<ads> wrote in message
My system is similarly assembled from whatever I could find
second-hand or build, a little smaller because my property is mostly
shaded. I made V-shaped fold-out legs for my Grape panels from 1/2"
EMT conduit and move them around to dodge shadows when I need several
hundred Watts for discharged batteries, otherwise 1-2A from panels in
fixed locations keeps the backup batteries topped off.
The parts I designed and built because they aren't commecially
available are a 25A fast charger and a float charger for battery
maintenance composed of an LM350 adjustable linear voltage regulator
and this voltage and current meter for feedback:
Th voltmeter helps find the lead-acid gassing threshold and then stay
just below it, and the ammeter indicates when the battery is coming
up, fully charged, or degrading from age. The numbers to look for are
in the battery manufacturer's data sheets.
The 25A fast charger is a Variac driving a "50A" (at 20% duty cycle)
arc welder transformer, rectifier and capacitor etc. I designed it
more for experimenting and component testing but it can charge any
battery between 1.5V and 48V and the Variac adapts it to a poorly
regulated generator. If you already have the parts or find them cheap
it's a good use for them, although the welder voltage/current
characteristic is constant current and the voltage can rise too high
if left unattended or unregulated. This DPS5015 switching regulator
works really well and is controllable enough to charge bare Lithiums
or NiCads. I bought it before the 20A model became available.
I learned how to charge sample batteries with lab power supplies when
I became the battery tech at Segway.
I add a series diode to keep battery voltage from feeding back into
the power supply if it's switched off.. The DC desulfation technique
they mention does work, sometimes. If you are serious about salvaging
old 12V batteries the Harbor Freight Carbon Pile tester is very
In cool weather the Alpi C20 works well enough as an indoor freezer
set at -18C. Right now my kitchen is at 17C and in midwinter I let the
house drop to 13C. When I put the Alpi in the back of my white SUV on
a sunny 28C day it ran continuously at -12 to -15C until I covered the
cold compartment with a winter parka, leaving the vents clear.
Here in the Northeast USA we suffer summer hurricane and winter ice
storm power outages, sometimes for a week or more. In that case I'd
reset it to -4C which keeps frozen food lightly frosted for a while
but doesn't freeze drinks solid, and greatly increases the battery run
On Sun, 03 Jun 2018 03:08:23 -0700, dolmen wrote:
I know where you're coming from. Sheesh! An extra 800 quid just to
upgrade that 99 quid Parkside inverter genset I'd bought back in April to
a quieter version. If you're going to use it for emergency home power,
there are much cheaper ways to deal with the noise pollution. Even the
A1 version that went on sale in UK Lidl stores last Thursday are still
one hell of a bargain at 129 quid versus the 280 quid 1200/1500W Impaq
models available from local Screwfix stores in the UK.
I'm afraid I can't offer any practical advice regarding Li-ion battery
banks and chargers. My experience is more to do with good old fashioned
lead acid battery setups, mainly to do with various UPSes I've used over
the past 20 years or so.
What I can say, if you're thinking of using lead acid batteries with a
1KW or higher output inverter, is not to make the mistake I've seen in
many a youtube vid of using 12v inverters with a bank or two's worth of
forklift truck batteries.
If you're going to buy a 1 or 2 KW inverter choose a 24v or, better yet,
a 48v inverter setup which will save a small fortune in heavy duty
battery cables as well as reduce I squared R losses. Instead of circa
100A per KW of grid voltage output from a 12v battery (which is starter
cranking amps territory), a 48v battery will reduce this to just under 25
amps per KW of grid voltage power.
 There are plenty of youtube vids demonstrating the many ways of how
*not* to create quiet generator enclosures by folk who have totally
underestimated the problems of containing the noise pollution in a
plastic or wooden box breached by the relatively large holes required to
vent the enclosure to prevent the generator from cooking itself with (and
choking on) its own exhaust fumes.
A suitcase styled inverter generator out of necessity, provides its own
forced air ventilation to both cool the inverter module and the engine
and, in particular, the exhaust muffler to prevent it melting the plastic
Installed into a properly designed brick enclosure, it shouldn't need
any additional fan cooling if the sound absorbent lined ventilation tunnel
 for the exhaust is sized a little larger in CSA to that of the
exhaust vent that typically encloses the muffler's exhaust pipe. A few
inches of separation between the rear of the generator and the mouth of
the exhaust vent needs to be provided to utilise the venturi effect to
draw additional air past the sides of the generator to prevent heat build
up within the enclosure.
Obviously a similarly sized intake vent will be needed at the opposite
end, with a suitably labyrinthine pathway to the intake end of the
generator with blocks of sound absorbent material strategically placed so
as not to choke down the intake path.
Also, just like the exhaust end there needs to be clearance for the
extra air drawn in by the exhaust venturi effect to work its magic of
removing any residual heat build up from conducted and radiated heat that
would otherwise normally escape direct to the atmosphere. I doesn't need
much of an airflow to achieve this goal in the case of suitcase styled
inverter gensets compared to a typical open framed generator.
In any case, it would only be prudent to monitor the interior air
temperature to be verify that there's no overheating risk to the petrol/
gas tank contents or the generator itself. This should be done as part of
the commissioning tests at the very least.
Depending on the results of those tests, you can decide whether or not
there's any need to permanently monitor the enclosure temperature to
provide an overheat alarm which could be used to start a timer to shut
the generator off automatically for your own peace of mind.
 Most of which can consist of a vertical brick chimney (say 6 foot or
so tall) to take advantage of the exhaust heat energy to generate an
additional draw assist to the ventilation airflow and to direct the
residual noise skywards and away from neighbouring properties.
Any weatherproofing measures against rain ingress should ideally be
effectively sonically transparent to avoid deflecting residual exhaust
noise back towards your immediate neighbours. This trick of simply
deflecting the noise skywards can account for a 6dB reduction in the
horizontal plane so it's worth trying to avoid spoiling this effect with
a standard rain proofing cowl if you can.
Johnny B Good