Dead battery question

Draining a battery will not kill it, usually.

It should work fine. Life may be slightly shorter if you do it often.

Dont know about warranty. Usually the battery is covered under the battery manufacturers warranty.

 

your battery is only a couple year's old... It might die sooner but that's still a year or two or even more away....

 

if it works fine, it is fine for now. if the car exhibits any odd behavior in the future, start diagnosis by testing the battery.

 

It helps that the Prius 12V is a deep cycle AGM battery and can better stand deep discharges compared to a normal starting battery with their thin, warp prone plates. Just fully recharge the 12V (several hours driving will do that).
I have a small battery charger / maintainer / desulfator that has it's wiring harness connected directly to the 12V battery, with the small charger stored in the plastic package tray under the rear floor. If I partally discharge the 12V and will not drive it for a few days, or will not be driving the Prius for several weeks, I connect the charger to the battery pigtail route it outside through the rear deck seal and plug it into an extension cord. This recharges the battery and maintains it at full charge while removing any sulfation that developed on the battery plates from being discharged.
The one I like is the BatteryMINDer, sold by northern tool co. It is one of the few maintainers that are safe for an AGM battery. Others may dry out the limited supply of electrolyte contained in an AGM battery.
BatteryMINDer Charger/Maintainer/Desulfator — 1.3 Amp, 12 Volt, Model# 12117 | Battery Maintainers| Northern Tool + Equipment

 

Patrick recommends leaving the car in ready, and letting it charge for at least 8 hours after a battery depletion incident.