loss of cranking power to start engine........

[Boaty McBoaty]

Hi there.  My engine always starts fine and showed 12.6V today.  I noticed the starter battery had a very heavily corroded positive battery terminal but when I cleaned off all the corrosion I found the clamp was actually corroded right through.  Now it was only a loose fit with no way of tightening it on the post and the battery was now only showing 12.2V.  But I wanted to start engine to charge leisure bank so until I could fit a new clamp I tried to temporarily create a better connection at the terminal by packing tin foil between terminal post and corroded clamp and the volts jumped back up to 12.6V.  I turned on ignition and got the audio signal and glow plug lights etc as normal but when I turned the key to start engine it tried to turn over briefly but almost immediately stopped dead.  Will fit a new terminal clamp at weekend but has anyone got any ideas on the most likely issue I caused e.g. blown fuse on a circuit?  And if so the most likely circuit blown based on this scenario??  Thanks in advance........... 

 

Boaty McBoaty

[john.k]

I know someone who got a navy ship going by driving a screwdriver into a loose battery terminal..........after the commander had ordered abandon ship........there was of course a board of enquiry and a reprimand for using a screwdriver without authorization.

[Jen-in-Wellies]

The most likely scenario is that the bit of tin foil wasn't able to handle the hundred plus amps that were trying to go to the starter motor when starting. That was highly unlikely to work. Replacing the corroded clamp will most likely fix the problem. If not, then let us know.

Traditionally, smearing a bit of petroleum jelly, aka vaseline over them, was used to prevent battery clamps from going all green, furry and corroded. This still works and is a good idea for the new clamp and the others in your battery bank.

Jen

Edited April 21, 2022 by Jen-in-Wellies

[Tony Brooks]

What Jen said. typical of a bad/dirty/loose battery clamp connection. Did you clean the mating surfaces to bright metal? If not that may be the problem.

[Jen-in-Wellies]

Before I forget. If you don't already know. The battery posts are "handed". The positive post will be a different diameter from the negative, so you need to make sure that the new clamp terminal is for the correct polarity.

Jen

Edited April 21, 2022 by Jen-in-Wellies

[Bee]

Jubilee clip the cable to the post?

[Tony Brooks]

52 minutes ago, Bee said:

Jubilee clip the cable to the post?

I am sure that would do as an emergency measure. I was thinking mole grips to clamp the broken terminal to the post.

[nb Innisfree]

Also make sure starter motor has a good earth return, check by running a jump lead from neg post to starter motor casing. 

 

 

[Ex Brummie]

And when you buy a new clamp, buy two, so that next time you can fix the problem immediately. They cost little, eat nothing, and occupy little space. You have several batteries. I've seen batteries with a similar clamp problem caused by the seal between the terminal and casing with the venting therefrom degrading the clamp.

[Tony Brooks]

7 minutes ago, Ex Brummie said:

I've seen batteries with a similar clamp problem caused by the seal between the terminal and casing with the venting therefrom degrading the clamp.

 

That is why it is best to dress the terminal and post with Vaseline or Terminal Dressing. It puts a barrier between the post & terminal and the acid fumes.

[Boaty McBoaty]

Hi All.  Great advice/guidance and tips so many thanks indeed and will try fitting the new clamp with vaseline/dressing Saturday morning.  Fingers crossed.  

 

My only thought is that after the failed tin foil fiasco I didn't appear to have any volts showing at the meter so was worried I blew a fuse somewhere.  I would have expected to maybe still see some voltage at the meter afterwards or is that not unusual in this type of situation? 

 

 

[jonathanA]

I think I would have swapped the clamp with one off one of the domestic Bank batteries. 

.

I can't prove this scientifically but I think multiple layers if tin foil which is of course aluminium,  do not a good conductor make...

 

I can't see why you would have blown any fuse and suspect the problem is just a bad connection.  

 

A probe about with a multimeter should help clarify where the volts are going or not going! 

[Tony Brooks]

As I understand it Aluminum oxide is an insulator so if the current caused the foil to oxidize that might be the reason for zero volts. Also acid inside the clamps can cause hard black lead oxide to form, especially on the negative, and that seems to be an insulator.

 

I can't see how what you described could blow a fuse.

[Boaty McBoaty]

Ok. Thanks for that. All still a learning curve for me but really appreciate all the great tips from everyone 😀  Just collected the new clamp now so will head down to Boaty on Saturday to clean it all up and refit it and let you know the outcome! 

 

 

 

[Alan de Enfield]

22 minutes ago, Tony Brooks said:

I can't see how what you described could blow a fuse.

 

Unless it is the multimeter fuse that has blown ?

(selected amps and not volts maybe ?)

[Boaty McBoaty]

Not sure we are talking about same ‘meter’ but the meter I am referring to is the hard wired unit which I believe connects to elec system circuits via a couple of shunts somewhere. So the foil insulation comments made sense in that context I think……

[Tracy D'arth]

1 minute ago, Boaty McBoaty said:

Not sure we are talking about same ‘meter’ but the meter I am referring to is the hard wired unit which I believe connects to elec system circuits via a couple of shunts somewhere. So the foil insulation comments made sense in that context I think……

Ah, A BMS then.

[Tony Brooks]

1 hour ago, Tracy D'arth said:

Ah, A BMS then.

 

and if so Boaty McBoaty have you been using such scales as % Charged discharged or Ah/time left in the batter to inform your charging regime. if the answer is no then well done, if yes, unless you fully understand the units use and limitations, it has probably been giving you plenty of encouragement to destroy your batteries.

 

FWIW the shunt(s) are used to get an ammeter reading, voltmeters do not use shunts although they may connect to one.

[Boaty McBoaty]

Partially to largely true………it’s an Acorn display panel with a volts and amps display but I usually just run the engine by default in winter to get hot water etc irrespective of V-A display figures but I do very often rely on it in summer as a guide as to when to start the engine on board to charge leisures when volts drop on display to show 12.1/12.2…..,,

 

so for my learning on the BMS then, if the amps are displayed via the shunts does the display have a second set of connections direct to the batteries for the volts display? 

[Tracy D'arth]

Oh dear, the dreaded Acorn battery wrecker.

[Tony Brooks]

6 minutes ago, Boaty McBoaty said:

Partially to largely true………it’s an Acorn display panel with a volts and amps display but I usually just run the engine by default in winter to get hot water etc irrespective of V-A display figures but I do very often rely on it in summer as a guide as to when to start the engine on board to charge leisures when volts drop on display to show 12.1/12.2…..,,

 

so for my learning on the BMS then, if the amps are displayed via the shunts does the display have a second set of connections direct to the batteries for the volts display? 

 

Probably not direct to the batteries but to where the batteries connect to the shunt for one connection and may be the other to the batteries or a bus bar some where.

 

You are doing right with that use of the voltmeter although I would use 12.2V as time to recharge. However you really need to use the ammeter to tell you when charging is more or less done. You can not do this if any charge source has dropped to float so as it normally takes many hours either solar or a mains charger will probably have dropped into float long before the batteries are fully charged. You need to keep charging at in excess of 14.2 volts (14.4 is better) until the charging current is 1% to 2% of battery capacity and/or the current has not dropped over the previous hour.

 

 

[Tracy D'arth]

13 minutes ago, Boaty McBoaty said:

Partially to largely true………it’s an Acorn display panel with a volts and amps display but I usually just run the engine by default in winter to get hot water etc irrespective of V-A display figures but I do very often rely on it in summer as a guide as to when to start the engine on board to charge leisures when volts drop on display to show 12.1/12.2…..,,

 

so for my learning on the BMS then, if the amps are displayed via the shunts does the display have a second set of connections direct to the batteries for the volts display? 

Effectively just one extra wire for the volts display and the erroneous percentage and time to charge. The 2 off the shunt on the negative of the battery bank do the current.

[Tony Brooks]

2 minutes ago, Tracy D'arth said:

Oh dear, the dreaded Acorn battery wrecker.

 

Well, if he is using their Kestrel alternator controller I would agree, but not sure how a battery monitor can wreck the batteries apart from misinforming the boater but that applies to other makes as well.

[Tracy D'arth]

2 minutes ago, Tony Brooks said:

 

Well, if he is using their Kestrel alternator controller I would agree, but not sure how a battery monitor can wreck the batteries apart from misinforming the boater but that applies to other makes as well.

Has anyone a good word to say about the Kestrel?  I have removed several over the years.

A beautiful bird on the wing.

[Tony Brooks]

Just now, Tracy D'arth said:

Has anyone a good word to say about the Kestrel?  I have removed several over the years.

A beautiful bird on the wing.

 

It was the re-trigger button that got me, quiet apart from what seemed to just be a timed boosted voltage without much intelligence about it. That re-trigger button is an invitation to keep re-triggering in an attempt to use knackered batteries with the effect they quickly become even more knackered.