Battery / alternator test

G

Guest

Guest
I=92m damn sure this has been posted before but now that I need it I can=92t
find it.

How can I test to determine whether I have a knackered battery or a
knackered alternator (or maybe even both?

The cruiser is not used much at the moment =96 maybe once a week. A couple of
weeks ago I had a dead battery, totally dead, not a glimmer. I charged it up
for a day on trickle charge and it was fine, I used it a couple of days and
it started perfectly OK.

It was then left for best part of a week until I came to use it yesterday
when there was some charge in the battery but not enough to turn the
starter. I started it from a starter pack and did the usual battery loading
before disconnecting the pack. The need was urgent so I drove off for a
twenty mile drive after which I was sure I=92d have sufficient charge to
restart a warm engine =96 no such luck! I stopped with the engine off for ten
minutes and then went to restart and=85=85 nothing. I had to jump it.

So, I=92m not sure whether I have a duff battery or a duff alternator.
Obviously I could take the battery out and take to an auto electrics place
for testing but is there an in-situ test that I can do to check which it is?
I have a multimeter but no other diagnostic gear.

Should I charge the battery for a day before testing?

Any advice gratefully received.

Pete
1995 FZJ 80 Auto
HYPERLINK "mailto:[Email address removed]"[Email address removed]
(email and MSN)



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Guest
Basic check to see if the alternator is functioning. Measure the voltage at
the battery terminals the start the engine and measure again with the engine
running. If the alternator is OK will be higher when running than the
battery voltage before starting. Voltage with the engine running will vary
depending on the state of charge of the battery but should be around 13V to
14V.
Malcolm Bagley
Stafford, UK
1975 FJ45 Pickup (In Work)
_______________________________
How can I test to determine whether I have a knackered battery or a
knackered alternator (or maybe even both?
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Peter

Sounds very like a battery not holding charge to me.

To check alternator function measure the battery voltage with the engine
stopped (should be in range 12v to 13v), then start it, rev up a little
and measure again (should be 14v plus). Main beam headlights should
brighten a touch when you rev up from tickover, or if it's daylight turn
on the fan blower to full blast and listen for a slight change in fan
speed as you rev up. If there is no obvious voltage rise with the
engine running you have alternator trouble.


To check the battery itself you need a hygrometer. (Big pipette that
sucks out acid and measures its specific gravity). If you haven't got
one the easiest thing is, as you say, take the battery to a battery
place and get it checked.

Christopher Bell

How can I test to determine whether I have a knackered battery
or a knackered alternator (or maybe even both?

____________________________________________________________
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Guest
Quite correct Chris, I forgot to say rev it a little, although many of the
alternators now seem to start outputting at very low rpm.
I have two gadgets which are useful for batteries, one an optical device to
check the specific gravity (used refraction, also works for antifreeze) and
an electronic tester which determines the AH (capacity) of the battery. So
far both have proved very useful and quite accurate they are quite pricey at
around =A365 and =A3200 respectively, OK for the commercial user (me), perhaps
more than I would want to invest personally.
Malcolm Bagley
Stafford, UK
1975 FJ45 Pickup (In Work)
_______________________________


To check alternator function measure the battery voltage with the engine
stopped (should be in range 12v to 13v), then start it, rev up a little
and measure again (should be 14v plus
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Malcolm
Yes, I've seen my local garage using the optical thingy. There is a
similar (? same) gadget for anti-freeze is there not?
Me, I use my trusty old hygrometer (free with a charger I bought). But
I admit it is messy!
My alternator needs engine revs of about 1000 rpm to deliver full
voltage under load, but it was described as a "bit lazy" when tested the
other day.
CB
|Quite correct Chris, I forgot to say rev it a little, although many of
the
|alternators now seem to start outputting at very low rpm.
|
|I have two gadgets which are useful for batteries, one an optical
device to
|check the specific gravity (used refraction, also works for antifreeze)
and
|an electronic tester which determines the AH (capacity) of the battery.
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Same device does anti-freeze, also does screenwash if you are realy fussy!.
Malcolm Bagley
Stafford, UK
1975 FJ45 Pickup (In Work)
_______________________________
Yes, I've seen my local garage using the optical thingy. There is a
similar (? same) gadget for anti-freeze is there not?
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Hi Peter

Check the earth of the battery and starter for rust/dirt. It could be
that your batteries are still fine but that it's not earthed well enough
to deliver the surge necessary to start the cruiser.

Hope this fixes it for you...

paul


________________________________
From: [Email address removed] [mailto:[Email address removed]]
On Behalf Of Peter Browning
Sent: 11 December 2006 10:09
To: [Email address removed]
Subject: [ELCO] Battery / alternator test
I'm damn sure this has been posted before but now that I need it I can't
find it.

How can I test to determine whether I have a knackered battery or a
knackered alternator (or maybe even both?

The cruiser is not used much at the moment - maybe once a week. A couple
of weeks ago I had a dead battery, totally dead, not a glimmer. I
charged it up for a day on trickle charge and it was fine, I used it a
couple of days and it started perfectly OK.

It was then left for best part of a week until I came to use it
yesterday when there was some charge in the battery but not enough to
turn the starter. I started it from a starter pack and did the usual
battery loading before disconnecting the pack. The need was urgent so I
drove off for a twenty mile drive after which I was sure I'd have
sufficient charge to restart a warm engine - no such luck! I stopped
with the engine off for ten minutes and then went to restart and......
nothing. I had to jump it.

So, I'm not sure whether I have a duff battery or a duff alternator.
Obviously I could take the battery out and take to an auto electrics
place for testing but is there an in-situ test that I can do to check
which it is? I have a multimeter but no other diagnostic gear.

Should I charge the battery for a day before testing?

Any advice gratefully received.

Pete
1995 FZJ 80 Auto
[Email address removed] (email and MSN)



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Guest

Guest
Thanks everyone.

I=92ll have a look at it tomorrow.

Pete
1995 FZJ 80 Auto
HYPERLINK "mailto:[Email address removed]"[Email address removed]
(email and MSN)

We would not seek a battle as we are, yet as we are, we say we will not shun
it.



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Guest

Guest
Well, it appears that neither the battery nor the alternator are at fault.
So I have to start hunting for an excessive idle power drain now.
Pete
1995 FZJ 80 Auto
HYPERLINK "mailto:[Email address removed]"[Email address removed]
(email and MSN)
We would not seek a battle as we are, yet as we are, we say we will not shun
it.
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No virus found in this outgoing message.
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18:13
 
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