How to ruin 05 Prius 12v battery

Looks like you're reached the right conclusion. Gentle/normal discharges don't produce shorted cells. The battery was probably initially defective and somebody's making some $$$ at 179 a copy. Any gold on the terminals.?

Others here will have more insight from Toyota's perspective, but to me as an owner this sounds like a warranty issue. If your dealer balks, follow the chain upward. You might have to buy the replacement to get back on the road, but eventually there should be a reimbursement.

The matter of fault is blurred. I worked for GM years ago, and we designed in expectation of owners' imperfect behavior. I suspect that at any given moment there are many cars worldwide with their lights unintentionally on.

Good luck, Brent

Leaving lights on will not produce a shorted circuit in the 12 volt battery. Leaving the battery in a discharged state will sulfate the battery, reducing its ability to hold a charge. 3 days does seem a little quick to ruin the battery, and hopefully, the dealership will cover it under warranty for you.

good luck!

Someone's getting hosed at that price - but you knew that... ;-)

That accessory battery shouldn't have gone bad on the first deep discharge, you should be able to get away with that mistake a few times at least. That said, they should warranty it at least once.

Once you are out of warranty, FWIH you can just put a regular car battery in there - judging from the last half of that "S26B24" part number, previous discussions in the newsgroup, and Interstate's website where a search on Prius popped the Group 24 page up, it's a standard BCA Group 24 wet cell. And no three week wait, the worst you have is overnight for the local delivery truck if they don't have the exact size you need on the shelf.

That 12V battery is there to boot up the computer, run the radio and accessories, the dome lights, and the emergency flashers in case of a breakdown - the high voltage NIMH battery pack does the actual engine starting duties.

The ONLY difference might be in the battery charging circuit voltage, and that only requires matching the battery chemistry type and the same amp-hour size range. Doesn't require a PhD to get right.

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Thanks, FanJet, Brent, Ray and Bruce - - The new battery is in and working perfectly. Stevens Creek Toyota was the only dealership in Silicon Valley that had the battery and they stocked one of each (one 28800-21180 Nippon Denchi S35B20L for 2001 - 2003 Prius, and one 28800-21170 Nippon Denchi S46B24R for 2004-2006 Prius). The price was $152.57 plus tax or $165.16, and I had to go back to retrieve the small fitting, that attaches to a rubber gas vent tube, from the battery I turned in. To do the entire job, all you need are 10mm and 12mm, 3/8-drive sockets on a long extension bar, 3/8 ratchet handle, and a 10mm end wrench, taking care to remove the ground wire first and reattach it last. The computer system took a little time to come to its senses, but after a short time at Ig-On, exercising the driver's window until its automatic mode worked correctly, and opening and closing the rear hatch a couple of times, it remembered how much gas is left in the tank, and allowed me to re-program the radio stations. Since my car was purchased as a salvage vehicle, there was no warranty possible on the battery, but the new battery is warranted for 1 year, so that's not too bad.

Chuck

I dunno...this wasn't so on the Prius 'Classic'. When the wet cell went dead, you were done. Have your AAA paid up!

I'm pretty sure Bruce is right, going by recollections of the manual (rather long, rather repetitious, rather dull, yet quite informative).

The manual describes a process to use if the secondary battery dies, which involves opening the bonnet (US:hood) and connecting jump leads to terminals in the engine compartment. You need to do this because the boot (US:trunk) lid is unlocked electrically, by the secondary battery which lurks in there. This sounds like another of those changes made during the inter-model revamp.