04-09 prius battery and charging specs

I am thinking about a stealth kind of mod to the prius HV battery system, I.E using certain circuits to pretend to have the right voltage at the modules, and use a total number of lifepo4 or li-ion that will simulate the combined two module bank. At an increased useable capacity. Which could be charged by plug-in as well. From what I have read so far the prius has a 1.3 kWh battery of which only approximately 400 Wh are actually routinely used. And a max usable capacity of about 44% 38 to 82 soc which numerically adds up to about 572 Wh.

What I am hoping for as an end result is a battery that can increase the useable capacity in hybrid mode while keeping the weight the same as well as allowing for a plug in boost that , will keep the car thinking it's in the upper green bar area till the plugged in part of the charge is depleted. So leaving plenty of room in the hybrid as well as the plug-in mode for regenerative braking and longevity margins.
I need the following data: what voltage and current does regenerative braking and motor charging deliver to the HV battery,
What other data can you folks supply?
I Figure I can use about 8 328p-pu chips to "fake" the 8 banks voltages while keeping the overall voltage with-in specs
And data would be appreciated
terramir

 

Well there are, several small wires that detect the voltage of 14 blocks of 2 modules each.
So there is a combined voltage 7.2V (1.2x6)x2 so 14.4 nominal, however realty is that each of those blocks may have a voltage up to 9.6V (6x1.6V) so 9.6Vx2 = 19.2 V for each block but this is just NiMH theory.
It is also untrue that the battery only charges to 82%, while in normal operation the goal is to keep the SOC around 60% and between 38% and 82% truth of the matter is if your going down a mountain you may reach 95%+ SOC. But I need some specifics on how the prius handles it exactly because I could use, for example 5 or 6x3.2V nominal (about 3.65Vx5 or 6 fully charged) to approximate the NiMH cells some trickery will be necessary to end up with about the same voltage range.
So I need some more data to design a proper approximation.
Goal would be total voltage that would only exceed the NiMH when charged externally further goal would be that the prius would only charge the total battery to about 50-70% SOC max but believe the SOC of 70 % is like 82 or even more like 85 maybe.
The biggest problem is that some blocks would be 5x 3.2 nominal and some would be 6x3.2 nominal to get a total voltage of about 201.6V approximately in the nominal range. So the 14 blocks would need a translation so the battery computer won't freak out.
Also at 9.6V the total voltage translates to like 268 V and there is so much I need to know about charging voltage to what voltages exactly correspond to what SOC in order to design this right and safely.
terramir

Oh sorry for the long post but a few more things :
1. The overall capacity of this battery would be at least 50 to 100% more that the original priuses battery and the plan is to use a overall SOC down to about 20% from about 70 in hybrid charging and anywhere from 85 to 100 SOC down to 20 when charging from public outlets.
2. The car currently only uses about 400-600 Wh theoretically of the HV batteries theoretical 1.3 kWh capacity I would like to see a 1.2 - 1.6 kWh of useable capacity in the end out of a maybe 2-2.6 kWh a HV battery.
3.This should be doable because a, lifepo4 are fairly rugged 2k plus full DoD lifespan, and with the prius if designed right they should float between 30 and 70% most of the time.
4. A lifepo4 cell has specific energy of 90 to 110 Wh per kg a specific power around 2.4kW/kg and energy density around 220 Wh/L. Comparatively smaller specs apply to the prius NiMH of the 2 gen 0nly 46 Wh/kg and only 1.3kW/kg specific power. So a LiFePo4 conversion could be a good solution it would take at nominal voltage 63 cells 3.2Vx63 to equal the nominal voltage of the prius battery the catch is it would take about 74 for the theoretical max .9.6Vx28 = approx 74x3.65V so I middle ground would need to be sought there. but I would really have to look into the dis-/charge properties as well before I really could put my finger on a number.
5. the higher specific power (about 84% higher) plus the about double specific energy could mean I could get quite a bit more power out of this. and if I could fit about twice the capacity in there at the same weight this would mean the discharge efficiency would also be much higher. because discharge efficency is strongly tied to "C" discharge-rates.
terramir

PS: Exact things I need for this design V=x% SOC I need numbers that will tell me exactly how the computer thinks about this battery and any oddities that might come my way like special charging discharging modes the battery computer might ask for if it gets certain data.

 

Well actually,
1.) I will not be using li-po cells just too dangerous , (vent with flame just means I'm exploding )
2.) if your numbers are accurate I was wrong about 5 and 6 cells it's more like either 5 cells each in which case I'm giving up some capacity depending on the actual charging voltage, but I can throw the trickery out, or 5 cells in most blocks and 4 cells in some. in which case I could use some high resistance dividers for the 5 cell blocks and some sort of faking boost with micro processors on the 4 blocks.
3.) If I go with JeffD data that during charging the cells get a little bit over 8V that would be 16 volts for a block 3.2V x 5= 16 V So I would need 70 cells with a capacity of greater than 6.5 Ah or alternatively the multiple of 70 with several parallel banks.
This all depends on cell availability etc.
this could be alot simpler than I thought and well at 70 cells I would have a safety margin that is quite great. I.e. because 70x3.65V= 255.5V and well at 3.6 it would still be 252V
4.) But at 70x3.2 V= 224V and 70x 3.33V= 233.1V (full resting voltage) I wonder how the battery computer would react? would it throw error codes or as long as it is consistent among the modules can it take it in stride? Because if it can accept those higher module voltages 3.2Vx5=16V 3.33Vx 5=16.65V I could create a plug-in component that would charge them fairly full which would allow for in-city EV mode at a greater distance as well as higher utilization in freeway driving of the electric motors since the computer will think the SOC is quite high.

So I still need quite a bit of input because this is actually getting less complicated than I thought it would be if the assumptions I am making are correct.
Assumption:
A. the charging voltage is greater than 8V per module i.e. greater than 224V and is dragged down by the modules themselves.
B. the battery computer and the inverter can handle a slightly higher input of 16.65V x 14 = 233.1V
C. the capacity and voltage drop during discharge will not interfere with the prius'es charging algorithm too much,
at 5C from 100 to 10 percent capacity the voltage is about 2.8V per cell at 3C about 3V that would be 5x 2.8= 14V 5x3 V 15V it goes a little lower at higher discharge rates, but the higher the actual capacity I can fit in there the less the voltage drop.
I don't know the actual voltage drop, because that depends on what it usually drawn from the motors I know the original battery pack can deliver about 20 kW at like 50% charge at 200V that is like 100A which would probably be around 7.7C if I can achieve my goal of double the capacity with the same weight and with far greater useful charge.

Input is still needed Please ;-)
terramir

 

Lifepo4 cells come in various flavors, and 10C drain and 10C charge rates below 80% SOC. Are far from unheard of.

If I heard of broken plug-in kits for sale I might just be interested, but honestly whoever designed that 40 Ah cell system added a bunch of weight. If I can find the right cells even a 1 kWh boost from the original would be a vast improvement over the almost dead battery I got now. I got a second junkyard battery with three ebay cells I added and somewhere around 60% of original capacity. Will be trying to install that in the next few days and the try to cycle mine a few times and the choose the best shape modules ones for a temporary battery till I can build this project.
But honestly I would rather boost the usable capacity to around double. Because currently heck I might be able 20-30 mph in the city, freeway well at 55-60 I can actually get 50-60 mpg. The dying battery is killing my city mpg.
terramir

 

I'm in los Angeles lol, my salvage vehicle cost me like an arm and a leg, around here priuses cost a fortune, then again gas prices are much higher than the national average.
terramir

 

California registered cars are different would be a pita to get them transfers doable yes but would be a pain in the area
terramir

 

Doubling batteries and gaining weight would not improve much of anything, except if the batteries are already dying.
But doubling capacity on new batteries with the same weight should improve the mpg in the city just a wee bit.
terramir