sla charging schematics ?

[John Tserkezis]

terryc wrote:

Subject? Er, when I was in school they called it "Electronics". Who
would have thought? And that was starting in year 8 or 9 I think.

Wow, something useful,,,, or not. I thought it was mostly mickey mouse
subects now.

Well, that was then. Now, I have no idea. At my school, I heard they
canned the Electronics subject the year after I left, because the only
teacher teaching it had left, and no-one similarly trained filled their
place.

I can only presume he was replaced by a highly trained individual
teaching English, and how many times one can say the word "like" within
a sentence and still make sense.

They don't teach you, (and you don't have to know) the detailed
workings of the inndards of the component you're working with, basic
theory of operation is enough to get you by for now.

Circuit analysis, 2nd year uni for me.

Oh, perhaps things *have* changed. In my second year of TAFE, we were
learning about transistor theory. That is, what happens, and why it
does what it does at the molecular level. I'm quite sure it was dumbed
down a bit, but still.

This was perhaps a nearly 20 years ago, but I'm sure classic bipolar
transistor theory hasn't changed *that* much.

 

[John Tserkezis]

terryc wrote:

As John said. It is basically my undestanding of the level at which this
might be YOUR project. In which case, you should be able to do something
as basic as search the internet and find a circuit that could be used and/
or modified.

The point about school work is that you should do the work and learn from
it and this is actually a good project for that. You do not learn much,
if anything if it is dished up to you.

Well, that has been given to you anyway. Now your job is to build it.

Thank you. That was what I *meant* to say.

Clearly, diplomacy is not my strong point.

 

[John Tserkezis]

Charlie+ wrote:

Sorry in above post - for C200 Read L200 and here is any ole website from
search, with schematic ....
http://www.zen22142.zen.co.uk/Circuits/Power/l200.html

For that kind of pin count, I'd rather go for a switcher like an LM2576
or similar. You can have adjustable Vout max AND Imax, more current
capability than the L200, AND lower heatsink requirements to boot.

It would cost more, but the transformer/power supply would weigh with a
significant part of that anyway.

Would still cost more than a commercially built one of course, but
you'd learn a great deal.

On second thoughts, if you're currently dealing with the basics, this
might be a bit steep to design from scratch...

 

[ian field]

"mark krawczuk" <krawczuk@adam.com.au> wrote in message
news:YtedncSTb-DDk5LRnZ2dnUVZ_u6dnZ2d@adnap.net.au...

hi, after some schematics to charge 6 volt and 12 volt sla ( sealed lead
acid ) batteries.... basically dont need to charge them flat out , cause
they dont get used much, something i can leave on trickle charge for a
week or so , would be good....

any body have any or know of any links ?

For absolute simplicity there's the so called "wattless dropper" - used in
the fading days of valve TVs in the UK, a capacitor was used instead of a
dropper resistor in series with the 300mA heater chain.

It worked on the principle that Xc was high in comparison with Rl and
masquerades as a constant current source, IIRC the capacitance was 4.3uF for
the 300mA heater chain - its easy to find formula on the web to calculate
the capacitance to pass the current you want.

There are some pretty important safety cautions however, firstly; you have
to use a non reversible mains plug - the charger pretty much consists of
just a bridge rectifier and a capacitor, one AC terminal of the rectifier
goes to the mains neutral and the other goes via the capacitor to live - if
you reverse that the rectifier and battery will be at full mains potential!

The capacitor must be so rated that you could leave it connected permanently
across the mains without it blowing a hole in the side - X2 class mains
filter capacitors meet this requirement.

The bridge rectifier must be rated to take the full mains voltage otherwise
it will fail if the battery connection is broken.

Obviously from the above - if its plugged in with no battery the rectifier +
& - terminals will be live!

As such there is no voltage limiting, so you can use the charger for
recovering sulphated batteries (sealed LA or open).

 

[Grant]

On Thu, 10 Jun 2010 21:28:14 +0100, "ian field" <gangprobing.alien@ntlworld.com> wrote:

"mark krawczuk" <krawczuk@adam.com.au> wrote in message
news:YtedncSTb-DDk5LRnZ2dnUVZ_u6dnZ2d@adnap.net.au...
hi, after some schematics to charge 6 volt and 12 volt sla ( sealed lead
acid ) batteries.... basically dont need to charge them flat out , cause
they dont get used much, something i can leave on trickle charge for a
week or so , would be good....

any body have any or know of any links ?


For absolute simplicity there's the so called "wattless dropper" - used in
the fading days of valve TVs in the UK, a capacitor was used instead of a
dropper resistor in series with the 300mA heater chain.

It worked on the principle that Xc was high in comparison with Rl and
masquerades as a constant current source, IIRC the capacitance was 4.3uF for
the 300mA heater chain - its easy to find formula on the web to calculate
the capacitance to pass the current you want.

There are some pretty important safety cautions however, firstly; you have
to use a non reversible mains plug - the charger pretty much consists of
just a bridge rectifier and a capacitor, one AC terminal of the rectifier
goes to the mains neutral and the other goes via the capacitor to live - if
you reverse that the rectifier and battery will be at full mains potential!

The capacitor must be so rated that you could leave it connected permanently
across the mains without it blowing a hole in the side - X2 class mains
filter capacitors meet this requirement.

The bridge rectifier must be rated to take the full mains voltage otherwise
it will fail if the battery connection is broken.

Obviously from the above - if its plugged in with no battery the rectifier +
& - terminals will be live!

As such there is no voltage limiting, so you can use the charger for
recovering sulphated batteries (sealed LA or open).

A project for seriously dedicated people who are immune from shock?

I use cap droppers for some low-level (nightlight) LED lighting, one
still should have a resistor in dropper the chain to limit spike
current. No bridge needed for LEDs, just wire identical LEDs in
inverse parallel. The 50Hz (over here) flicker is noticeable at
times.

I'm tempted to see what 240V rectified through high impedance can do
for a sulphated battery One could setup some LEDs to indicate
rough voltage across the battery, the thing is cured when voltage
drops below about 16V for a 12V battery. I've read only about 30%
can be recovered, this is a cheap way to try that. An isolating
transformer (maybe stepdown to 115V too) might be safer, saner...

Grant.
--
http://bugs.id.au/

 

[mark krawczuk]

well, what are you on here for ????

anyways , if you want to know, i have 2 sla batteries, a 6 volt and a 12
volt..
and IF YOU READ my earlier post , i was looking sorta, for a specific
schematic for charging them .

did i ask you to design one ? NO

did i ask you to build me one ? NO

did i ask you for the parts ? NO

SO TELL ME L, , WHAT HOME WORK WAS IT THAT YOU WHERE GOING TO DO FOR ME ?


did you help your kids with their homework ? if you didnt , well, what can i
say.... ???



"John Tserkezis" <jt@techniciansyndrome.org.invalid> wrote in message
news:4c108762$0$17178$afc38c87@news.optusnet.com.au...

mark krawczuk wrote:

its not a school project , and so what if it was ????

I'm not doing your homework for you.

The answers you seek are available on the net, which you clearly have
access to since you're posting on newsgroups.

 

[ian field]

"Grant" <omg@grrr.id.au> wrote in message
news:teu2161f5u2197romh1oc51dufo5jpir0r@4ax.com...

On Thu, 10 Jun 2010 21:28:14 +0100, "ian field"
gangprobing.alien@ntlworld.com> wrote:


"mark krawczuk" <krawczuk@adam.com.au> wrote in message
news:YtedncSTb-DDk5LRnZ2dnUVZ_u6dnZ2d@adnap.net.au...
hi, after some schematics to charge 6 volt and 12 volt sla ( sealed
lead
acid ) batteries.... basically dont need to charge them flat out ,
cause
they dont get used much, something i can leave on trickle charge for a
week or so , would be good....

any body have any or know of any links ?


For absolute simplicity there's the so called "wattless dropper" - used in
the fading days of valve TVs in the UK, a capacitor was used instead of a
dropper resistor in series with the 300mA heater chain.

It worked on the principle that Xc was high in comparison with Rl and
masquerades as a constant current source, IIRC the capacitance was 4.3uF
for
the 300mA heater chain - its easy to find formula on the web to calculate
the capacitance to pass the current you want.

There are some pretty important safety cautions however, firstly; you have
to use a non reversible mains plug - the charger pretty much consists of
just a bridge rectifier and a capacitor, one AC terminal of the rectifier
goes to the mains neutral and the other goes via the capacitor to live -
if
you reverse that the rectifier and battery will be at full mains
potential!

The capacitor must be so rated that you could leave it connected
permanently
across the mains without it blowing a hole in the side - X2 class mains
filter capacitors meet this requirement.

The bridge rectifier must be rated to take the full mains voltage
otherwise
it will fail if the battery connection is broken.

Obviously from the above - if its plugged in with no battery the rectifier
+
& - terminals will be live!

As such there is no voltage limiting, so you can use the charger for
recovering sulphated batteries (sealed LA or open).

A project for seriously dedicated people who are immune from shock?
I use cap droppers for some low-level (nightlight) LED lighting, one
still should have a resistor in dropper the chain to limit spike
current.

Spikes aren't neccessarily a bad thing for charging lead-acid batteries -
I'd even consider using fast recovery diodes for the bridge.

A slightly safer alternative is the simple voltage doubling rectifier, one
side of the battery is directly connected to mains neutral. The disadvantage
is you need about twice the capacitance.

If the open circuit voltage is that serious a worry, you can always add a
thyristor crowbar protection circuit, the capacitor fed dropper is a good
approximation to a constant current source so shorting the output won't do
any harm.

 

[Grant]

On Fri, 11 Jun 2010 16:27:50 +0100, "ian field" <gangprobing.alien@ntlworld.com> wrote:

"Grant" <omg@grrr.id.au> wrote in message
news:teu2161f5u2197romh1oc51dufo5jpir0r@4ax.com...
On Thu, 10 Jun 2010 21:28:14 +0100, "ian field"
gangprobing.alien@ntlworld.com> wrote:


"mark krawczuk" <krawczuk@adam.com.au> wrote in message
news:YtedncSTb-DDk5LRnZ2dnUVZ_u6dnZ2d@adnap.net.au...
hi, after some schematics to charge 6 volt and 12 volt sla ( sealed
lead
acid ) batteries.... basically dont need to charge them flat out ,
cause
they dont get used much, something i can leave on trickle charge for a
week or so , would be good....

any body have any or know of any links ?


For absolute simplicity there's the so called "wattless dropper" - used in
the fading days of valve TVs in the UK, a capacitor was used instead of a
dropper resistor in series with the 300mA heater chain.

It worked on the principle that Xc was high in comparison with Rl and
masquerades as a constant current source, IIRC the capacitance was 4.3uF
for
the 300mA heater chain - its easy to find formula on the web to calculate
the capacitance to pass the current you want.

There are some pretty important safety cautions however, firstly; you have
to use a non reversible mains plug - the charger pretty much consists of
just a bridge rectifier and a capacitor, one AC terminal of the rectifier
goes to the mains neutral and the other goes via the capacitor to live -
if
you reverse that the rectifier and battery will be at full mains
potential!

The capacitor must be so rated that you could leave it connected
permanently
across the mains without it blowing a hole in the side - X2 class mains
filter capacitors meet this requirement.

The bridge rectifier must be rated to take the full mains voltage
otherwise
it will fail if the battery connection is broken.

Obviously from the above - if its plugged in with no battery the rectifier
+
& - terminals will be live!

As such there is no voltage limiting, so you can use the charger for
recovering sulphated batteries (sealed LA or open).

A project for seriously dedicated people who are immune from shock?
I use cap droppers for some low-level (nightlight) LED lighting, one
still should have a resistor in dropper the chain to limit spike
current.

Spikes aren't neccessarily a bad thing for charging lead-acid batteries -
I'd even consider using fast recovery diodes for the bridge.

A slightly safer alternative is the simple voltage doubling rectifier, one
side of the battery is directly connected to mains neutral. The disadvantage
is you need about twice the capacitance.

Hmm, until one plugs into a reverse wired point. I prefer to leave things
live with a big red sign, or do it safely At home I'm comfortable with
a mains powered LED nightlight sitting on top of the fridge, a clear plastic
bag covers the live LEDs. Visitors look but don't touch -- as the bare
wires are showing and most people have some respect for bare wires and
devices emitting light -- they know it's alive with electricity.

If the open circuit voltage is that serious a worry, you can always add a
thyristor crowbar protection circuit, the capacitor fed dropper is a good
approximation to a constant current source so shorting the output won't do
any harm.

Yeah I thought about that, but the whole idea is to present a ridiculously
high voltage across the battery, besides as you say, the current limiting
makes it reasonably safe.

TVS diodes (like a big zener) are available for various voltages, one
could put one of them in circuit. Don't think I'd bother with an SCR
and associated circuitry for this current limited situation.

Grant.
--
http://bugs.id.au/

 

[who where]

On Wed, 9 Jun 2010 13:14:58 +0930, "mark krawczuk"
<krawczuk@adam.com.au> wrote:

hi, after some schematics to charge 6 volt and 12 volt sla ( sealed lead
acid ) batteries.... basically dont need to charge them flat out , cause
they dont get used much, something i can leave on trickle charge for a week
or so , would be good....

any body have any or know of any links ?

First do a google search for slua115.pdf, which is an app-note for the
Unitrode/TI SLA charger chip. Apart from giving you some of the best
care and feeding info, it shows a schematic for a dead-simple SLA
charger (Fig4, p 4/12). The kit which Altronics/Jaycar(?) produced
several years back was a very close copy of that schematic.

 

[atec7 7]

who where wrote:

On Wed, 9 Jun 2010 13:14:58 +0930, "mark krawczuk"
krawczuk@adam.com.au> wrote:

hi, after some schematics to charge 6 volt and 12 volt sla ( sealed lead
acid ) batteries.... basically dont need to charge them flat out , cause
they dont get used much, something i can leave on trickle charge for a week
or so , would be good....

any body have any or know of any links ?

First do a google search for slua115.pdf, which is an app-note for the
Unitrode/TI SLA charger chip. Apart from giving you some of the best
care and feeding info, it shows a schematic for a dead-simple SLA
charger (Fig4, p 4/12). The kit which Altronics/Jaycar(?) produced
several years back was a very close copy of that schematic.
http://www.pdfdownloadlibrary.com/topics/battery-charger-schematic/page/4