Increased battery range after service for check engine light

[Lonewarrior]

The two coldest days we've had so far this year. First occurrence, cold soak, overnight early morning temp was 29F, but low 30's by the time I launched (after pre-heating with lvl 2 plugged in) and likely mid to high 30's at onset of cautions.

It made a re-appearance this past Sunday after an overnight/early morning temp of 23F, in this case, a few hours away from home overnight outside in the driveway plugged into lvl 1 at my son's house. We were babysitting a grandson and fairly early in the morning I unplugged and moved it out into the cul-de-sac in the sunshine. Pre-warmed on battery before departing in the early afternoon and got a recurrence of the HV batt codes and simultaneous "power system" caution 240 miles after the first occurrence. It was probably about mid-30's again at onset of the problem. Again, running in HV/Sport at onset, about 55-60 mph steady state.

Cleared codes, re-charged. Took it to town and back in sport, all EV operation, and actual miles driven were 80% of EV miles depleted.
No codes, but it was warmish today, low to mid 60's.

The code appeared as a result of the pre-warming. A cold and older battery charges more slowly, and when pre-warming begins it immediately places a heavy demand on an already weaker pack, causing the vehicle to draw power from the charging station at its maximum rate. That in return triggered something the BMS didn't like.

Next time, take a look at the charging speed when the battery is cold and observe what happens to the charging power when the climate control is activated. I’ve seen many instances where charging power was limited to around 4 kW due to low temperatures, only to surge immediately to 7 kW (maximum power) once the climate control was turned on.

I don’t believe this indicates any harm to the car; rather, it’s simply the vehicle signaling that the battery pack is aging.

 

[PriusGeek]

OP, any updates? More codes, battery range back to normal?

As it turns out, yes! It took a few months, but after completing a road trip from Texas to Wisconsin in October (12V crapped out on the way, but that's a different story!) the same codes reappeared along with the "power system" warning and the range slowly returned to where it was or thereabouts. Its a bit tricky to know what the actual range is because of the massive temp change up here (70f when we left Texas, -10F last week here) and the fact that we don't have access to regular charging (using the self-charge to keep the bees at bay), but its absolutely less than it was. Per the dealer we took it to last time, I believe this is going to result in a battery pack replacement. Of course that could take a couple of years and we may or may not own the car then...

 

[Keith Smith]

Bad cell/bank?

 

[Lonewarrior]

Bad cell/bank?

Likely not. The car will brick itself if there’s a truly bad cell. In fact, as I mentioned in a previous post, one owner drove for nearly two years with the same fault codes before the battery pack was eventually replaced. If there are no observable symptoms associated with a given set of codes, it strongly suggests normal (or abnormal in some cases) battery aging rather than an imminent failure.

It’s almost ironic how many of us, including myself, kept a hawk’s eye on the 36.6 Ah mark. 6-7 years later, it turns out the car will ultimately tell us when the time has come.

 

[PriusGeek]

I honestly don't know the details yet. The car is out in the open and its been so cold here that I haven't wanted to sit in the car and take the time go through finding the data I need to troubleshoot! I plan to take a more detailed look when I get back to Texas (and 80f weather!) next week. And to second Lonewarrior's comment, the car drives normally and has shown no signs of odd behavior since this started last summer. The dealer told me last summer that they have at least one Clarity that has been waiting for a battery pack for more than a year, so I hope I can wait out the replacement.

 

[Landshark]

Next time, take a look at the charging speed when the battery is cold and observe what happens to the charging power when the climate control is activated. I’ve seen many instances where charging power was limited to around 4 kW due to low temperatures, only to surge immediately to 7 kW (maximum power) once the climate control was turned on.

You’re seeing 7kW because you turned on climate control. It’s drawing more power. It isn’t necessarily charging at a higher rate.

 

[Lonewarrior]

You’re seeing 7kW because you turned on climate control. It’s drawing more power. It isn’t necessarily charging at a higher rate.

What I understand is that the electricity is still going through the battery pack first then the pack supplies power to the heater. Unless when the climate control is on, the heater or AC somehow disconnects from the battery pack and draws power directly from the station.