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Charging/ Electronic Question



 
 
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  #1 (permalink)  
Old July 8th 03, 02:48 PM posted to uk.rec.caravanning
Paul
external usenet poster
 
Posts: 54
Default Charging/ Electronic Question

If I had a battery that has a charging system in place and decided to add
another charge source say solar, if we were on mains so the charger is
delivering 14v or whatever and it was a sunny day and solar was delivering
some sort of charge will the two methods upset each other?

I know a diode will stop one voltage damaging the opposite source but what
about the differance in voltage?

Would you have to fit some type of manager that will allow charging from one
source only?

Now I think about it, this type of thing could happen if you were on site
with mains and the car still plugged in with engine running.

Hope there is someone out there who can straighten the random thoughts that
are meandering through my head at this time.

Many thanks

Paul


Ads
  #3 (permalink)  
Old July 8th 03, 06:43 PM posted to uk.rec.caravanning
Tony Maris
external usenet poster
 
Posts: 161
Default Charging/ Electronic Question

Hi Paul,

The only time I've had to resolve a potential problem like this was when
fitting a wind generator for a customer. We fitted a Rutland 913 which is
capable of supplying fairly high voltages in certain wind conditions. Up to
around 20 volts IIRC. This would not do the battery a lot of good!

We installed a Marlec voltage regulator into the system. This was capable
of handling two separate batteries and could handle solar panel supply in
addition to the wind generator. Don't ask me how it did it, all I did was
fit it. I know it works though......

Regards

--
Tony M
Towbars & Trailers
Chesterfield
Specialists in Towing Equipment
NTTA Council Member
http://www.towitall.co.uk
QSA accredited for Towbars and Trailers



"Paul" wrote in message
...
If I had a battery that has a charging system in place and decided to add
another charge source say solar, if we were on mains so the charger is
delivering 14v or whatever and it was a sunny day and solar was delivering
some sort of charge will the two methods upset each other?

I know a diode will stop one voltage damaging the opposite source but what
about the differance in voltage?

Would you have to fit some type of manager that will allow charging from

one
source only?

Now I think about it, this type of thing could happen if you were on site
with mains and the car still plugged in with engine running.

Hope there is someone out there who can straighten the random thoughts

that
are meandering through my head at this time.

Many thanks

Paul




  #4 (permalink)  
Old July 10th 03, 11:07 AM posted to uk.rec.caravanning
Mike Williams
external usenet poster
 
Posts: 56
Default Charging/ Electronic Question

"Paul" wrote in message
...

This power supply has a 0.5 ohm 55w resistor in series with the output of
the Thyristor feeding the battery (which has fried along with the other
bits) so your answer makes it clearer as to what its for.


Actually I haven't had many dealings with switched mode chargers (although I
have had a lot of experience with high power standard regulation chargers
and thyristor switched mode power controllers that drive fork lift truck
traction motors at variable speeds by switching the battery supply to them).
That stuff was over twenty years ago, though, and I think I have now
forgotten most of what I knew then!

By the way, was your charger that "fired itself to death" an old unit? I
would imagine that these days manufacturers would use a choke / freewheel
diode combination rather than a resistor, which would smooth the output
current pulses as well as controlling their average value without losing (or
"burning") any significant amount of energy in the process, especially if
the thyristor control unit is designed to deliver multiple separate small
pulses within each "top of the sinewave" portion rather than the simpler
single pulse per wave.

Anyway, I'm pleased that my explanation was of some help to you. Actually it
was a very simplified explanation (no long stories on the newsgroups!) and
things are a bit more complex than that for various reasons, not the least
of which is the fact that the transformer secondary in combination with the
rectifier provides a full wave rectified sine wave output and any standard
DC voltmeter you use to measure the "no load" output will merely tell you
the average value of that, which is significantly less than its peak value.
The actual voltage output available to charge the battery is the portion of
the rectified sine wave that "lies above" the opposing battery voltage. This
effective charging voltage is a 100 Hz pulse waveform and in a switched mode
battery charger it is the thyristor (or other controller) that switches
"portions" of that pulse waveform to the battery. Maybe that makes things a
little clearer for you.

As I have already said, my knowledge of electronics and related stuff is
receding into the mists of time, so I hope that anyone who might wish to
pick me up on the finer points will remember that fact and will make
allowances for my age :-)

Mike




  #5 (permalink)  
Old July 10th 03, 03:47 PM posted to uk.rec.caravanning
Paul
external usenet poster
 
Posts: 54
Default Charging/ Electronic Question


"Mike Williams" wrote in message
...
"Paul" wrote in message
...

This power supply has a 0.5 ohm 55w resistor in series with the output

of
the Thyristor feeding the battery (which has fried along with the other
bits) so your answer makes it clearer as to what its for.


Actually I haven't had many dealings with switched mode chargers (although

I
have had a lot of experience with high power standard regulation chargers
and thyristor switched mode power controllers that drive fork lift truck
traction motors at variable speeds by switching the battery supply to

them).
That stuff was over twenty years ago, though, and I think I have now
forgotten most of what I knew then!

By the way, was your charger that "fired itself to death" an old unit? I
would imagine that these days manufacturers would use a choke / freewheel
diode combination rather than a resistor, which would smooth the output
current pulses as well as controlling their average value without losing

(or
"burning") any significant amount of energy in the process, especially if
the thyristor control unit is designed to deliver multiple separate small
pulses within each "top of the sinewave" portion rather than the simpler
single pulse per wave.

Anyway, I'm pleased that my explanation was of some help to you. Actually

it
was a very simplified explanation (no long stories on the newsgroups!) and
things are a bit more complex than that for various reasons, not the least
of which is the fact that the transformer secondary in combination with

the
rectifier provides a full wave rectified sine wave output and any standard
DC voltmeter you use to measure the "no load" output will merely tell you
the average value of that, which is significantly less than its peak

value.
The actual voltage output available to charge the battery is the portion

of
the rectified sine wave that "lies above" the opposing battery voltage.

This
effective charging voltage is a 100 Hz pulse waveform and in a switched

mode
battery charger it is the thyristor (or other controller) that switches
"portions" of that pulse waveform to the battery. Maybe that makes things

a
little clearer for you.

As I have already said, my knowledge of electronics and related stuff is
receding into the mists of time, so I hope that anyone who might wish to
pick me up on the finer points will remember that fact and will make
allowances for my age :-)

Mike


The power supply is not very old probally 3 years however, it is from
accross the water where in a lot of case kiss rules. 3 phase 30A supplies
on camp grounds are not uncommon. The electronics look very basic but there
is a small circuit strapped to the thyristor doing the regulation.

I am not an electronics engineer, however I am a computer engineer and
before PCs took over I used scopes and frequency meters to fix computers and
peripherals - show me what wave form to find on a given pin and I'm off.

I got the scope on the power supply before opening up and of course a full
sine wave leaped out. I'm not sure what killed the supply battery cooked
first and damaged the supply or the other way round. Once I have replaced
the big fat components then we will see if the regulator circuit has suffer
the same fate.

The problem I see with this unit is that the battery will be supplied a
charge voltage all the time, required or not. The charger in my van gives a
six hour boost then turns off if the battery voltage shows a full charge.

The thing that would annoy me about this unit is a sodding great transformer
buzzing all night.

So when you talk about the 100Hz pulse that should show up on a scope if I
ever get this thing going. The truth is the owner is too tight to buy a 30A
supply/battery charger, I hope he doesn't have news group access!!!

Thanks once again, --- I would appreciate any light spread on the unit
providing a voltage for charge all the time. I appreciate the current drawn
will diminish as the battery takes a charge but what this voltage?

Paul


  #6 (permalink)  
Old July 10th 03, 05:48 PM posted to uk.rec.caravanning
Mike Williams
external usenet poster
 
Posts: 56
Default Charging/ Electronic Question

"Paul" wrote in message
...

So when you talk about the 100Hz pulse that should show up
on a scope if I ever get this thing going . . .


It all depends on the precise design of the unit and it is difficult to say
what operational waveforms you should get at the various points without
seeing a circuit diagram of the charger and perhaps a circuit description.
However, if it is a simple full wave rectified output connected via a single
thyristor and a 0.5 ohm resistor to the battery (which I suspect it might be
in your case) then it is quite likely that the thyristor control circuit
simply waits a variable amount of time from the start time of each of the
100 Hz charging "pulse" voltages and triggers to the on condition some time
between the start and end of the pulse period. The thyristor would, of
course, automatically turn itself off again at the end of each of the 100 Hz
pulse waveforms when the instantaneous current through it dropped to zero.
The control circuit could vary the avarage output current simply by varying
the amount of time that it waits from the start of each pulse. This "varying
amount of waiting time" could itself be controlled by the circuit in all
sorts of ways by monitoring the elapsed time or the battery terminal voltage
or both of these. There can be a lot more to it than this, of course, if the
charging circuit is a more complex design.

You haven't said which compents have burned out on the unit, so the best
thing (if it is a simple circuit of the kind I have suggested) is to simply
bypass the thyristor and temporarily swap the 0.5 ohm 55 watt resistor for a
4.7 Ohm 7 watt resistor (so that you simply have the transformer secondary,
the full wave bridge rectifier, the 4.7 ohm resistor and the battery in
circuit and run it and see how it goes. It is a wild guess, of course, but
the fact that the existing resistor is rated at 55 watts suggests to me that
the maximum average charging voltage (the "top bits" of the rectified sine
wave when a line showing the battery voltage is drawn across the sine
waveform) have an average value of about five volts or so and that the
maximum charger output current is less than about ten amps. So, with the
thyristor bypassed and the 4.7 Ohm resistor in circuit you should expect to
measure a battary charge current of about one amp and your 'scope should see
the 100 Hz pulses across the resistor. At least in that way you will be able
to see that the transformer and the rectifier are working properly. If you
then get the thyristor and control circuitry working again and refit the
original 0.5 ohm resistor you should then see the same 100 Hz pulse waveform
across the "thyristor and resistor series pair" with similar (but less wide)
100 Hz pulses being measured across the resistor alone showing that the
thyristor is trigerring into the on condition some way into each pulse under
the influence of the control circuitry.

Thanks once again, --- I would appreciate any light spread on
the unit providing a voltage for charge all the time. I appreciate
the current drawn will diminish as the battery takes a charge
but what this voltage?


It isn't normal for any half decent charger to remain fully on permanently,
even though the charge current will reduce as the battery voltage increases.
The cheap and nasty chargers that you buy from the average car shop do
exactly that, but I would certainly never use such a beast myself. These
chargers (simple "on all the time" chargers) rely on the charge reducing to
a trickle as the battery gets to 14 volts and above and so they are designed
such that the peak value of the rectified output voltage is fairly low. This
causes them to undercharge batteries in places where the mains voltage is a
bit on the low side and to overcharge them in places where the mains voltage
is high. If your unit was such a charger then the manufacturers wouldn't
have bothered to include a thyristor circuit (unless they are simply using
the thyristor as a temperature sensed "crowbar" protection, which I very
much doubt). It is more likely that your unit controls the pulse rate (or
the delay time that I have already mentioned) so that the charge current is
initially high and then reduces to a much lower value once the battery
reaches 2.35 volts per cell. It may then carry on with this lower
"equalising" current for a pre determined time and then may reduce the
average charging current still further, to a trickle charge. It's hard to
say without seeing the full circuit diagram, and so much of this is purely
guess work on my part. (Actually, it's nearly all guess work!).

By the way, you said that the charger was of foreign make (I can't recall
where you said it came from). I take it that it is not a 110 volt unit being
driven by our 240 volts mains!

Mike



  #7 (permalink)  
Old July 10th 03, 08:22 PM posted to uk.rec.caravanning
Capitol
external usenet poster
 
Posts: 31
Default Charging/ Electronic Question

Very sound suggestions. If it's a US unit, it originally will have been
designed for 85-135V operation. Their mains supplies are less well
controlled than ours. They would simply change the xfmr for 240V operation.
New designs are using switched mode power factor correction circuitry if the
power level is 80W. Sorting out one of these can be extremely difficult.
Regards
Capitol

Mike Williams wrote in message ...
"Paul" wrote in message
...

So when you talk about the 100Hz pulse that should show up
on a scope if I ever get this thing going . . .



By the way, you said that the charger was of foreign make (I can't recall
where you said it came from). I take it that it is not a 110 volt unit

being
driven by our 240 volts mains!

Mike





  #8 (permalink)  
Old July 11th 03, 08:55 AM posted to uk.rec.caravanning
Paul
external usenet poster
 
Posts: 54
Default Charging/ Electronic Question


"Mike Williams" wrote in message
...
"Paul" wrote in message
...

You haven't said which compents have burned out on the unit,


Both rectifying diodes and the thyristor were open circuit in all directions
and the resistor had burned out.

so the best
thing (if it is a simple circuit of the kind I have suggested) is to

simply
bypass the thyristor and temporarily swap the 0.5 ohm 55 watt resistor for

a
4.7 Ohm 7 watt resistor (so that you simply have the transformer

secondary,
the full wave bridge rectifier, the 4.7 ohm resistor and the battery in
circuit and run it and see how it goes. It is a wild guess, of course, but
the fact that the existing resistor is rated at 55 watts suggests to me

that
the maximum average charging voltage (the "top bits" of the rectified sine
wave when a line showing the battery voltage is drawn across the sine
waveform) have an average value of about five volts or so and that the
maximum charger output current is less than about ten amps. So, with the
thyristor bypassed and the 4.7 Ohm resistor in circuit you should expect

to
measure a battary charge current of about one amp and your 'scope should

see
the 100 Hz pulses across the resistor. At least in that way you will be

able
to see that the transformer and the rectifier are working properly. If you
then get the thyristor and control circuitry working again and refit the
original 0.5 ohm resistor you should then see the same 100 Hz pulse

waveform
across the "thyristor and resistor series pair" with similar (but less

wide)
100 Hz pulses being measured across the resistor alone showing that the
thyristor is trigerring into the on condition some way into each pulse

under
the influence of the control circuitry.

Thanks once again, --- I would appreciate any light spread on
the unit providing a voltage for charge all the time. I appreciate
the current drawn will diminish as the battery takes a charge
but what this voltage?


It isn't normal for any half decent charger to remain fully on

permanently,
even though the charge current will reduce as the battery voltage

increases.
The cheap and nasty chargers that you buy from the average car shop do
exactly that, but I would certainly never use such a beast myself. These
chargers (simple "on all the time" chargers) rely on the charge reducing

to
a trickle as the battery gets to 14 volts and above and so they are

designed
such that the peak value of the rectified output voltage is fairly low.

This
causes them to undercharge batteries in places where the mains voltage is

a
bit on the low side and to overcharge them in places where the mains

voltage
is high. If your unit was such a charger then the manufacturers wouldn't
have bothered to include a thyristor circuit (unless they are simply using
the thyristor as a temperature sensed "crowbar" protection, which I very
much doubt). It is more likely that your unit controls the pulse rate (or
the delay time that I have already mentioned) so that the charge current

is
initially high and then reduces to a much lower value once the battery
reaches 2.35 volts per cell. It may then carry on with this lower
"equalising" current for a pre determined time and then may reduce the
average charging current still further, to a trickle charge. It's hard to
say without seeing the full circuit diagram, and so much of this is purely
guess work on my part. (Actually, it's nearly all guess work!).

By the way, you said that the charger was of foreign make (I can't recall
where you said it came from). I take it that it is not a 110 volt unit

being
driven by our 240 volts mains!

Mike

I have e-mailled you a rough!! circuit diagram. The battery gets fed by the
little circuit board when on mains. I have to get the unit back here and
draw up the charge circuit but for now and as the owner wants the swamp
cooler working rather than the battery being charge priority is to get the
PSU working, charging later.

When the components arrive I shall see how much other damage there was ---
in actual fact there is not alot else in the thing.

Paul


  #9 (permalink)  
Old July 11th 03, 09:01 AM posted to uk.rec.caravanning
Paul
external usenet poster
 
Posts: 54
Default Charging/ Electronic Question


"Capitol" wrote in message
...
Very sound suggestions. If it's a US unit, it originally will have been
designed for 85-135V operation. Their mains supplies are less well
controlled than ours. They would simply change the xfmr for 240V

operation.
New designs are using switched mode power factor correction circuitry if

the
power level is 80W. Sorting out one of these can be extremely difficult.
Regards
Capitol

Mike Williams wrote in message ...
"Paul" wrote in message
...

So when you talk about the 100Hz pulse that should show up
on a scope if I ever get this thing going . . .



By the way, you said that the charger was of foreign make (I can't recall
where you said it came from). I take it that it is not a 110 volt unit

being
driven by our 240 volts mains!

Mike

The unit was modified, well they wired up different windings on the xformer
for 220/240v.

The unit has been in use on european mains for 2-3 years

Paul


  #10 (permalink)  
Old July 11th 03, 09:59 AM posted to uk.rec.caravanning
Mike Williams
external usenet poster
 
Posts: 56
Default Charging/ Electronic Question

"Capitol" wrote in message
...

New designs are using switched mode power factor correction
circuitry if the power level is 80W. Sorting out one of these
can be extremely difficult.


Yeah. Influenced by the Americans, no doubt. Power factor correction has
always been important over here too, of course, in industrial situations,
but for the sort of loads we are talking about I think that it's a bit of
overkill. Mind you, power factor correction is much more important on their
mains than it is on ours, so they probably have more of a "thing" about it.
It is never a bad thing, of course. It's just that to me, at least for the
sort of loads we are talking about, it makes the circuit more complicated
and (almost by definition!) more likely to go wrong!

Mike




 



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