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Most of my battery experience is with flooded lead/acid batteries, since I am an experienced RVer. There, one doesn't want to leave a battery in a long term half charge state.

I'm wondering if there are any longevity rules as to the SOC on shutdown. I try as best I can to minimize the amount of assist I use, but in city driving or low speed hilly terrain, the SOC is frequently at about 1/2 on shutdown.

Should I deliberately change my driving habits to have full/near full SOC at shutdown.

Doesn't matter for NiMH.

I believe I read on Insight Central that they prefer to be parked at a partial charge state, just not for a prolonged period. Ron who refurbishes the batteries says if they've sat for three or four months, as a salvage battery might, that when put back in service they will fail within nine months or so. If you're not aware of his service he is refurbing the Insight and Civic hybrid batteries for $600-1000 by replacing the one or two bad sticks and rebalancing the whole. Claims good for at least another five years. Beats the heck out $5000 to Honda. All you're getting from Honda is a refurb for five times the $.

Jim, I prefer to park mine full, but then I don't use much in the way of SoC anyway. The logic is that then I don't have to fight charging to get high numbers on the next trip.

The NiMH battery itself won't be harmed by whatever state you which to leave it in... the issue is more with the BCM... Self discharging will eventually result in the SoC not being what the BCM calculated it to be... which then often results in a recal as the BCM tries to recalculate the current SoC.... this gets worse as not all the cells will have identical Self Discharge rates ... which can end up giving a false IMA error code... as the SoC of the cell and subpacks get out of balance with each other.

Jim, I prefer to park mine full, but then I don't use much in the way of SoC anyway. The logic is that then I don't have to fight charging to get high numbers on the next trip.
Ditto here. It's hilly enough around here that I have to go into the battery a bit. If it's gotten really low I'll sacrifice mpg on the way home to bump up the SOC before I park it. Not to completely full but to at least 2/3 full.

I'll sacrifice mpg on the way home to bump up the SOC before I park it. Not to completely full but to at least 2/3 full.

I did that today on way home after some congested driving with lots of auto stops. Actually got SOC so low that the car would no longer auto stop. The practice sure knock daylights out of FE. I guess it depends on how one looks at it. The engery to achieve decent FE under difficult conditions has to come from the battery, so it has to be replaced - leading to poor FE for a short period. No free lunch ;-)