garygid said:
Battery-Cell Management - a difficult task:
<snips>
The Quick-Charge ("L3") apparently stops without spending time trying to "balance", so the more conservate 80%-charge figure is given. In fact, with a well-balanced battery pack, there is no good reason that a Rapid-Charge could not get a 90%, or even 95% charge.
Maybe, Gary. It sounds like you're describing 'top balancing' where the system must completely fill each cell to the designated 'max'. There are other methods available for balancing - some of these made easier by the more lead-acid-like slope of the LiMn charge/discharge curve over the relatively flat curve of LiFePO4 or LiPo. If the car is monitoring the capacity of each parallel group, for example, it can shuttle energy around so the pack's balanced at, say, 60%. We have no indication that Nissan's actually doing that, though - just like we really don't know if they're top balancing.
What's more likely - and what's already been done with earlier cars - is that the system will keep voltages in check day to day while allowing everything else to shift a bit with time. When the pack and car's computer get out of sync, the car will likely call for service (throw an error code) and we'll (er, I mean the dealer tech...) will follow the discharge/recharge re-sync process in the shop. This is required now for things like laptop computer packs and earlier EVs like the Ranger and S10.
Here's an example procedure.
I don't agree with your assessment of a 90 or 95% quick charge - even if only talking 90-95% of the smaller 'user' charge range - solely because of heat.
Pack balancing is not something that's going to be left to us users - we don't have to think about it or worry about it. We don't even have access to the top or bottom range of the pack - so top- or bottom-balancing isn't even something we can do! Best we can do is label it "FM" (freakin' magic) and move on.