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Why Didn't We Think of This? — Parallax Forums

Why Didn't We Think of This?

ercoerco Posts: 20,255
edited 2024-04-05 18:04 in General Discussion

So clever and innovative, a "crime ring" near me (!) was selling electronic gizmos which faked a clean smog test through the OBD port. OBC (Jeff) should have seized this opportunity! But stayed out of jail. :)


  • Why would you even want to do this instead of just fixing your car such that it passes the test?

  • ercoerco Posts: 20,255

    Besides repair cost avoidance, many people make engine mods that won't pass smog checks and aren't easily reversible for a test.

    Of course I'm not condoning breaking laws and doing things bad for the environment, but it's clever tech approach.

  • msrobotsmsrobots Posts: 3,709

    Wouldn't helped with my car anyways. In 1978 there was no OBD port.

  • evanhevanh Posts: 15,420
    edited 2024-04-06 02:28

    I once had a car with electric windows. Couldn't stand the way the windows stopped working without the keys. Sadly, the chassis management computer is separate from the engine management computer. As far as I know, you can't just buy a cheap OBD kit to reprogram those. Anyway, got rid of that one.

    I've had a small amount of motoring repair experiences myself recently ... My newest car, just last year, is now an EV converted 1993 Ford Fiesta suitable for around town commuting. I purchased it already converted. It's since broken down twice but all is go right now. First failure, not long after I got it, was that the pillaged forklift's 72 volt electric motor used a 24 volt coil on its contactor. But strangely this was wired directly to the 12 volt ignition switch. I'm amazed it ever worked for the original owner. The cheapest reliable fix was to attach a 12/24 voltage converter to the contactor, so I did that.

    The second breakdown was a lot more serious and he had hinted I might need the kit he provided for doing this repair. The home built splined coupler between the forklift motor and the manual gear box had stripped all its splines. Luckily, work footed the bill to get a new coupler professionally custom made by a gear-cutting outfit. I just had to fit it. They reckon it won't wear out again so that'll be nice.

    The electric heater never worked. So that's something I might get around to looking at in the future. I suspect it's another 12/24 volt issue. He seems to have used thrown away parts all over the place. The one big exception being the battery. It was originally all lead-acids, as per the certification docs, but was later upgraded to them nice Chinese built Lithium-Phosphates. He said the battery kit was purchased, preconfigured, as one: 24 cell pack + charger + BMC + touchscreen. So I've not tinkered with that myself either.

    If I was to tinker there, the first thing I'd add is 12 volt monitoring. Since the 12 V battery has its own 230/12 volt charger it also is only charged while the car is plugged in at the wall. I think I've found I need to leave the car plugged in longer than it takes to charge the 72 volt battery to also keep the 12 volt battery from slowly going flat ... I think.

    PS: The lithium battery is rated around 9 kWh capacity new. I've not attempted to measure it and am happy so far with the BMS's gauge. Each way to work is 15 minutes mostly driving at top speed (150 Amps). I figure an average of maybe 120 Amps - Which is also the Amp-hour rating of the cells. The BMS is consistently reporting around 50% charge remaining after each round trip. So that all matches up well. Lowest I've gone is 25% remaining.

  • evanhevanh Posts: 15,420
    edited 2024-04-08 00:29

    And yes, 150 x 72 = 11 kW is the best this combination can do. Because it's rated at 48 Volts the motor badge says 5500 Watt rating. The badge doesn't say the RPM nor current but steady max current rating of the motor is likely well over 100 Amps. In hindsight I should have tested the unloaded motor RPM on the bench when I had it out. Something else informative for the touchscreen to show too.

    Anyway, it gets me up to around 80 km/h in fifth gear. Third, fifth and reverse is sufficient normally. Being such a weak motor it's very lacklustre starting in fifth.

    Next repair is expected to be the motor brushes. That's something I should make an effort to find some replacements for earlier rather than later.

    EDIT: Replaced the picture with a higher compressed one that uses less data. Looks like Parallax have removed the automatic image resizing they had for a while.

    Also found a nice graph of general performance of electric motors:

    I presume the max efficiency point is related to resistive heating losses in the windings.

  • ercoerco Posts: 20,255

    A good graph for DC motors, generally peak power is at 50% no-load speed, max efficiency at around 75% no load speed. Interesting that you need to row the gearbox with a DC motor to stay near max power. Most EVs these days use AC motors (driven from 400-800VDC) and have a fixed ratio gearbox.

  • evanhevanh Posts: 15,420

    Well, daylight saving dropped out yesterday and today is first time in a while driving home with headlights running. The 12 volt battery went flat again even though I've been leaving it charging longer of late. So looks like I need a new 12 volt battery too.

    Will be looking at a deep cycle one me thinks. The existing one is just a larger sized starter battery. Which figures, starter batteries are cheaper than deep cycle batteries.

  • evanhevanh Posts: 15,420

    @erco said:
    Interesting that you need to row the gearbox with a DC motor to stay near max power.

    The motor is rather wimpy, but nevertheless is good enough for the commute and around town shopping. It would've been from one of those indoor loader/stacking type forklifts where it powers an hydraulic pump. Pillaging a scraped forklift was clearly a cheap solution to convert the car to EV.

    The motor uses electromagnets for both field and armature. I know little about motor construction but I presume such an arrangement has extra losses over a permanent magnet arrangement. Double the resistive losses? And of course the power-to-weight of a 3-phase rare-earth PM arrangement will be far off.

    Consolation, I don't have demagnetisation concerns.

  • evanhevanh Posts: 15,420
    edited 2024-04-09 07:33

    Hmm, deep cycle batteries aren't an ideal fit. They tend to be a narrow aspect where automotive batteries are much more of a square block aspect. So then I'd end up with a smaller battery not filling the space available.

    I had a chat about the application with a salesman and he suggested I go with an "enhanced flooded" battery. They're apparently tailored for hybrid cars where larger charge/discharge cycling occurs. So I've now got a new 65 Ah enhanced flooded lead-acid battery. The old one was a 55 Ah "calcium" lead-acid - Which are the weakest/cheapest type he said. And AGM's are best but cost more.

    Okay, so the onboard charger looks fancy, see attached. It's an early IC15 model with Power Supply mode instead of Lithium mode. It was set to Calcium mode. I'm tossing up between selecting AGM or Wet mode. Reading the manual, the big difference is final boost "reconditioning" charge before "float"ing. With AGM mode it doesn't actually boost at all. It's the same 14.4 volts as the bulk/absorption charging. Whereas Wet and Calcium modes boost up to 16 volts. I'm wondering if this is what ruined the old battery so quickly.

    Anyone have experience/opinions on lead-acid cycling? I'm thinking maybe treating it more like a deep cycle might be the way to go. Given the nature of my daily charging/discharging I'm inclined not to have the boost, ie: Go with AGM. Maybe switch it to Wet for one long charge every few months or something.

    Pity I didn't read this manual first. I might have spent the extra on an AGM battery instead.

  • I think gas engines pollute until the catalytic converter gets hot enough to work. So are they fooling the system

  • GenetixGenetix Posts: 1,748


    All fueled engines pollute more until they are warmed up so they are designed to get up to operating temperature as fast as possible.

    Most likely this is a cheat for the newer "Plug-In" Emission Test.
    Older OBD-II vehicles here in California need a 'Treadmill' test that includes an Engine Monitor Cycle that varies from vehicle to vehicle.

    The cheater bypasses the Engine computer completely.
    It makes the Emission Tester think it's talking to a vehicle, so it always gives a perfect response to any of the Inquires that are sent.
    Trouble Codes - None
    Engine Monitors - All Complete
    Sensors - In Specification

  • evanhevanh Posts: 15,420

    I'm not sure if Bob is talking about there being some crappy pollution escaping just at warm up time, or that the engine always puffs out Smile which the catalytic converter then has to wastefully deal with?

    The whole point is to reduce toxicity to humans and the environment generally. On that front the catalytic converter is impressive performance. It does that with no mechanical parts and without degrading.

  • @Mickster said:
    Remember the Stan Meyer "Hoax"?


    How about providing a transcript of it, for those of us who do not follow the myriad ways of Youtube.
    Mascot watching.

  • MicksterMickster Posts: 2,646

    @"Buck Rogers" said:

    @Mickster said:
    Remember the Stan Meyer "Hoax"?


    How about providing a transcript of it, for those of us who do not follow the myriad ways of Youtube.
    Mascot watching.

    If I comment, I get accused of believing in over-unity, perpetual-motion, etc. Which it is not
    It's been almost 200 years since Faraday and things have moved on a bit. Water-splitting can be achieved by using high-voltage and high-frequencies instead of Faraday's energy-hungry method.
    Problem being that if you do it, you end-up unalive. Let's see if Toyota can bring it to market.

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