On Sat, 19 May 2018 09:58:43 -0700, tabbypurr wrote:

On Friday, 18 May 2018 22:45:49 UTC+1, Johnny B Good wrote:

====snip====


The rectifier volt drops for even the lower 200 volt alternator case
will now only represent a mere 1% loss (the 230/240 inverter genset's
400vdc alternator output reduces this to a 0.5% loss). The inverter
losses are unlikely to exceed 2 or 3 % making such a genset a whole lot
more efficient than even a simple basic single phase 230/120vac 50/60
Hz alternator driven directly at 3000/3600 rpm let alone a
franken-genset comprised of car alternator and 12v to 120/230v inverter
box.

This, BTW, was a heads up for any of the more ambitious DIY
enthusiasts
monitoring this thread who might happen to be contemplating homebrewing
their own inverter genset 'on the cheap'. :-)

of course that isn't true if you let the alternator produce more than
12v

If you're prepared to run the alternator fast enough and replace/modify
the regulator, you could probably get away with letting it output 28 or
maybe even 42 volts (assuming you limit the excitation voltage source to
14v to prevent burning out the field coil). The PIV rating of the
rectifier pack is probably 200v or more which should leave some margin
for voltage spikes.

However, you might do better to start with a 28v truck alternator and
double up to 56 volts to feed a 48v inverter module (perhaps one
recovered from a defunct SmartUPS2000 or another 48v battery backed UPS).
In this case, the excitation voltage source can be limited to the higher
28v max limit but there's no guarantee that the PIV rating will be any
higher than that of a diode pack used in a 12v alternator - you might
need to upgrade the rectifier pack to one with a three or four hundred
volt rating. It is possible to test the PIV ratings of silicon diodes
when you can't identify them in order to look it up on a datasheet.

All this assumes a very keen polymath DIY enthusiast prepared to
assemble such a franken-beast of a genset made up of cast off bits of
24/36/48 volt battery backed UPS inverters and cobble up a controller
using an Arduino or RPi with a stepper motor bolted onto the carburettor
body. Somehow or other, it just seems so much easier to simply[1] spend
99 quid on a Lidl Parkside PGI 1200 B2 inverter genset and have done with
it. :-)

[1] It's a relative term as I eventually discovered during my own genset
purchasing saga just last month. The trouble with "Lidl Specials" like
this is they may well have clocked a few thousand miles in the back of 38
tonners going up and down UK motorways before you even get your grubby
mitts on one at your local store.

Such treatment often leaves them with a couple easy to fix (once you
know how) stock faults for the more nervous purchaser to return as DoA
faulty goods in the small hope of getting working genset in exchange or
else a full refund (small consolation for those who truly appreciate just
what a bargain a *working* 1200W peak (30 seconds, not 5!) inverter genset
is at this price).

All this is a direct result of Lidl's policy of never allowing such
'promotions' to last more than a week or two at each of their stores
before the arrival of the "Next Promotion" forces the store manager to
make room for the 'new line' and ship them off once more to stores in
other UK regions. It seems the store itself is its own warehousing space.
What's hidden, back of store, is just a small temporary holding pen for
stock that's about to be sent on yet another motorway journey.

For all I know, Aldi might be using exactly the same strategy but I
don't seem get to visit Aldi stores when such "generator specials" are
being promoted. Indeed, it's been several years now since I last saw any
type of genset on sale in an Aldi store (mind you, until recently, I
could say the same of Lidl).

Indeed, the amount of 'interesting bargains' in electronic tech and
genset rarities seem to have become vanishingly rarified over the past
few years in both Aldi and Lidl stores. There was a time when I used to
look forward to browsing the non-food sections whilst SWIMBI did the
weekly shop but not for the past two or three years now. :-(

--
Johnny B Good