Custom built, large Ah HV Pack replacement

Discussion in 'Generation 1 Prius Discussion' started by TexomaEV, May 19, 2010.

  1. TexomaEV

    TexomaEV Member

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    Has anyone experimented with building/replacing the original HV pack, with a custom built unit from 20Ah or higher 6 volt batteries? Note: 6volt Pb/Acid will charge out to 7.45vdc

    I plan to purchase a 2001 Prius, with a bad HV pack, and want to custom build my own pack , and attach the sense leads from the original NiMh modules to the 6volt batteries making up the new HV pack. The new HV pack will be 20Ah or higher, depending upon cost of the individual 38ea 6 volt batteries.

    Once it's installed, an onboard charger will attach to the new HV battery as well for plugin (grid) charging.

    If a Pb/Acid pack works, then when it's at end of life, rebuilding with a LiFePO4 pack would be the next experiment.
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    What is your motivation to do this:

    1) You want a higher capacity battery than the original
    2) You want a less expensive alternative for battery replacement
    3) or ??

    If 1), the Prius is not really set up to use a higher capacity battery than it is equipped with.

    If 2), my guess is that you could spend $1.5K or more on 38 6 volt batteries, they collectively would be quite heavy, and this is not an economical alternative compared to buying a salvage battery, for example.

    If you have some other motivation for doing this, let us know what it is.
     
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  4. TexomaEV

    TexomaEV Member

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    Good Questions: Yes, I'd like #1. In order for a higher capacity battery, which I suspect would hold up under EV load/mode for more miles than the original pack.

    #2. Now I know the computer monitors two modules at a time, so I should be able to get away with 12volt batteries, of which I've priced out to be $450 for the set. This pack would also have an OnBoard Charger attached for PlugIn Charging with standard household outlet.

    #3. Under taking the above if I fail at rebuilding the OEM pack myself, or if the cost to rebuild will be more than the custom pack.

    #4. I like to think outside of the box, at least while free from my padded cell..... lol - My most recent completed/successful project was using the DC/DC Converter from an Enginer Prius Plugin Kit, and building an EV Extender/Rescue trailer for my other pure EV autos. When the system will let me post a link to my other EV Projects, I'll do so. Apparently I'm still to new to this forum, and can't submit links in postings.

    Please pardon my ignorance, working with a Prius, is completely new to me, yet I think it will be much fun, and I figure you guys can rescue me when needed!
     
  5. Flaninacupboard

    Flaninacupboard Senior Member

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    You could make a double pack with the BMS+ system, and also add a 2kwh enginer style system. that way you have a big traction pack for longer EV and large regen, and can top off from an auxiliary pack as well. Although, the einginer system allows better mpg by keeping the traction battery at a high SOC, but yours would stay lower if using the BMS+ system.

    I'd rebuild it with normal gen2 cells, and add an Enginer style plugin auxiliary pack.
     
  6. bwilson4web

    bwilson4web BMW i3 and Model 3

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    You might consider posting "hello" to get your posting count up to 5, which I understand is the threshold. Perhaps, "Testing 3" with a link, "Testing 4" with a link, and "Testing 5" with a link.

    I think you may want to reconsider some of your assumptions by comparing the various battery charging curves and characteristics. Orange4Boy posted a note about a modified 12 V battery configuration that included a separate set of cells from another, partially destroyed battery. This gave him a 14 V, lead-acid battery for his plugin that drives the 12 V DC system. I suspect you may need something along the same lines.

    Bob Wilson
     
  7. TexomaEV

    TexomaEV Member

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    Good news - I rebuilt the OEM HV Battery this morning. It had 2 dead, zip, zero vdc modules. Weird thing about those modules, they both had "X"'s on them, from maybe when a TSB was performed?

    Anyhow, I replaced them with some a very good friend had given me awhile back to play with in some of my EV projects, and now the "MAIN BATTERY" has gone away, and the car actually drives like a normal vehicle. Other than the engine dying at stop signs, which will certainly take some getting used to.

    If the pack holds up, I'll install a hitch, and use the EV Extender Trailer on it. It's built with 200Ah of LiFePO4 cells, running an Enginer DC/DC Converter.
     
  8. bisco

    bisco cookie crumbler

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    sweet! and you can pulg itin as well?
     
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  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Congratulations to you!

    Please do not say that the engine is "dying", unless the car logs DTC P3191.

    Absent any DTC being logged, the engine is merely "resting". :rolleyes:
     
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  10. TexomaEV

    TexomaEV Member

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    Didn't think about it that way, sorta like we who also drive pure EV's ask you not to call the accelerater pedal, the gas pedal...... lol
     
  11. TexomaEV

    TexomaEV Member

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    Since, School is out for the summer, I thought I'd do some experimenting with the Prius's HV Battery.

    I put together a duel lithium battery/capacitor bank and paralleled a section to each half of the HV battery pack itself.

    First test drive (6 miles mixed highway/city- hills/flat) the SOC stayed steady at 75% and never veered off that reading. Before it would fluctuate constantly.

    Not sure if it's any enhancement, but at least I don't have to watch the SOC go up and down constantly ...... lol

    Next is to figure out how I can recharge the contraption with a plugin charger on each half, so it's fully charged and ready to rumble every time I take it for a spin. Anyone got a couple of 160volt chargers lying around the garage? or suggestions?
     

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  12. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Calculate the peak-voltage for half-wave, 120 AC. My rough order magnitude calculation is 1.414 * 120 ~= 169.7 V.

    So take a power cord and power diode and 200 VDC capacitor. Wire it up so the capacitor is charged from the AC line and measure the DC voltage on the capacitor.

    The power factor s*cks but you'll be pretty close to 160 V. AC.

    Now if you want to draw some serious power, two caps and two power rectifiers. you should easily achieve ~300 VDC and be able to draw some serious power. You'll probably want a switching buck regulator to bring the output voltage down to a reasonable level but we can go into that in another posting. Or get a full-wave rectifier from Radio Shack (you can get less but you can't pay more) and a single cap. Toss in a choke and you can put something together, quickly.

    Bob Wilson
     
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  13. TexomaEV

    TexomaEV Member

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    Thanks, I'll give that a go. Could I use a light bulb to limit the output current. I'd like for it to be no more than 1 amp.
     
  14. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Yes but think of this simple power supply as a quick hack ... more of a 'I need something right now.' Also, be very, very careful about the hot and neutral. Without an isolation transformer, any piece of earth ground could be lethal. . . .

    You might check Ebay as I've often seen lab supplies for reasonable numbers. They often have voltage and current readout and are isolated from line power.

    Designing and building power supplies is a lot of fun the first two or three times. But it is much easier to buy one and concentrate on the interesting physics.

    Bob Wilson
     
  15. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Statultra built one from scrap parts. Unfortunately he removed the pictures. Might want to try and contact him. Pretty funny since he used a big tin can as the charger body. It has been done and proven to work.
     
  16. hobbit

    hobbit Senior Member

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    Is it truly parallel with the stock pack? If so, what are you
    doing with the point where the mid-pack safety plug hooks in?
    .
    Be prepared for problems if you're paralleling mixed chemistries
    without any kind of current limiting between them. I have a
    minor rant on this in the recent battery exploration, and have
    gotten more than one report of stock packs and ECUs getting
    totally confused by what's going on with direct-connect based
    systems.
    .
    Now if you design a nice bidirectional switching current regulator
    for the whole thing, be sure to post your schematics!
    .
    _H*
     
  17. TexomaEV

    TexomaEV Member

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    Thanks, I built Mr. Wilson's quick design, my meter is reading 175vdc Open Circuit, will use a AC light bulb for current limiting, to see if it'll work for a short while, until I find something more sophisticated.

    I'll try and get in touch with him, maybe he'll send me the schematic.
     
  18. TexomaEV

    TexomaEV Member

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    I have feeder wires connected to each half of the OEM HV Battery pack. Therefore the car doesn't have to be active/running to gain access to the voltage of both halves.

    Those feeder wires are attached to the lithium/capacitor banks.

    I used enough lithium batteries to equal the chargout voltage of the NiMh batteries in the HV unit. This keeps me from overcharging the NiMh batteries, and just slightly under charging the lithiums. The capacitors help with harsh regen, and initial surge of current required during acceleration. More capacitors the better, this small pack is just for a quick experiment.

    I've been mixing battery chemistries and capacitors for quite awhile now, without problems (knocking on wood at the very moment) in some of my other EV projects, yet they of course aren't as sophisticated as the Prius, so point well taken on possible problems in the future.....
     
  19. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Since the traction battery banks are normally isolated from the chassis, the risk is somewhat mitigated. I would recommend using a polarized, AC plug, and make sure the neutral is on the nominal ground or negative lead.

    One quick hack for a current limiter uses an LM317T:
    Regulators and Power Supplies

    The LM317T is available from Radio Shack and rated at ~35 V. As long as the voltage difference between the pack and the regulator is less than 35 V, the part should handle current regulation. Just make sure you have a heat-sink and thermal paste. You'll probably want to limit the current to 500 ma or less just to stay on the safe side.

    Now I'm a fan of using solid-state relays because they typically have a low-voltage control line. A simple voltage divider can provide the feedback in either a current limit or voltage limit mode. Ebay shows a bunch under $10.

    Bob Wilson
     
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  20. statultra

    statultra uber-Senior Member

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    i didnt remove the pictures, i guess it removed itself ( imageshack ) . well anyway i havent touched my charger since 2005, ill dig it out and take it apart and take pictures, it goes to like 160-170 volts floating above the half of the hv battery, its a very low amp charger that way i dont blow up my battery.
     
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