grid charging benefits on battery that hasn't failed?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by howardc64, Aug 23, 2026 at 10:04 AM.

  1. howardc64

    howardc64 Member

    Joined:
    Nov 11, 2011
    150
    58
    0
    Location:
    Pacific Northwest
    Vehicle:
    2011 Prius
    Model:
    Two
    11 155k miles HV battery in good working condition although capacity seems to be less than new (Goes less distance in pure EV mode) Curious what are people's grid charging benefits on batteries that haven't failed.

    Cell voltages differences (imbalance) seems to shrink quite a bit when operating the car. <= 100mV quite frequently. Although data include cell read latency errors as diag tool (Dr Prius app) could be pulling cell voltages serially and the computing the difference (What happens in my Tesla Model S) More accuracy is possible with are more constant load/charge so cells voltages remain steady longer. Anyway, not sure grid charging balancing benefit is so huge compared to the car just top balancing on its charging while operating. I guess grid charging will do a better job balance closer to 100% SOC with slow charge topping off.

    Reducing memory effect might have bigger gain recovering capacity? What are people's experiences? Is slow discharge cycle required or just drive the car in EV mode until lower SOC although BMS will probably never let it go very low.
     
    #1 howardc64, Aug 23, 2026 at 10:04 AM
    PrimeDan and bisco like this.
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    115,525
    52,914
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    grid charging was designed to extend the life of the battery before it dies. after it is dead, it doesn't work.
     
    #2 bisco, Aug 23, 2026 at 8:44 PM
  3. rjparker

    rjparker Tu Humilde Sirviente

    Joined:
    Jun 6, 2008
    11,150
    6,989
    7
    Location:
    Texas Hill Country
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    The primary use of grid charging is to provide a discharged hv battery enough juice to start the engine. Generally this situation occurs because someone parked the car for many months or could not resolve an engine no start and cranked the engine one too many times.

    These scenarios happen so rarely that most dealers have to have a hybrid battery charger sent to them when needed.

    Typically users that buy one end up selling it.

    Dr Prius and Techstream pull module voltages, 14 pairs of modules to be exact. Each of the 28 individual modules have several nimh cells wired in series. As a result you don't get a good look at one module much less the individual cells. But when a pair of modules are significantly different than another pair you lose capacity and the car will code.
     
    #3 rjparker, Aug 23, 2026 at 9:59 PM
(You must log in or sign up to post here.)