Ericbecky suggested it and I tried it, using a scooter or computer UPS battery as a 12v replacement battery. So far after about a year, my results have been without incident, The only thing about this battery is that you have to get creative to get the battery hooked up to your Prius. Here's the link: Sealed Lead Acid Battery 12 V 33 AMP VRLA AGM SLA (12V) (33AH) | eBay As you can see, the price is very reasonable. I've had it about 10 months and put about 5k miles on the car since replacing the old one. Hope this helps
