Re: (ET) controller, today and tomorrow!

["Monty McGraw" <mmcgraw74 hotmail com>]

My plan is to use 6 eight volt Trojan T-875 golf cart (special Club Car
design) batteries for a 48v pack in my E20.  This will sacrifice some
range - roughly proportional to the voltage change - for higher power to 
the
main drive - roughly proportional to the voltage increase squared or around
70% more power.

To charge the system I bought a Trace DR-1500 inverter charger which
requires a 24v battery pack (:
They don't have 36 or 48v versions.  The Trace inverter can do 1500watts
continuous and surge loads of 2500 watts, which should start up any AC 
tools
that plug into standard outlets.  As a charger, the Trace will put out 50A
in bulk charge mode and has microprocessor algorithms to taper the charge
for not only lead acid, but several other battery chemistries as well.  It
also is switchable to provide equalizing charges.  I plan to squeeze it
above the front battery pack, where the GE inverter was designed to mount.
I can mount AC convenience outlets on the right side similar to the PTO
connector mount on the left side.

This means I have to add a couple of SPDT contactors to switch between 24v
parallel (for charging) and 48v for main tractor operation.  I plan to have
one of the 24v packs connected to the inverter when the main contactor
closes - so I can have 110VAC power while the tractor is operating.  These
contactors are powered by 24v and switch 24v.

I bought a small 1QD-70 amp controller (48v) to drive the mower deck at 36v
using a fixed voltage input to that controller.  I could switch that 
voltage
down to 18v for the lift motors, but that would be mutually exclusive of
running the PTO circuit.  Lee Hart suggested I might not need to drop the
48v pack for the mower motors, but I'm not sure after reading the user
manual.  I'm trying to avoid tapping the battery pack, so I don't end up
with weaker batteries that get undercharged.  I think that by putting the
two 24v strings back in parallel (when the tractor is off), that the
stronger side will dump current into the weaker until they are better
equalized.

I picked up a 48V golf cart battery level meter and had Westach make me
a -100A to +300A current meter (catalog item) so I can monitor both charge
current and discharge current with their matching shunt.

I won't be using any of the original wiring or other components.  I don't
know if any of the boards or contactors is worth saving.  My E20 had
apparently been previously used for spare parts.

Monty McGraw

----- Original Message -----
From: Hazen, Dwight L <hazen indiana edu>
To: electrak list <elec-trak cosmos5 phy tufts edu>
Sent: Tuesday, December 14, 1999 12:14 PM
Subject: (ET) controller, today and tomorrow!



I have a E20 frame on saw horses in my basement with fresh paint and most 
of
the hardware back on it. Now I have to start thinking about how to supply
power to it. So I am most interested in any discussion on how to do this.

 It looks like there are two off the shelf controllers that might work?

Curtis,
http://www.curtisinst.com/datasheets/faxmasters/controllers/1244fax.pdf
http://www.wilde-evolutions.com/PriceList.htm

4QD controllers, http://www.4qd.co.uk/ 4QD-300-36 . . £220.00 . . $396.00
Looks like this would cost under $400 for a full featured 300 amp
controller. Do we even need a 300 amp controller? Should you get a 48 volt
controller and add an extra 6 volt battery to the tractor? Would you want a
simple controller then for the mower deck? 36   volts when the grass is
short, hit the turbo button for full battery voltage to the deck when the
grass is high. What about the snow thrower and roto tiller, is 42 volts to
much for them?