Yamaha Outboard Charging Circuit - Help needed

[Travesso]

Whooohooo!! the new leads work a treat! they are 1/0 AWG (so about 50mm2) and have been professionally crimped and heatshrunk. I also used self amalgamating tape to seal up the terminals properly too.

Due to the size (about 16mm OD each lead) I had to cut a bit out of the yamaha outboard cable grommet but everything has gone in snug again without undue pressure on the fuel or pitot pipes.

The overall length is slightly longer than my old cables too but when i checked the voltage drop at the starter last night it was well less than a volt, compared to the old cable dropping 4v!

Looks like Im back in business... I will check out how the engine charges through these new cables... hopefully no more nervous anticipation when reaching for the ignition key when 25km offshore!

PS: good one Scotty! I do miss the charm of bashing the battery terminals with a shifter to get it started!!

[oldboot]

and the important lesson here is.

you only have 12 volts......you only have to lose a couple of those to be in trouble.

you have to be 20 times more fussy about cable size and connection quality than a household electrician.

cheers

[finga]

and the important lesson here is.

you only have 12 volts......you only have to lose a couple of those to be in trouble.

you have to be 20 times more fussy about cable size and connection quality than a household electrician.

cheers

Sorry for saying so but CRAP!!
I know. I'm a licensed sparky used to working in voltages up to 132kV and if you have a bad connection or undersized cable in even a domestic residence you'll know about it.
We have for more stringent testing procedures to make sure joints are correct (especially in the earthing side of things) and far stiffer penalties if undersized cable is used.
A bad joint or undersized cable can burn a house down to say the least.

[oldboot]

not crap at all.......simple maths and ohms law.

even in the earthing system by 240v regs you are allowed a total of a couple of ohms by the time you run from your earth common, thru the house wiring, the extension cord and the appliance cord...there will be at least that in the active and neutral lines... and that does not account for contact resistance in the plugs switches and breaker.


so how does your 12volt system cope with 4 ohms in the circuit...... you only need to be drawing 1 amp to be short 4 volts.

the mains electrical system has been robust enough to sustain a legeslated 10 volt drop in power supply voltage... check it out the power supply is now officialy 230 volts not 240volts


20 times less voltage means 20 times more current to do the same work and therefore the cables need to have proportionaly less ( 20 times less) resistance.

try this.......take your insulation tester set to the low ohms range and start looking at contact resistances thru some standard 240V (sorry 230V) switch gear and plug ware....particularly if it has a bit of age......half an ohm here an ohm there.

sure the requirement for workmanship remains the same....and the consiquences will be different.......... but the need for a low resistance path is more important the lowerer the voltage gets.

cheers

[finga]

not crap at all.......simple maths and ohms law.

even in the earthing system by 240v regs you are allowed a total of a couple of ohms by the time you run from your earth common, thru the house wiring, the extension cord and the appliance cord...there will be at least that in the active and neutral lines... and that does not account for contact resistance in the plugs switches and breaker.


so how does your 12volt system cope with 4 ohms in the circuit...... you only need to be drawing 1 amp to be short 4 volts.

the mains electrical system has been robust enough to sustain a legeslated 10 volt drop in power supply voltage... check it out the power supply is now officialy 230 volts not 240volts


20 times less voltage means 20 times more current to do the same work and therefore the cables need to have proportionaly less ( 20 times less) resistance.

try this.......take your insulation tester set to the low ohms range and start looking at contact resistances thru some standard 240V (sorry 230V) switch gear and plug ware....particularly if it has a bit of age......half an ohm here an ohm there.

sure the requirement for workmanship remains the same....and the consiquences will be different.......... but the need for a low resistance path is more important the lowerer the voltage gets.

cheers

Sometimes maths and basic electrical principles are not all that's important or considered.
That's why an electrical fitter/mechanic based apprenticeship takes about 4 years not 30 minutes in a physics class in high school.

But if basic maths is to be considered try another angle.
Consider the 2v drop on the 12v system as a percentage.
That will give you a voltage drop of close to 17%
Voltage drop on a 240 (or yes, more accurately 230v as per AS 60038) system is deemed to be a maximum of 5% of the nominal supply voltage whether it be single phase or 3 (not the quoted legislated 10 volts...it's actually a higher figure in reality) as per AS 3000:2007 clause 3.6.2 so if a 17% voltage drops occurs something is really wrong and if that problem was circuit design then the person who designed it could be in deep do-do if if the voltage drop is due to a fault present then things are not going to work too well, especially items that use a bit of current.

Very low resistance readings are very evident, and regulated, in main stream house wiring, and especially so, where high currents are used as resistance figures in home are more accurately, and more typically, worked out as an impedance figure or earth fault-loop impedance.
True, some total circuit resistances can be as low as a couple of ohms but each total impedance reading needs, and is, to be assessed on it's own merits.
Some examples of low resistance joints needed in single phase (230v) wiring:
In clause 5.4.6.3 of AS 3000 "Earthing of parts of structural metalwork, including conductive building materials, may be effected by the connection of a protective earthing conductor of appropriate size at one point of the metalwork provided that the resistance between the earth bar and any part required to be earthed
does not exceed 0.5 Ω."
Or clause 5.5.1.4 states "The resistance of the main earthing conductor, measured between the main earthing terminal/connection or bar and the earth electrode, including the connection to the earth electrode, shall be not more than 0.5 Ω."
Or if you consider a current of 200A at the nominal voltage of 230V (roughly the current in a 12v starter motor as in this thread) the total earth fault-loop impedance is a whopping 0.29 ohms.
That is the total impedance allowable for that circuit. (as referenced from AS 3017:2007 table 3.1)

I will not start on bad connections in power point or extension cord plugs and sockets because we all know what happens to them eventually. They burn. It has happened to all of us especially if a high current user ie jug, heater or welder is used..and that resistance may only be a couple of ohms.

So if a 2 ohm joint exists in a 12volt system things might not work too well.
A 2 ohm joint in a simple 230/240volt AC installation could mean someone could die or something might burn if a fault occurs so there could be arguments on which will be deemed more critical/important to the statement "the need for a low resistance path is more important the lowerer the voltage gets."

There is more to been an electrician then the ability to make something work.
.

[finga]

As a side note clause 20.9.2 of AS/ACIF S009:2006 states in a note "If required, the termination within the ferrule of a cable lug may be filled with solder after crimping to exclude moisture." so does that mean the corrosive effects of flux mentioned previously is not as critical as the exclusion of moisture to the joint in cables over 2.5mm or 4mm in size?

[oldboot]

Oh come on finga...all I am trying to point out is that in 12 volt systems low circuit resistance is an important issue..... joints need to be good, cables need to be of adequate size..........much bigger than the untrained person would be used to seeing in the houshold wiring they are familiar with............a matter and concept that people consistently fail to grasp.

the vast majority of 240V wiring is done by trained people.......on the other hand a considerable amount of 12V wiring is done by untrained & unlicenced people.

hopefully those reading this will understand that like for like..... a 12 volt system... carries 20 times the current than houshold mains, therfore the circuit resistance needs to be proportionaly lower......20 times lower.

If a battery fails to charge, a engine fails to start and the radio fails to transmit.....a poor connection in a 12 volt system can just as easily kill someone or a whole boat full.

as for the reference to S009 correct me if I am wrong but that is the communication cabling standard and that crimp lug would only be on a land bassed communications earth....the cable & lug would not typicaly be exposed to salt water or vibration ( in fact most likly it would be high and dry within a comunications enclosure, service duct or switch room) and nor should it be carrying heavy currents under normal circumstances .......additionaly those cables would typicaly be heavy stranded cables, not fine stranded cables we use in battery circuits..........heavy stranded cables do not pack and conform as well as fine stranded cables.

Additionaly S009 permits a great many things that would not be permissable in electrical wiring and prohibits a great many things that would be normal practice in elecrtical wiring.
for example, double insulation is not factored in communications wiring... this alone changes many things.

cheers