Dips in DC mains voltage with weird knocking noises

[Ruthine]

Can anyone advise?

Whilst moored in the marina, we experienced dips in DC mains voltage with the low voltage management system also bleeping intermittently.
The voltage indicator would dip slightly and briefly when the low voltage manager bleeped, then return to its previous position.
We also had a weird noise like something hitting the side and underneath of the boat. It would reverberate through the boat.

At the time we were using fridge, freezer, and three cabin lights.
We turned off the fridge, freezer and two cabin lights but no change.

All issues were resolved when we briefly turned off the main DC switch and then turned it back on again. After that, the weird noises stopped and the DC manager no longer bleeped intermittently.

(For background info) We were not running the engine, were connected to the marina mains and also have solar power.

 

[Davidasailor26]

What was the voltage when it wasn’t giving the error? Was the bank actively charging from shore and/or solar? Was it deeply discharged? Do you have fuses on the battery terminals or within a few inches of them?

My first guess was that something was rattling around and causing a short, but I don’t see how cycling the switch would stop that.

 

[Ruthine]

Hi David, thank you so much for replying. We are newbies to this - just bought the boat and our first week aboard! Lots to learn… The voltage was showing as 13 amps on the DC voltage meter but dipping to around 12. Since we are connected to the marina mains we don’t understand why the batteries aren’t charging from the mains. The boat electrical panel shows our DC running the lights, fridge, freezer, water pump etc., the AC is running our elec plugs (outlets) and battery charger BUT the battery doesn’t appear to be charging from mains. The thing that is most mystifying is the weird noises. They haven’t returned & we still dont know what caused them.

 

[JoeWhite]

It sound like there is a corroded terminal somewhere. You can locate this connection by moving large lugs around and find the one causing this problem.
The noise might have been the start and stop of charger's cooling fans.

 

[Ruthine]

Thanks Joe. We will try this.

 

[dLj]

Hi David, thank you so much for replying. We are newbies to this - just bought the boat and our first week aboard! Lots to learn… The voltage was showing as 13 amps on the DC voltage meter but dipping to around 12. Since we are connected to the marina mains we don’t understand why the batteries aren’t charging from the mains. The boat electrical panel shows our DC running the lights, fridge, freezer, water pump etc., the AC is running our elec plugs (outlets) and battery charger BUT the battery doesn’t appear to be charging from mains. The thing that is most mystifying is the weird noises. They haven’t returned & we still dont know what caused them.

Are you located just North of Gibraltar in Southern Spain? Just curious.

All intermittent noises can be really hard to diagnose if they don't return so you can find them. Just sayin'...

Do you have a multimeter? Above you mention looking at a panel meter to report voltages - if you don't have a multimeter, id suggest getting one. The one I would recommend is the Fluke 325. It's a multimeter with amp clamp that runs AC and DC. It's a bit spendy but not bad for a Fluke - I've no idea how easily available they are in Spain. I have numerous multimeters but have found this one to be the most useful for working on boats with both AC and DC systems. It also comes with a thermocouple so it can measure contact (meaning you have to put the thermocouple in contact with what you are measuring) temperatures.

What kind of charger do you have? There may be a switch to connect the charger to the batteries to charge them.

On my boat I have an inverter/charger - if I connect to shore power, all my AC electrical will run directly from the shore power. But if I want to also charge my batteries, I have turn a switch allowing the unit to charge the batteries. If I'm not on shore power then turning that switch on takes my batteries and uses them to energize my AC system. You need to learn what you have.

dj

 

[Davidasailor26]

dj’s suggestion to start with a multimeter to troubleshoot is a good one. That will give you a better indication of what’s really happening than the panel meters.

The voltage was showing as 13 amps on the DC voltage meter but dipping to around 12.

I presume it was 13 volts, not amps? If so that suggests the batteries were charging, or at least connected to a charger in a float mode. Lead acid batteries rest around 12.7 volts when full, so anything higher than that means they’re on a charger. If their health is poor and the charger cuts out (maybe because of a bad connection like Joe said) they may quickly drift to the low 12’s or less, which could’ve made the alarm sound.

For more troubleshooting I’d get a multimeter and check the voltage at the battery terminals. Find the breaker to turn off the chargers and see how the voltage reacts. Try this with various loads on and off. If the voltages all seem good at the battery then try to access the back of the DC panel to do the same voltage checks there. That will help show if there may be a bad connection and voltage drop somewhere between the batteries and panel.

It might also be good to pick up a book like Nigel Calder’s Boatowner’s Mechanical and Electrical Manual. That has lots of great instruction on how boat electrical systems are laid out and how to look for problems in them.

 

[Ruthine]

Are you located just North of Gibraltar in Southern Spain? Just curious.

All intermittent noises can be really hard to diagnose if they don't return so you can find them. Just sayin'...

Do you have a multimeter? Above you mention looking at a panel meter to report voltages - if you don't have a multimeter, id suggest getting one. The one I would recommend is the Fluke 325. It's a multimeter with amp clamp that runs AC and DC. It's a bit spendy but not bad for a Fluke - I've no idea how easily available they are in Spain. I have numerous multimeters but have found this one to be the most useful for working on boats with both AC and DC systems. It also comes with a thermocouple so it can measure contact (meaning you have to put the thermocouple in contact with what you are measuring) temperatures.

What kind of charger do you have? There may be a switch to connect the charger to the batteries to charge them.

On my boat I have an inverter/charger - if I connect to shore power, all my AC electrical will run directly from the shore power. But if I want to also charge my batteries, I have turn a switch allowing the unit to charge the batteries. If I'm not on shore power then turning that switch on takes my batteries and uses them to energize my AC system. You need to learn what you have.

dj

Hi dj, thank you for this detailed help - it helps so much to get pointed in the right direction. Not sure what charger we have (sorry complete newbie) will check our boat manual to find out. We have been connected to shore power since boarding boat a week ago and presumed batteries were charging but have had this problem of the ‘Low Voltage manager’ (DC) beeping it’s warning a couple of times this week. We don’t seem to have had a problem on the AC electrical side. We’ll keep trouble shooting and investigate getting a Fluke I think. Thanks again.
We are moored in Alcadeisa marina in La Linea. A 15 minutes walk from Gibraltar.

 

[Ruthine]

dj’s suggestion to start with a multimeter to troubleshoot is a good one. That will give you a better indication of what’s really happening than the panel meters.



I presume it was 13 volts, not amps? If so that suggests the batteries were charging, or at least connected to a charger in a float mode. Lead acid batteries rest around 12.7 volts when full, so anything higher than that means they’re on a charger. If their health is poor and the charger cuts out (maybe because of a bad connection like Joe said) they may quickly drift to the low 12’s or less, which could’ve made the alarm sound.

For more troubleshooting I’d get a multimeter and check the voltage at the battery terminals. Find the breaker to turn off the chargers and see how the voltage reacts. Try this with various loads on and off. If the voltages all seem good at the battery then try to access the back of the DC panel to do the same voltage checks there. That will help show if there may be a bad connection and voltage drop somewhere between the batteries and panel.

It might also be good to pick up a book like Nigel Calder’s Boatowner’s Mechanical and Electrical Manual. That has lots of great instruction on how boat electrical systems are laid out and how to look for problems in them.

Hi David, thank you for this detailed help, and for book recommendation. A good start for me as a newbie. Will do as you and dj suggest: get a multimeter and start doing checks of voltage.
Thanks again. Ru

 

[Davidasailor26]

Not sure what charger we have (sorry complete newbie) will check our boat manual to find out.

It’s very likely that over the years a previous owner has changed out the charger, possibly with a different model. They might’ve also changed other parts of the wiring around when adding solar. The manual might be a starting point, but I wouldn’t trust it for troubleshooting unless/until you can trace wires and check components to see what’s really there. That’s just one of the joys that goes with owning a new-to-you boat .

 

[dLj]

Hi dj, thank you for this detailed help - it helps so much to get pointed in the right direction. Not sure what charger we have (sorry complete newbie) will check our boat manual to find out. We have been connected to shore power since boarding boat a week ago and presumed batteries were charging but have had this problem of the ‘Low Voltage manager’ (DC) beeping it’s warning a couple of times this week. We don’t seem to have had a problem on the AC electrical side. We’ll keep trouble shooting and investigate getting a Fluke I think. Thanks again.
We are moored in Alcadeisa marina in La Linea. A 15 minutes walk from Gibraltar.

As @Davidasailor26 said - it may not be the same as in the manual. Better would be to find it, take a picture and post. It may also be useful to take some pictures of your electrical panel, your battery switches, batteries etc.

What year is the boat?

I'm guessing in the week you have been onboard, the charger not charging the DC system, your batteries are now quite low, hence the low voltage alarm going off frequently. You definitely need to get a decent quality multimeter. Measurement of voltage on your batteries require precision to 0.1 volt range in order to really understand where they are at. It's also very useful to know temperature of your batteries but first lets get to basics...

dj

 

[Ruthine]

It’s very likely that over the years a previous owner has changed out the charger, possibly with a different model. They might’ve also changed other parts of the wiring around when adding solar. The manual might be a starting point, but I wouldn’t trust it for troubleshooting unless/until you can trace wires and check components to see what’s really there. That’s just one of the joys that goes with owning a new-to-you boat .

Thanks David. We are first-time boat owners too, so this is new and scary but also for us a new adventure. Learning how to use and repair the boat was always for us a part of this new journey… Money not unlimited tho’ so we are hoping we can solve the battery problem ourselves and cheaply!!

 

[Ruthine]

As @Davidasailor26 said - it may not be the same as in the manual. Better would be to find it, take a picture and post. I may also be useful to take some pictures of your electrical panel, your battery switches, batteries etc.

What year is the boat?

I'm guessing in the week you have been onboard, the charger not charging the DC system, your batteries are now quite low, hence the low voltage alarm going off frequently. You definitely need to get a decent quality multimeter. Measurement of voltage on your batteries require precision to 0.1 volt range in order to really understand where they are at. It's also very useful to know temperature of your batteries but first lets get to basics...

dj

Hi DLJ, thank you, will take some pics and post. Great idea. We’ve just had the low voltage alarm go off again (turning off fridge and lights as I type). The boat is from 1995 so quite old. Whoops there it goes again. Okay turning off freezer now! Luckily have some portable solar lights

 

[dLj]

Will your batteries charge running your engine? You may want to run your engine for awhile to begin the get those batteries charged back up a bit...

dj

 

[dlochner]

How old are the batteries? What type of batteries are they, flooded lead acid, AGM, Gel? How long have they been stored without being used and recharged?

Voltage alone will indicate whether the battery is fully charged, but it won't tell you the battery's actual capacity. If your batteries are old and/or poorly maintained they may not have enough capacity to handle the electrical loads causing the DC voltage to drop. Over time and use all lead acid batteries lose capacity. With the charger on the voltage drop will be minimized because the charger will act as another power source, i.e, the charger's output will go running the loads and not charge the battery.

If you have flooded lead acid batteries check the water level and if necessary add distilled water (Agua destilada).

 

[Ruthine]

How old are the batteries? What type of batteries are they, flooded lead acid, AGM, Gel? How long have they been stored without being used and recharged?

Voltage alone will indicate whether the battery is fully charged, but it won't tell you the battery's actual capacity. If your batteries are old and/or poorly maintained they may not have enough capacity to handle the electrical loads causing the DC voltage to drop. Over time and use all lead acid batteries lose capacity. With the charger on the voltage drop will be minimized because the charger will act as another power source, i.e, the charger's output will go running the loads and not charge the battery.

If you have flooded lead acid batteries check the water level and if necessary add distilled water (Agua destilada).

Thank you for this help. The batteries are Platinum Marine Plus - a lead acid type according to google. We have located them and found corrosion so need to repair and likely replace them.

 

[Ruthine]

Are you located just North of Gibraltar in Southern Spain? Just curious.

All intermittent noises can be really hard to diagnose if they don't return so you can find them. Just sayin'...

Do you have a multimeter? Above you mention looking at a panel meter to report voltages - if you don't have a multimeter, id suggest getting one. The one I would recommend is the Fluke 325. It's a multimeter with amp clamp that runs AC and DC. It's a bit spendy but not bad for a Fluke - I've no idea how easily available they are in Spain. I have numerous multimeters but have found this one to be the most useful for working on boats with both AC and DC systems. It also comes with a thermocouple so it can measure contact (meaning you have to put the thermocouple in contact with what you are measuring) temperatures.

What kind of charger do you have? There may be a switch to connect the charger to the batteries to charge them.

On my boat I have an inverter/charger - if I connect to shore power, all my AC electrical will run directly from the shore power. But if I want to also charge my batteries, I have turn a switch allowing the unit to charge the batteries. If I'm not on shore power then turning that switch on takes my batteries and uses them to energize my AC system. You need to learn what you have.

dj

Hi DJ,
We do have a switch on the panel (on the AC side) to turn on battery charging. The batteries were just not responding very well. We have now located the batteries and they have some corrosion so we know we will need to do repairs or even may need to replace them… Thanks for your advice though. We are looking into getting a multimeter.

 

[dlochner]

Thank you for this help. The batteries are Platinum Marine Plus - a lead acid type according to google. We have located them and found corrosion so need to repair and likely replace them.

This could be the problem. Aged batteries have less capacity and will draw down quickly. The sound you are hearing could be a solenoid controlling some device like a heater or air conditioner. Or maybe the contactors in an inverter.

 

[dLj]

Hi DJ,
We do have a switch on the panel (on the AC side) to turn on battery charging. The batteries were just not responding very well. We have now located the batteries and they have some corrosion so we know we will need to do repairs or even may need to replace them… Thanks for your advice though. We are looking into getting a multimeter.

That's actually good news.

You do want a good digital multimeter. It can help you know if the batteries need replacing.

Keep us posted, happy to help as much as possible.

dj

 

[Ruthine]

Will your batteries charge running your engine? You may want to run your engine for awhile to begin the get those batteries charged back up a bit...

dj

Thank you for this advice. We ran the engine today as it was a very dull day in La Linea (pouring now) and the batteries weren’t charging at all from the solar panels. We think they aren’t getting charged at all from the AC.