Re: (ET) Ok now that the Dust is Cleared.

[Pieter Litchfield <pieter_litch yahoo com>]

This is a tough one.  Because my family's vacation/group house is
"off grid" 24-7-365 but occupied by someone year round, the use
of a generator charging batteries makes sense.  In a generator only
system, there are time at night when the draw is almost nothing, but the
generator is still consuming almost as much fuel as if running at full
load.  By using the generator to charge batteries, the load can vary
widely, and a set of "intelligent" inverter/chargers can jump
on and off line to match the required power draw.  In my system, the
inverters call for the generator when the batteries hit a low voltage
threshhold.  The generator is sized to both charge the batteries and
run the house at the same time.  The house is switched
(automatically by the inverters) to generator power, the batteries get a
charge, the generator is shut off and the house goes back to battery
power.  If there is little house load, the batteries charge
fast.  If there is a lot of house load (daytime, evening), the
batteries charge slowly.  This system has 12kw worth of intelligent
inverters ( 6 x 2k Outbacks) and a 40 kw diesel generator set. 

However, if your need is for emergency standby power only, I'd be tempted
to use only a standby generator and, if you wish, an inverter with your
tractors.  Why?  You can go without electricity at night, even
in the winter.  Use a wood stove, or get up during the night and run
the generator for an hour to get the pipes warm again.  You could
also use your e-traks to run an inverter.  I guess if the load
wasn't too big for the cable and connectors, you could cable them in
parallel so that you would have 36 volts and a whole bunch of amp hours
of capacity, or you could just use a single e-trak till it was exhausted
and then attach the inverter to the next.  While you are running
your home appliances on the generator, you could also use the on board
etrak charger to charge them one or two at a time.

Where I live full time (100% on grid) , I have to run a shallow well pump
(1/2 hp) , the fan and 3 circulators (1/4 hp ea) on my oil burner, and my
refrigerator.  I also run some lights and the TV.  I do not run
the standby generator continuously.  I get the house warm, the water
pressure up, and the "flushing buckets" filled, and then shut
it down for a few hours.  Repeat cycle.  10 gallons of gas goes
a long way with this type of use.  Heat is augmented by a wood
stove.  We have battery radios, candles, lanterns, etc.  I have
an electric stove, and I won't try to size a generator for that, but I
have a single burner gas camping stove, the wood stove, and a gas BBQ, so
I have cooking options.

I don't like to run much on the generator since they are prone to spikes
and "dirty" sine waves which are tough on appliances.  If
you have big electric motors that start under load, investigate replacing
them with capacitor start units to reduce startup loads which could
exceed the capacity of your system.   

My home standby generator is 5000 watts full duty cycle, which is more
than enough for my needs.  I'm not sure how much capacity is used
when charging a etrak battery set, but one might want to go higher than
5000 watts.  I am just guessing, but it sounds like 5000 watts is
probably plenty for the loads you have listed.

In short, I would not try to size a generator set to charge all your
etraks at the same time.  IGiven that you already own a bunch of
tractors, it may make sense to think about getting a 36 volt inverter big
enough to run your short list of stuff and charging a single ET from the
standby generator while also running the house directly.  I would
NOT think about using a generator to only charge the ETs while they in
turn ran an inverter.  I doubt if the battery chargers are big
enough or efficient enough to have this make sense. 

Finally, I must confess I am neither an electrician or electrical
engineer.  But I saw an article or letter-to-the-editor in
"Home Power" in the last few months which described the usual
components for off-grid, on-grid, and pure standby (emergency)
systems.  I believe the article suggested that the use of battery
banks in an  emergency system is not justified, because the
batteries will eventually fail even if the system is never used, and they
are way more expensive to amortize that any fuel they might save on a
purely standby basis.  However, since you already have the tractors,
the logic is somewhat different.

By the way, look at their web site for info on larger inverters.

http://www.homepower.com/




At 12:00 PM 12/13/2007, soltrak wrote:
>  Do you think it would be
> possible to connect the ETs together using dryer cords with double ends
> from one to the other? This way you could line em all up and just connect
> from one end again using a dryer cord to the inverter. Just plug them all
> together and you have a lot of amp/hrs. at 36 volt. I suppose differing
> battery bank condition might be a problem, but not if you keep them all
> charged together from one charger and if you use one then charge it up
> first before reconnecting it to the others. Soneil does make a larger amp
> 36 volt charger.
>
>
> On Dec 13, 2007, at 11:01 AM, Thompson, Geof wrote:
>
> > Hello All
> > Now that the dust has cleared here is what I am going to do
> > as a result of the discussion about back-up power I now have a plan for
> > my new country place. 
> >
> > I am going to line up all my ET that have battery packs. I
> > might as well use them if I've got them)  In my barn which will soon
> > have a 100 Amp service (inspected and approved). I am going to keep all
> > these Battery Packs up with Soniels
> >
> >  ( Darryl stand by for a bulk order). Then find and
> > inverter that will give me enough power to run my Gas furnace The
> > Microwave, and the TV (need something to do if you snowed in)  not
> > necessarily all at the same time.  (likely a UPS/ back-up system).
> > These are cheap without batteries the kind they use on-board ships
> > generally 24V but we have 36V here at work.  
> >
> > If I need emergency power I will systematically connect/ tap
> > off The required Vs. to the inverter 
> >
> > I have a few calculation to do yet. 
> > 1) What is the current draw of my Gas Furnace?  And
> > what is an average cycle time? 
> > 2) What is the total capacity of my battery packs
> > 3) How many days should I be able to sustain the system EMO
> > up here say 7 Days for a water supply. 
> > 4) How much money my wife will let me spend on this project
> > (smile) 
> >
> > It lacks a few details, but I think it's a practical and
> > measured solution. 
> >
> > This is a sort'a of a risk management exercise. But, I need
> > to keep up the batteries anyway, I might as well get two rides for one
> > ticket.
> >
> > Addition options to this would be go partly off grid and
> > collect power by solar and wind, Or add a generator to charge the
> > batteries to extend the usable time. However, I think more batteries and
> > more charger is also a valid option.
> >
> > Thoughts?  
> >
> >
> > Geof Thompson 
> > A-60, 
> > E-81X2 
> > ER8-36, 
> > R-36 
> > E-8, 
> > E-10x2, 
> > E-12M, 
> > E-12, 
> > E15x2, 
> > E-20x2, 
> > B-145X2, 
> > C-185, 
> > E-141X3. 
> > I-5 
> >
> >
> >
> >
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