How to make Prius "forget" the battery's SOC?

I will hate myself for asking, but why do you want to do this?

 

It may work on the Prius but it quickly recovers and recalculates the current state when you hook it back up and put the car in "Ready".
No, it's not as accurate as it was, but no, it's never all that accurate. It's very difficult to -know- the state of charge of any battery.

 

The only true way to accurately monitor the SOC is with a ScanGauge. The car monitor is some what of a novelty and resetting it will not let you improve it's accuracy.

 

If you just drive your Civic around a bit, it will realize it's perception of state-of-charge is off, and initiate a recalibration, without your intervention.

A month is pushing the limit for IMA battery health. We had ours in the shop for a month, and I suspect that was instrumental in the battery's demise:

 

Unlike the Honda, the Prius battery is fine for several months. It does slowly loose charge but it's not necessary to mess with it. Pearl S sits in the garage for 6 months of winter with no ill effects. I DO keep a Battery Tender on the 12V battery if it's going to sit for more than three weeks. It can have problems if left to its' own devices.

 

Yes, but there are different flavors of NiMH battery including low self-discharge ones. Honda must have used really cheap ones or maybe even defective ones.

 

If so, why prius doesn't brick after 1 month or even 6 months of storage like some people do here. The only instances people reported completely discharged HV battery (in Prius) was when they kept driving with no fuel ($$$$ mistake).

 

When the Prius starts, the engine comes on and starts charging the battery. There is little or no drain during start-up.

 

The fact you never saw doesn't prove it doesn't exist. This was well studied and people use that (common) knowledge to rebuild HV batteries: http://researchcommons.waikato.ac.nz/bitstream/handle/10289/5714/PriusBatteryRebuildability-LeijenScott2011.pdf?sequence=1

Of course it takes a lot of driving and time for that to happen (more than 10 years on average).

 

Of course they did address it.
They said the center cells were weaker due to higher temps.

 

If I understand my battery hygiene 101 correctly, one leads to the other.
ie: higher temps of the cell modules in the middle of the pack lead to imbalance of the cell modules in the pack.

This is not the only reason cell modules become unbalanced, but it is a real good example of one of the reasons.

And according to a trusted authority on hybrid batteries, trusted by me, the prius NiMH modules far out preform the honda NiMH sticks

 

I drove one of those gen 1 prius for a weekend test in Oct. 200(1)? / pics archived somewhere.
I'm sure glad toyota followed a different path then honda followed for pack cells.
Don't get me wrong, I'm glad to have the hch and a few backup packs, as opposed to a non hybrid
but that is about as far as I'd recommend it to anyone other than a normal non hybrid driver,
as that is how they drive for the most part. In my biased view anyways.
The pack issues are typically personal and have several different scenarios that play out,
from the reports I've read. There are a lot of complaints about how honda dealt with them in the past.
ie: changing the pack warranty at least twice as they worked on a viable system update.
Besides honda is into space these days, not sure what that says about the cars.
I do still like their motor scooters. I could put a set of wings on their 375 lbs 900RR model.
And the old single swing shaft drive 800 interceptor was a marvel of engineering skill.
It had extra valves that engaged at 4k rpm I'm told, which I think are probably close to the same thing as vtec in the cars.
Lots of stories of riders accelerating into a corner as the extra valves opened up.