Weird Electrical Problem

[Dockhead]

We are in Cuxhaven waiting for our new sail to turn up so that we can start out across the North Sea.

My Victron charger/inverter started to act funny, which lead me to jump to the conclusion that it is failing again . It started giving me overload indicators when loads were in norm and started failing to power boost. Intermittently.

But now I'm not so sure it's the Victron. I have 230 volts of power when I first switch on shore power. But then when the charger starts to work (there is a time delay, the voltage falls to 200 or less. Then rises again. Under some load, even with the inverter switched to "charge only" (so no power boost), the voltage falls. With shore power switched off, the inverter seems to work normally, running a 2500 watt electric kettle with normal AC voltage and no overload lights.

What gives? Is it dodgy shore power? What would make shore power voltage fall like that? I understand why DC voltage would fall, but AC power is generally mysterious to me. I will be grateful as always for any enlightenment.

If it's a voltage sag in the shore power, I guess I can understand why the Victron would act funny -- when power boosting, it would be trying to match the incoming AC voltage, and the capacity of the system would be seriously reduced at 190 volts compared to 230.

I sure hope that's the case, because I sure as hell don't want to have to replace this charger inverter again. It is a royal PITA to R&R.

[skipmac]

Hi Dockhead,

Not sure about things on the other side of the pond, but back here in the USA it is not uncommon at all to have bad AC power on docks. Living in the marine environment just isn't conducive to long term health of wiring, connections, plugs and such. And you are correct that in this regard AC will act like DC IE low voltage will cause higher power draw from the system.

One question, do I recall that you also have a Victron isolation transformer in the system? As well as isolating that unit should also be taking the dockside AC supply boost voltage if the dock supply is low. So if I'm correct you could have a problem with the transformer or dockside power is beyond the capability to fix.

Otherwise, I would guess like you that the inverter is working correctly.

Skip

[skipmac]

Another thought, I recall btrayfors has a problem with his inverter not kicking into boost mode with his onboard Nexgen generator due to a really dirty AC power output. Less likely with shorepower but maybe a contributing factor as well.

[Dockhead]

Originally Posted by skipmac

Hi Dockhead,

Not sure about things on the other side of the pond, but back here in the USA it is not uncommon at all to have bad AC power on docks. Living in the marine environment just isn't conducive to long term health of wiring, connections, plugs and such. And you are correct that in this regard AC will act like DC IE low voltage will cause higher power draw from the system.

One question, do I recall that you also have a Victron isolation transformer in the system? As well as isolating that unit should also be taking the dockside AC supply boost voltage if the dock supply is low. So if I'm correct you could have a problem with the transformer or dockside power is beyond the capability to fix.

Otherwise, I would guess like you that the inverter is working correctly.

Skip

Thanks, Skip, that's helpful.

My Victron isolation transformer failed (known defect with bad input breakers; solution is to simply remove the breakers; haven't gotten around to it), so I'm taking shore power straight to the charger/inverter.

I guess the voltage will be boosted at the cost of more amps, correct? So you might get ok voltage, but the capacity of the shore power will be reduced proportionately. I guess I need to get that unit working and try it.

[skipmac]

Originally Posted by Dockhead

Thanks, Skip, that's helpful.

My Victron isolation transformer failed (known defect with bad input breakers; solution is to simply remove the breakers; haven't gotten around to it), so I'm taking shore power straight to the charger/inverter.

I guess the voltage will be boosted at the cost of more amps, correct? So you might get ok voltage, but the capacity of the shore power will be reduced proportionately. I guess I need to get that unit working and try it.

Hi Dockhead,

The details are a bit more complicated than this but the simplified version is yes, lower voltage in the supply can require more amps to run a load.
Again, a simplification but for example, your 2500 Watt kettle means X volts times Y amps to make 2500. So if X gets smaller Y has to get bigger to give the same power.

One other thought, the AC power does have to pass through the inverter even if it is in charge only mode. I guess there could be some problem in the inverter that could effect the power going through even with the boost off. Have you checked the AC voltage before it reaches the inverter input? Anyone else on the dock report power problems?

[transmitterdan]

Dockhead,

Somewhere there is likely to be a bad connection in the shore power feed. If this just happened when you connected to a new dock power stand for the first time then the shore side is the most likely suspect. As the Victron begins to charge the mains current increases from the dock pedestal. Because there is high resistance somewhere the voltage sags. The Victron cannot boost to help the charging AC voltage. It will only boost when it senses total shore current above whatever you have set the boost point. Depending on the options it will reduce charging first until charging stops, then if load current continues to increase it will switch to inverter mode and boost the shore power. But it doesn't care about the shore voltage. It only cares about current. It will boost the current to keep the shore current at the set point. If the shore voltage is 200 then the Victron will not increase it.

Wherever the bad connection is it will likely be getting very hot. You should be able to feel your shore cable connectors at either end to see if the hot spot is there. I would switch over to internal genset power if that is an option. Try another pedestal if that is possible. If same issue happens on your genset then the problem is in your boat and you must find it ASAP. A 40 volt drop at even just a few amperes is a lot of lost watts and the bad connection will get hot very quickly.

BTW, the problem is between wherever your mains volt meter is connected and the source of mains AC.

[Dockhead]

Originally Posted by transmitterdan

Dockhead,

Somewhere there is likely to be a bad connection in the shore power feed. If this just happened when you connected to a new dock power stand for the first time then the shore side is the most likely suspect. As the Victron begins to charge the mains current increases from the dock pedestal. Because there is high resistance somewhere the voltage sags. The Victron cannot boost to help the charging AC voltage. It will only boost when it senses total shore current above whatever you have set the boost point. Depending on the options it will reduce charging first until charging stops, then if load current continues to increase it will switch to inverter mode and boost the shore power. But it doesn't care about the shore voltage. It only cares about current. It will boost the current to keep the shore current at the set point. If the shore voltage is 200 then the Victron will not increase it.

Wherever the bad connection is it will likely be getting very hot. You should be able to feel your shore cable connectors at either end to see if the hot spot is there. I would switch over to internal genset power if that is an option. Try another pedestal if that is possible. If same issue happens on your genset then the problem is in your boat and you must find it ASAP. A 40 volt drop at even just a few amperes is a lot of lost watts and the bad connection will get hot very quickly.

BTW, the problem is between wherever your mains volt meter is connected and the source of mains AC.

OK, thanks, that was a key point.

I put on the genset and loaded it with 20 amps and there was no voltage sag at all and the Victron functions fine.

So it's just the shorepower. Thanks very much for helping track this down.

[transmitterdan]

Dockhead,

Take a look at all the mains connections right at the Victron. If one of the mains cable connections has loosened that will cause this issue. It may have already overheated and you may be able to see evidence of discoloration or melting plastic.

[transmitterdan]

Originally Posted by Dockhead

OK, thanks, that was a key point.

I put on the genset and loaded it with 20 amps and there was no voltage sag at all and the Victron functions fine.

So it's just the shorepower. Thanks very much for helping track this down.

Ok, that's good news. Try another shore pedestal. If its in the marina wiring every pedestal on that pontoon may have the same result. If so, you need to move somewhere else.

[Kenomac]

I had the same thing happen in A Caruna. The shore power was the problem.

[Fuss]

Originally Posted by Dockhead

I have 230 volts of power when I first switch on shore power. But then when the charger starts to work (there is a time delay, the voltage falls to 200 or less. Then rises again. Under some load, even with the inverter switched to "charge only" (so no power boost), the voltage falls. With shore power switched off, the inverter seems to work normally, running a 2500 watt electric kettle with normal AC voltage and no overload lights.

To test the shore power.....
Run the 2100watt jug off 230v shore power... what is the AC voltage...should drop to 210-220 if all sort of ok.
If more then its probably the shore power, try another box or try when less people using it.
The victron remote enables you to reduce the amps under charger. Set to charger only and reduce the amps to 0, whats the 230v voltage, now slowly increase the voltage and see what happens. If the volts stay above 200 then all ok with the shore power.
Another test for the victon...set the switch to auto and limit the charge amps to say 10 or at least near the low end of the dial, now see how the victron and the shore power react.
Sounds to me like a shore power problem either at the box or in your cabling or connectors

[DeepFrz]

Dockhead, the first thing I would check is the shore power plug at the boat connection. One of the biggest causes of fires on boats. Check to see if its warm. I would bet you have an infra red thermometer. Use that in your troubleshooting. I, E and R work pretty much the same AC or DC.

[Dockhead]

Originally Posted by DeepFrz

Dockhead, the first thing I would check is the shore power plug at the boat connection. One of the biggest causes of fires on boats. Check to see if its warm. I would bet you have an infra red thermometer. Use that in your troubleshooting. I, E and R work pretty much the same AC or DC.

Thanks very much.

The shore power plug to the boat is ok and is not hot. It's an oversized 32 amp connector for a 16 amp system (x 230v). I replaced it myself two years ago. The plug at the pedestal (a normal 16 amp blue marine plug) is warm, but not dangerously. I change to a different socket, but no change.

I think I am going to put this down to bad shore power and not worry about it unless the scenario is repeated somewhere else.

I have done the other tests suggested, and the voltage drops for every large consumer added -- seems to be a more or less linear function.

Maybe it's even the wiring to the pedestal, and not any connection. I would expect undersized wiring might react that way. I was in the same marina in May and had no problem with power, but I was in a berth near the quay. I am now on the furthest away pontoon.