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Modern Alternaters don't charge?

Submitted: Sunday, Sep 03, 2006 at 10:41

John R (SA)

Yesterday morning I had my second battery replaced as the old one just didn't seem to be holding a charge. The beaurepaires bloke informed me that 'the problem with alternaters in modern vehicles is that they don't charge like the old generators would. Now they just keep the system at a bit over 12v'.

I've heard this before and it would correlate with my own observations (ie if my aux battery is dead, I need to go on a bloody long drive to get much charge back in to it). What do you wise folk think/know?

I presume the answer is to hook up a charger overnight if you've got stuff constantly drawing on the system, not rely on daily use to keep the batteries charged.

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AnswerID: 192462   Submitted: Sunday, Sep 03, 2006 at 11:02

Member - andrew B (Kununurra) replied:

Gday John

Pretty sure my alternator puts out 13.8v constantly, you may have a fault with your alternator or charging system.

Cheers Andrew
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Reply 1 of 10
AnswerID: 192465   Submitted: Sunday, Sep 03, 2006 at 11:22

Member - Fred replied:

My battery voltage is 12,8 after standing overnight
Alternator voltage with engine running 14,3
This is certainly keeping the battery voltage more than just over 12 volts
Reply 2 of 10
AnswerID: 192466   Submitted: Sunday, Sep 03, 2006 at 11:25

Derek from Affordable Batteries & Radiators replied:

I would not expect the tyre guys to advise you on alternators.

Most batteries sit at 12.3 to 12.5 volts when the engine is not running.

Sounds like he is guessing. Buy yourself a cheap $20.00 multimeter and test it yourself. You should have min 13.8 volts and max 14.8 volts. Ideal is around the 14.3 to 14.4 mark. Your Hi-lux looks quite new. Is it still under warranty.

What is drawing power from the battery ?

Do you have a dual battery ?

What isolator are you using ?

Regards Derek.
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Reply 3 of 10
FollowupID: 450308   Submitted: Sunday, Sep 03, 2006 at 11:39

John R (SA) posted:

The battery that was pulled out, according to their tester, registered 6 volts under load. (he quite happily said that electrics were not his area, which is probably why he stuck a new battery in at no cost).

Pulling power all the time at the moment are a uhf & also grn radio. I know the former doesn't pull much, but the latter have a habit of flattening batteries even when turned off.

Piranha dual battery system installed.

I do plan to get hold of a mulitmeter and learn how to drive it . . . soonish!

FollowUp 1 of 1
AnswerID: 192468   Submitted: Sunday, Sep 03, 2006 at 11:34

Jimbo replied:

The bloke from Beaurepaires is a goose.

Generators got superceded 40 years ago, for good reason. Alternators put out between 14.1 and 14.4 volts because that is what a battery needs to charge.

From first hand experience I have seen a car with a flat battery jump started and two hours later it got sunk in a bog hole. That same battery then cranked the motor over for an eternity until it finally fired up. Being a start battery it accepted a heap of charge in a short time.

The slow charging of your aux battery may have something to do with the type of battery. If it is a basic deep cycle wet cell, I believe they only accept charge at a slow rate, I've heard as little as 5 amps/hour.

Still, there could be a problem with your alternator. Get a multi meter and check the voltage going into the battery; if it's under 14 I'd get it looked at. However I'm no Auto Elec and some professional advice may be needed.

Cheers,

Jim.
Reply 4 of 10
FollowupID: 450331   Submitted: Sunday, Sep 03, 2006 at 13:44

Bonz (Vic) posted:

YER! What Jim said

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FollowUp 1 of 2
FollowupID: 450336   Submitted: Sunday, Sep 03, 2006 at 14:15

Exploder posted:

And a generator is heavy and unreliable when compared to an alternator.

On the Plus side a generator will charge a dead battery an alternator won’t.
FollowUp 2 of 2
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AnswerID: 192474   Submitted: Sunday, Sep 03, 2006 at 11:47

madfisher replied:

I agree with what Jimo said, Generators Do NOT charge at idle altenators do, mind you the last car i owned with a generator was an fc holden , my first car, had more ground clearance than some modern soft roaders
Cheers Pete
Reply 5 of 10
FollowupID: 450313   Submitted: Sunday, Sep 03, 2006 at 12:01

Jimbo posted:

Pete,

My last and only one with a gennie (back in 79, my first car) was also an FC. Ah, generator, vacumm operated wipers, no heating.

I was going through some junk the other day and came across a little book put out by GMH back in 77 called "The Holden Story". The weight of the FC was 2349 lbs or about 1070 kg. Amazing for a car that could seat six blokes wearing top hats. Bench seats that offered a comfortable nights sleep after a session on the juice.

Memories.

Cheers,

Jim.
FollowUp 1 of 2
FollowupID: 450314   Submitted: Sunday, Sep 03, 2006 at 12:06

Shaker posted:

Generators Do NOT charge at idle altenators do ........ alternators don't charge dead flat batteries, generators do!
I am not saying for a moment that gennies are better though.
FollowUp 2 of 2
AnswerID: 192476   Submitted: Sunday, Sep 03, 2006 at 11:55

Member - Mike DID replied:

The charging voltage on alternators hasn't changed in the last 30 years.

Cars that are fitted with Calcium-calcium batteries will charge up to 14.8 volts.

Don't ask an Auto Electrician for advice about tyre problems, don't ask a Tyre dealer to do any more than bolt in a battery.
Mike R
Reply 6 of 10
AnswerID: 192478   Submitted: Sunday, Sep 03, 2006 at 12:02

John R (SA) replied:

Go easy on the bloke, he was just trying to be helpful! Even if he is wrong!

At least it got me thinking a little more.

To highlight my ignorance a little more . . can someone point me at some instructions on how to use a mulitmetre to measure current draw? ie to find out what a radio / gadget / whatever is drawing from the battery?

Cheers,
John

Reply 7 of 10
FollowupID: 450333   Submitted: Sunday, Sep 03, 2006 at 13:49

Bonz (Vic) posted:

Ok, current draw is measured like parallel parking, everything in line. So you need to take off a wire, connect the appropriate miltimeter between where you took off this wire and the wire u took off, this is called a series connection, be careful to have the right multimeter, (i.e. one that will measure up to say 20 amps) and have it already switched to the current setting, or get a clamp on type AC/DC multimeter for about $120 (ish) and just clamp it around the one wire you want to check.

Voltage is measured in parallel, like 90 degree angle parking, side by side, like when youre at the lights. Put the leads on the battery with the meter set on volts and read it.

QED

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FollowUp 1 of 2
FollowupID: 450406   Submitted: Sunday, Sep 03, 2006 at 21:26

Angler posted:

First important hint for a novice using a multimeter.

NEVER EVER SWITCH IT TO AMPS, NEVER EVER TRY TO MEASURE AMPS.

ALWAYS MEASURE VOLTS.

I have seen many people test a battery by checking on how many AMPS it puts out using a multimeter. The battery survives but the meter dies. (very quickly)

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FollowUp 2 of 2
AnswerID: 192482   Submitted: Sunday, Sep 03, 2006 at 12:15

Derek from Affordable Batteries & Radiators replied:

You need to buy one that has a built in 10 or 20 amp test function.

Disconnect the battery positive and place the multimeter between the two.

If there is more than a 1/2 amp draw start pulling fuses and accessories till the draw drops.

Make sure you know where the multimeter fuse is and buy some spares.

Regards Derek.
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Reply 8 of 10
FollowupID: 450317   Submitted: Sunday, Sep 03, 2006 at 12:19

John R (SA) posted:

Thankyou Derek.

Thanks to all the others for your comments too.

John
FollowUp 1 of 3
FollowupID: 450322   Submitted: Sunday, Sep 03, 2006 at 12:46

Max - Sydney posted:

John

What Derek said is dead set simple and right. But - if you don't know multimeters I can think of several mistakes you can make.

You need a book - Jaycar have one for about $7 - look it up at

Site Link

Happy learning -its not hard

Max
FollowUp 2 of 3
FollowupID: 450334   Submitted: Sunday, Sep 03, 2006 at 13:51

Bonz (Vic) posted:

Max, it is hard, you are misleading poor John. We electrical engineers go to school for years to learn about it, Derek would agree, thats why we can charge hundreds of dollars to check something a $10 meter can.....with a little learning.....oops I thunk I dun meself outta sum munny. :)

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FollowUp 3 of 3
AnswerID: 192484   Submitted: Sunday, Sep 03, 2006 at 12:57

madfisher replied:

Jimbo hi,
Off topic i know, But i get all nostagic about my fc. Owned in 69 70. Wish i still had it in a shed. Mate of mine just paid thousands for one with orinigal 70000m on it . Had chractor
Cheers Pete
Reply 9 of 10
FollowupID: 450323   Submitted: Sunday, Sep 03, 2006 at 13:03

Jimbo posted:

Mine was an absolute Gem. A one owner I bought after an old bloke died. 85,000 miles and perfect. I paid $350 for it and got $200 as a trade in.

It was affectionately known as "The Coach". LIke you, I still kick myself for getting rid of it.
FollowUp 1 of 3
FollowupID: 450338   Submitted: Sunday, Sep 03, 2006 at 14:21

Exploder posted:

Mate the old man had a XY GTHO falcon from new, He Sold it in 1981 isn’t he kicking himself now, I spotted one for sale the other day for the tidy some of $110,000!!!
FollowUp 2 of 3
FollowupID: 450352   Submitted: Sunday, Sep 03, 2006 at 16:17

madfisher posted:

I think we all get a bit nostagic about our first car. My first 4by was a LJ80 susi, boy did i give that a workout. Use to go 4wheeling mostr nights, Actually drove in and outr of a drainage ditch dug by a kato. Would claw through mud you could not stand up in. Only paid $1800.00 for it in 86 sold it 3 years later for $3000.00, mind you their was not much i had not rebuilt
Cheers Pete
FollowUp 3 of 3
AnswerID: 192501   Submitted: Sunday, Sep 03, 2006 at 16:53

Rhys replied:

If your dual battery set up is not right it will restrict the charge to the 2nd battery before it is fully charged, maybe get someone familiar with the piranha system to have a look at it.
Reply 10 of 10

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