loss of 9v power

[mike n]

Hi I wodered if any one can point me in the right direction of where to start to investigate the cause of the problem...

I have recently travelled from droitwich towards Birmingham and have lost all 9v power to the cabin of my boat.  24v via the inverter works and the engine starts and appears to run OK. My voltage display on my fuse board no longer displays anything for my leisure batteries but displays a reading of 12.9v for the starter battery.

 

Any help or advice greatly received

[LadyG]

Hi there, I'm not able to assist, but others will be along. Can you post a few photos?

How many battery banks and what voltages your systems run on? Most of mine are 12 volt and I get 240 v via the inverter.

[Tracy D'arth]

Confused by the voltages on your boat.  Is the cabin power supposed to be 12v, I have never had a boat with 9v?

Do you mean 240v AC power off the inverter not 24v DC?  Read your post and edit please to correct it.

I would suggest you check at the batteries and work away from them via isolator switches and fuse/circuit breakers. You obviously have a multimeter and know how to use it.

Is there a red key isolator in the feed to the cabin fuse box? They are famous for failing. 

Starter battery is right and fully charged.

Do you have 2 alternators or just 1?

How does the cabin battery charge, split charge relay or diode splitter or VDR?  Pictures of what you have will always help.

[MoominPapa]

Flat battery?

 

MP.

 

[Higgs]

1 hour ago, LadyG said:

Hi there, I'm not able to assist, but others will be along. Can you post a few photos?

How many battery banks and what voltages your systems run on? Most of mine are 12 volt and I get 240 v via the inverter.

 

The OP probably just missed adding a zero to the AC output figure. But has 9v ever been mentioned before on this forum? 

 

 

[MtB]

1 hour ago, mike n said:

Hi I wodered if any one can point me in the right direction of where to start to investigate the cause of the problem...

I have recently travelled from droitwich towards Birmingham and have lost all 9v power to the cabin of my boat.  24v via the inverter works and the engine starts and appears to run OK. My voltage display on my fuse board no longer displays anything for my leisure batteries but displays a reading of 12.9v for the starter battery.

 

Any help or advice greatly received

 

Hi Mike, welcome to the forum.

 

First off, can we discuss why you think your cabin power is 9V please? This is almost unheard of (usually 12V) but if you know for a fact it is 9V, then nothing about your boat is standard and most other comments in this thread will apply to 12V systems mainly, not yours.

[Tony Brooks]

Take note of what Tracy said ref Red Key and Mike ref the supposed 9V system.

 

If you have been seeing 9V of your domestic battery voltmeter and the master switch is OK then it suggests the domestic batteries were shorting on and have now failed, or you have never been charging them enough (very common beginners mistake). How are you charging the domestic bank and for how long each day during the week.

[dmr]

6 hours ago, MoominPapa said:

Flat battery?

 

MP.

 

 

When my daughter was about 6 she spotted a discarded PP3 in the gutter and said "look, there's one of those flat batteries that you keep talking about"

[mike n]

Thanks all for the help.  To confirm yes I have a 12V system to the cabin and 240V AC from the inverter. Apologies for the confusion it was a late night and after completing the 40 odd locks from Droitwich to the top of Tardebigge in one day I was exhausted and this was the last straw .

 

I have checked the red isolator keys and all seem to be working fine. Or at least I get the same problem no matter what key I use.

 

I have two alternators. 

 

The main battery is charged and holding charge, as are the two leisure batteries (I have solar panels so can see they are charging) and holding charge as the invertor is producing 240V. 

 

I am currently not on the boat but will post some pics shortly.

 

 

[Alan de Enfield]

6 minutes ago, mike n said:

hanks all for the help.  To confirm yes I have a 12V system to the cabin

 

So, is the problem solely that you have no 12v power to the cabin ?

(everything else is OK ?)

 

It is generally not the 'red key' that causes the problem but the internals of the switch.

Try disconnecting the wires off one side of the switch and reconnect it onto the other side (so the switch is islolated) does that solve the problem ?

 

Do you have the 12v system going thru a 'fuse box' ?

Is the feed into the fuse box OK ?

Edited April 11, 2023 by Alan de Enfield

[Tony Brooks]

1 minute ago, mike n said:

Thanks all for the help.  To confirm yes I have a 12V system to the cabin and 240V AC from the inverter. Apologies for the confusion it was a late night and after completing the 40 odd locks from Droitwich to the top of Tardebigge in one day I was exhausted and this was the last straw .

 

I have checked the red isolator keys and all seem to be working fine. Or at least I get the same problem no matter what key I use.

 

I have two alternators. 

 

The main battery is charged and holding charge, as are the two leisure batteries (I have solar panels so can see they are charging) and holding charge as the invertor is producing 240V. 

 

I am currently not on the boat but will post some pics shortly.

 

 

 

For clarity - it is not the red keys in master switches that cause the problems, it is the internal contacts the key pushes on and the low melting point plastic that the internal parts are made from. Such switches are very optimistically rated so tend to overheat and soften internal plastic so the contacts no longer make a decent low resistant connection.

 

As a test, bridge the two terminals on the back of the switch or put all the wires on one stud. If the fault goes, then it is the switch that needs replacing.

[nicknorman]

42 minutes ago, mike n said:

Thanks all for the help.  To confirm yes I have a 12V system to the cabin and 240V AC from the inverter. Apologies for the confusion it was a late night and after completing the 40 odd locks from Droitwich to the top of Tardebigge in one day I was exhausted and this was the last straw .

 

I have checked the red isolator keys and all seem to be working fine. Or at least I get the same problem no matter what key I use.

 

I have two alternators. 

 

The main battery is charged and holding charge, as are the two leisure batteries (I have solar panels so can see they are charging) and holding charge as the invertor is producing 240V. 

 

I am currently not on the boat but will post some pics shortly.

 

 

you can rule out (or not) the battery isolator switch by following the suggestions above to temporarily bypass the switch. Or even just hold a screwdriver across the 2 switch terminals (be careful the screwdriver doesn’t touch anything else!).

 

Another way is to put a multimeter across the boat side (non-battery side) of the switch and check for around 12v between that and the hull or engine metalwork, with some lights etc switched on.

 

If there is definitely 12v getting through the switch then it must be a bad connection between there and the fuse board. Some types of fuses are renowned for getting a bit of corrosion and hence bad connection, so just wiggling or removing and reinserting the fuses can help. As well as the 12v getting through, of course the battery negative has to get through to the other side of the circuit and a bad connection on that side of things is possible too. It is just a matter of moving along the various bits of circuitry with a multimeter until you find the point where the 12v difference between positive and negative disappears.

 

[Tony Brooks]

Building on what Nick said about fuses. If you have the torpedo shaped fuses with the pointy metal end caps that fit into holes in the metal fuse holder, then my advice would be that faulty or not, plan to replace them with modern push in fuses as now used in cars. Torpedo fuses have been causing problems for the 65 years I have been dealing with them on cars, especially Italian cars!

[Ken X]

I second that, torpedo fuses are horrible horrible things.

The first thing we did on cars sporting these was to open the fuse box and run a finger over them to spin them before even trying to fault find. Cured the vast majority of electrical faults instantly.

[dmr]

20 hours ago, Tony Brooks said:

Building on what Nick said about fuses. If you have the torpedo shaped fuses with the pointy metal end caps that fit into holes in the metal fuse holder, then my advice would be that faulty or not, plan to replace them with modern push in fuses as now used in cars. Torpedo fuses have been causing problems for the 65 years I have been dealing with them on cars, especially Italian cars!

 

Sometimes known as continental fuses?  They were used on my old VW camper so even the Germans get their engineering wrong sometimes. Still common inside some 12volt "cigar lighter" plugs.

[mike n]

Thank you all for the advice. The problem has been resolved. It was a faulty main battery isolator switch. 

[TheBiscuits]

48 minutes ago, mike n said:

Thank you all for the advice. The problem has been resolved. It was a faulty main battery isolator switch. 

 

It's usually the first thing to check - many of them are rubbish!

 

I've replaced all mine with proper grown up switches as I got tired of wiggling the keys in the bad ones.

[MtB]

53 minutes ago, mike n said:

Thank you all for the advice. The problem has been resolved. It was a faulty main battery isolator switch. 

 

Thanks for the update, glad you fixed it! Not everyone comes back and tells the board.

 

 

[Tony Brooks]

I, too, thank you for your feedback.