue.

Or, you could mount a DPDT waterproof switch in the vicinity of the master battery selector to allow a disconnect for the voltmeters. One more switch to remember to disable, though, when shutting down the boat.
 
Hee, hee. I never needed to push start my North American car that has an automatic transmission and no clutch.
I bought my first car brand new and it had a crank that I tried one time. It started immediately. My lawnmower started the first time this year on the first pull on its starting cord.
 
Thanks Cowboybob, actually both fuses and relays will be about a metre away from the batteries and the console with ignition switch about a metre from them. I think it can be done but I thank you for the options.

Cheers Tony K
 
Status
Not open for further replies.

Similar threads

  • Question
Help sourcing two resistors
2
Replies
27
Views
10K
drtechno
D
  • Question
Radiator fan - why four wires instead of two ?
Replies
15
Views
6K
Grossel
J
  • Question
Help identifying plug and pins
Replies
8
Views
5K
Jakuzi1
J
N
  • Article
The first two Digits faded on this display
Replies
4
Views
7K
Tony Stewart
L
  • Question
Where to solder my car key + and - ?
Replies
3
Views
5K
narkeleptk
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…