actually, this is an incorrect statement. the problem with ima is not that the system can only recharge from regenerative braking. both the hch and hah are capable of recharging through the ice and absolutely do not require braking to recharge. energy is sapped off the ice directly generally if your battery level falls below half and you're not braking. you will see the ecu kick in recharging.

ima only implements a single motor, the motor can't simultaneously act as a generator and a motor. but, ima could be reprogrammed to use a lot more of its battery power and then kick in regeneration to recharge it back up. that system however is less efficient than hsd because of losses inherent in energy recapture. the hsd system can directly power its generator which in turn can supply electrical energy to a second motor and therefore does not have the 20%-30% energy loss associated with converting mechanical energy into electrical.

basically, hsd has more power paths than ima. but it comes at the cost of a more complex system.

this is an unfair statement. there is no evidence that ima is inferior to hsd. taking into account cost/complexity and results, we see that ima is less costly, less complex and delivers relatively the same mpg results as hsd.