Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

On Sat, 24 Mar 2012 12:25:02 -0400, wrote:

On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

OK, except I can't see anything inside the charger that looks like a
rectifier: aside from the main transformer, there is just a small
coil of wire (the buzzer?) and a 6V/12V switch.

On Sat, 24 Mar 2012 12:39:01 -0400, Gary wrote:

On Sat, 24 Mar 2012 12:25:02 -0400, wrote:

On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

OK, except I can't see anything inside the charger that looks like a
rectifier: aside from the main transformer, there is just a small
coil of wire (the buzzer?) and a 6V/12V switch.

Depending on the age of the charger, it could have a selenium
rectifier (looks like a stack of square or round metal plates wih
washers between them) or it could use solid state diode(s). Depending
on the amp rating of the charger, a solid state diode(usually silicon)
coud be stud mounted or it could look like a "blob" on a wire.

When the selenium rectifier in an old adjustable EICO 6/12 volt
battery eliminator/charger (that I've had for years) finally died, I
replaced it with a silicon bridge rectifier on a heat sink. The
maximum output voltage is now higher, thanks to the differece in
voltage drop across a silicon diode (0.6 volt reardless of load)
versus the several volt drop (that increases with load) across the
original selenium rectifier.

You need DC (even if it's unfiltered) to charge a battery - AC won't
work.

On Sat, 24 Mar 2012 13:07:44 -0400, wrote:

On Sat, 24 Mar 2012 12:39:01 -0400, Gary wrote:

On Sat, 24 Mar 2012 12:25:02 -0400, wrote:

On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

OK, except I can't see anything inside the charger that looks like a
rectifier: aside from the main transformer, there is just a small
coil of wire (the buzzer?) and a 6V/12V switch.

Depending on the age of the charger, it could have a selenium
rectifier (looks like a stack of square or round metal plates wih
washers between them) or it could use solid state diode(s). Depending
on the amp rating of the charger, a solid state diode(usually silicon)
coud be stud mounted or it could look like a "blob" on a wire.

When the selenium rectifier in an old adjustable EICO 6/12 volt
battery eliminator/charger (that I've had for years) finally died, I
replaced it with a silicon bridge rectifier on a heat sink. The
maximum output voltage is now higher, thanks to the differece in
voltage drop across a silicon diode (0.6 volt reardless of load)
versus the several volt drop (that increases with load) across the
original selenium rectifier.

You need DC (even if it's unfiltered) to charge a battery - AC won't
work.

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger - what exactly did you mean?

Any reason why AC can't be used to charge a car battery?

No, not if you don't mind the battery exploding and spraying hot sulfuric
acid in your face.

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal of the battery.

I urge you NOT to do this. There is no guarantee this charger will correctly
charge your battery. Find someone knowledgeable to help you. Or pay a
service shop to charge the battery. Or buy a new, working charger.

On 3/24/2012 9:25 AM, wrote:
On Sat, 24 Mar 2012 12:12:39 -0400, wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

How do you know it's putting out AC?

For an AC input, a typical voltmeter will show the voltage
on an AC scale, but about zero on a DC scale.

Rectified, but unfiltered DC will show significant readings on
both AC and DC scales.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

This is a risky experiment.
OP says he thinks it's putting out AC. If that's an accurate
statement, like due to a shorted diode, be prepared for an exploded
cap.

I tried to come up with an answer to the original question,
"why AC can't be used to charge a car battery?"

I couldn't think of an answer that would not require a complete
explanation of the difference between AC and DC. Closest thing
I could think of was, "AC goes negative every cycle and batteries can't."

On Mar 24, 9:39*am, Gary wrote:
On Sat, 24 Mar 2012 12:25:02 -0400, wrote:
On Sat, 24 Mar 2012 12:12:39 -0400, Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? *Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

OK, except I can't see anything inside the charger that looks like a
rectifier: *aside from the main transformer, there is just a small
coil of wire (the buzzer?) and a 6V/12V switch.

Think: If you attempted to charge a battery with AC, the charge
deposited when the current swung positive would be discharged when the
current swung positive. All you would be doing is heating the battery,
not charging. Take out your ohmmeter and look to see if there's a
diode between any two points.

Also, look for modifications. When I was a sprout, we had a battery
charger purported to rejuvenate the carbon zinc cells of the day. The
light went out, and the charger quit charging. Not knowing any better,
to make it work, I jumpered the light, which apparently acted as the
charge current regulator. At which point the diode went "Sproing."
Somebody might have taken your charger's diode out in the belief it
would improve things.

Gary wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.
yeah sure, put the battery on a turn table and electrodes off the side
and the spin the table at 50/60hz, what ever your country system is.

Have this magical little charger of yours make contact on the
electrodes at the appropriate time.

or, one could simply get a bridge rectifier and maybe a resistor
(ballast) for current limiting.


Jamie

On Sat, 24 Mar 2012 10:39:01 -0700, mike wrote:

On 3/24/2012 9:25 AM, wrote:
On Sat, 24 Mar 2012 12:12:39 -0400, wrote:

Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

How do you know it's putting out AC?

For an AC input, a typical voltmeter will show the voltage
on an AC scale, but about zero on a DC scale.

That's what I'm getting.

Rectified, but unfiltered DC will show significant readings on
both AC and DC scales.

More likely, the charger puts out rectified but unfiltered DC.

Put a 100mf 30 volt capacitor on the output of the charger (watch
polarity) then measure the DC voltage.

If there is no DC voltage across the capacitor, then the rectifier(s)
in the charger are toast.

This is a risky experiment.
OP says he thinks it's putting out AC. If that's an accurate
statement, like due to a shorted diode, be prepared for an exploded
cap.

I tried to come up with an answer to the original question,
"why AC can't be used to charge a car battery?"

I couldn't think of an answer that would not require a complete
explanation of the difference between AC and DC. Closest thing
I could think of was, "AC goes negative every cycle and batteries can't."

I knew there was a good reason.

Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

If this thing is ac, you need a rectifier. Need more info. You also might
need current limiter.

I'm reminded of some old chargers we had in the army, in the battery room.
Big box with switched levels of pulsating voltage to control charge rate. I
think the transformer had multiple taps. Charged and cycled batteries about
the size of motorcycle batteries. These were for RCAT's , remote controlled
aircraft targets.

Greg

On 3/24/2012 10:32 AM, William Sommerwerck wrote:
OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal of the battery.

I urge you NOT to do this. There is no guarantee this charger will correctly
charge your battery. Find someone knowledgeable to help you. Or pay a
service shop to charge the battery. Or buy a new, working charger.

I agree ...why not just buy one? A real charger is not that expensive:
http://www.amazon.com/b?ie=UTF8&node=15707061

On Sat, 24 Mar 2012 10:32:31 -0700, "William Sommerwerck"
wrote:

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal of the battery.

I'm aware of that. I was asking about how the polarity of the AC
output affects how the capacitor should be placed?

I urge you NOT to do this. There is no guarantee this charger will correctly
charge your battery. Find someone knowledgeable to help you. Or pay a
service shop to charge the battery. Or buy a new, working charger.

You're missing the point. Sometimes we play around with old, obsolete
kit, just to see if it'll work.

You said something about watching the polarity across
the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal
of the battery.

I'm aware of that. I was asking about how the polarity of the
AC output affects how the capacitor should be placed?

AC has no polarity.

gregz wrote in

rg:

Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

If this thing is ac, you need a rectifier. Need more info. You also
might need current limiter.

I'm reminded of some old chargers we had in the army, in the battery
room. Big box with switched levels of pulsating voltage to control
charge rate. I think the transformer had multiple taps. Charged and
cycled batteries about the size of motorcycle batteries. These were
for RCAT's , remote controlled aircraft targets.

Greg


you want to regulate the charge voltage,too.
go too high and you boil your electrolyte away,ruin your battery.

--
Jim Yanik
jyanik
at
localnet
dot com

On Mar 25, 6:13*pm, Jim Yanik wrote:
gregz wrote
rg:









Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? *Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

If this thing is ac, you need a rectifier. Need more info. You also
might need current limiter.

I'm reminded of some old chargers we had in the army, in the battery
room. Big box with switched levels of pulsating voltage to control
charge rate. I think the transformer had multiple taps. Charged and
cycled batteries about the size of motorcycle batteries. These were
for RCAT's , remote controlled aircraft targets.

Greg

you want to regulate the charge voltage,too.
go too high and you boil your electrolyte away,ruin your battery.


The car's electrical system is designed around a standard of 13.8 V, I
was always told. That's what one should shoot for, I would think.

Jim Yanik wrote:
gregz wrote in

rg:

Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

If this thing is ac, you need a rectifier. Need more info. You also
might need current limiter.

I'm reminded of some old chargers we had in the army, in the battery
room. Big box with switched levels of pulsating voltage to control
charge rate. I think the transformer had multiple taps. Charged and
cycled batteries about the size of motorcycle batteries. These were
for RCAT's , remote controlled aircraft targets.

Greg


you want to regulate the charge voltage,too.
go too high and you boil your electrolyte away,ruin your battery.

We used to have regulated supplies on some battery backup gear on NASA
equipment. We adjusted by the bubble method. You were supposed to cycle
them once in a while .

Greg

spamtrap1888 wrote:
On Mar 25, 6:13 pm, Jim Yanik wrote:
gregz wrote

rg:









Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

If this thing is ac, you need a rectifier. Need more info. You also
might need current limiter.

I'm reminded of some old chargers we had in the army, in the battery
room. Big box with switched levels of pulsating voltage to control
charge rate. I think the transformer had multiple taps. Charged and
cycled batteries about the size of motorcycle batteries. These were
for RCAT's , remote controlled aircraft targets.

Greg

you want to regulate the charge voltage,too.
go too high and you boil your electrolyte away,ruin your battery.


The car's electrical system is designed around a standard of 13.8 V, I
was always told. That's what one should shoot for, I would think.

That's true, but any electronic item must be designed to live at 16 volts.
I remember the specs on my datsun mechanical regulator, got up over 15
volts. 13.8 is maximum long term use, but you need higher voltage to fully
charge or overcharge to clear contamination.

Greg

On Sun, 25 Mar 2012 15:36:44 -0700, "William Sommerwerck"
wrote:

You said something about watching the polarity across
the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal
of the battery.

I'm aware of that. I was asking about how the polarity of the
AC output affects how the capacitor should be placed?

AC has no polarity.

Exactly my point. So does it matter how the capacitor is placed
across the output leads?

"Gary" wrote in message
...
On Sun, 25 Mar 2012 15:36:44 -0700, "William Sommerwerck"
wrote:

You said something about watching the polarity across
the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal
of the battery.

I'm aware of that. I was asking about how the polarity of
the AC output affects how the capacitor should be placed?

AC has no polarity.

Exactly my point. So does it matter how the capacitor is
placed across the output leads?

You wouldn't normally place a capacitor across /any/ device with an AC
output. The only obvious uses that come to mind would be for stability, or
to mop up high-frequency junk. Neither would be likely in a charger.

In article ,
Gary wrote:

I'm aware of that. I was asking about how the polarity of the
AC output affects how the capacitor should be placed?

AC has no polarity.

Exactly my point. So does it matter how the capacitor is placed
across the output leads?

No. If it's truly an AC output, the capacitor will explode equally
well with either orientation.

Unless I am missing something here, you're trying to do something
futile... you *cannot* charge a car battery using an AC waveform of
the sort you'd get out of a transformer. The net amount of charge
delivered into the battery will be zero, with or without a filter
capacitor... all you'll do is heat up the battery to no good effect,
and (if you install a filter capacitor) overheat the capacitor and
make it blast its guts out all over the room. This is spectacular but
not terribly useful :-)

You *must* rectify the AC (either half-wave or full-wave
rectification). Once you do so, you no longer have AC - you have a
pulsed DC.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
In article ,
Gary wrote:

I'm aware of that. I was asking about how the polarity of the
AC output affects how the capacitor should be placed?

AC has no polarity.

Exactly my point. So does it matter how the capacitor is placed
across the output leads?

No. If it's truly an AC output, the capacitor will explode equally
well with either orientation.

Unless I am missing something here, you're trying to do something
futile... you *cannot* charge a car battery using an AC waveform of
the sort you'd get out of a transformer. The net amount of charge
delivered into the battery will be zero, with or without a filter
capacitor... all you'll do is heat up the battery to no good effect,
and (if you install a filter capacitor) overheat the capacitor and
make it blast its guts out all over the room. This is spectacular but
not terribly useful :-)

You *must* rectify the AC (either half-wave or full-wave
rectification). Once you do so, you no longer have AC - you have a
pulsed DC.


Gary keeps ignoring this.

Greg

On Sun, 25 Mar 2012 17:42:53 -0400, Gary wrote:

On Sat, 24 Mar 2012 10:32:31 -0700, "William Sommerwerck"
wrote:

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger -- what exactly did you mean?

The plus output of the charger goes to the plus terminal of the battery.

I'm aware of that. I was asking about how the polarity of the AC
output affects how the capacitor should be placed?

I urge you NOT to do this. There is no guarantee this charger will correctly
charge your battery. Find someone knowledgeable to help you. Or pay a
service shop to charge the battery. Or buy a new, working charger.

You're missing the point. Sometimes we play around with old, obsolete
kit, just to see if it'll work.
To cut out a lot of the BS, there is a simple test you can perform.
Set a DMM to the 20VDC range and connect it to the output of the
battery charger. If you get a reading of over 14VDC the charger is
probably good. If you get a reading of a lower voltage, suspect the
charger is bad (unless there is a 6/12 switch). If you get a reading
of 0 VDC, but a reading of 12 -15 VAC, the rectifiers are shorted.

It MIGHT be possible that selenium rectifiers are so leaky that you
would not get a DC reading, but I would doubt it.

PlainBill

On Saturday, March 24, 2012 12:12:39 PM UTC-4, Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

You cannot charge a battery on AC. Battery chargers have to be properly current regulated at the nominal charging voltage for the battery. You do not want to have any kind of battery rupture, and especially a car battery! The acid will do a lot of damage.

Invest in a proper safe battery charger!

Jerry G.

"Gary" wrote in message ...

OK, I will try as you suggest. You said something about watching the
polarity across the output of the charger - what exactly did you mean?

I have rigged up all kinds of circuits as an elec tech, but this would be too risky for me. I would only use a commercial charger and even then would not make any modifications to it. Charging lead-acid batteries always produces hydrogen. Even a little spark or high temp can ignite an explosion which can spray sulfuric acid mist all over. I have never seen an explosion first hand, but have talked to a fellow who is super careful and even he blew one up years ago.

Too many warnings probably, but be sure and connect to the batter first before connecting the charger to the AC source. I also connect the charger to an ext cord, and then (several feet away) connect to the AC receptacle.

FYI, here's a photo of a $25 battery charger I have used for 10+ years. a good investment for other projects.

Battery exploding
http://www.youtube.com/watch?v=d_TnsHu2u4c

Battery getting damaged from improper charging
http://www.youtube.com/watch?v=1APmCDhnuVU

Schumacher 1.5A On-Board Charger Model SE-1-12S. Input 120VAC 4A 60HZ. Output 12VDC 1.5A:
http://imageshack.us/f/205/chargerki.jpg/

On 03/24/12 16:12, Gary wrote:
Hi everyone!

Any reason why AC can't be used to charge a car battery? Reason I'm
asking is that I have an old Fedtro Powerhouse charger
which is outputting AC.

Hopefully your face is in the car battery when it explodes, you stupid
*******.