today i'm starting off with mill street
brewery's draft style vanilla porter
beer with natural vanilla extract from
mill street brewing in
Toronto.  our generous use of
natural vanilla extract gives this
classic porter a deep complex flavor
that you won't soon forget
so today i'm going to be doing a
teardown of this battery charger
now this is more of an automotive
battery charger except for it's a 24
volt battery charger
so this is used typically with the
batteries on larger diesel engines
either in
semi-trucks and stuff like that or
in  in this case it used to be mounted
onto the side of a backup generator a
stationary diesel generator
so this one is an enerwatt ewc
24-124 24 volts one slash two slash four
amps charging current and it can do
various different chemistries can be
either a calcium pure lead
or an agm and wet
cell  is that
something glass mat i think or a gel
cell
you can either put it in conditioning
mode or equalization mode equalization
mode basically
boosts the output voltage a little bit
to try and get
each cell voltage um a little bit more
equal
to the others
and then of course you can set the
charging current to
uh one two or four amps if i remember
correctly this one was just left on a
one amp trickle charge
on the batteries to start the generator
um but i said it failed
and the diesel mechanic just replaced it
so i grabbed it see if i can see what
goes on inside it just for curiosity see
if there's anything obvious broken in it
should be fun should be good to satisfy
my curiosity
so this battery charger is far from
obsolete it's still a current listed
item
uh sells for 115 dollars canadian plus
tax plus shipping and all that good
stuff so before i start
uh just to see if it even works i'm
gonna have to put some connectors on it
as i guess when the mechanic was pulling
it out he wasn't wasting any time and he
just
chopped the wire short so this will be
the ec
input 120 volt 60 hertz 2 amp max
and this will be the dc output 24 volts
at one or two or
four amps
so since this is just a two wire input
cable the whole thing is double
insulated so it didn't need to
have a ground i will just
put eek put this two wire cable on it
with some of these handy dandy little
wiggle connectors
i'm really getting to like these things
i wish they were more common in north
american usage
i've only really seen them in some
imported pieces of equipment
okay that took a bit more time than i
thought but
i've got my tests set up here um
the kilowatt cone over here
this guy i've got uh meter connected
onto the dc
side see what happens when you plug it
in
it's drawing 3.8 watts it's not putting
any voltage out
possibly because it's open circuit
possibly because it's not working let's
try
different modes equalization mode now
nothing
okay different battery modes
nope
nothing so it's only drawing enough
current basically 2 watts
49 milliamps 50 milliamps that's
basically just those leds
okay well i guess that's why it was
taken out of service
so i'm guessing that underneath these
feet
is where there's some screws yeah
there's some phillips screws down there
all right
okay i'll just clamp show apart sure
we don't need that tie wrap on there
anymore
oh that's uh fairly beefy tracks on
there which i guess makes sense given
this thing's job
tip that right out
okay the little control panel thing
is on the connector which pops out
fairly easily
hmm this one chip
and it's a double-sided actually no a
single sided board
let's uh pop that guy out
i guess i should probably deal with
those two little screws down there first
screws and clips holding this board in
interesting so okay on this side he's
got
three little tactile switches and
four seventy nine ten leds
just surf oh and these two up here a
dozen leds
or their boats okay so what is that
chip 74 hc 595.
gee that sounds familiar doesn't it who
else was yelling at their screen that
this
is the good ol uh hc 574 hc 595
8-bit shift register yep
the same one that comes in just about
every uh
arduino starter kit there it is just a
serial data in
and a clock in a selection of clocks and
an enable
but you can get away with just the clock
and the data
and that'll give you eight outputs from
your arduino
very very handy and there's the table a
serial data bit comes in
uh first clock pulse puts it to the
first output second clock pulse moves it
along
clock pulse clock pulse all the way
along
yeah um pretty standard little chip and
really handy for a bunch of different
applications a good chip to know about
okay so that was the side
project let's get into the main meat
over here
actually would it be so obvious as just
the fuse
nah couldn't be
nope fuse is not blown okay so that's uh
that's always the first thing you want
to check isn't it
that's the output fuse is there an input
fuse oh no
even if there is an input fuse we know
it's not blown
because the display board had power
coming to it so it's at least got a 5
volt power supply
so what do we have here ac
power coming in there's a fuse there
4 amp 250 volts
there is a suppression capacitor by the
looks of it
there is a suppression choke
thermistor for inrush um and another
capacitor uh
class y2 capacitor ah yeah there we go
this first one is a class x2 capacitor
here
that's a class y capacitor there another
choke
then we go to the full bridge rectifier
no i'm not going to say it like uh like
electro boom i'm just not as cool as him
with some really chunky diodes and we
have a 220 micro farad
uh smoothing capacitor after that
and then q1
on here which
can i read that
g20 m50c it is a big
power mosfet up to what's
80 amps no let's drain a continuous
20 amp drain okay
that's more than enough for the circuit
that it's in certainly
so what is that mosfet doing in that
part of the circuit do you suppose
ah there we go little eight pin
chip completely anonymous little eight
pin
chip that looks for all the world okay
switching power supply controller
doesn't it
just the way it's all configured there
i'm gonna say that's exactly what's
going on
so switching power supply chip there
driving a mosfet which is
chopping up the dc from these diodes
feeding it through this isolation
transformer
note the isolation big wide
gap the only thing that's bridging the
gap is there and there and
this is two capacitors
in series with a little island between
them
these guys are class y2 capacitors both
of them
and the other thing that is bridging the
gap
is this little four pin device over here
what do we know that comes in four pin
dip style packages that
is going to be an off to isolator isn't
it of course it is what else would it be
just over here on the diode on the led
side of it we have a zener diode
and just a rectifier regular diode and a
capacitor there
a couple more capacitors or a couple
more resistors diodes hanging around
over there yeah
so this is just classic switch mode
power supply stuff
so that's the high voltage side there's
the isolation
now we're on the low voltage side over
here
we have two devices here and here on 220
packages
to 220 packages mark d10
and d something else they are clearly
going to be
diodes they will be rectifying what's
coming out of here then there's the
filtering capacitors
then there's an inductor in series
to knock down high frequency stuff
another inductor
what's underneath that little blob of
elastic there
maybe that's just holding could be i
don't see any component under it okay
over here we have a transistor which is
probably
doing current limiting q3 q5
tip42c it's just a
normal pnp transistor okay capable of
six amps
reasonable enough it's on a solid
heatsink so it should be able to do all
of that
so yeah that will be probably
doing the current limiting for the
charging current
so the current sensing is most likely
being done
across this big resistor here right at
the output
it's kind of difficult to measure the
main circuit but it's
it's measuring in the one ohm range so
that's
probably not unreasonable
less than an ohm because i've got half
an ohm in my probes
so that's probably what that guy is up
to um
and of course reporting that back to the
microcontroller down there
which again is an anonymous auto
microcontroller type thing i'm guessing
yeah so it's it's got several tracks
going over that header pin
which is there which goes up to our
little
control panel board that we saw earlier
so let's get a little bit dangerous here
so first thing to look at here's the
capacitor after the bridge rectifier and
the dc
on the low uh or the high voltage side
rather 168 and a half
volts close enough 170 volts that is
what you'd expect out of rectified
means voltage so
then we go through mr mosfet and we go
to the primary of the transformer
it's both isolation and step down uh
and here we have the ac
coming out of that transformer let's
measure it in ac volts mode
5 volts 4.9 volts i don't think so
but that's probably going to be a higher
frequency than this cheap little meter
is capable of
let's try a slightly less cheap cheap
little meter
no it's not picking it up either
okay time to break out the big guns
so we'll go since this is isolated it's
completely isolated from the mains
i can put the ground side of my pro my
scope probe on to just about anything
over here and it should be safe
so if we put our probe across that
transformer across the secondary of that
transformer
we've got these oddball little pulses
here
just a quick measurement of those guys
those are near enough to 60 hertz
that wasn't what i was expecting let's
just zoom in on these pulses a little
bit
oh hello
that's more the kind of frequency i was
expecting
let's go there yeah 62
kilohertz 61 kilohertz something in that
range
so you can see the square wave happening
there
um and then a bunch of harmonic uh
stuff let's just brighten that up a bit
you can see all the various different
harmonics and stuff happening in there
that's just uh square waves are just
naturally noisy like that
um which is why you want all kinds of
filtering in this power supply clearly
but
i would have expected there to be
a lot more consistent uh like
not just let's just turn the voltage off
no where's the
yeah times there's the time
like that pulse is 680 microseconds long
i would have expected
this entire thing to be showing me that
higher frequency rather than just
pulsing like that
so there's clearly something not happy
in the control side of this
circuit that's not created that's not
continuing the square wave right across
okay well that's a data point
let's see what else we can see just from
that so here we have
there's the uh the two main secondary
windings and there's a
couple of smaller ones so it looks like
this
winding is providing
uh the power supply the five volt power
supply i'm
guessing this is all going over into
this stuff here
and down in here just chasing the
circuitry around this
guy appears to be a five volt regulator
so that's where five volts is coming
from
and if i trace those around properly
yeah there's our five volts so that's
that little regulator in there
okay so that's where the five volts is
coming from to power
this little microprocessor over here
and the shift register there so that's
that makes a certain amount of sense
so is there anything left that i haven't
talked about over here oh
still got some voltages to measure i
guess
even though we know we're not getting
the proper voltage coming out of here
because it's just a super low duty cycle
and it's not providing enough oomph to
do anything
we still have a certain amount of power
coming out so here is these two
diodes there and there
they are in common
and come in
so yeah they're not capable of
sustaining a proper voltage but it is
going
up to 35 volts occasionally but they're
just not able to sustain a proper
voltage because
they're not getting enough input feed
so i'm going to guess that
either this microcontroller or this
switchboard power supply chip is
probably unhappy
internally the microcontrollers
may be okay because this little control
board over here works properly
although who knows uh one of its current
sense input might be smacked its voltage
input might be uh
our voltage sensing input might be
damaged or something like that
it's it's so hard to tell because these
are both very anonymous chips
and we can guess at what they are for
just from what they're doing but
who knows what their actual part number
is i'm going to unplug that
before i get too carried away in here
i should just have this visible to make
sure that everybody knows
that i'm not being stupidly risky
but yeah i don't know that there's much
else to be learned
in here but that's okay i uh i grabbed
this
not so much to try and repair it as just
to do the
teardown although if there was an
obvious problem
like the fuse or something then i
clearly would have just replaced that
but
that was an interesting little power
supply to dive into
and i'm guessing that the majority of
the power components
are still good so
things to salvage out of there possibly
um
inductors are always a handy thing to
have fuse capacitors
sure some nice big chunky diodes to play
with
i will add this to the scrap bin of
salvage
but i think that's about all we can
learn out of this thing tonight
that was a interesting little
exploration i
kind of wondered what was going on
inside one of these things and now i
know
thanks for joining me on my little
curiosity teardown um if you have any
questions or comments
down in the comment section as usual
uh thanks for watching i'll talk to you
later
