Xantrex Link 20 Monitor Readings

[sailcapt340]

I have a Xantrex Link 20 Battery Monitor on board my 2000 340. I have 2 banks: House = 3 AGM Group 31 / Starting = 1 AGM Group 31 (all batteries were purchased and installed at the same time, all are 5 years old)
I am getting (Link 20) readings on the House Side of 12.90 - 13.25 V and with my hand held digital meter I get the same readings.
On the start side I get (Link 20) readings of 11.45 - 11.75 V and with my hand held I get 12.90 - 13.25V.
Why the difference on only the starting battery bank and why so much? Is it the Xantrex Link 20 monitor?
I have check with another hand held and the readings are the same, it agrees with the Link 20 on the House side and the same lower readings on the start side.
Any insight is appreciated and thanks for the help. I'm not in the water yet, so these are just standing readings.

 

[JWC]

So both hand helds give the same readings on both banks? Only the Link 20 reports low voltage on the start side? If so the obvious thing is bad connections or wire on the Link from the start battery causing a voltage drop to that side of the monitor or switching mechanism in the monitor if sharing the same contacts perhaps?

 

[Bill Roosa]

There should not be much of any kind of voltage drop in the start circuit unless there is current flowing, which there should not be typically.
Where are you measuring the start voltage with the link?

 

[sailcapt340]

Measurements

The connections for the Link 20 have the positive wire to the positive of the start battery (same for the house) and the grounds share at the battery switch. I have cleaned all posts, connectors etc. involved but there is a real noticeable voltage drop on the start side.
There is nothing running at this time as the boat is out of the water. I did disconnect the bilge pump thinking that may be the reason for the voltage loss, but still no luck.
Thanks for the help and information. I'll be checking all the Link 20 wiring from the battery to the monitor next and keep you all posted as to what if anything I find.

 

[Bill Roosa]

You have your battery switch on the ground side??? not dangerous but not typical. Perhaps I'm not understanding how the grounds are shared at the battery switch.
Are there any "auto charging" devices in use? Some use diodes which have the magnitude of the voltage drop you are seeing.

 

[sailcapt340]

Going back this week

I'll be going back this week to check the entire system again. I'll be better able to update you after that.

 

[Ivan]

Something fishy here

If you consistently get the same readings on both banks there is something very wrong. It may be that the measuring point that you think is on the start battery side is actually connected to the house battery line somewhere, because otherwise the readings would not be identical hardly ever, unless you have an automatic paralleling switch.

 

[artboas]

Bad connection is wrong answer

If you consistently get the same readings on both banks there is something very wrong. It may be that the measuring point that you think is on the start battery side is actually connected to the house battery line somewhere, because otherwise the readings would not be identical hardly ever, unless you have an automatic paralleling switch.

A high resistance connection will only drop voltage if there is lots of current running through the wire. The link takes no current. You could have 100 ohm series resistance with the input, and you'd still see no drop.
On the other hand, if you had a 3 ohm resistance in series with the starter motor, you'd lose significant voltage.
It's ohm's law. V=IR
The voltage drop across a resistance equals the resistance x the current.

So, to figure out if its the meter, reverse the battery inputs to the link.
See if the fault stays with the start, or goes to the house.

We can pick up from there

 

[sailcapt340]

Found the problem

The problem was in the wire from the fuse holder. There are 2 fuse holders, 1 for each bank. The wires were pulled to tight. My guess is the battery boxes shifted and pulled on the fuse holders.
The wire actually was loose in the holder.
A quick change over to a new holder, cleaned all the cable ends and the readings are perfect.
Thanks for all the help and watch for those batteries moving in the compartments, it really doesn't take much to cause a problem.