Adding 2nd Lithium pack in Parallel

I was focused on whether fuel economy would be improved, not on acceleration. However, I don't see how it would increase acceleration since the software that controls the hybrid system wouldn't change and currently, to my knowledge, acceleration is not affected by how much charge the battery has. When the battery is nearly depleted, the ICE revs more to send some more power to the electrical system to maintain torque/power.

I live in Colorado with long uphill drives in the mountains, including a 14 mile, 2,000 ft elevation gain near my home, and never felt a loss of acceleration. So I don't expect that adding battery would change that.

 

this is an interesting study about the topic.. it seems to give positive answer to both the questions "is it possible" and "is it worth"

 

just added to this thread a relevant study about the topic, hope u'll take notice of that. You're right along all the line.

 

interesting study, but i couldn't find the answer to 'is it worth it', or any cost involved

 

Ask @jacktheripper if he thinks it's worth it.

It's a complex system that is only getting more complex as battery technology advances.
It's expensive to add another pack to a car and the benefits are not completely doubled as most might believe at first when pondering the issues.
If you can DIY than it can easily pay for itself within the lifetime of the car, but there are a lot of reasons for that not necessarily related to the extra battery pack itself.