unknow wire on battery

[Ric Moseley]

Does anyone know what this wire is used for pictured before? It's connected to the positive terminal on the backup battery but it was a label on it that says 'must be connected to common battery negative" which is odd and I have never noticed it before. The other end goes into the digital voltage sensitive relay' also pictured below. Thanks for your help in advance.

 

[F.M.]

It should be connected to a negative terminal on one of the batteries. It’s the wire that turns on the dvsr when the boat is running.

 

[Ric Moseley]

What would it do if it's been hooked up to the positive all this time?

 

[F.M.]

Not work correctly. Just move it to the negative terminal. No damage done.

 

[Bottom Bracket]

Your DVSR looks like it has been messed with.

 

[F.M.]

As soon as you connect it to the negative terminal, you should see a red light on the dvsr come on then go back out.

 

[FSH 210 Sport]

What would it do if it's been hooked up to the positive all this time?

It would not be doing its job to tie the start battery to the house battery after the start battery has come up to 13.2 volts, and to start charging the house battery.

This is the way the dvsr works… the output cables from the engines alternators go to the start battery, you need to verify that by the way. Once the engines start they start putting voltage/current into the start battery, once the start battery comes up to 13.2 volts the dvsr will close the contact to parallel / tie the start and house batteries together so that the house battery will charge. Once the motors are off and the voltage decays to 12.7 volts the dvsr opens the contact and breaks parallel / un ties the connection between the start and the house battery, leaving the start battery isolated with no load so that it is ready to start the engines and nothing else. Its quite an elegant system.



Since the negative wire for the dvsr was connected to a positive terminal, no current could flow through the coil that closes the contact since both wires were at the same potential.. once you connect the ground wire to a negative current will be able to flow from the negative to the positive when directed to do so by the dvsr, this will enable the coil to do its job and close the contact.