Does each block have to be 14V?

I would like to experiment and replace the HVB with lifepo4 batteries. The only ones I can find online all seem to be 12.8V, with four cells of 3.2V wired in series. Im assuming they have a built in BMS already for the battery.

The issue is, 12.8V will not equal the equivilent of the NIMHs 14V, and while I could just add two extra blocks to make a total of 16 instead of 14, the prius battery system only has 14 sensors. And i am not fully aware of how the priuses BMS uses these sensors plus temp readings to calculate charging, discharging, and state of charge.

I notice my OBD2 readings at 30% SoC the voltage is around 13V, and highest 60% SoC got 18V max for each block.

A battery of 12.8V would potentially be overcharged at 18V, no? Or does the volts not matter for the system as long as all the batteries are wired in series to equal to 201V as close as possible?

I took a look at nexpower being taken apart on youtube and found that they use total of 12 cells per block, paired together in parallel, making 6 cells of 3.2V wired in series, which should equal 19.2V. Thats about 268V all together if theres 14 in total. My question is, does the prius let them drop as far down as 13V before recharging or does it know its boundaries and charges it before it gets that low? If so, how?

And next, what could potentially go wrong if I did wire 16, 12.8V batteries in series for a total of 204V? With two of them not being read by the prius considering they wont have any volt sensor attached. Is there a better way to configure perhaps?

 

You are correct. Rewatched and noticed one of the empty slots was where they stored the BMS in. This makes a lot more sense now, considering 3.2x5= 16V. And 16V falls conveniently within the minimum and maximum charge of the original perimeters of the HVB. That should also keep it within spec of 201V, only slightly higher at 224V. Which can only be advantageous to slight power output.

Its a shame 16V batteries are not common like the 12V ones. Time to wire up 3.2V and look for 16V BMS i guess.

Ive noticed, and thinking about it some more i dont think if I add 16x12v in series will work without reprogramming the whole controller. Im going to guess id get hybrid triangle simply because itll read as low volts. My best solution is to go 16V similar to nexpower without changing much else. Im sure hondas and subus have less safety nets, but i never owned any to mess around with. I specifically chose prius because its the most common and abundant hybrid on the road, that there is extensive knowledge and parts for it available. This website being a good example.