Parasitic Battery Drain

[Happy Place]

Everything is turned off. The master breakers are off. So why am I seeing negative numbers in Voltage and power? Am I reading this wrong? My solar is putting in power right now ...is a negative number indicating power going in?

 

[JMarshallR25]

Just an anecdote, but the factory wired the shunt for my Victron battery monitor backwards. In that case it will read power coming in as negative. You can add a large load (a/c, water heater) and see if this is the case for you. If that shows up as positive, your shunt is backwards. You may want to check that basic issue before hunting down what might be creating this draw.

 

[Lake Effect]

View attachment 25303Everything is turned off. The master breakers are off. So why am I seeing negative numbers in Voltage and power? Am I reading this wrong? My solar is putting in power right now ...is a negative number indicating power going in?

What did you find out?

 

[Submariner]

Just an anecdote, but the factory wired the shunt for my Victron battery monitor backwards. In that case it will read power coming in as negative. You can add a large load (a/c, water heater) and see if this is the case for you. If that shows up as positive, your shunt is backwards. You may want to check that basic issue before hunting down what might be creating this draw.

The most recent version of software updates for the Victron shunts now has a feature called "Current Measurement Direction", the default is "Normal" There is an option for "Reversed", making it easy to correct should the shunt be wired in backwards.

 

[DDean]

In my case the actual wiring for the boat was different than the schematics with the difference being that the positive from the solar is on the thruster battery and not one of the house batteries. So when I installed my shunt, I capture the negative from the solar (now on a bar) but not the positive. That leads my shunt to reading input from solar as a negative - I think anyways. I’m not looking forward to dragging those batteries out again to confirm.

Perhaps you’re in the same boat?

 

[Submariner]

In my case the actual wiring for the boat was different than the schematics with the difference being that the positive from the solar is on the thruster battery and not one of the house batteries. So when I installed my shunt, I capture the negative from the solar (now on a bar) but not the positive. That leads my shunt to reading input from solar as a negative - I think anyways. I’m not looking forward to dragging those batteries out again to confirm.

Shunt's don't measure the positive size of 12 volt. They look only at the negative side. If the solar was wired directly to the thruster battery on the positive side, then solar is charging your thruster battery and not your house, until the ACR closes, paralleling the house and thruster, allowing solar to charge the house bank.

On the R27-OB (NW edition), there are 3 batteries in the port laz. The aft two batteries are house, the most forward battery is the thruster battery. The negatives from the thruster and house batteries are all connected. When installing a shunt, it's important to move the negative jumper that is between the house and thruster, and move that cable so it's thruster negative to bus bar installed for the shunt. The flow of electrons need to go house #2 negative to house #1 negative, to shunt, to bus bar. There can be no other connections on the negative posts of house #1 and house #2 battery. This will ensure nothing bypasses the shunt and will give accurate readings for charging and discharging.

 

[Submariner]

In my case the actual wiring for the boat was different than the schematics with the difference being that the positive from the solar is on the thruster battery and not one of the house batteries. So when I installed my shunt, I capture the negative from the solar (now on a bar) but not the positive. That leads my shunt to reading input from solar as a negative - I think anyways. I’m not looking forward to dragging those batteries out again to confirm.

Perhaps you’re in the same boat?

To pull out the batteries is relatively easy.
Looking at the port laz, there are two screws that hold the starboard in place (it's a tray the batteries sit on). Remove the two screws. I also take a sharpie and mark the outboard corner onto the fiberglass which makes it easier to line up the starboard screw holes for when I put it back.

Then remove the first house battery as it's in the clear. Wrap the electrical connections with electrical tape to reduce the risk of an accidental short.
With the first battery removed, you can slide the battery tray starboard backwards about 7 inches to get access to the second house battery. Remove it.
Then slide the tray the rest of the way out to access the thruster battery.

Putting them back in is the reverse of the above. The batteries are 67 lbs a piece, the most you should have to move is 2 of them on that tray, about 7 inches.

 

[DDean]

Shunt's don't measure the positive size of 12 volt. They look only at the negative side. If the solar was wired directly to the thruster battery on the positive side, then solar is charging your thruster battery and not your house, until the ACR closes, paralleling the house and thruster, allowing solar to charge the house bank.

On the R27-OB (NW edition), there are 3 batteries in the port laz. The aft two batteries are house, the most forward battery is the thruster battery. The negatives from the thruster and house batteries are all connected. When installing a shunt, it's important to move the negative jumper that is between the house and thruster, and move that cable so it's thruster negative to bus bar installed for the shunt. The flow of electrons need to go house #2 negative to house #1 negative, to shunt, to bus bar. There can be no other connections on the negative posts of house #1 and house #2 battery. This will ensure nothing bypasses the shunt and will give accurate readings for charging and discharging.

Thank you!!!! I didn’t realize that the bridge needed to be removed as well. I moved all the others over, not the bridge. That’s probably my issue with the negative being the solar off balance?

I think that the positive is bridged too. I thought it was odd. I will have to confirm

 

[DDean]

To pull out the batteries is relatively easy.
Looking at the port laz, there are two screws that hold the starboard in place (it's a tray the batteries sit on). Remove the two screws. I also take a sharpie and mark the outboard corner onto the fiberglass which makes it easier to line up the starboard screw holes for when I put it back.

Then remove the first house battery as it's in the clear. Wrap the electrical connections with electrical tape to reduce the risk of an accidental short.
With the first battery removed, you can slide the battery tray starboard backwards about 7 inches to get access to the second house battery. Remove it.
Then slide the tray the rest of the way out to access the thruster battery.

Putting them back in is the reverse of the above. The batteries are 67 lbs a piece, the most you should have to move is 2 of them on that tray, about 7 inches.

Last time I did not remove the batteries, I manhandled the whole board with the batteries still attached back into its position to match the holes. Obviously really heavy and precise hole matching. Was not fun but felt it would be easier.

 

[Submariner]

I think that the positive is bridged too. I thought it was odd. I will have to confirm

Positives doesn't matter with respect to the shunt. You need the positives connected via the jumper cable for the two house batteries only.