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PriUPS Bonus: Multiple Supply Examples - The SMALL

Here are details of the "small" system, using a non-rack-mount UPS and a single 24V switcher.  As of the moment, I have not found a suitable UPS on eBay meeting my criteria.  I got what I thought was a perfect one, i.e., for almost free, but when I tried to use it I found it didn't have "cold start," which is critical.  More info as it becomes available...

  Small System
Power Available ~800W at 115VAC
Power source

Prius HV system - no power from 12V

Converters used One Unipower 24V 50A switcher (RMP24/50)
Voltage supplied to UPS 28VDC - runs UPS and charges UPS batteries
DC from Prius HV 210-230VDC,  6Amps
UPS model APC Back-UPS Pro 1400
System Weight w/o Batteries 23lbs UPS, 9lbs switcher = 32lbs


I was able to pick up an APC 1400kVA UPS on eBay for the usual song.  It was offered without batteries, which partly accounted for the very low price, but was complete with the Anderson connectors and the parts that make up the battery pack.  I realized after a quick look that this one would be almost trivial to modify. 
The yellow connector in the rear, as supplied, simply interrupts the ground conductor from the battery pack, rendering the UPS inoperable.  The UPS is activated by shorting the battery ground to the unit ground with the yellow jumper plug.
Here is a side view of the original wiring, with the two black ground conductors going to the yellow connector block.

My goal was to provide 24 volts from an external supply directly to the UPS.

1:  Remove the yellow connector from the chassis and pop the connector pin on the black wire going to the UPS circuitry.

2:  Remove the connector pin on the black wire in the battery compartment connector (top photo) and put it aside.

3:  Connect the black wire removed in step 1 to the battery compartment connector.

4:  Mount the battery compartment connector (grey) where the yellow connector was removed.

Performing the 4 steps listed above leaves the unit with the 24V input to the UPS circuitry on the rear panel connector.

The parts in front of the reassembled UPS are left over.  The two yellow Anderson connectors are unused.  The fuse link (blue cube) that would normally protect against overcurrent from the battery is unnecessary because the 24V power supply is current limited. 

Total weight of the slightly modified UPS and the 24V power supply is under 32 pounds. 

With a bit more work and a bit more weight one could rewire this system so that the batteries remained in the UPS and would be charged when the 24V supply was running.  This would allow it to provide power with the Prius turned off.  Since I received no batteries with the unit, I did it the easy way.

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Updated 26 April 2006