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Can I build an EV bike battery using Prius HV modules?

Discussion in 'Gen 3 Prius Technical Discussion' started by GreenTea&SaltWater, May 22, 2022.

  1. GreenTea&SaltWater

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    Hello I just bought an electric bike conversion kit (without the battery) and I want to know if I can save $250 by just building my own battery instead. I have 28 spare Gen 3 modules because I did a repair and replaced them all.

    The kit that I bought as shown in the file attachment, is for 36v at 450w. If each module is 8v fully charged and I connect four then I have ~32v so it seems fitting. But aside from that I don't know if I'd be able to connect it to my kit somehow using a BMS (Battery Management System) and any other wiring I would need. Most tutorials online are of Lithium batteries and I haven't seen one of NiHM like what the prius modules are. I saw reviews on the page where people were powering the kit up with 12v motorcycle batteries so maybe there is some versatility.

    Have any of you ever done something like this?
     

    Attached Files:

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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Use a 5th cellmodule because 99% of the time they won't be completely full.

    A 40v (nameplate) series battery with a motor load on it will drop a lot closer to 32v anyway. You'd also need to make certain everything was safe up to 48v so there's headroom for the charger.
     
  3. GreenTea&SaltWater

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    Would it be a good idea to just disconnect it from the bike every time I want to charge it then?

    So say I'm using 5 cells. I know that they go in pair or blocks, but does that only apply to when they're on a Prius? How would I go about wiring up the 5 cells to what kind of BMS that will then hook up to that component with the wire plugs
     
  4. Hybrid Hound

    Hybrid Hound Junior Member

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    Can't say I did exactly that, but...I did do 2 ebikes that were 36 volt. On one I used 2 Ryobi batteries (18 volt each), and the other one (a 3 wheeler with a basket on the back) using 3 17AH 12 volt SLA lawnmower batteries. On the Ryobi conversion, I used the Ryobi charger, on the other one, I bought a 36 volt small (20 amp) golf cart charger that would put out 42 volts. IF...BIG IF, you can wire them in series to produce around 40 volts, your ebike kit can handle that just fine. And...IF your charger will charge the Prius batteries (it should) to a total of 40 volts...you should be able to pull off a neat conversion. Hope this helps, but if not...have to say you are on track to have a cool ebike. I ended up selling both of mine and using the money to buy a factory produced ebike. But...building the kits was WAY MORE FUNNER!!
     
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  5. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I don't know if there's a ready-made BMS you can use, but the radio controlled hobby world developed a lot of expertise with NiMH batteries before lithium became available. Consequently you can use chargers, meters and tools from that world.

    I guess I don't see a downside of isolating the motor controller when you need to apply a charge. Heck, for some rides you want to pop the battery off and carry it in to a charger that isn't onboard for security and weight savings.
     
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  6. GreenTea&SaltWater

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    What tutorials do you recommend I look at that will best help me understand how I can hook these modules up to the kit I bought. I'm a complete noob
     
  7. GreenTea&SaltWater

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    Would you mind showing me an example of what parts I would need for this
     
  8. bisco

    bisco cookie crumbler

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    does the kit have a battery recommendation?
     
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  9. PriusCamper

    PriusCamper Senior Member

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    In general NiMH technology is 30 years older and way heavier than Lithium... Using a small number of Prius modules will discharge so quickly on your motor that your time and effort put into this will feel like wasted time once you're done.

    The modules for Prius are not good at holding a sustained charge under load, especially in small numbers. But what they are good at is handling large amounts of amps going into or going out of the pack. But without a Prius engine, transmission and inverter connected to them it's gonna be disappointing how fast they drain down versus how long they take to charge.

    I'd encourage you to use a lighter weight and more legit lithium based battery that's specific to what this device was designed for. One way to do it on the cheap is buy a box of old laptop batteries and take them apart and harvest the cells inside and test all of them and then use the best ones. There's other ways similar to this as well.
     
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  10. GreenTea&SaltWater

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    Ok then I will halt this project and choose another way to get a battery. Or maybe just return this and get an engine kit instead
     
  11. Dxta

    Dxta Senior Member

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    Another similar way I think, is harvesting one of the modules of any of lithium ion based vehicles. I currently have some modules from a Hyundai sonata hybrid, that I recently worked on.

    I have a scooter with 2 12V blas(can't remember the amps now though). The batteries are wet cells, and dead. I intend to harvest some of those modules, and use them for a future ebike. I have tested one of the modules. They are 30V each. It ran so well on the scooter I tested it on. My concerns, is I have to be monitoring the charge, as the battery is being charged with an external, 48V 1.0A charger.
    Motor on the scooter is a 24V one.
     
  12. PriusCamper

    PriusCamper Senior Member

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    You also might want to follow Jehu Garcia on YouTube as he's constantly buying surplus battery power from electric bike & scooter companies so the electricity you need is already in a package that's easy to mount to a bicycle. Like his latest ones from his most recent uploads:



     
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  13. GreenTea&SaltWater

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    I ended up just building a gas powered bike
     
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  14. bisco

    bisco cookie crumbler

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    discretion is the better part of valor
     
  15. Grit

    Grit Senior Member

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    Because saving gas costs a lot of Money.
     
  16. Grit

    Grit Senior Member

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    He’s got great cold temperature cut off bms stuff so your lifepo4 batt didn’t charge below 32F and not deteriorate itself.