Elec issue

PabloPicasso

PabloPicasso

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Sailing and everything electriclal went off

Came back on again.

So intermitent fault.

Voltage was bouncing all over the place. Between 3.8 & 12.4

Later got low voltage warning.

TESTED BATT 12.4V
TESTED bus bars Got 11.8v with B&G plotter on. 12.4v without it.

Is it a dud battery? I can't work out whats going on? The plotter can't be drawing high power can it?
 
Voltages sound low but don't tell you much about the state of the battery unless at rest for some time after use. Do you have a battery monitor?

First thing is to check all connections as varying voltages often come from poor connections.
 
PabloPicasso said:
Is it a dud battery?
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It could be, but it is more likely to be a poor connection as Tranona indicated. The fact that all the electrics turned off suggests it is a connection reasonably close to the battery, so troubleshooting should not be too difficult.
 
I spent a good bit of time today checking all the 12v +&- connections at the battery and at the bus bar.

But I'm not finding anything awry.

Not sure what to try next
 
Assuming you have your house battery in the same place as me (and therefore you can’t accommodate something more than 100-120ah) and assuming as the boat is fairly new to you and therefore you probs didn’t fit this battery, I’d just roll 150 quid (price of a pub meal for two with New Zealand wine!) on a new battery and start there.

I used to buy expensive house batteries from Rolls to get 120ah capacity into the tiny space available, after the second one died this winter from a lack of care/oversight whilst in the yard, I fitted a cheapo 100ah from a local supplier, cost 100 quid and it’s performance has been excellent. Like yourself it is powering a plotter (older Simrad eqv to the original Zeus).

Its performance is so good I think I might just buy a brand new one annually rather than ever chase problems around in future.

If you’re definite it’s not the battery of course, different matter, but problems like this usually are a tired old battery that is difficult to properly assess. More fun to go sailing!
 
The erratic behaviour sounds like a dodgy connection, and possibly the boat’s motion contributed. I was somewhere in the North Sea in the middle of the night when I got a low voltage warning. Having turned everything off, lights and all, except the GPS, I had a look with a torch and soon found a small wire loose in the engine compartment. It had clearly come off a connection on the alternator and even my ignorance couldn’t stop me from making an effective repair by sticking in back on. I don’t imagine that your problem is same, but it could be something apparently trivial.
 
bitbaltic said:
Assuming you have your house battery in the same place as me (and therefore you can’t accommodate something more than 100-120ah) and assuming as the boat is fairly new to you and therefore you probs didn’t fit this battery, I’d just roll 150 quid (price of a pub meal for two with New Zealand wine!) on a new battery and start there.

I used to buy expensive house batteries from Rolls to get 120ah capacity into the tiny space available, after the second one died this winter from a lack of care/oversight whilst in the yard, I fitted a cheapo 100ah from a local supplier, cost 100 quid and it’s performance has been excellent. Like yourself it is powering a plotter (older Simrad eqv to the original Zeus).

Its performance is so good I think I might just buy a brand new one annually rather than ever chase problems around in future.

If you’re definite it’s not the battery of course, different matter, but problems like this usually are a tired old battery that is difficult to properly assess. More fun to go sailing!
Click to expand...
Worth a try.
 
When I had similar it was corrosion on the main fuse - a big 100A NH00 type, with a fairly large context area between it and the holder. Emery paper on the fuse's blades wasn't enough and I had to replace the holder too - presumably it was 25 years old. The problem only showed under load, and not when just the cabin lights were on - i.e. the inverter would give a battery low error., and stopped after replacing the fuse holder. I think the lights used to dim when the fridge kicked on, and now no longer do.

Had similar again with the main 12v isolation switch, one of those biggies with the red removable plastic key.
 
johnalison said:
The erratic behaviour sounds like a dodgy connection, and possibly the boat’s motion contributed. I was somewhere in the North Sea in the middle of the night when I got a low voltage warning. Having turned everything off, lights and all, except the GPS, I had a look with a torch and soon found a small wire loose in the engine compartment. It had clearly come off a connection on the alternator and even my ignorance couldn’t stop me from making an effective repair by sticking in back on. I don’t imagine that your problem is same, but it could be something apparently trivial.
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I hope so

I'll check the alternator connections as well
 
KompetentKrew said:
When I had similar it was corrosion on the main fuse - a big 100A NH00 type, with a fairly large context area between it and the holder. Emery paper on the fuse's blades wasn't enough and I had to replace the holder too - presumably it was 25 years old. The problem only showed under load, and not when just the cabin lights were on - i.e. the inverter would give a battery low error., and stopped after replacing the fuse holder. I think the lights used to dim when the fridge kicked on, and now no longer do.

Had similar again with the main 12v isolation switch, one of those biggies with the red removable plastic key.
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I can temporarily bypass the key switch to rule that out. If that doesn't work perhaps I'll run with just the engine battery powering everything and see if that overcomes it too. That would rule out/in a dud aux batt.
 
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DipperToo said:
Me too. Just touching the switch caused issues.
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I have a new key switch from an old project, and never used. So I can swap that.

If not likely its the battery.
I only have a plotter, depth/wind/log, a vhf, and some lights. No fridge. So demand is not high.
 
johnalison said:
The erratic behaviour sounds like a dodgy connection, and possibly the boat’s motion contributed. I was somewhere in the North Sea in the middle of the night when I got a low voltage warning. Having turned everything off, lights and all, except the GPS, I had a look with a torch and soon found a small wire loose in the engine compartment. It had clearly come off a connection on the alternator and even my ignorance couldn’t stop me from making an effective repair by sticking in back on. I don’t imagine that your problem is same, but it could be something apparently trivial.
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This.

If the fault is intermittent, it's not the batteries. Batteries don't fail that way. It's some connection.
 
Not likely the battery itself. They either fail slowly and gracefully with load or drop dramtically and permanently. Fuses switches and wiring connections are all to be suspected. But do not discount wire itself. I had a supply wire fail mid section. Turns out it got insulation damaged which let moisture and corrosion in eventually breaking connection. ol'will
 
DipperToo said:
Me too. Just touching the switch caused issues.
Click to expand...
In my case it seemed almost like the contacts had broken loose inside the switch's plastic housing. For a while closing it firmly would get a good connection and then it deteriorated. The good thing about those switches is that testing is easy - you can hotwire past them using a screwdriver and the exposed lugs on the back.
 
Certainly don’t rule out the main battery switch as the cause of the problem.

I have five failed Blue Sea battery switches to show that not all battery switches are reliable. The issue is a common fault with these particular switches. Unfortunately, Blue Sea does not seem interested in providing replacements.

IMG_7421.jpeg
 
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