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PriUPS Bonus: Multiple Supply Examples
I am putting together some "systems" in addition to the primary PriUPS system which resides at home. In addition to demonstrating feasibility, they will let my Prius have more adventures since it will be renowned as a power plant on wheels. All of these systems are completely portable and can provide power while the Prius is in motion as well as when stationary. Here are the specs:
| Power Available | ~800W 115VAC | ~1.4kW at 115VAC | 2.7kW at 115VAC | 2.7kW at 115VAC |
| Power source |
Prius HV system - no power from 12V |
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| Converters used | One Unipower 24V 50A switcher (RMP24/50) | One Cherokee 48V 30A switcher | Two Cherokee 48V 30A switchers | 5 Unipower 24V 50A |
| Voltage supplied to UPS | 28VDC - runs UPS | 48VDC - runs UPS and fits in empty battery compartment | 104VDC - runs UPS and fits in empty battery compartment | 140VDC - runs UPS and charges UPS batteries (if five switchers used) |
| DC from Prius HV | 210-230VDC, 6Amps | 210-230VDC, 10Amps | 210-230VDC, 17Amps | 210-230VDC, 17Amps |
| UPS model | APC Back-UPS Pro 1400 | HP/COMPAQ R1500XR (2U rackmount) | HP/COMPAQ XR 3000 (2U rackmount) | HP/COMPAQ XR 3000 (2U rackmount) |
| Weight incl. UPS batteries | 23 lbs UPS 9 lbs switcher. No batteries | 30 lbs UPS, 8 lbs switcher. No batteries. | 35 lbs UPS, 16 lbs switcher. No batteries. | 80 lbs UPS, 45 lbs switchers = 125lbs (preliminary) |
| Weight w/o UPS batteries | 32 pounds total | 38lbs | 51 lbs | (I'm leaving the batteries in the system) |
As you can see, carrying around the 800W supply has a negligible weight penalty. Even the largest 2.7kW system only weighs about the same as a small passenger. There are additional opportunities for weight savings. Although I show the weight of the system with and without the batteries that are part of the UPS itself, removing them is optional. Running the UPS from an external source of voltage equivalent to their internal batteries works fine for the APC, R1500 and R3000, but I'm not sure that's universally true. Batteries can provide much greater peak currents than the swtichers can. Adding a largish capacitor (a pound or so) to replace the battery packs in each UPS might salve my conscience, but would also reduce the versatility of the UPS since it could only be used with the Prius running. On batteries it can supply power briefly without bothering to turn the car on. Another consideration: if the switcher is only to run the UPS rather than also charge the batteries, it can run at the battery nominal voltage, e.g. 48V, instead of the correct charging voltage, e.g., 56V. This is convenient if, for example, your supply is fixed at 48V.
I'm working on four systems, as detailed in the table above. The small, medium and large "A" system are complete as of this writing, 08 April 2006 (and update, 26 April 2006). I've been keeping one or another running in the trunk as I drive around and using it to power loads in the car. The large system "B" is under construction - I'll add to the linked information (top line of the table) as they progress.
Updated 26 April 2006