Can A Shunt Be Faulty?

[by'eck]

The shunt has not been touched. The connections from the shunt to the meter have not been touched. I had a wiring diagram of the original installation so I know that it's wired correctly. The earth was reconnected when there was no load so that could not have been an issue but could connecting the live side of the meter have caused the meter to break and show incorrect readings? Could there have been a surge or something. It doesn't seem likely but I'm definitely no expert!!

 

I have been in contact with Blue Seas and they have offered to replace the meter even though its just over 3 years old. I don't want to ask for a replacement meter and find out I've still got the same issues.

 

I would jump at the chance of a free replacement display. What have you got to loose?

 

If you haven't moved the shunt, have you considered the possibility of some added wiring that inadvertently allows current to bypass the shunt?

 

Although you have the wiring diagram, physically tracing cabling may help. Remember you claimed it worked fine before you changed the battery bank!

 

ETA: Instructions here - note absolutely nothing should be connected to the common battery negative connection before the shunt. This includes hull negative strap which should be after the shunt.

Edited August 6, 2013 by by'eck

[ditchcrawler]

Why not disconnect the sense wires and stick a meter set to mV across the shunt and see what indication you get when running a high load. The sensitivity of the shunt is usually marked on it so you should be able to 'roughly' calculate the current being drawn and check that it's in the right ball park.

Looking at Blue Sea shunts on ebay the current /volts are stamped on the side. 500A 50mv or 50A 50mv so I would suspect yours will be marked as well.

[Old Son]

I will have another check of the shunt at the weekend and see what readings I get. Thanks for your replies.

[smileypete]

You could remove and test on a bench with a supply as a sanity check, but maybe just send back as is.

 

If they're offering a replacement then go for it, hopefully it should be a better and more robust design.

 

cheers, Pete.

~smpt~

[arcsyst]

 

This is why I suspected the shunt might be at fault. The reading on the twisted pair connected to the amp meter was 56mv and the meter was showing - 56amp so the conversion seems right (even if I've got my units mixed up)

 

Sounds like a perfectly serviceable 1mv/A shunt to me. Despite protestations something has had it's earthy side moved from the true 'hull' ground to the battery -ve terminal.thus bypassing the shunt. Check the voltage across the shunt on a low load to check that the measuring device isn't ignoring low inputs. Just a thought... you replaced the batteries (plural) are ALL the negatives EXACTLY as they were before

[boathunter]

Thread from the dead...

I have battery monitor with the thin wires as described in this thread.

It appears to be reporting the domestic bank correctly, but reads 11.8v for the starter battery, where my multimeter reads 13.4. I charged it up yesterday and this morning.

There is a blade fuse in the +ve wire to the meter.

Any ideas?

Edited May 25, 2016 by boathunter

[cuthound]

High resistance joint either on the fuse holder, or at the battery end or meter end of the thin wires.

[WotEver]

High resistance joint either on the fuse holder, or at the battery end or meter end of the thin wires.

 

Undoubtedly this.

[bizzard]

Once upon a time I saw many faulty shunts when train spotting at Goodmayes hump marshaling yard when the wagon wheel retarders were set wrongly. There would be a thunderous clanging crash as rapidly moving buffers struck stationary buffers which left carnage of a few derailed wagons.

[boathunter]

Thanks chaps I'll look at the connections.

[boathunter]

High resistance joint either on the fuse holder, or at the battery end or meter end of the thin wires.

 

Undoubtedly this.

Kind of.

I found the +ve batteryterminal loose and sense wire is on a ring terminal on the clamp bolt. Bingo!

Tightened up but still reading 11.7v. Checked all at the battery end to no avail.

 

Pulled the remote panel off and the -ve was snapped at the terminal and flapping about. Still reading 11.8, someone cleverer than me could explain that no doubt.

Connected back up and all is well.

Thanks for getting me going on this little job.

[WotEver]

A snapped wire is a VERY high resistance

[boathunter]

A snapped wire is a VERY high resistance

As it was the -ve and the battery has a -ve bond to the leisure battery bank, I assume that explains the 11.8v reading. It was convincing, dipping to 11.7 and back as these things do. I'd been assured by an engineer (who to be fair was doing something else), that the battery was kaput. It's connected to the secondary 3A charger output of a mastervolt charger, does the team think the lack of sense wire stopped it being charged and the high 13.4v reading is in fact because it's npw being charged?

 

This is all new to me, nearest I get is simple motorhome elecs, this stuff is on another scale!

Edited May 26, 2016 by boathunter

[WotEver]

...does the team think the lack of sense wire stopped it being charged...

 

Nope. Not if it was to a battery 'monitor' as you stated. That has no effect on the charging.

 

Tony

[boathunter]

 

Nope. Not if it was to a battery 'monitor' as you stated. That has no effect on the charging.

 

Tony

Apologies I wasn't clear, it's the charger/inverter control panel. The sense wires are connected directly to it.

[WotEver]

Apologies I wasn't clear, it's the charger/inverter control panel. The sense wires are connected directly to it.

Which charger/inverter?

[boathunter]

Which charger/inverter?

mastervolt 12/80-2 charger and mastervolt sine 12/2000 (I think) inverter. I haven't switched the inverter on as I'm hooked up to 240v while I get on top of things.

 

The controller goes under the impressive name of "masterlink mass inverter charger control".

 

Hefty kit, looks a bit dated but goes along with a 3.5kva diesel generator so I'm not complaining. It must have cost arm + leg when it was installed.

Edited May 30, 2016 by boathunter