P0A80 code for hybrid battery, but no decreased MPG

2010 Prius - 176,407 miles on the odometer as I write this

So I am getting the P0A80 code with no loss if MPG, peak of about 50-52 mpg before and after (17inch rim option and traffic so 45-48 average and 50-52 peak is as well as I have ever done in this one when looking at the every 5 minute record of MPG in the display). It seems a fairly reasonable assumption that it may be an issue other than an actual bad battery, correct? Curious other peoples thoughts.

A couple of my last few trips I got some shaking/knocking on start up that some say is ICE related (getting in sync?) or condensation in the intake manifold causing temporary vapor lock I think I read. Possibly related as it is a new symptom, but possibly unrelated since the car hadn't been driven in 3 weeks. Prior to the first time I thought it was from the oil draining out of the engine due to not driving it for 3 weeks (girlfriend had COVID), but then it did it the next drive also so it wasn't an oil drained down issue. Not sure if this is separate issues with the "check hybrid system" or related trouble. The only code was P0A80. The code wasn't thrown till 5 trips after the first shaking and the P0A80 code says it is for a second in a row trip failure.

A few months ago I drove through 5 inches of flood water and got the check hybrid system (didn't get the code checked before the lights went off), which went away after the car dried up over night in the garage. I had seen a post on here that someone's car had done that occasionally for years. (I lost my undercarriage plastic running over a truck tire on the highway and really need to replace it).

So that's some background. Yesterday I got the code again and hadn't run through water, but the code is for a second failure so perhaps the previous time it got wet wiring. It has been raining but generally this is not an issue so I didn't pay attention to if I ran through puddles that previous trip.

That's a lot of confusion symptom and background wise, but I figured I would see if anyone had any thoughts. My current plan is to watch the MPG and battery charge level. I should note that as I started driving it this morning the battery had about 3 bars and is doesn't show to be charging but when I arrived at my destination the charge was maybe twice as many bars. In settings for the display is shows ECO, so maybe the system is showing not to be working on the display but might be stuck in ECO mode and possibly working, explaining the lack of a drop in mileage?

It's worth noting, that although the mileage has remained unchanged and the battery bars increased, I don not believe it has been running in battery only mode at all. I will verify this on my next drive. I've driven about 70 miles since the code so if the battery was not contributing to my MPG, surely the MPG would have dropped by now. I'm a bit confused by this. If nothing else I figured it would be nice for me to document this experience for others searching old posts in the future (generally my go to procedure with so much good info already discussed here).

Oh, one last note. Originally when the lights went on, the anti-skid light and one other was on, as well as the brake system warning light. After turning off and back on, only the death triangle and check engine light remain, plus the check hybrid system display.

After last time I had issues, all worked just fine after the lights went away, and in fact, aside from no performance or battery mode, the car runs and operates as before, just with lights and some hybrid functions not working. Will update soon.

 

This time my check hybrid system lights have stayed on. MPG remain high but it tends to hesitate/stumble a bit in stop and go traffic, I believe when it wants to turn off the gas engine but they realizes oh crap, can’t run this car on the battery alone.

I think I’m going to take a chance on the Prolong deep discharge and charging system. I have seen good results on youtube from others using a much cheaper home made version, but fool proof and easy have to be worth something, as does not having to piece items together and hunt down supplies. Plus it might recoup some cost in resale value if I ever sell the car.

 

Also, a lesser investment if I learn it is something other than the battery, but with the P0A80 code it seems to be the battery.

Will hope for the best and update my experience later.