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
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