I don't understand why my 2005 HAH sometimes does not engage the charge regeneration upon coasting and/or braking.

Even when I've been driving for a while (i.e., the car is fully warmed up) and the battery charge gauge is showing only 3 bars, it will sometimes fail to engage the charging mechanism when I expect it to. (That is, the brakes do all the work of stopping, just like a non-hybrid.) I notice this behavior at in-town speeds (20-40 miles per hour), although perhaps it happens at higher speeds too, but most of my driving is in-town. If the battery charge gauge showed 4 bars, then this behavior would make more sense. But I don't understand why it would pass up the opportunity to charge up some when coasting or braking at only 3 bars. In fact, sometimes when I begin a deceleration, it begins to engage the recharging mechanism, but then stops recharging inexplicably while still at 3 bars, long before I have slowed to near AutoStop speed.

Most of the time after it has warmed up it behaves as expected, i.e., the recharging engages with all coasting and braking. Just not always.

Anyone else?