Thanks Dominick. That explains why the Honda battery has such a low energy density. Nonetheless, Lithium batteries are not harmed by frequent, low percentage charges. In fact, studies indicate that one can maximize battery life by keeping the SOC near 50% and doing frequent, shallow charges. For the OP, if he's able to do frequent shallow charges, that's great but to maximize battery life, he should keep the SOC hovering around 50% (e.g., charge to 70-80% and charge no lower than 30%). If he does that, he should also charge to 100% about once a month for cell balancing.
I think it's possible that this would help, the question is how much. In my opinion doing partial charging for the chance of some possible increased battery life makes sense only if the following criteria are met:
1. There is no sacrifice of EV miles, i.e. having to use some gas because of not charging to full, or using gas to avoid running EV miles down to 0.
2. It is convenient to partially charge, i.e. it doesn't take much effort.
3. The owner enjoys doing this, i.e. they find it interesting and sort of fun.
I think for most people #2 is the problem for the Clarity. It's not very convenient because it requires doing scheduled charging and some mental math. Even if someone is already using scheduled charging because they are on a time of use rate plan, they can no longer just leave it on autopilot with a fixed daily schedule, but instead have to modify the ending time each day to get the desired level of charging. Although in some cases partial charging can be done by simply not plugging in when you know that you have enough charge to get through the next day.
If it's not convenient then #3 is probably unlikely also. Which means they are diminishing the enjoyment of their car now just for some possible slight gain later on.
But if someone likes doing all of this, go for it. But I agree they should still charge to full every once in a while. In fact I wonder if cell balancing only occurs when charging from 0 to full in one session? That's how the battery capacity measurement seems to work, the value displayed doesn't seem to change unless charging from 0 to full in one session. Maybe the battery capacity value only updates after cell balancing has occurred, which would indicate that cell balancing only occurs after charging from 0 to full. This could explain why the owners manual says, "To help extend the lifespan of the battery, it is recommended that you fully charge the battery each time prior to driving".