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Double batteries? What can go wrong?

Discussion in 'Gen 3 Prius Technical Discussion' started by Priipriii, Aug 14, 2022.

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  1. Priipriii

    Priipriii Member

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    Hi all, Ive been spending numerous, and I mean NUMEROUS days studying and researching on how NiMH works, what BMS is, how to deep discharge/charge batteries + balancing them, and taking them off and on, off and on again and again to find the faulty ones. It got me thinking of something that I wonder about and I want a concrete answer for those of you that are more experienced than I when it comes to electricity and Priuses.

    Ok, so I have no real plans to attempt it (mainly due to the lack of batteries I have available), but hypothetically, what would happen if I bought 28 more NiMH batteries, and turned them upside down to connect them in parallel (+ to + and - to -) to make a total of 210 volts/7amps vs the normal 210/3.5amps. So for each module, it would be a total of 4 batteries, but the prius will read it as two since it wont be able to distinguish the ones connected in parallel.

    I know I have a feeling that due to the ECU, it will only let a certain amount of volts and amps in and out, so does that make my entire concept useless, or will in practice I be able to accelerate the electric motor for twice as long due to holding twice the wattage in total? As well as engine running twice as long to charge and being off for twice as long?

    Now the second part to this, IF i cannot get the ECU to let me output the desired power I want to the motor, can I switch out the ECU to a different car model (say rav4 hybrid for example) to give me a bigger torque output? Not sure if rav4 hybrid has similar or different ECU, but I assume it lets out more voltage and amps since the motor is also bigger. Again, this is all hypothetical and I would like some real answers on why this can or cant work so I can be educated. But it's been a goal of mine to make the prius a performance car even if its at the cost of mpg.

    I also understand I can just get rav4 hybrid or whatever for performance, but I dont have that sort of income and this to me is just wishful thinking and seeing if its worth the effort to even attempt it if I get good feedback and know what my risk and rewards are.

    So please, discuss and don't be afraid to burst my bubble.
     
    #1 Priipriii, Aug 14, 2022
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  2. Tombukt2

    Tombukt2 Senior Member

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    I'm not a hardcore electrician but I would think as long as you stay in the voltage range you could turn your whole trunk into a battery of course You're back end would be dragging the ground then batteries aren't lightweight.
     
    #2 Tombukt2, Aug 14, 2022
  3. PriusCamper

    PriusCamper Senior Member

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    If it was 15 years ago you'd have a whole community on PriusChat and beyond to work with... The idea you have was quite popular back then and it led to several startups adding a second pack. Some of those people built stuff that burned garages down while charging and some built ones that are still on the road today and occasionally show up for sale as used Gen2 Prius. In fact, the idea proved to be so appealing that Toyota copied them and in 2012 introduced the first Plugin Prius, which sadly sent all the 2nd battery start ups into bankruptcy.
     
    #3 PriusCamper, Aug 14, 2022
  4. Priipriii

    Priipriii Member

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    So really what this idea is, is just a step closer to prius prime? Is there anyway to adjust the ECU to output more power to the electric engine or is that not something that can be done or has been done by Toyota or aftermarket
     
    #4 Priipriii, Aug 14, 2022
  5. PriusCamper

    PriusCamper Senior Member

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    Correct. If you owned a plugin-Prius you'd own exact thing you're curious about building, but without the hassle.

    Also Read/Write access to all the ECUs is still uncracked for Honda and Toyota hybrids. The culture of ecu hacking of Hondas, Subaru, etc has been limited to needs of race track motivations instead of mpg. Us hybrid car nerds don't have that level of competition to motivate us... At least yet.

    For the time being, all the advancements in after market hybrid car batteries requires battery ECU to get near same signals as OEM or you get warning lights and limp mode.
     
    #5 PriusCamper, Aug 15, 2022
    Last edited: Aug 15, 2022
  6. Tombukt2

    Tombukt2 Senior Member

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    Maybe someday the guys over on toy mods might pick up this model for modification but I kind of doubt it because it would be very limited and a lot of work for not a whole lot of game especially for what's coming down the pipeline. The guys on toy mods since the '80s Yes I've been interested in performance mods mainly not so much MPG and we also did a lot of swaps over there Jz engines in the cars that aren't supposed to have them 3S GTE beams conversions things like that stuff that wouldn't interest folks here. I spent about 24 years over there knew a lot of the people and other countries on this list pretty good community
     
    #6 Tombukt2, Aug 15, 2022
  7. bisco

    bisco cookie crumbler

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    it would take 4 batteries to equal the pip, and 8 to equal the prime, and you'd never get the same range due to battery improvements.
    best you could hope for is a few mpg's, and not a total house fire. don't park it near anything combustible
     
    #7 bisco, Aug 15, 2022
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