Originally Posted by Grzpdlr
....every once in a while, it inexplicably drops to 50% or a smidgen less. Then the regin stays on at about 4 bars and it won't go much above 6 bars even with heavy breaking. If I do a reset, after a long delay, it returns to 19 or 20 bars. If I drive for long enough it will suddenly go back to a normal 19 bars. Is there a good explanation for this?
This generally sounds like a negative recal, caused by a weak battery, except for a couple small differences. The main one is that your SoC gauge is dropping only to half way rather than the 2 or 3 bars typical of the 'full-on' negative recal. Also, after a full-on negative recal, manual assist and regen are locked out while a forced-charge takes over; you say a forced charge takes over, but then you can add some regen by braking. This latter aspect tends to be normal after a full-on negative recal yet only after the HV battery has charged up some.
So, sounds like you're getting some kind of negative recal due to one or another kind of weakness of your battery... Unbalanced, one or more bad cells, maybe just overall deterioration... This would be my guess... And, by the way, just because the SoC gauge shows 19 bars most of the time doesn't suggest that the battery is 'great'; a better indicator of a decent battery is if the SoC gauge can drop low commensurate with the amount of demand on the battery (i.e. use a lot of assist, lose a lot of battery juice, gauge drops incrementally). And, if you've got only, say, 5 bars on the gauge, and you can still command a good amount of assist - that's an indicator of a good battery. With a bad battery the gauge will plummet after only losing few bars.
One more thing: there's a 'background' charge that kicks in when your HV battery reaches some kind of low threshold; mine seems to kick in around <65% SoC. This charge doesn't show up on the in-dash chrg gauge. It tends to be around 10 amps or less, depending on the engine load due to driving conditions and circumstances. You can still command assist and regen, but the charge will kick back in once you're cruising again. It will last until the SoC reaches some threshold; mine seems to be 70% SoC...