Any relationship between battery fan and lack of charge?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by davidj08, Aug 26, 2014.

  1. davidj08

    davidj08 Junior Member

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    2008 Prius w/114k miles. 08/22 we drove 75 mi to Lassen Natl Park, climbing from 300' to 8500' and then down to 7500' where, at noon, we parked Prius for 3 hrs. Ambient temp 75. Upon starting vehicle at 3pm, we noticed battery fan came on. When we looked at battery status on MFD, we observed batt was down to one purple bar. Battery status seemed normal, given we had just made a good climb into the Park. Fan stayed on for about 5 min then cycled off. About 10 min later fan came on again for another 5 min or so. As we descended out of the Park batt began to charge. By the time we were at 5500' batt was fully charged and green. Fan never came on again that day or since. In the six years we've owned vehicle we have never heard the fan come on. The question is: what conditions gave rise to a battery temp that activated fan?
     
  2. wjtracy

    wjtracy Senior Member

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    Possibly on the descent down to from 8500 down to 7500 you were at fully green (full batt) when parked for 3 hours?
    The battery is expected to heat up when shut down in this situation.
    We sometimes recommend not to park car when fully charged on hot day, especially for those with commutes that would make this a daily habit. The fix is to just take a bar or two off the batt before parking.
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I think you answered your own question: the climb to 8,500 feet took substantial power out of the battery, heating it up. Since the MFD only showed one bar at 7,500 feet, the battery didn't get much charging during that 1,000 ft descent.
     
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  4. davidj08

    davidj08 Junior Member

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    Many thanks to WJTracy and Patrick Wong for their review of this concern. What I learned from this episode is that when drawing down the battery, it heats up. I didn't know that. We've drawn the batt down a time or two before, for example in summer heat (95-100), sitting with ICE off and AC on, during a 15 min road construction delay. Batt went to purple, then ICE came on to charge it. Fan never came on because cabin was cool. Thanks again.
     
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