Voltage Drop - Analog versus Link 1000

[wgkenney]

Hi all,

I have a question around voltage readings. I have a Freedom 20 charger / inverter that is controlled by a Link 1000 on my 2006 Beneteau 473. I generally use the Link 1000 to read the voltage on my house and reserve banks. The reading are consistent and I understand where the voltage is being read from. Use the Link for Amps, AmpHrs etc. This seems to work fine for me.

My question is around the analog and other voltage readings. I have 4 or 5 places on the boat that will actually give me a voltage reading. There is an analog meter on my DC panel, several of my insturments have a voltage reading and even my tank level meter has a voltage reading. They all seem to be from the same source reading and they are all lower than the Link 1000. Sometimes significantly. I've even had occasions when the Link had me at 12.3 or 12.4 Volts and the other readings were below 11.0 volts. The batteries seem to perform in line with the Link readings so I have not thought to much about it. But I was curious as to why this difference might occur. I'm not really sure where the anolog reading taps in to get the voltage.

Any thoughts here?

Glenn

 

[Rick486]

Hi all,

I have a question around voltage readings. I have a Freedom 20 charger / inverter that is controlled by a Link 1000 on my 2006 Beneteau 473. I generally use the Link 1000 to read the voltage on my house and reserve banks. The reading are consistent and I understand where the voltage is being read from. Use the Link for Amps, AmpHrs etc. This seems to work fine for me.

My question is around the analog and other voltage readings. I have 4 or 5 places on the boat that will actually give me a voltage reading. There is an analog meter on my DC panel, several of my insturments have a voltage reading and even my tank level meter has a voltage reading. They all seem to be from the same source reading and they are all lower than the Link 1000. Sometimes significantly. I've even had occasions when the Link had me at 12.3 or 12.4 Volts and the other readings were below 11.0 volts. The batteries seem to perform in line with the Link readings so I have not thought to much about it. But I was curious as to why this difference might occur. I'm not really sure where the anolog reading taps in to get the voltage.

Any thoughts here?

Glenn

I just went through something like this and the very short answer is that the analog VMs are notoriously inaccurate. I finally figured that out with help from this board, and calibrated my analog VM on the DC panel against my Freedom charger and a separate digital VM. It turned out that the analog VM was reading about 0.5 volts LOW. There is an adjustment screw on the analog VM so I was able to adjust it to read correctly.
hope this helps.

 

[wgkenney]

Similar Delta at times on mine for the analog.

It is the other digital readings that seem odd as they will sometimes be close to the Link 1000 and sometimes 0.5V or more low. So on my Raymarine multidata instrument there is an "Environmental" tab and voltage is one of the subtabs. That one is sometimes close to the link and sometime way off. Same for my tank level gage. It has a battery voltage display that is sometimes on and sometimes off. Was wondering if the take off point is the issue and it is moving more signficantly than the Link take off point when loads are on.

Glenn

 

[heritage]

The highest voltage reading with no charging going on, will always be at the batteries. I assume that is where the Link measures it's voltage from. Most other voltage meters, whether analog or digital, get their readings from the small wire behind the instrument. If that wire has no load on it, the voltage reading will be slightly lower than the batteries because of the resistance in the wire. If that wire has a load on it, then the voltage can be considerably lower than the actual battery voltage. It will be especially noticeable if the wire is of a small guage, or is a great distance from the battery, or the load is significant.

But a remote voltage gauge is useful, because it shows the actual voltage that the equipment/instrument is experiencing. It can forewarn of a corroded connection or undersized wiring.

 

[Stu Jackson]

Good answers, use them both. There have also been reports that navigation instrument voltages are notoriously incorrect (Garmin IIRC was one mentioned, could be yours, too, and could be from hertiage's answer).

 

[wgkenney]

Thanks, I think that is what is going on. The Link measures right off the posts on the battery switches which are right next to the batteries. I can ID every wire on the posts and there are none for the analog or other digital. So I think you are right. They must be measuring off the wires at the panel or insturments which are a bit away. The pattern is correct as well, in that with load on I am seeing much different voltage and without load it is close.

Thanks!

 

[wgkenney]

Thanks Stu. Now that I think I understand this both voltages are of use.

 

[RAD]

Good answers, use them both. There have also been reports that navigation instrument voltages are notoriously incorrect (Garmin IIRC was one mentioned, could be yours, too, and could be from hertiage's answer).

So that explains why I had to turn off the voltage alarm in my chart plotter