Battery charging current

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greengem85
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Battery charging current

Post by greengem85 »

Might be a silly question but... the wire that goes from the alternator to the battery (fat white one) via a black fusible link, carries the charging current, yes? If the alternator charges at 75A (rated at or charges at?), and the fusible link is rated at 26A, why doesnt it blow? im asking because i found that the link had blown, and couldn't find a replacement, so i swapped it with a 25A blade type fuse, under the impression that 1A shouldnt make too much difference, should it reach 25A, but as soon as it begins to charge, the fuse blows...
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madmike
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Post by madmike »

first question why didn't you just replace it with another fusible link???????
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wedgenut
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Post by wedgenut »

its all done by smoke and mirrors, it is very unlikely the link wire will ever be asked to carry the full 75amps.
The purpose of a fusible link is to melt down and disconnect the circuit before the wiring it is protecting fails and causes serious problems or even a fire. It will however fail quickly in a dead short situation the same as a fuse will.

If you say short out a connection with a spanner touch or something a fuse will blow instantly, a link won't. It is designed to take slight overloads without failing. It's multistrand design allows it to handle these situations better than a standard fuse. Most modern cars have gone away from links and moved to high capacity fuses which do the same job. A bit like motor rated fuses that will take excess current for a pre determined time before failing to allow for high starting current on grinders, drills, lathes and welders. A fusible link is exactly like that.

When you first start the car and say the battery is a bit low, grab one of the links and you might find it is warm and getting warmer. As the battery comes up and the draw decreases the link will cool down again. A fuse isn't that smart and will have a premature ejaculation the minute it gets exited.

Now go and buy some link wire it is cheap as chips butr make sure you crimp AND solder the end connections as a bad joint will come back and bite you.
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Post by greengem85 »

madmike wrote:first question why didn't you just replace it with another fusible link???????
went into supercheap, all they had was sorta like a dummy plug/fuse/link wire. however on the one i blew, there were a couple of other connections and couldnt really adapt the supercheap link to it.

will have a look around for another...
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Post by wedgenut »

Forget supercrap and repco and all other space wasters, go to an auto electrician and ask him, make sure you get the right colour wire, they are rated for different amperages and they have universal colours.

If you smile sweetly and show hiom your wallet he will even crimp on the right connectors for you

From memory the ratings are:

Green 16 amp
red 21 amp
Yellow 23 amp
black 26 amp
blue 35 amp
Usually comes in pieces about 200mm long or 8 inches in old money

Don't faff about with dodgy make do's as you could fry your alternator if you run the engine with a broken link wire and that will set you back more than a few measly bucks for the right link
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Post by IZU069 »

Too late - but FYI:
Don't confuse a "75A" alternator with a battery's charging current.
The 75A is what the alternator can supply and includes the car's electrical load.
A battery would never take 75A, and charging more than about 7A long-term may damage it. (I think the general rule is 10% of its AH rating - ie, 70AH x 1/10 = 7A, but sometimes 20% is used (ie, 14A) - it depends on the battery, its C (AH) rating etc.)

It's likely that a heavy load has been added somewhere - maybe off the battery terminals, or there is a short or faulty circuit.
25A is not a big fuse - it may be too small for (say) 300W driving lights taken off the battery.
The loads should be taken from the alternator output (B or B+ terminal), but ultimately if the battery powers the load with the engine/alternator off, the battery-alternator link must be able to handle that load. These were not fused on old days, and I don't see why the fuselink should be less than what the alternator can output (eg 75A means an 80A fuselink).

You may need to isolate different "downstream" loads to figure out what is causing the link to blow.
I reckon the original Piazza fusible link wiring (off the battery terminal) is "not good" and is better replaced by a proper fuselink box (off a Shuttle, else Jackaroo, RB Gemini etc).
I was going to replace the links with fuselinks (ie, those color-coded "block" fuses commonly available up to 80A in 10A increments), but this assumes the links can be replaced with 20A & 30A fuselinks instead of the Piazza'a 16A (green), 21A (red), 26A (black), and brown (13A?), but this needs a bit of confirmation....
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Post by wedgenut »

Not seekin an argument with anyone but but be very very cautious about fitting over rated fuses or even fusible links. The ratuing they have is to protect your downstream wiring from melting and starting a barbecue.
I have only just finished replacing an entire loom from alternator back through to the dash and heater etc (and that is the biggest effing loom in a piazza) all because some clown with a propeller sticking out of his empty effing head replaced a fusible link with a pretty red coloured wire of humungous proportions. His rationale was that the bigger the wire the more copper there is, correct, well done son. The more copper there is the less resistance there is, correct again young man. Less resistance means less likely to cause a problem. No you dipstick, what it actually means is that the short you had to the body where the loom went through the inner guard and under the dash caused a serious melting of a truck load of wires. There are about 58 wires in the loom at that point. They feed everthing at the rear of the car, both doors, all lighting and heating circuits, wipers speedo etc etc etc. In fact just about everything except engine management.

DO YOU FEEL LUCKY?
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Post by IZU069 »

No argument from me Wedgy! I totally agree with what you have said - and sorry if anyone interpreted my blurb as suggesting bigger fuses - it was NOT intended that way!
I too have seen people replace (house & car) fuses with aluminium- or tin-foil, or nails etc "to stop that annoying fuse blowing" only to be annoyed soon afterwards by fire-engines and insurance paper work. They might suddenly find out that their (house) insurance is void because they performed unlicensed electrical work.
Or they might find out - as per Wedgenut's case above - that something else will act as a "more expensive" fuse.
And isn't it amazing how the one wire that acts like a fuse gets so hot that it melts the insulation on the other (58?) wires and ......
Only then do they seem to understand what "sacrificial fuse" means - it is the $1 component that destroys itself to save a $10k car or $500k house.

Blow-prone fuses can be replaced by circuit breakers. This is usually not a solution, but may aid diagnosis.

As to Wedgenut's and similar examples - ever seen a starter motor cable burn out? Maybe seen a burnt-out Jag XJ6 shell? Their starter cable runs from the battery on one side, around the firewall to the starter on the opposite side. Eventually it would fray/rub somewhere. That's an example of an un-fused "thick copper" burn. (That's one reason I do NOT like cockpit ammeters (of the non-remote sensing type).)

A typical car battery can supply 1,000A into a short circuit. Sealed types (AGM) typically 2,000 Amps. That's a lot of energy!
There is no single "correct" fusing solution - it all depends on what you are protecting etc. But standard vehicle fusing is usually there for a reason. (Well usually, especially if it's Japanese!)

If you do muck around with wiring and fuses, make sure you know what you are doing!
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Post by wedgenut »

Maybe seen a burnt-out Jag XJ6 shell? Their starter cable runs from the battery on one side, around the firewall to the starter on the opposite side.


Yes it does and it goes via a big nasty termination stud on the fire wall that lights up like christmas when you hit it with a spanner

Don't talk to me about farking Jaguar XJ6's. Its real nice coming back to your car after a couple of hours shopping to find the bloody thing has wandered across the carpark and lodged itself in someones front garden. Moral of the story: throw away the naff starter relay of mr Lucas (prince of bloody darkness) origin because when they fail they fail closed circuit and energise the starter and never park it in gear. At least with an auto it can't start or move if in park.

And some people think Piazzas have problems :finga: I have a real cool thing that describes lucas stuff and If I can find it I will post it up
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Post by IZU069 »

Lucas! It's all in a name. Anything Lucas......!!
I recently fitted a Pulsar N13 Bosch alternator with internal regulator to my G161-OHV Wasp.
Yet I have always sworn against internal regs. Why? Lucas. They were the first and were farn hopeless.
But things have changed over 30 years.
I LUV the new alternator - even though it's Bosch. (Luv my LUV pun?)
It seems Bosch too has improved over the years, but it still gets me how I am still biased against a "technology" because of one (ancient) company that implemented it.

Mind you, there was the Lucas Rita ignition system. That was fan-f'n-tastic (and great guys too). But I think the Rita was as Lucas as the Mac was Apple.

(The key was always knowing. Eg Leyland P76 - replace rocker-cover fuel pump, and Lucas switches (wipers etc). Piazza (as with any "old" car) - disconnect and reconnect (preferably clean) ALL electrical connections to PREVENT problems.)
(Another key - don't get dikhed mechanics. Bartarmann's couldn't "test fuel pumps" etc, took over 1 week, blew the EMS etc etc. Bartamann later found the problem himself. It was one of the first things I suggested he check, and I had told him 3-6 months earlier he would have problems (later). It took me 5 minutes to clean up those battery terminal fusible links and solve the problem for good. Pity about the 2 weeks delay, the blown EMS, the several hours removing and replacing fuel pumps and many pluggable modules etc etc.)
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Post by IZU069 »

And old post I know, but still in theme....

Three faults with the Piazza fuselink wiring:

1. fuselinks suspended "in air" and prone to bad connection - should be upgraded to a panel or battery mounted fuse(link) block; preferably with newer plastic fuselinks (20A, 30A, 40A ....100A etc).

The next 2 are common to many cars:

2. A "master" or single fuselink followed by others in parallel. Stupid - a single point of failure. Though later fuselink-block'd Jackaroos etc had this, it seems recent vehicles do not. The argument of limiting battery current seems invalid (whether charge or discharge).

3. There seems to be no reason for an Alternator to Battery fuselink EXCEPT to protect alternator diodes/rectifiers in case of reverse battery connection. It is not to limit battery nor alternator currents.
This is something I am currently confirming with various gurus.

Be aware that the "wire" fuselinks used (Piazza & other Jap) cover 13A, 16A, 21A & 26A (0.3Br, 0.4G, 0.7R & 1.0B). IMO this is a "ridiculous" resolution. Even downstream fusebox fuses are 5, 7.5, 10, 15, 20, 25, 30 etc.
Many modern vehicles - also with 70A alternators but smaller batteries than Piazza - have 80A links between Alt & Batt. And larger sub-links typically of 30A & 40A.

A few more inquiries and I should initiate a thread about the Alt-Batt link.

And to clarify earlier about NOT increasing fuse ratings, this is more for downstream fuses after the fuselinks (eg, in the fusebox, and particularly those in equipment like aircon etc). The fuselinks themselves do NOT seem to be critical - the wires they attach to handle far more than the fuselink rating.
But more on this some other time.
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Post by IZU069 »

I obtained a nice Toyota flink box that attaches to the +ve battery post.
Although it has space for 3 female plastic fuselinks, only 2 are connected to the battery post; the remaining one is floating.
There is also a flying lead off the battery post connection where the other leads exit.

I fitted it to my Wasp yesterday. I used a twin-lead feed from the 70 Bosch alternator (with intermediate connector - from a Shuttle I think).
One lead is to the isolated/floating fuse which I use for my hi-beams (ie, off the alternator as per rally pedantics) and the other via one of the two remaining flinks to the battery.
The other battery flink goes to the vehicle electrics via the body-mounted starter solenoid (the original Bendix starter's solenoid was retained in later Belletts and used as the starter's solenoid solenoid. Confused?).
The main feed to the battery goes from box's batterypost mount.
And I've used the flying lead to go to a fuse "Ignition relay" (used to connect battery +ve voltage to the voltage regulator). I'm just using 40A & 30A flinks for now. I'll increase the alt-bat flink to (say) 80A later.

This Toyota box could be used as a substitute for the Piazza's 3 "flying fuselinks" though I reckon the 5-fuse box from the KE Laser (and other 1988-ish 323 & 626 Mazdas) and the VN & VP Commodores would be better to replace all the Piazza fuselinks.
The "main" centre flink in the KE & Mazdas however bolts in (male 80A) but I haven't seen if the Commodores do the same.
But all its flinks share a common buss - as do all Piazza flinks (assuming the 1.0Black flink is NOT in series with the 0.3Br wiper flink).

I'd use the main bolt-in flink to replace the 1.0Bk that feeds the main fuesbox.


FYI - my "Wasp" flink motivation was to replace flying 3 blade fuses that fed hi-beams, audio, and an aux battery. Like most older cars, it had no alt-battery fuse. I was going to use the 5-way LE/VN/VP flink box, but its mounting wasn't ideal. Hence I tried the battery-post solution which required no mounting.

I could provide pics if anyone is interested. And maybe a master Piazza wiring fig (I have a good one but it lacks headlamp & alternator connections).

There is no problem that I can see in substituting the Piazza's wire flinks with the next sized plastic plugin. I'd even suggest (say) 80A for the alt-batt flink. (And maybe larger for the others depending on downstream wiring and fusing.)
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Post by IZU069 »

And why not resurrect this yet again?

Not much change from the above (except BOSCH) and that the battery-alternator fusing is NOT to protect the alternator:- the reason is normal battery-cable protection (hence fuse at battery end - not in the middle or at the alternator end, though many hi-output (eg, 250A) alternators may fuse both ends).


I ditched Bosch after finding their common N13 vintage alternators have pathetically weak main diodes - I always wondered where that spousetale about "leaving jumper batteries connected for a while after starting" came from. Though thanks to a Camira-Delco book, I did discover that their S terminal is a true S terminal (hence is connected to the battery full time) though it uses significantly more current than Hitachi & other alternators.


I've since tried a few Hitachi LR-170 alternators (eg, Pulsar N13), then a 3-wire SLI Hitachi off a Subaru and my latest are 2-wire S&L Mitsubishi (Hitachi) also off Subarus.
I managed to blow ONE only Hitachi and that was only the diode feeding its v-reg unsoldering itself. Despite charging two batteries - the rear powering a winch and the main powering my reduction starter (splugs in; coil disabled) in a effort to get unbogged - the alternator was otherwise fine, and I suspect it de-soldered whilst packing up the winch after the 1-hour de-bogging...


The only other thing I've found is that Aussies have an amazing gullibility for buying multi-$hundred equipment that is not necessary.
And if you dare offer alternatives, the amateurs with chop your poppy off else those selling the stuff. (That's why Chip /n Dayle went overseas!)


Meanwhile I laugh at fast-flashing LED indicators, or marvel at drivers that don't realise they have a blown indicator - though at least they attempt to indicate.
Australia - the biggest road slaughterhouse per capita in the "civilised" world.

[Updated 7Dec10 - fixed the italics.]
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