RE: Pre heating and cooling
I don't know. Yet. I have bought a current/energy monitor and I asked the installer to leave a loop of the live wire inside a junction box when he fitted it. [Stupidly, I did not ask if he could fit a 3 pin outlet on the same circuit, so I'll not be able to repeat that with the 10A lead.)
So at some stage, I will set it up to monitor input power/energy. I'll familiarise myself with the characteristics of the Fluence's charging behaviour, then I'll have a better idea what is going on.
With the 10A lead, it'd be charging less that the '0.15C' rate, which would ordinarily be considered to be sufficiently slow that there would not be a saturation charge. But I expect there will always be 'a little' saturation charge, and I expect that is, indeed, what you are seeing.
As an Li-ion battery is charged, the 'actual' open-circuit voltage at rest for a fully 100% charged cell should be 4.2V for 100%. So the charger will get the cells up to 4.2V. An 'instantaneous' evaluation of the cells might then determine that they are at 100%, but actually the cell voltage will drop when the charging current is discontinued.
Or alternatively the current is ramped down once the cells are at 4.2V, until the current drops below some pre-set value, rather than simply shutting of the charge current. This is the start of the 'saturation' charge. However, once the battery is 'rested' by the monitoring electronics, the cell voltage will drop again, and applied charge may, again, exceed the pre-set minimum current for charging. It will keep iterating this, until both a) the cell voltage is 4.2V, and b) an applied charge current does not exceed the pre-set minimum.
If charging were to continue above this, the cell voltage would become dangerously elevated. Above 4.3V the cell electrodes begin to become plated in lithium, permanently damaging capacity, and if it continues too long then it may produce a short, through which the other cells in parallel with it may discharge and cause a 'thermal event'. So it is essential not to apply too high a current that might lead to the cells exceeding 4.2V.
It is quite possible that Renault have designed the system not to even get to 4.2V, but instead to regard a lower cell voltage as max, such that you only see 22kWh of what might actually be a 25kWh battery. In fact, the Leaf battery is a 24kWh battery for which only 21.5kWh is made available. Consider the actual battery pack of the Leaf is 200kg and the Fluence is 250kg, I would have guessed that Renault have built in quite a big overhead in the unused battery capacity. GM claim the Chevy Volt only uses 64% of its full battery capacity, missing 20% at low SOC and 16% at high SOC. This keeps the cells well within their optimum range for maximum longevity.
I might guess that Renault do likewise as their batteries are leased, and they want to maximise their survival. It may also be that as the battery ages, the software is set to make use of some of that overhead capacity, so the battery does not appear to age quite as badly as it might be - I don't know if that is true, but it is possible they might have done it this way.
For example, equipment that is routinely held on charge, such as emergency equipment with Li cells, will cycle between, say, 4.0V and 4.05V, such that 4.05V is considered the cell max voltage. This reduces voltage stress considerably and extends life when held at that voltage. It is always best to avoid high cell voltages altogether if the battery is to be left for any length of time. If you charge to 100%, try to do so only just before you set off, so the battery spends the least time to those high voltage stress levels.
For fast charging - not that this applies to our current model Fluences - the reason the charging only goes up to 80% is because fast charging does not enter the saturation charging regime. In other words, it applies a constant maximal charging current, and as soon as the cells hit 4.2V then the charging stops, so there is no ramp-down of the charging current.
(All of the above is to the best of my understanding of Li-ion tech, and if I have any of the specifics in error, then I'm happy to be corrected and educated further!)