Piston Slap: Long Term Ramifications of Prius Abuse?

Sajeev Mehta
by Sajeev Mehta
piston slap long term ramifications of prius abuse

TTAC Commentator 1981.911.sc writes:

So, today I passed a guy putting gas in his Prius on the side of the road. I assume he ran out of gas. Irony?

My question: can a Prius run on just battery power when the gas tank is empty? And if this guy ran it out of gas AND drained the battery, was he FUBAR? I assume it has to have a good battery to run, gas in the tank or not.

Sajeev Replies:

The short answer is yes: according to this Prius owner it can go a couple of miles on battery power alone. But the Prius isn’t supposed to run like an EV: running a Hybrid on empty is murder on a battery pack. Most, if not all, batteries do not play nice after running below their voltage range. In the case of a Prius (according to Google) that is 273.6 volts coming from 228 batteries with 1.2 volts each.

The question is, at what voltage does a gas-less Prius resign: completely taking a dump, telling its owner to go pound sand? Conversely, will a Prius save itself to live to fight another day?

Because if it will not, the battery pack is Tonya Harding’d and on a short and painful road to the recycling center. See the “Over Discharging” section of Wikipedia’s Nickel-metal hydride battery page to see how/why this happens.

Don’t you just love it when answering a question opens a whole new can of worms?

(Send your queries to mehta@ttac.com)

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5 of 26 comments
  • Pgcooldad Pgcooldad on Jan 08, 2010

    Forget the Prius. Which make is that nice looking white truck in the background?

    • Sajeev Mehta Sajeev Mehta on Jan 08, 2010

      "It's a Hyundai. Yes Hyundai."

      (if you remember those advertisements, kudos to you.)

  • JuniperBug JuniperBug on Jan 09, 2010

    While I'm sure that running a fuel pump without gas to lubricate and cool it is bad for it, how long would the pump actually be running in such a condition? On any injected system, it seems to me that the pump would prime for 5 seconds or so when you turn the key to run, and then run for the few seconds that you're cranking the engine. At any other time, the ECU should sense that the engine isn't turning and therefore not energize the pump. How much could a little pump overheat by occasionally running dry a few seconds at a time? When you start a cold engine, you're basically turning it over unlubricated for the couple of seconds until oil pressure builds, too, and that's a completely normal operating condition.

  • AJ AJ on Jan 09, 2010

    I can understand this, as I have several Jeeps that get 14 to 17 mpg vs. my daily driver a Civic that gets 34 mpg and sometimes I just push it with Civic thinking it can go a little longer (I like to hit 400 miles per tank). With the Jeeps, I'm just use to filling them up. (lol)

  • Ronman Ronman on Jan 11, 2010

    i know voltages don't compare, but after my experience with R/C cars, discharging batteries NiMh batteries helps extending their lifespan. in any case, my 7.2V 3000mah packs were used always to almost complete discharge, that was the rule to keep them for longer anyway...unless the people that told me so were wrong in the first place yaykes....