Tuesday, December 20, 2011

Restoring an Elec-Trak Tractor and Integrating it With Our PV System

Last summer, we bought a used Elec-Trak tractor -- I suppose "used" is a bit redundant since the last Elec-Trak left the factory in the 80's.

Our "new" Elec-Trak after some TLC.

The Elec-Traks are all electric tractors powered by a set of on-board lead acid (golf cart) batteries.  They were made by GE for several years during the 70's, and were popular with more than 30,000 made.  They are very durable and functional machines with a wide range of all electric accessories.  The Elec-Traks have a strong following with an online owner forum and good parts support.   Many of these tractors have been rebuilt and are serving people well.  Being electric, these machines are cleaner, cheaper to run, and low maintenance than equivalent gasoline models.

The Elec-Trac with new charger/inverter supplying 120 VAC power out in the field.

In addition to the usual mowing and snow blowing tasks, we wanted to be able to use the Elec-Trak to power our home during power outages -- it has a large enough battery pack to power a few critical loads like the fridge and furnace for something in excess of a day.   This proved to be a relatively easy thing to do using a commercial charger/inverter from Tripplite.

In addition,  we wanted to work out a way to use our grid-tied PV array to charge the Elec-Trak battery pack during power outages.  This proved to be more of a challenge in that grid-tied PV arrays are designed to stop operating as soon as a power outage is detected, and to stay offline until the grid comes back.  After a bit of head scratching, we did work out a way that is fairly easy and effective if not terribly elegant.  The nice thing about our arrangement is that we get most of the benefits of a grid-tied with battery backup PV system, but without the considerable initial expense of these systems and without the need to maintain and replace a set of batteries that is almost never used.  See the link below for details.

Charging the Elec-Trak batteries during a simulated power outage using our PV array.

All the detail on our Elec-Trak project -- from scraping and painting to integrating it with our grid-tie PV system -- about 20 pages in all...

More Elec-Trak stuff:
For a rundown on the history of the Elec-Trak and a description of the various models, see Mark's article...

The Build-It-Solar section on Elec-Traks and similar electric machines...

One of my favorite Elec-Trac sites is George's My Elec-Traks site...  He has restored just about every model and also has lots of the Elec-Trak manuals and brochures.

The online Elec-Trak owners forum...

Just a bit of rust to clean up.

The new charger/inverter rides with the Elec-Trak when power is needed for 120VAC loads, or can stay back in the barn for charging.

The new charge controller that allows the grid-tie PV
array to temporarily be used as an off-grid PV array to charge
the Elec-Trak during power outages.

December 21, 2011

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