DC to DC charger - not needed for boats with proper alternators.

[newhaul]

Originally Posted by CaptainRivet

Just measure to see if you have a problem or not. You should be able to do this on achor, an engine room that has constant temp must be quite spacious.
Paralell cable must be same length, rough depends on length 20cm on 10m no problem, but on 2m it is. And the other cable is old so potentially much more resistance.
Hope you added postive and negative cable...

Really I don't think he cares . Sounds like he replaced the crap cable and it improved his charging system so he's happy.

[CaptainRivet]

Originally Posted by newhaul

Really I don't think he cares . Sounds like he replaced the crap cable and it improved his charging system so he's happy.

He didn't replace,he put it parallel. If he would have replaced, no issue but having an old most likely not in best shape cable and parallel not same length new can cause a fire.assume its not fused too as in this loaction you don't have to.
ABYC and Iso is very clear on that and that has reasons...
And to figure if you have an issue measure both cables, if rougly +/- 5% the same current its ok. If not better disconnect the old.

[newhaul]

Originally Posted by CaptainRivet

He didn't replace,he put it parallel. If he would have replaced, no issue but having an old most likely not in best shape cable and parallel not same length new can cause a fire.assume its not fused too as in this loaction you don't have to.
ABYC and Iso is very clear on that and that has reasons...
And to figure if you have an issue measure both cables, if rougly +/- 5% the same current its ok. If not better disconnect the old.

Still don't think he cares
And as to the ABYC they are not a governing body and neither are applicable to him in any way . He is in Australia. Also he is a diy .

Not same length is not an issue .

[Simi 60]

Originally Posted by CaptainRivet

.
Hope you added postive and negative cable...

Of course

Originally Posted by newhaul

Still don't think he cares
And as to the ABYC they are not a governing body and neither are applicable to him in any way . He is in Australia. Also he is a diy . .

Correct

Though I did have my lifepo4, multiplus and mppt installation installed by someone else.

Not same length is not an issue

I haven't got out the micrometre to measure but as they run alongside the old one I'm suggesting they are close enough

[Fuss]

Originally Posted by CaptainRivet

Hope the added cable is same length and diameter then existing. How old is the existing one...
Suggest to use a clamp meter to check if current is equally splitted, if not suggest to replace old one too.
More current,more temps.
That's exactly what saved hundreds of alternators from burning when owners added drop in lifepo4.

I don't understand what you mean...
what saved hundreds of alternators from burning when owners added drop in lifepo4?

[CaptainRivet]

Originally Posted by newhaul

Still don't think he cares
And as to the ABYC they are not a governing body and neither are applicable to him in any way . He is in Australia. Also he is a diy .

Not same length is not an issue .

Sure they have similar in aussie, I don't care about these norms either but trying to get/understand the reasons behind it. You can learn a lot what can happen you don't think about and can adapt your installation/design...on the other side especially ABYC often they are just cover the ass for the dumbest user like "don't put your cat/dog in the microwave...or caution coffee cup is hot" creating unnecessary cost and complexity which I ignore.
But several have real and significant reasons and these I follow, paralleling cables is one of them with both requiring parallel cables need to have exact same length. iso is realistic while ABYC over the top here. Iso allows splitting current to spec cable used while ABYC allows paralleling only to reduce voltage drop which is bs.
Cables in engine bay can be very good as grease from engine protects them from corrosion or they can be very bad as when unprotected heat and salt water plus vibration ages a cable quite quick. Very old crap and parallel new is a dangerous combo...

[donradcliffe]

Originally Posted by CaptainRivet

But several have real and significant reasons and these I follow, paralleling cables is one of them with both requiring parallel cables need to have exact same length. iso is realistic while ABYC over the top here. Iso allows splitting current to spec cable used while ABYC allows paralleling only to reduce voltage drop which is bs.
Cables in engine bay can be very good as grease from engine protects them from corrosion or they can be very bad as when unprotected heat and salt water plus vibration ages a cable quite quick. Very old crap and parallel new is a dangerous combo...

You must have missed this lecture.

https://www.youtube.com/watch?v=6tFKFTNSH0o

It demonstrates from Ohms law that a very old vs new, or shorter vs longer cable is never going to be a problem as long as at least one of the cables has sufficient current carrying capacity. The majority of the current will flow in the cable that has the least resistance.

[noelex 77]

With multiple cables the only safety requirement is that each (rather than at least one) conductor should have sufficient ampacity for the expected current and be protected by a fuse that would be suitable for any single conductor.


One conductor could become disconnected, or develop a high resistance without any obvious fault condition being apparent so it is important that the remaining wire be of an adequate size for the expected current and still be protected by an adequate fuse.

If this requirement is met, the resistance of wires can be different without creating any significant safety issues, although a single conductor is generally preferred if this is feasible.

[Fuss]

Originally Posted by CaptainRivet

Hope the added cable is same length and diameter then existing. How old is the existing one...
Suggest to use a clamp meter to check if current is equally splitted, if not suggest to replace old one too.
More current,more temps.
That's exactly what saved hundreds of alternators from burning when owners added drop in lifepo4.

I still don't understand what you mean...
what saved hundreds of alternators from burning when owners added drop in lifepo4?

[CaptainRivet]

Originally Posted by Fuss

I still don't understand what you mean...
what saved hundreds of alternators from burning when owners added drop in lifepo4?

An underdimenioned and/or corroded and or strands broken wire between alternator via starter or directly to batteries. This crap cable with high resistance limits the current drawn from the alternator and saved it this way.

Lifepo4 or eg a huge agm bank is basically a short and a proper sized new wire presents a low restistance too so the alternator would have delivered full throttle wide open full power with running flag till it dies.

[CaptainRivet]

Originally Posted by donradcliffe

You must have missed this lecture.

It demonstrates from Ohms law that a very old vs new, or shorter vs longer cable is never going to be a problem as long as at least one of the cables has sufficient current carrying capacity. The majority of the current will flow in the cable that has the least resistance.

Why does then ISO and ABYC require parallel cables to be the exact same length and exact same diameter?
Iso then specs you can spec the 2 cable with half current carry capabilities each while ABYC requires same current capabilities then 1 cable and paralleling is for reducing voltage drop only.

[Fuss]

Originally Posted by CaptainRivet

An underdimenioned and/or corroded and or strands broken wire between alternator via starter or directly to batteries. This crap cable with high resistance limits the current drawn from the alternator and saved it this way.

Lifepo4 or eg a huge agm bank is basically a short and a proper sized new wire presents a low restistance too so the alternator would have delivered full throttle wide open full power with running flag till it dies.

So what you are saying is, that if I have a corroded wire or a thin wire, then the alternator can’t put out its full current and so is saved from overheating…

[Simi 60]

Originally Posted by Fuss

So what you are saying is, that if I have a corroded wire or a thin wire, then the alternator can’t put out its full current and so is saved from overheating…

Strange how my apparently, old, crap and possibly undersized alt cabling never saved the two previous big frame atls from cooking while charging AGM

[CaptainRivet]

Originally Posted by Fuss

So what you are saying is, that if I have a corroded wire or a thin wire, then the alternator can’t put out its full current and so is saved from overheating…

Exactly.
Just a new cable parallel gave him 3A more that created already 4 degrees at alternator.
The 36Si delco Simi is using here is a beefy large case school bus alternator optimsed for low rpm means relying mostly on self cooling. This one can actually output its 100A @24V in a good ventilated engine room all day long.
And Simi derated it to 70% and still then just 3A more cause already a raise of 4 degrees at the alt in his installtion. His crusing rpm is basically idle speed for the alternator.
You cannot get much better alternator without paying a liver for it but you need the space for to install it.
So and now take that to a small case alternator optimized for higher rpm like most engines have stock which has a very small self cooling capacity. 3A is easliy 10 degrees or more for them. A large case won't fit on many engines or engine rooms.

[CaptainRivet]

Originally Posted by Simi 60

Strange how my apparently, old, crap and possibly undersized alt cabling never saved the two previous big frame atls from cooking while charging AGM

Was the regulator internal or externally ?
The crappy high resistance cable fouls the internal regulator to output less. If the regulator was externally it cannot be fouled, so they delivery full output but less reaches the battery while basically running at idle=not much self coooling capacity.

Which big case exactly? High rpm alternator big case, which are majority out there have significant self cooling capacity only above 25-30% of max rpm. At idle they have a bit more then small case in the end when they heated up but they need significant longer time till they heat up then small case. Good Small case like 115A Mitsubishi typically needs 20min, big case high rpm 50-60min under same conditions till they reach critical temps if running full throttle while a low rpm should need approx 2h...