The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

--
*If at first you don't succeed, destroy all evidence that you tried *

Dave Plowman London SW
To e-mail, change noise into sound.

On 05/04/2018 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.



Some of the rip-off merchants are asking £145 for it! The leisure market
is a right scam. Always buy from elsewhere if possible.

Bill

Some stuff sourced for Ham radio operators seem to be quite good for this
purpose I think, but they are not cheap if well built with adequate cooling.
Most are switch mode these days which may well help with the problems of
dissipation greatly, though many have a minimum current as well as a max
one.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Bill Wright" wrote in message
news
On 05/04/2018 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.



Some of the rip-off merchants are asking £145 for it! The leisure market
is a right scam. Always buy from elsewhere if possible.

Bill

Dave Plowman (News) used his keyboard to write :
It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

There is a UK after market replacement with a good reputation, at
around the same cost. My own PSU was mounted to draw cool air in via
the floor. I soon found the disadvantage with that, was that on the
road all sorts of muck would be ingested. It had a better heatsink than
you described, but the cooling fan had failed due to the muck it had
swallowed. New fan and move it to not draw air from the outside and it
has been fine since.

On 05/04/18 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.


£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

Tim Watts wrote:
On 05/04/18 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.


£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

It *should* be rather more than a 'simple' PSU as the battery charging
circuit needs to have some cleverness to charge a lead acid battery
properly.


Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

--
Chris Green
·

On 06/04/2018 09:00, Chris Green wrote:
Tim Watts wrote:
On 05/04/18 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.


£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

It *should* be rather more than a 'simple' PSU as the battery charging
circuit needs to have some cleverness to charge a lead acid battery
properly.


Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).


JOOI do motorhomes separate the battery from the distribution circuits
when connected to the mains? I ask only as I wondered if it might work
out cheaper to fit (a) a "Smart" battery charger (£20) and (b) a
separate 12V PSU (eg LED driver). Also avoids single point of failure.

--
Robin
reply-to address is (intended to be) valid

Robin used his keyboard to write :
JOOI do motorhomes separate the battery from the distribution circuits when
connected to the mains? I ask only as I wondered if it might work out
cheaper to fit (a) a "Smart" battery charger (£20) and (b) a separate 12V
PSU (eg LED driver). Also avoids single point of failure.

They use a system of the battery supplying the load, with a charger/PSU
in parallel with the battery - so PSU is able to both source the load
and charge the battery. Some of the later PSU are able to act
intelligently in their charging of the battery. I seem to recall some
have a link able to be set, for the various battery chemistries.

Harry Bloomfield wrote:
Robin used his keyboard to write :
JOOI do motorhomes separate the battery from the distribution circuits when
connected to the mains? I ask only as I wondered if it might work out
cheaper to fit (a) a "Smart" battery charger (£20) and (b) a separate 12V
PSU (eg LED driver). Also avoids single point of failure.

They use a system of the battery supplying the load, with a charger/PSU
in parallel with the battery - so PSU is able to both source the load
and charge the battery. Some of the later PSU are able to act
intelligently in their charging of the battery. I seem to recall some
have a link able to be set, for the various battery chemistries.

Yes, our chargers have settings for different battery types (not
different chemistries really, they're all lead-acid).

--
Chris Green
·

Robin wrote:
On 06/04/2018 09:00, Chris Green wrote:
Tim Watts wrote:
[snip]

Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).


JOOI do motorhomes separate the battery from the distribution circuits
when connected to the mains? I ask only as I wondered if it might work
out cheaper to fit (a) a "Smart" battery charger (£20) and (b) a
separate 12V PSU (eg LED driver). Also avoids single point of failure.

We are 'boatey' people but have essentially similar setup, a large
bank of leisure batteries which are used to make us independent of
mains electricity when away from moorings with mains power.

We don't ever disconnect the batteries when using shore power, the
chargers we have (mains powered, rarely used now, and solar powered
which provide most of what we need) are simply left permanently
connected to the batteries. So there's no requirement for a separate
12 volt power supply for use when mains is available.

I did have a power supply on a boat in the UK (the above one is in
France) which could be switched between 'charger' mode and '12v
supply' mode but I assumed the '12v supply' mode was for use when one
wanted to disconnect the battery completely for some reason.
Otherwise I always left it in 'charger' mode with the battery
providing voltage stability.

--
Chris Green
·

On 06/04/2018 10:50, Chris Green wrote:
Robin wrote:
On 06/04/2018 09:00, Chris Green wrote:
Tim Watts wrote:
[snip]

Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).


JOOI do motorhomes separate the battery from the distribution circuits
when connected to the mains? I ask only as I wondered if it might work
out cheaper to fit (a) a "Smart" battery charger (£20) and (b) a
separate 12V PSU (eg LED driver). Also avoids single point of failure.

We are 'boatey' people but have essentially similar setup, a large
bank of leisure batteries which are used to make us independent of
mains electricity when away from moorings with mains power.

We don't ever disconnect the batteries when using shore power, the
chargers we have (mains powered, rarely used now, and solar powered
which provide most of what we need) are simply left permanently
connected to the batteries. So there's no requirement for a separate
12 volt power supply for use when mains is available.

I did have a power supply on a boat in the UK (the above one is in
France) which could be switched between 'charger' mode and '12v
supply' mode but I assumed the '12v supply' mode was for use when one
wanted to disconnect the battery completely for some reason.
Otherwise I always left it in 'charger' mode with the battery
providing voltage stability.


Thanks (and to others who commented). And I can see that allows the
batteries to meet peak loads which would otherwise demand a bigger PSU.
Anyhow, clearly no turnip for me for my cunning plan

--
Robin
reply-to address is (intended to be) valid

I've been thinking about using a Lidl smart charger with a mobility scooter battery to power a dvr and a couple of security cameras since a local shop in a shed was broken into after the mains supply to the shed was torn out, leaving the cctv useless.
The charger seems to cut in and out according to voltage being between 12.5 volts and 14 when used with the battery and a light as load.
I'm asking myself if the voltage variations might adversely affect the cctv equipment. Any thoughts?

On 06/04/2018 10:15, Robin wrote:

I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey.Â* A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).


JOOI do motorhomes separate the battery from the distribution circuits
when connected to the mains?Â* I ask only as I wondered if it might work
out cheaper to fit (a) a "Smart" battery charger (£20) and (b) a
separate 12V PSU (eg LED driver).Â* Also avoids single point of failure.

I was wondering the same thing.

In article ,
Chris Green wrote:
£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

It *should* be rather more than a 'simple' PSU as the battery charging
circuit needs to have some cleverness to charge a lead acid battery
properly.

Blurb with it suggests it's just a regulated 13.8v PS. Which should be OK
for the sort of charging use it would normally get.

--
*I pretend to work. - they pretend to pay me.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote:
In article ,
Chris Green wrote:
£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

It *should* be rather more than a 'simple' PSU as the battery charging
circuit needs to have some cleverness to charge a lead acid battery
properly.

Blurb with it suggests it's just a regulated 13.8v PS. Which should be OK
for the sort of charging use it would normally get.

Not really. A lead-acid battery should be charged to something like
14.5 volts to get it fully charged (and it's important to get them
fully charged sometimes). Then, when it's fully charged, the charger
should drop back to 13.5 volts or so to maintain the battery in
'float'. Most 'intelligent' lead-acid battery chargers will do
something like this, the 14.5 volts guarantees full charge but if
maintained long term will make the battery gas. Really clever
chargers will occasionally wake up out of float mode and do a sort of
battery conditioning sequence.

(All voltages above are 'typical', they're the ones that vary slightly
with battery chemistry and temperature)

--
Chris Green
·

In article ,
Chris Green wrote:
Not really. A lead-acid battery should be charged to something like
14.5 volts to get it fully charged (and it's important to get them
fully charged sometimes). Then, when it's fully charged, the charger
should drop back to 13.5 volts or so to maintain the battery in
'float'. Most 'intelligent' lead-acid battery chargers will do
something like this, the 14.5 volts guarantees full charge but if
maintained long term will make the battery gas. Really clever
chargers will occasionally wake up out of float mode and do a sort of
battery conditioning sequence.

Very odd. SLA batteries have been charged at constant voltage for many
many years. What has changed?

--
*Many people quit looking for work when they find a job *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) brought next idea :
Blurb with it suggests it's just a regulated 13.8v PS. Which should be OK
for the sort of charging use it would normally get.

Which is what I have and despite the assurances that 13.8v will not
damage batteries if left on permanently, having lost batteries before
due to evaporated electrolyte when left on....

My regime now is to leave the PSU on, but disconnect the battery after
a couple of days of non-use. I put it back on throughout storage, maybe
once a month for a couple of days. Sometimes I will put it on a proper
charger, just to bring it to a full charge. The battery is only there
for the mover and as a backup to the mains and the PSU.

Harry Bloomfield wrote:
Dave Plowman (News) brought next idea :
Blurb with it suggests it's just a regulated 13.8v PS. Which should be OK
for the sort of charging use it would normally get.

Which is what I have and despite the assurances that 13.8v will not
damage batteries if left on permanently, having lost batteries before
due to evaporated electrolyte when left on....

Yes, 13.8v is a little too high I think, 13.4/13.5 is the normally
quoted 'float' voltage.

--
Chris Green
·

Chris Green wrote:
I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886

and it's possible to tweak the voltage upwards:
https://www.experimental-engineering...y-voltage-mod/
slightly easier on a different version:
https://www.experimental-engineering...y-voltage-mod/

Theo

On 06/04/18 11:10, Theo wrote:
Chris Green wrote:
I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886

and it's possible to tweak the voltage upwards:
https://www.experimental-engineering...y-voltage-mod/
slightly easier on a different version:
https://www.experimental-engineering...y-voltage-mod/

Theo


Why does a Playstation need 32A? Could it be perhaps 3.2A?

Brian Reay wrote:
On 06/04/18 11:10, Theo wrote:
12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886

Why does a Playstation need 32A? Could it be perhaps 3.2A?

No, it's 32A. The PS3 was as powerful as a contemporary gaming PC, which
often took 500W+. As time went on they shrunk to smaller silicon processes
which reduced the power consumption substantially - that's why the early
PS3s are best for getting a high current PSU.

Theo

On Fri, 06 Apr 2018 11:30:17 +0100, Brian Reay wrote:

On 06/04/18 11:10, Theo wrote:
Chris Green wrote:
I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...pply-Unit-PSU-
APS-227-for-60GB-CECHC/152246465886

and it's possible to tweak the voltage upwards:
https://www.experimental-engineering...aps-227-power-
supply-voltage-mod/
slightly easier on a different version:
https://www.experimental-engineering...-power-supply-
voltage-mod/

Theo


Why does a Playstation need 32A? Could it be perhaps 3.2A?

That was my first thought too but, apparently and incredibly, that 32A
rating is correct!! The description by 'The Engineer' mentions the use of
power FET synchronous rectification which eliminates, in this case, a
wasteful circa half volt drop in the 32A line due to the more typical of
PC power supplies cheap 'n' cheerful shotky barrier diode rectifier
forward volt drop, exchanging it for a more palatable 100mV or less volt
drop of a power FET's N or P channel synchronously hard biassed on
resistance of mere milliohms.

This is a feature more likely to be found on the 3.3 and 5.0 volt rails
since the circa half volt drop of a shotky rectifier diode represents an
even larger power loss on these low voltage supply rails. In this case,
we could be looking at a PSU efficiency (mains input power to 12vdc
output power) of better than 95%!

That PS3 power supply looks a very tempting substitute for my earlier
60A PSU described below, especially considering their very low price (I
think I paid something like a tenner each for the pair of 5v 60A smpsus I
bought some 30 odd years ago when a tenner was far from being the mere
pocket change it represents today).

Just over 30 years ago, I bought some ex late 70s mini/mainframe 5v
smpsus (10 and 60 amp units) which I modified to produce 7.05v (10A
Advance units) and 6.9v (60A units) to provide a float charger for
400AH's worth of battery via a 20A Shotky rectifier and a 60A 13.8v
transceiver supply respectively by wiring them in pairs to series connect
their outputs.

Sadly, one of the 60A units blew up a year or two later (some 30 years
ago now) but the float charging pair, much to my surprise, are still
going strong despite the battery being retired from service and
dismantled about ten years ago and my 10A 'charger' being left unused in
a damp basement radio shack environment (along with a Kenwood TS140s and
other kit).

I recently retrieved the Kenwood and the 'charger' from their basement
home a couple of weeks ago to save them from further deterioration. I'm
happy to say that the transceiver appears to have survived its ordeal by
high humidity quite well - it only needed its slider and switch controls
exercising to restore them back to their original operational state and
all seems well.

I've not been able to check the frequency calibration against WWV on
10.000MHz but reception of Radio Merseyside on 1485KHz using either USB
or LSB shows no perceptible shift of the demodulated audio frequencies
which is an encouraging testament to the frequency stability of this
transceiver after well over a decade's worth of 'irresponsible storage'.

Getting back to the issue of using/modifying smpsus, the higher spec
units bring out their sense amp inputs to additional terminals so that
they can compensate for the volt drop in the current carrying cables that
feed the load. In the case of ATX psus, the 3.3v supply uses a sense wire
connection to one of the three orange wires going to the MoBo connector.
Ideally, there should also be a sense amp connection to one of the zero
volt connectors as well which looks to be the case with the test rig ATX
psu I have on my workbench.

When it comes to modifying such old skool smpsus for a higher voltage,
the sense amplifier terminals prove to be a Godsend in that if offers a
quick 'n' dirty way to boost the voltage output[1]. The sense amplifier
input is normally a high impedance input and will normally be connected
internally to their respective negative and positive output terminals via
a hundred ohms or so resistor so that the output voltage remains
regulated even when the sense wires are unused (perhaps rising by a
millivolt or two in this case). Using the external sense wires will
override the internal resistor's influence by virtue of their typically
sub ohmic connection.

What this means is that we can leave the external sense amp connections
open circuit and add a shunt resistor across the sense amp terminals
which forms a potential divider with the built in resistor links which
increases the output voltage to restore the sense amp input voltage back
to the set voltage.

We can either 'measure' the resistance of the internal sense amp
connections so as to calculate the required shunt resistor value or else
just 'steam in' with a high starting resistor value to get an indication
of what order of magnitude value of variable resistor will be needed to
empirically arrive at a required resistor value. If the smpsu has an
accessible voltage trimpot as mine did, then the closest E12 series
resistor value can be arrived at and wired directly across the sense amp
input, leaving any final calibration to the built in trimpot.

I suspect the mods described by the 'Experimental Engineer' are simply a
variation of the above relying on leaving the external sense amp
connections unused in their new repurposed configuration.

[1] Output filter capacitor voltage rating allowing - a point well made
in those articles by the "Experimental Engineer". Also, another thing to
consider is whether a 'damping load resistor' is wired across the output
and what value and rating it is since it might need to be replaced with a
larger value resistor of a suitable wattage rating. Last, but not least,
is the issue of 'overvolt protection' which may limit the amount of
voltage 'boost' you can apply.

Some O/V protection circuits simply work to an absolute set limit,
others, more intelligently, work to a percentage overvolting factor (this
was the type of AT PSU that could be tripped by voltages backfed through
the PC's printer port during the initial voltage build up from switch on
- a level of 'intelligence' that was a little too effective for its own
good).

The damping resistor loading was something else I had to consider with
my own voltage mods. Indeed, the presence of such loading resistors was
the reason I had to include a blocking diode between the battery and my
'14.1v charging brick'. In this case, I'd replaced the original 8.2 ohm
5W resistors with 24 ohm 3W resistors.

Whilst modern low power designs of smpsu may have done away with such
damping resistor loading, high power units such as those Play Station
ones might still incorporate a damping resistor. However, in view of the
use of high efficiency synchronous switching rectification, I'd expect
such resistive loading (if any exists) to be a lot lower than was typical
of more traditional designs so might not be an issue in this case.

--
Johnny B Good

On 06/04/2018 11:30, Brian Reay wrote:
On 06/04/18 11:10, Theo wrote:
Chris Green wrote:
I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey.Â* A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886


and it's possible to tweak the voltage upwards:
https://www.experimental-engineering...y-voltage-mod/

slightly easier on a different version:
https://www.experimental-engineering...y-voltage-mod/


Theo


Why does a Playstation need 32A?Â* Could it be perhaps 3.2A?

Looking at the moulding, it looks like the rating on the PSU is 23.5A at
12V, plus 0.6A at 5V. That is 285W

Some PC video cards are a fair chunk of that, plus 90 to 125W for the
processor, so it's not really surprising for a games console to need
that much.

SteveW

Theo wrote:
Chris Green wrote:
I think you'd be surprised how expensive that would be, transformers
in particular are quite pricey. A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).

12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886

That will be a switch mode supply I think, no big mains transformer in
it. The above is more like the 'PC switch mode PSU' which I said
would be cheaper.

--
Chris Green
·

Chris Green wrote:
Theo wrote:
Chris Green wrote:
12V 32A, silent, six quid:
http://www.ebay.co.uk/itm/Sony-PlayS...C/152246465886

That will be a switch mode supply I think, no big mains transformer in
it. The above is more like the 'PC switch mode PSU' which I said
would be cheaper.

Yes, it's a SMPSU. I'm just pointing out how cheap you can get one,
that might fulfil the OP's requirement with a little tweaking.

Theo

On 06/04/2018 09:00, Chris Green wrote:

A PC switch mode PSU would probably
be cheaper for that sort of rating (though would likely have lots of
5v and 3.3v output as well).


It would need to output 14.2V, not 12V.

Bill

Bill Wright submitted this idea :
It would need to output 14.2V, not 12V.

But, they are really easy to modify to output any voltage within a
range. Lots of info on the web, usually just a fixed potential divider,
providing feedback to the switching circuit. My shack has a 50v 50amp
telecoms PSU, which I modified to output 13.8v.

It happens that Tim Watts formulated :
Sounds like a good application for a 200VA transformer, bridge rectifier and
nice lumpy heatsink.

I'm not sure I would want that across an expensive leisure battery.

Harry Bloomfield wrote:
It happens that Tim Watts formulated :
Sounds like a good application for a 200VA transformer, bridge rectifier and
nice lumpy heatsink.

I'm not sure I would want that across an expensive leisure battery.

I think the OP seemed to have separate battery charger and 12v supply
hardware.

--
Chris Green
·

In article ,
Chris Green wrote:
Harry Bloomfield wrote:
It happens that Tim Watts formulated :
Sounds like a good application for a 200VA transformer, bridge rectifier and
nice lumpy heatsink.

I'm not sure I would want that across an expensive leisure battery.

I think the OP seemed to have separate battery charger and 12v supply
hardware.

Not so. It's just a 13.8v power supply which both charges the battery and
supplies low volts for whatever needs it. In this case mainly lighting.

Although in my pal's case he travels to his place in Spain and back a few
times a year - with dog. And needs a working fridge for his medication. So
needs it to work from gas, mains, car electrics, or leisure battery. To
give the maximum number of choices.

--
*Kill one man and you're a murderer, kill a million youand 're a conqueror.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Tim Watts wrote:
£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

Think you'd be hard pressed to make a 20 amp limear supply to retail at
about 100 quid?

--
*Don't sweat the petty things and don't pet the sweaty things.

Dave Plowman London SW
To e-mail, change noise into sound.

On 06/04/18 10:37, Dave Plowman (News) wrote:
In article ,
Tim Watts wrote:
£100 for a simple PSU - and they still couldn't make it properly? Jesus
wept

Sounds like a good application for a 200VA transformer, bridge rectifier
and nice lumpy heatsink.

Think you'd be hard pressed to make a 20 amp limear supply to retail at
about 100 quid?


There are some switch mode ones around which aren't bad, mainly for the
amateur radio market BUT they are power supplies not chargers- which is
(hopefully) what was being used to charge the battery in the motorhome.
A proper charger will help ensure the battery/batteries are not over
heated etc and, assuming the motorhome has a proper smart controller,
interface with it to ensure the vehicle battery is also charged when on
mains, the leisure battery/batteries are charged by the vehicle when the
engine is running, and interface to any solar system.

I think the charger in mine is about £140. Allowing for the extra
functions it has, over and about a basic switch mode PSU, and its
quality, it isn't a bad price. I'm not sure how expensive the main
control unit is- several hundred at a guess.


Sticking in just a transformer, rectifier, etc is a sure fire way to
ruin a leisure battery BDQ.


'Ready made' conversions seem to come with integrated 'smart'
electronic/electrical systems these days. Mine has a unit which controls
the 12V and mains- well the breakers for the mains- and interfaces with
the vehicle system and a battery charger. It does everything from
controlling the 12V master switches to sensing water levels in fresh and
waste tanks. Later ones even interface with your phone.


Those who do their own conversions seem to go for discrete
sub-subsystems- you can buy sensors and displays for water levels etc. -
and simply install a domestic consumer unit and a battery charger etc.

To comply with the 'construction and use' regs, much of the 'domestic'
electrics should be disabled when the vehicle is in motion- the
commercial control boxes do this but I suspect most self builds don't
bother. No doubt, in time, someone will decide this needs to be checked
as part of the MOT ;-(

In article ,
Brian Reay wrote:
Think you'd be hard pressed to make a 20 amp limear supply to retail at
about 100 quid?


There are some switch mode ones around which aren't bad, mainly for the
amateur radio market BUT they are power supplies not chargers- which is
(hopefully) what was being used to charge the battery in the motorhome.

No. It's is a simple 13.8v regulated supply. As has been used to charge
SLA (constant voltage) from the year dot. Wet car batteries may well be a
different matter.
A proper charger will help ensure the battery/batteries are not over
heated etc and, assuming the motorhome has a proper smart controller,
interface with it to ensure the vehicle battery is also charged when on
mains, the leisure battery/batteries are charged by the vehicle when the
engine is running, and interface to any solar system.

The charger to my burglar alarm SLA battery is 13.8v regulated. And no
mobile device is going to be on charge constantly like that. Battery lasts
about 10 years.

--
*I speak fluent patriarchy but it's not my mother tongue

Dave Plowman London SW
To e-mail, change noise into sound.

On 05/04/2018 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

This is one I purchased recently, though not from this seller:

https://www.ebay.co.uk/itm/12V-20A-C...t/122314362986

In article ,
Fredxx wrote:
On 05/04/2018 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

This is one I purchased recently, though not from this seller:

https://www.ebay.co.uk/itm/12V-20A-C...t/122314362986

It certainly looks better than the one I have here. Which looks decidedly
home made, case wise. ;-)

But wonder if that unit could be used as a stand alone power supply for
12v stuff in the van, with no battery present? The current one can.

--
*Do infants enjoy infancy as much as adults enjoy adultery?

Dave Plowman London SW
To e-mail, change noise into sound.

On 07/04/2018 11:26, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
On 05/04/2018 23:47, Dave Plowman (News) wrote:
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

This is one I purchased recently, though not from this seller:

https://www.ebay.co.uk/itm/12V-20A-C...t/122314362986

It certainly looks better than the one I have here. Which looks decidedly
home made, case wise. ;-)

But wonder if that unit could be used as a stand alone power supply for
12v stuff in the van, with no battery present? The current one can.

I haven't tried that. I always have batteries in situ. It's the only way
I can provide the additional power for a microwave through a 3kW inverter.

In article ,
Fredxx wrote:
But wonder if that unit could be used as a stand alone power supply for
12v stuff in the van, with no battery present? The current one can.

I haven't tried that. I always have batteries in situ. It's the only way
I can provide the additional power for a microwave through a 3kW
inverter.

It does say reverse polarity protected, so may not even fire up if the
battery is totally flat.

--
*Verbs HAS to agree with their subjects *

Dave Plowman London SW
To e-mail, change noise into sound.

In article , "Dave Plowman (News)"
writes
The mains to 12v power supplied failed in a mate's motorhome, so although
he got it replaced I offered to look at it to see if it could be repaired
as a spare.

It is branded PowerPart, and is a 20 amp 13.8v device which charges the
leisure battery as well as running any 12v things when on mains. Cost
about 100 quid.

It was well and truly fried. Only heatsink for the power Mosfets was the
thin ally case - and a small cooling fan. Not that much for a device
likely mounted inside a cupboard of some sort.

Rectifier was short circuit and a transformer burnt with half the
laminations lying loose inside the case, so gave up.

Get a Zig. And I don't think any of my leisure vehicles including, 2
campervans, one motorhome and 5 caravans having a cooling fan.
--
bert