HV Battery theory and possible substitution

My HV battery is close to dead as I door nail (ten modules have about 5.5 to 6 Ah capacity the rest are in the low 4's to 3's) 28.5 mpg right now and part of this is due to using the AC all the time (temps in the 80's in LA right now).
Well my gift to my self it's my birthday today is a back-up plan. I have gathered about 34 older modules I will do re-hydration experiments on but I acquired 2 PACK! 40V 18.4AH 736WH LITHIUM LIFEPO4 96 A123 26650 POWERWALL DIY EV BATTERY | eBay this today well two the pair offered for a total of 384 A123 lifepo4 26650 cells coming my way.
want to talk about theory and my theory here if the other experiment doesn't pan out.
350 of these cells 5x70 would produce a nominal 231V about 10Ah battery which should fit with-in the casing of the toyota hv battery. if I do the math 5x5 cells would produce a 10Ah 16.5V battery (11.5Ah nominal but I'm considering the wear) 16.5V is a pretty full block on the NiMH side of things and well when discharging lifepo4 can go down to 2.5V min (2.8V is much better in this respect) which is 12.5V which would be dead discharged for a NiMH block. a little less than 14V is pretty much where a prius would start charging it with the motor
I'm thinking it could serve as a drop-in replacement that should last quite a few years with some maintenance occasionally.
The prius is a bms on it's own but I am thinking an additional bms-lite 14 little arduino's with shift registers that will check the voltages after the car is turned off and discharge the highest voltage cells and charge the lowest voltage cells and also once equalized it might also take a charge from a solar array I'm thinking of adding, however that would be a future upgrade :- ) (yes I got a bunch of solar cells laying around that would suit that purpose. ;- ) )
Question #1 what are the actual operating voltages i.e. when does the engine start charging (stop charging) and
Question #2 when does the car say no more on regen-braking. what does it consider 100%?
saw some numbers like 180V - 239V but I am not sure that is correct.
I know that it attempts to keep the battery between 80% and 38% which leads me to
Question #3 what are those voltages and the ones between by bar would be nice to have.
I am thinking and musing that I might utilize less capacity of the lifepo4, but since it has more overall capacity I might get a slight boost in actual usable capacity i.e. 500 Wh vs 400Wh in the case of a new NiMH. But dramatically more than with my current battery if I'm utilizing 200Wh I think I would consider myself lucky.

terramir

 

Theoretically the monitoring system should be happy as long as it's charged by the prius itself however if it's charged by solar cells / plug-in I need to ensure that the cut-off voltage is low enough to keep the prius happy I. E the voltage cannot be higher than the max voltage the regular battery might have if I turn it off after a huge hill. It should never tank too far on it's own I know there is a " knee" but the car should never reach that on its own unless I run out of gas
But I really need the voltages for the bars resting as well as charge discharge to really get a full understanding of the cavity
terramir

 

I have a cable and a laptop, but I do not know I can trust those values because I do not know how adaptive the prius is with batteries that are weak which mine is.
so I was wondering if someone had them right off the top of their head for a good battery.
terramir