Lidl (UK) has Parkside inverter generator on offer next Thursday 31st May 2018 - Page 4

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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:
https://www.amazon.com/DROK-Digital-0-33-00V-0-3-000A-Measurement/dp/B00IZU4D4Q/ref=sr_1_173?s=industrial&srs19938011&ie=UTF8&qid 96089483&sr=1-173
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.
https://www.amazon.com/uniquegoods-Step-down-Programmable-Adjustable-Regulator/dp/B01N3YSE6S/ref=sr_1_1?s=industrial&ie=UTF8&qid 28198322&sr=1-1&keywords=dps5015

I learned how to charge sample batteries with lab power supplies when  
I became the battery tech at Segway.
http://batteryuniversity.com/learn/article/charging_with_a_power_supply  
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  
useful.

-jsw  

  On Sunday, June 3, 2018 at 8:37:48 PM UTC+1, Jim Wilkins wrote:


Thanks Jim like I say I've no knowledge on how to build it myself so gathering info in the hope I can get enough to perhaps DIY
Interesting re the Alpicool I've looked at a few DC powered units and thought they were mostly shy of having enough insulation so haven't bought one yet.

 
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  
time.

-jsw  

 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[1]. 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.

[1] 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  
casing.

 Installed into a properly designed brick enclosure, it shouldn't need  
any additional fan cooling if the sound absorbent lined ventilation tunnel
[2] 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.

[2]  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