AC voltage measured between negative battery terminal and ground

[Nor]

I have a separate 48V battery system that runs the inverter. The 48V battery + and - are connected directly to the Victron inverter (with a fuse and switch), the negative is not connected to other boat earth. I measure 120V or so voltage between either battery terminals and metal on the boat. Is it normal to have a AC voltage between the batteries and ground?

I had an electrician here to install it, but I'm not sure if they did everything correctly. They seem to not have grounded the inverter.
Should the 48V battery negative be connected to the common ground, where the 12V system negative is also connected?

[ttex]

There is no way that is good.

[s/v Jedi]

Originally Posted by Nor

I have a separate 48V battery system that runs the inverter. The 48V battery + and - are connected directly to the Victron inverter (with a fuse and switch), the negative is not connected to other boat earth. I measure 120V or so voltage between either battery terminals and metal on the boat. Is it normal to have a AC voltage between the batteries and ground?

I had an electrician here to install it, but I'm not sure if they did everything correctly. They seem to not have grounded the inverter.
Should the 48V battery negative be connected to the common ground, where the 12V system negative is also connected?

We need a diagram incl. Inverter outputs and model number of the inverter.

[Nor]

48v battery + and - are directly connected to Victron multi rs 6000's battery terminals. The ac1 output is connected to a fuse box with 4 breakers/outputs. One of the outputs is connected to the boat's shore1 input. When I disable this output the voltage went down to about 60v.

[mlydon]

You should never have inverter output connected to inverter input, for starters. Make sure the inverter isn’t powered by one of those other breakers.

Here’s the manual -
https://www.victronenergy.com/media/...f-edbe1dba6f03

[Nor]

Originally Posted by mlydon

You should never have inverter output connected to inverter input, for starters. Make sure the inverter isn’t powered by one of those other breakers.

Here’s the manual -
https://www.victronenergy.com/media/...f-edbe1dba6f03

Sorry if that was unclear. The inverter's output is only connected to the ac breaker box and then goes to the boat's ac panel (through its shore1 input). The inverters ac input is currently not connected.

[ttex]

Man....I was thinking the inverter is wired backwards. Would that cause AC 120 to go to the battery?

[more]

Originally Posted by Nor

Sorry if that was unclear. The inverter's output is only connected to the ac breaker box and then goes to the boat's ac panel (through its shore1 input). The inverters ac input is currently not connected.

1/ Two-wire DC systems operating at 50-300 volts between conductors must be grounded.
2/ all dc 3-wire DC systems must have their 3 grounded conductor grounded.1 wire + second wire negative ,3 wire grounding to sea/earth. one side . other side must be conecct to metal part of user/source. inverter case/solar panel frame,
3/ dc sistem from 1-50 V dont need grounding.

In DC systems, grounding and bonding are usually separate systems, depending on the type and configuration of the DC source. Some DC sources, such as batteries or solar panels, are inherently isolated from the earth and do not require grounding. Other DC sources, such as generators or rectifiers, may have one or more terminals grounded to the earth for safety or performance reasons. In either case, bonding is still required to connect.


IF you have victron inverter charger

shore to shore fuse box. from shore fuse box to victron inverter. from victron inverter to boat AC fuse-distribution box



your victron inverter dont have charger

shore to shore fuse box. from shore fuse box changover switch or Automatic Transfer Switch to boat AC fuse-distribution box

from victron AC out to changover switch or Automatic Transfer Switch.


all cable must be proper fused.
fuse dont save human,eqipment,only purpose of fuse to protect cable from source to user eqipment.

sizing fuse use fuse calculator and for DC systems you must calculate length cable x2
type of cable,temperature around,type of isolation of cable. less 10-20% for security

[Nor]

Originally Posted by more

3/ dc sistem from 1-50 V dont need grounding.

Mine is 48V

Originally Posted by more

IF you have victron inverter charger

shore to shore fuse box. from shore fuse box to victron inverter. from victron inverter to boat AC fuse-distribution box

I don't have shore power connected yet. Just solar and inverter output. So how come there is AC120V (or more) between the batteries and the boat chassis?

The inverter is 230V.

[more]

Originally Posted by Nor

Mine is 48V


I don't have shore power connected yet. Just solar and inverter output. So how come there is AC120V (or more) between the batteries and the boat chassis?

The inverter is 230V.

1/ malfunction of inverter
2/wrong connection between dc panel and ac boat panel.
3 wrong your instrument (i think this is source what instrument you have)

what to do.

1/switch off inverter. test again
between the batteries and the boat chassis?
if show AC 120v instrument malufuction.

2/ disconect inverter AC cable onli live wire to fuse box and switch on
inverter. check again. if show ac 120v inverter malfunction
if ok
3/go furter return inverter fuse box all wire,drop fuse check again
if ok malufuction is on ac panel

on AC panel all switch down and 1 by one up and check.first wher you find shov ac on check site ,this is malufuction. check this cable or replace if need

[tanglewood]

You are measuring a floating/isolated DC source, so the measurement is meaningless. You will essentially get random values.

[Nor]

Originally Posted by tanglewood

You are measuring a floating/isolated DC source, so the measurement is meaningless. You will essentially get random values.

Ok interesting! But I thought I felt some electrical shock in my hand when tightening the dc negative bolt with a metal wrench. If I do measure ac120v between the battery and boat metal (ground) isn't that a concern?

[s/v Jedi]

Originally Posted by tanglewood

You are measuring a floating/isolated DC source, so the measurement is meaningless. You will essentially get random values.

Exactly. Ghost reading

Originally Posted by Nor

Ok interesting! But I thought I felt some electrical shock in my hand when tightening the dc negative bolt with a metal wrench. If I do measure ac120v between the battery and boat metal (ground) isn't that a concern?

Is your boat in a marina? Is there no shore power cord at all, even with open breaker? Does the battery positive only have one wire connecting to the inverter DC input and same for negative? Nothing else connected, not even a battery monitor or BMS?

Do you have access to a good multimeter with mV and mA for both AC and DC?

“Metal on your boat” what is this metal? Is the boat hull metal? If you take something like a screwdriver and test against the metal of that, do you also get the reading? Do you have that metal bonded to something else?

So you said you felt tingling when touching battery negative? Set meter to resistance and measure between metal and battery terminals as well as inverter housing. If the reading is infinite or MegaOhms, repeat the measurements described below for DC as well.

Configure meter to measure AC current, put one probe on battery negative and the other on the metal. Same for positive.

[Nor]

Originally Posted by s/v Jedi

Exactly. Ghost reading



Is your boat in a marina? Is there no shore power cord at all, even with open breaker? Does the battery positive only have one wire connecting to the inverter DC input and same for negative? Nothing else connected, not even a battery monitor or BMS?

Do you have access to a good multimeter with mV and mA for both AC and DC?

“Metal on your boat” what is this metal? Is the boat hull metal? If you take something like a screwdriver and test against the metal of that, do you also get the reading? Do you have that metal bonded to something else?

So you said you felt tingling when touching battery negative? Set meter to resistance and measure between metal and battery terminals as well as inverter housing. If the reading is infinite or MegaOhms, repeat the measurements described below for DC as well.

Configure meter to measure AC current, put one probe on battery negative and the other on the metal. Same for positive.

Thanks! I'll do this tomorrow, nighttime here now. Yes battery directly to inverter, only a fuse and on/off switch in between. On mooring, shore power not connected.
The metal on the boat is the helm chair.

[s/v Jedi]

Originally Posted by Nor

Thanks! I'll do this tomorrow, nighttime here now. Yes battery directly to inverter, only a fuse and on/off switch in between. On mooring, shore power not connected.
The metal on the boat is the helm chair.

Is the chair bonded with a wire? If you test resistance between the chair and other metal parts, is there conductivity? Is your boat made from metal? Do you have an underwater bonding plate?

Do you have access to resistors, like a 10kOhm resistor?