The brother-in-law has an old car that he wanted to take to the breakers
yard and asked if I could charge the battery. It had been stood for
several months without starting so was flatter than a witches tit. I
measured the voltage at the terminals and it read 1.6volts. I said it
may be too far knackered but would give it a try. I have 2 battery
chargers, one is a new 3 phase charger from Lidl and the other a donkeys
years old basic 6amp charger with switchable 6 or 12 volts.

I tried to charge using the new 3 phase charger but it would not even
come out of standby mode. I then tried the old 6amp charger and when I
switched it on the needle on the amp meter started to rise & rise and
went completely off the scale. It was only connected for a few moments
and when I measured the battery voltage it now read over 13v so I
disconnected the old charger and reconnected the new 3 phase charger and
it now went into charge mode and was fully charged about 15 hours later.

I think this has damaged the old charger as when I now try and connect
the charger leads to a battery it causes a short with loads of sparks
(this is before the charger is switched on). If I switch on the charger
without the leads connected the charger makes a clicking sound as though
it's continually cutting on & off. I'm guessing that trying to charge a
battery so flat has forced more current from the charger than it was
designed to give? Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.

Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.


I guess you old charger contains nothing more than a big transformer and a
bridge rectifier. The rectifier contains 4 diodes to convert the AC from the
transformer to the DC for the battery. If one of the diodes goes short
circuit then you will get the effect you are seeing.

If you really want to resurrect the charger you could probably replace the
old bridge rectifier with a new one from Maplins for couple of quid (AR84F
looks suitable). But as modern cars and batteries are more susceptible to
mistreatment I would be tempted to just get rid of it.

Chris

"redwood" wrote in message
...
The brother-in-law has an old car that he wanted to take to the breakers
yard and asked if I could charge the battery. It had been stood for
several months without starting so was flatter than a witches tit. I
measured the voltage at the terminals and it read 1.6volts. I said it
may be too far knackered but would give it a try. I have 2 battery
chargers, one is a new 3 phase charger from Lidl and the other a donkeys
years old basic 6amp charger with switchable 6 or 12 volts.

I tried to charge using the new 3 phase charger but it would not even
come out of standby mode. I then tried the old 6amp charger and when I
switched it on the needle on the amp meter started to rise & rise and
went completely off the scale. It was only connected for a few moments
and when I measured the battery voltage it now read over 13v so I
disconnected the old charger and reconnected the new 3 phase charger and
it now went into charge mode and was fully charged about 15 hours later.

I think this has damaged the old charger as when I now try and connect
the charger leads to a battery it causes a short with loads of sparks
(this is before the charger is switched on). If I switch on the charger
without the leads connected the charger makes a clicking sound as though
it's continually cutting on & off. I'm guessing that trying to charge a
battery so flat has forced more current from the charger than it was
designed to give? Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.

Older battery chargers are usually very basic, generally consisting of a
mains transformer, rectifier, ammeter, and a fuse... I'd guess by the sound
of it that the rectifier has gone short circuit.

"Chris" wrote in message
...
Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.


I guess you old charger contains nothing more than a big transformer
and a bridge rectifier. The rectifier contains 4 diodes to convert the
AC from the transformer to the DC for the battery. If one of the
diodes goes short circuit then you will get the effect you are seeing.

If you really want to resurrect the charger you could probably replace
the old bridge rectifier with a new one from Maplins for couple of
quid (AR84F looks suitable). But as modern cars and batteries are more
susceptible to mistreatment I would be tempted to just get rid of it.

Thanks for the quick replies. I have now taken the back off and yes it
does look very basic inside. I can see the rectifier which has 4
connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield). It has writing on the rectifier which says;

S4VB
10 (Hole) 84

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.

On Fri, 01 Dec 2006 20:15:54 -0000, redwood wrote:

"Chris" wrote in message
...
Before I take a look inside (or bin the thing) I just
wondered if anyone had an idea what might have gone kaput.


I guess you old charger contains nothing more than a big transformer
and a bridge rectifier. The rectifier contains 4 diodes to convert the
AC from the transformer to the DC for the battery. If one of the diodes
goes short circuit then you will get the effect you are seeing.

If you really want to resurrect the charger you could probably replace
the old bridge rectifier with a new one from Maplins for couple of quid
(AR84F looks suitable). But as modern cars and batteries are more
susceptible to mistreatment I would be tempted to just get rid of it.

Thanks for the quick replies. I have now taken the back off and yes it
does look very basic inside. I can see the rectifier which has 4
connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield). It has writing on the rectifier which says;

S4VB
10 (Hole) 84

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.


Nope, that'll be fine.

redwood wrote:

connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield).

That wil be a heat*sink* - deisnged to help cool the rectifier. You will
need to fit something similar to the replacement part.

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.

Bigger (in this application) will be fine.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article ,
"redwood" writes:

Thanks for the quick replies. I have now taken the back off and yes it
does look very basic inside. I can see the rectifier which has 4
connectors and a hole in the middle screwed into a thin sheet of metal
(or is that a heatshield). It has writing on the rectifier which says;

S4VB
10 (Hole) 84

I'm guessing that the 10 refers to 10amp (84 could be the year?). I've
looked at the Maplin code for AR84F and that is 25A. Would it cause any
problems using a higher amp or is it best to keep with a 10A? Cheers.

S4VB is a 4A bridge rectifier, and the 10 means 100V working.

A 10A or higher (50V or higher) bridge rectifier will be fine.
(A 4A bridge rectifier was obviously inadiquate.)
I would also get some heat sink compound to smear between the
new rectifier and the heatsink.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
S4VB is a 4A bridge rectifier, and the 10 means 100V working.

A 10A or higher (50V or higher) bridge rectifier will be fine.
(A 4A bridge rectifier was obviously inadiquate.)
I would also get some heat sink compound to smear between the
new rectifier and the heatsink.

Got the rectifier from my local Maplins and is now fitted. It's twice
the size of the original with bigger spade connectors so had to replace
the ends of the 4 wires. It was a bit confusing knowing which way round
the - wires go as the only markings on the new rectifier only displayed
on one side showing the AC & +. Going round in a clockwise direction,
if the 1st terminal is AC+, the 2nd terminal is DC+, I connected the 3rd
terminal to AC-, and the 4th terminal to DC-

I've not yet tried it connected to a battery but it now powers on
without clicking and connecting a DVM to the croc clips shows around
12.06v or 6.02 on the 6 volt setting. I shall give it a test on a
battery tomorrow.

On Sat, 02 Dec 2006 15:20:13 -0000, redwood wrote:

"Andrew Gabriel" wrote in message
S4VB is a 4A bridge rectifier, and the 10 means 100V working.

A 10A or higher (50V or higher) bridge rectifier will be fine.
(A 4A bridge rectifier was obviously inadiquate.)
I would also get some heat sink compound to smear between the
new rectifier and the heatsink.

Got the rectifier from my local Maplins and is now fitted. It's twice
the size of the original with bigger spade connectors so had to replace
the ends of the 4 wires. It was a bit confusing knowing which way round
the - wires go as the only markings on the new rectifier only displayed
on one side showing the AC & +. Going round in a clockwise direction,
if the 1st terminal is AC+, the 2nd terminal is DC+, I connected the 3rd
terminal to AC-, and the 4th terminal to DC-


That should be right.

I've not yet tried it connected to a battery but it now powers on
without clicking and connecting a DVM to the croc clips shows around
12.06v or 6.02 on the 6 volt setting. I shall give it a test on a
battery tomorrow.

"Duncan Wood" wrote in message
newsp.tjxupjhyyuobwl@lucy...
On Sat, 02 Dec 2006 15:20:13 -0000, redwood wrote:

"Andrew Gabriel" wrote in message
S4VB is a 4A bridge rectifier, and the 10 means 100V working.

A 10A or higher (50V or higher) bridge rectifier will be fine.
(A 4A bridge rectifier was obviously inadiquate.)
I would also get some heat sink compound to smear between the
new rectifier and the heatsink.

Got the rectifier from my local Maplins and is now fitted. It's twice
the size of the original with bigger spade connectors so had to replace
the ends of the 4 wires. It was a bit confusing knowing which way round
the - wires go as the only markings on the new rectifier only displayed
on one side showing the AC & +. Going round in a clockwise direction,
if the 1st terminal is AC+, the 2nd terminal is DC+, I connected the 3rd
terminal to AC-, and the 4th terminal to DC-


That should be right.

I've not yet tried it connected to a battery but it now powers on
without clicking and connecting a DVM to the croc clips shows around
12.06v or 6.02 on the 6 volt setting. I shall give it a test on a
battery tomorrow.

Is your meter reasonably accurate?
These voltage readings seem rather low.

Sylvain.