SPA T8 12V battery depletion after not driving for too long.
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    1. #1
      Junior Member Kranvagn's Avatar
      Join Date
      Nov 2018
      Silicon Valley, CA

      Post SPA T8 12V battery depletion after not driving for 2 weeks

      Over the holidays I spent 2 weeks out of town and returned home to a totally unresponsive XC60 T8, though thankfully this was in my garage and not in long term parking.
      After the fun of figuring out the emergency key and how to use it, I tested the battery terminals under the hood and found barely 4V.

      One nice thing was that 'jump-starting' the vehicle was easy, since you don't need to supply enough power to actually crank the engine (the SPA T8 ICE has both no starter and no alternator (and no dip stick! WTF is the world coming to...)), so simply enough amps to boot the computers and turn the vehicle 'on' was enough for the DC to DC converter to fire up and start charging the 12V system from the HV battery.
      And yes, my HV battery was full, she was plugged in the whole time. Note that only charges the HV battery pack, and the computer is supposed to be smart enough to then charge the 12V system from the HV battery periodically. Supposed to...

      Searched the forums and found that "Service Campaign A39981 : BECM Software Upgrade" is supposed to fix this, emailed to my favorite service advisor and she confirmed the likely diagnosis and set up a re-programming appointment under warranty. Just got the vehicle back last night and looks like they gave me a full reprogramming of all modules ()

      I find the notes interesting...sounds like there was a bug where if the HV SOC (state of charge I presume) is continuously full, the computer never cycles the DC to DC converter to charge the 12V system? Dumb logic there, I would presume it's now smart enough to cycle now and then even when the vehicle is never turned 'on'. Will look for a 2-3 week window ahead where I can strictly not drive my vehicle and see if it's really 'fixed' or not. Might be fun to figure out how to data-log the 12v system voltage during that duration too, hmmm...

      Anyway, just wanted to share the news for folks who run into similar problems.
      ps, no I'm not worried about the health of the 12v battery, it's AGM and designed to take some deep cycles.
      pss, yes I got a warning during my trip from the Volvo app that the vehicle was going into sleep mode to save power, though I didn't keep track of exactly when during that 2 weeks I got the warning.
      Last edited by Kranvagn; 01-23-2020 at 12:02 PM.
      2019 XC60 T8 Fusion Red R-Design - -

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    3. #2
      Member lamarguy's Avatar
      Join Date
      Aug 2006
      Interesting, I've left mine alone (not plugged in) for two week periods (3 - 4 times) since I've owned it. No issues.

      I do try to leave the HV battery in a 25 - 50% SOC for long stays, per Volvo's recommendation.
      OSD '18 XC60 T8 Momentum - 22" 10-spoke wheels, lowered air suspension, strut tower bar, Stealth hitch

    4. #3
      Member Gary-16-Xc90's Avatar
      Join Date
      May 2015
      Twin Cities, MN
      The recommendation in the manual is to leave your hybrid at ~25% charge while being gone for an extended time. Do NOT leave it plugged in.

      If the hybrid battery is 100% full, the EV charging will not be sufficient to re-charge the 12v batteries once you return and plug it in.

      Following the recommendation in the manual has worked 100% for me on extended non-driving, such as 50 continuous days.

      Sent from my iPhone using Tapatalk Pro
      2016 XC90 T8 Inscription | US 10/2015 Build| Crystal White | Blonde | Blonde | B&W | Air | HUD | Convenience Vision Climate | PAII + Mitigation Upgrades | Xpel + Gtechniq Ceramic | 3M Crystalline 50% Tint, 97% UV Rejection, 60% Solar Heat Rejection | 20" A/S & 22" Summer | Tow | Last TSU installed 17 Jan. 2020 | 46K miles | MPG 31.8 Lifetime including transcontinental trips, regional trips and even towing

    5. #4
      Junior Member skibum50's Avatar
      Join Date
      May 2017
      Northern Kentucky
      Wow, I'm very glad to learn this. Never noticed in the manual before. I've left mine plugged in for a month or so twice now, with no problem on my return, but apparently I was lucky.
      2018 XC60 Momentum T8 (OSD March 2018)

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