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Thread: Fast Lithium Power Indoor/off road Powerchair

  1. #11
    >>> One thing, by far, that determines the off pavement capability of a powerchair is where the drive wheels are located. Front wheel drive works best and eliminates the many difficulties encountered by leading with front casters.

    Yes. Rear drive or 4x4 works best as in the real world. As it does in the off road car or bike world. This chair, just like a motrocross bike, is very light on the front. It wheelies at will. Casters are 10 inches x 3 with good floatation. On soft sand the X5 casters sink... Almost all the weight on this chair is then on the drive wheels. I tried an X5. It was just as good outdoors as mine. Better on steep gradients because its long...

    But I need to be able to use one chair to drive my van, go to the pub, turn in tight places, get around my house with ease and walk the dog on the beach/woods etc. There was no chair that could do this.

    And its only a fraction over 25 inches wide, and very short. So it does all terrain, and indoor stuff, and full range, and fast charges, and is properly finished! In all it cost me hours of work, and about 1700 uk pounds. I built several of the MK2 ones, and am building 2 of the much faster more powerful mk3 ones now.

  2. #12
    Quote Originally Posted by buegerman View Post
    >>> 100A draw off your car for an hour? Who's going to charge your car back up! Even with the engine running, most vehicles can't sustain that type of power over a long period.

    The alternator easily catches up. After 5 mins only that 100 amps drops away to around 70 amps. And to about 50 after 10 mins. Most cars alternators hold the systems voltage steady at 14.4v after just a few mins, for the rest of the trip. It doesent even stress them.

    I also use a 20 amp charger on board at times too! And at home. You NEED one of these!!! http://www.wheelchairdriver.com/hype...t3-charger.htm It tests and graphs your batteries too... And can charge ANYTHING especially powerchairs.
    That's not true; The alternator is only capable of putting out a specific amount of current sustained. Most vehicles today don't have 100A capable alternators. Some higher-end vehicles are starting to have 90, 110, 120A and even 140A charging systems but that's not the majority. Plus, you can easily drain the battery super-fast with a 100A constant draw, so the engine would HAVE to be running... Still, most vehicles will not have 100A of constant overhead current available to dedicate to something else 100A for an hour. And running an alternator at peak charging capability does infact stress them. The more they charge, the harder they work. Simply put; otherwise you'd have 'free power' which doesn't exist. The more power the alternator has to put out, the harder the alternator has to work (and the more resistance it puts on the engine in turn). Nothing comes for free.

    I've been an Electrical Engineer for many decades and specialized in automotive design and customization. This is something I know for a fact. I've wound my own alternators from scratch to meet my specific requirements for a job and also designed my own storage systems.

    Furthermore, alternators do not work at peak efficiency until they are spinning quite rapidly. This is not IDLE, and often not even cruising speed necessarily. Generally speaking, the engine has to be upwards of 2k RPM to get the alternator's output capability up to it's rating. At idle, these can be a quarter or less. So your 120A Mean Green super-duty alternator may only put out a sustainable 40-50A at idle.

    And most cars today don't do a 14.4V capability.. .13.8V is your nominal sustained charging system level for today's vehicles all the way down to 11.5. Still, with alternators capable of over 15V... Anyhow, the battery is meant to start the car and do engine-off operations. The engine itself (alternator) will power everything after that accept for the alternator's exciter or regulator voltage (12V from the battery to initiate the field, this is why even with the engine running, removing the battery kills the engine in most modern vehicles). When you over-draw your alternator's capabilities, the battery takes over (at a lower voltage). These types of dips are commonly seen by the audio industry as dimming headlights. And often from systems far less potent than a 100A draw. It's still enough to dip away from the alternator's sustained power which in turn switches it (temporarily) from the 14.4V (wishful) output of the alternator to about 11.5ish from the battery. Since the brightness of lights is determined by their voltage, not their current, we see this as the dimming light symptom.

    Anyhow; most vehicles today won't sustain 100A constant draw for even an hour... At least not while not screaming down the road. They should have a much slower (20A-ish) feed option. I don't need the chair to be charged in an hour if it lasts for 30+ miles on a charge. I can take it charged, and recharge it overnight or while I'm taking a break or whatever. Especially if we're out at a track or trail where a tow-truck is unlikely even able to get to me. I want my charging systems to be as protected as possible. A dead battery here can actually kill a person (which is one reason why we have at least two in all of the vehicles).

    Plus, don't forget, your 100A alternator also has to run the entire vehicle, it's toys, etc. while trying to charge your chair. Some modern toyed up rigs can draw a sustained 70A or more just to run the engine, lights and the stock entertainment setup.

    Pulling 10-20A off the charging system at any given time is not too much for any stock system. But 10 times that very much can be. At the very least, it will drastically shorten the life of your alternator.

  3. #13
    Wrong on a number of counts. But I know where you are coming from.

    Almost all modern passenger cars charge at and run all the time you drive at 14.4 volts. Its just the norm nowadays with modern batteries and charging systems. 13.8v would take about 36 hours to fully charge a modern battery.

    Long range verhicles like trucks of yesteryear used to charge at 13.8v or a little more. Take your volt meter to your car and start it up. Measure it. From the moment it fires up it will be up to 14.4 give or take a couple of tenths of a volt. And it will stay there all day. Unless you are driving something out of the ark.

    Now its true if you have a small alternator and really flat batteries, that is maybe only 60Amp, then the alternator will put out 60, up until the battery voltage reaches its 14.4 and then amps will tail off rapidly until its only providing power for the ignition, sterio etc. Most vehicles sat idling with normal fully charged batteries have about 80 or more amps to spare.

    So connect your powerchair, and if it has very flat batteries, the full alternator output tries to make the vehicles electrical system reach 14.4v. Or whatever your vehicle may be. Its never MORE than 14.4 so safe for gel or AGM batteries we use. So if really flat you will see a huge bunch of amps flowing into the batteries. (measured with my clamp amp meter regularly) This current comes partly from the vehicles battery and partly from the cars alternator. Of which a great many are 100 amps or above.

    Then as the chairs battery voltage rises, which happens pretty fast at approx 100 amps initially, the amps start to decrease. This is the natural inrush current that occurs when you connect a flat battery to a fully charged one that is sat in your car idling away with its already topped up battery... After a few mins this naturally falls away to half that current.

    Then as the battery comes up to full charge it typically falls completely away to a few Ma only. It works, it works well and I have been doing it years,. And yes I spent time building race cars, bikes, automotive dyno systems, nitrous systems, as well as working as an auto electrician when I was an apprentice 35 years ago!

    Of course its not "free" energy! It burns fuel!!!

    When your car is warm and been running for a few mins its alternator is doing very little. Unless you have everything possible in your car turned on full! Test it with a clamp meter. Typically 10 or 15 amps only. That leaves 90 to go to the battery. Or 130 in my case. Even if you have a small alternator it will still charege your chair at say 50 amps as you drive!

    My vans alternator puts out almost EXACTLY 130 amps (measured) if you clamp its output lead at idle or in fact any rpm if you put a load (flat battery) on it. As do most others. There isnt any need to rev it! Although for max output this might need to be JUST above idle. But so what?


    >>> That's not true; The alternator is only capable of putting out a specific amount of current sustained. Most vehicles today don't have 100A capable alternators.

    So what, you get whatever they do have... Its always fast! My chrysler has a 130 amp alternator. (towing pack) but the stock ones are 100.

    >>> Furthermore, alternators do not work at peak efficiency until they are spinning quite rapidly. This is not IDLE, and often not even cruising speed necessarily. Generally speaking, the engine has to be upwards of 2k RPM to get the alternator's output capability up to it's rating. At idle, these can be a quarter or less. So your 120A Mean Green super-duty alternator may only put out a sustainable 40-50A at idle.

    I can easily disprove that by plugging my chair into the van, or my GFs honda, when pretty much discharged and clamping the alternator output cable. Which I have done already, FULL output at idle. Almost amazingly accurate to the rated output. Thats the reason alternators were used over dynamos years ago... Its possible with idle speed set too low that this isnt the case and maybe on the odd car but it isnt usual. And it will still charge anyway even if at a lower output. Or the ignition light will illuminate.

    For what its worth, my last 3 vans, my old mums ford, my VW, my bikes and my GFs car are all almost exactly 14.4v too.

    Dont understand your argument. I know it works, been doing it since 97, on 3 different vans, several cars, and also tested by others who are doing the same thing without issue. Maybe you should visit my forum! Trust me it works great!
    Last edited by buegerman; 02-01-2011 at 06:45 PM.

  4. #14

    Cool

    Well... Trying not to be condescending here but; An automotive battery will never reach 14.4V. It's just going to happen without some catastrophic failure. The charging system perhaps but never the battery. Automotive batteries have a fully charged potential of ~12V. The alternator itself is capable of considerably more which is then controlled by the regulator. The alternator itself is just a generator that puts out AC by nature... Not DC... The alternator itself is just a rotor, stator to which we add a rectifier and regulator converting it to DC.

    And if you have an alternator that puts out 130A regardless of spindle speed, you need to re-manufacture that and sell it. It's worth billions... Custom units that are designed specifically to put out a high draw at idle speeds are extremely expensive and in-turn limited to how high they can actually spin before it becomes detrimental (so unsuited for high-reeving engines). There's a huge difference between potential and demand. But I'm not going to give you a full lesson on basic electronics in an already off-topic item. Also, if you have a custom wound alternator for stronger idle performance and/or a custom pully system designed for similar effects, then that's hardly 'most' vehicles. These items would be more common for vehicles enhanced with a lot of power electrics like accessible vehicles though. But that's not the norm as they also rob power from the engine and lower economy. Not what the general market is after. Some installations also increase the idle to compensate bringing it from < 1k RPM to upwards of 1200-1500 RPM or even more to keep the power demands available. Again, not what the general public wants.

    Furthermore to say the automotive electrical system can never exceed 14.4V is also false. All it takes is a < $0.01 part failure in the regulator.

    But if the world worked as you seem to wish it would; we would have endless power. Hook up a bicycle pedal to an alternator and you could keep your electric vehicle fully charged with a mere slow pedal pace with almost no energy. Simply doesn't work that way. Plus, if the alternator forcefully pushed out any amperage it wanted to, regardless of demand upon it; you have some other quite dangerous issues to worry about.

    And if you think the system will run whatever you want no matter how powerful it is even with a tiny alternator and do so as long as you have fuel; you're horribly mistaken. It just doesn't work like that. You are pulling from the battery itself when you've maxed out the alternator's capabilities. And once the battery drops to low, the engine will die because the exciter voltage is no longer stable. (Unless you have a very old alternator without a sensing voltage of some form. No manufacturer has used these in quite a few decades to my knowledge.) This is basic electronics 101 stuff.

    Unsubscribing since this has gone quite OT. Cool chair, but needs to be eased up on the charging requirements for more general real-world use.
    Last edited by SirGCal; 02-01-2011 at 09:48 PM.

  5. #15
    --------------------------------------------------------------------------------
    Well... Trying not to be condescending here but;

    YOU NEED A LOT MORE KNOWLEDGE THAN YOU HAVE TO BE CONDECENDING i AM AFRAID!

    An automotive battery will never reach 14.4V.

    ON ALL MODERN VOLTAGE CONTROLLED QUALITY CHARGERS, AND THE VAST MAJORITY OF PRIVATE PASSENGER VEHICLES IT CERTAINLY WILL. 3 STAGE CC/CV/FLOATR CHARGERS ARE ALL DESIGNED TO CHARGE AT CONSTANT CURRENT AND THEN CONSTANT VOLTAGE INCLUDING THE COMPLEX HYPERION WHOSE CHARGE AGO I HAVE BEEN WORKING ON OVER THE LAST YEAR...

    It's just going to happen without some catastrophic failure.

    ABSOLUTELY WRONG, IT HAPPENS WITH EVERY DECENT CAR ALTERNATOR, AND MULTI STAGE CHARGER ALL OVER THE PLANET EVERY HOUR OF EVERY DAY!!!

    The charging system perhaps but never the battery.

    WHEN ON THE CC/CV STAGE OF CHARGING, AND ALL THE TIME YOUR ALTERNATOR IS SPINNING ITS HAPPENING. AFTER CHARGE AND AFTER THE BATTERY HAS BEEN ALLOWED TO LOSE THE SO CALLED SURFACE CHARGE (HALF A DAY TO SEVERAL DAYS) THEN ITS VOLTAGE WILL MEASURE BETWEEN 12.8 AND 13.21V DEPENDING ON CHEMISTRY.

    Automotive batteries have a fully charged potential of ~12V.

    WRONG. AFTER SITTING FOR A WHILE THEY ARE TYPICALLY FULLY CHARGED AT 12.8V OR ABOVE. 13.2 IN THE CASE OF A GEL BATTERY. AND SO DEAD AT 12V THAT THEY WILL NOT MOVE A POWERCHAIR. 12.2V PER BATTERY GIVES THE DREADED DEAD BATTERY AND NO GO ON MOST POWERCHAIRS.

    The alternator itself is capable of considerably more which is then controlled by the regulator. The alternator itself is just a generator that puts out AC by nature... Not DC... The alternator itself is just a rotor, stator to which we add a rectifier and regulator converting it to DC.

    SUPER BASIC OBVIOUS STUFF!!!

    And if you have an alternator that puts out 130A regardless of spindle speed, you need to re-manufacture that and sell it. It's worth billions...

    SORRY BUT ALL OF MY LAST 3 VEHICLES DID THAT WITHOUT ISSUE. AND EVEN IF YOURS DOESENT, IT WILL STILL CHARGE YOUR CHAIR MASSIVELY FASTER THAN A MOBILITY CHARGER? I DONT GET YOUR POINTLESS POINT???

    Furthermore to say the automotive electrical system can never exceed 14.4V is also false. All it takes is a < $0.01 part failure in the regulator.

    STRAWS... YOUR OVERNIGHT CHARGER CAN DO THAT TOO. SO DONT USE THAT! OR YOUR CAR! BECAUSE IT COULD FRY ITS BATTERY! THERE ARE RATHER A LOT OF CARS IN THE WORLD THAT ARE NOT FRYING BATTERIES THOUGH???

    But if the world worked as you seem to wish it would; we would have endless power. Hook up a bicycle pedal to an alternator and you could keep your electric vehicle fully charged with a mere slow pedal pace with almost no energy. Simply doesn't work that way. Plus, if the alternator forcefully pushed out any amperage it wanted to, regardless of demand upon it.

    I HAVE A DEGREE IN PHYSICS, 35 YEARS EXPERIENCE IN EVERYTHING FROM BUILDING FUEL INJECTION SYSTEMS, TURBO SYSTEMS, GAS TURBINE MOTORS, SCRATCH BUILT NITROUS OXIDE INJECTION AS WELL AS AUTOMOTIVE DYNAMOMETERS. AND A MENSA TESTED IQ OF 154. NOW NOBODY IN THEIR RIGHT MIND BELIEVES IN OVER UNITY!!! LEAST OF ALL ME! WHERE EXACTLY DID YOU GET THAT FROM???
    THE ENERGY REQUIRED FOR CHARGING COMES FROM THE EMF GENERATED. WHICH IN TURN COMES FROM THE ENGINE, WHICH IS LOADED SO ITS RPM IS REDUCED. WHICH IS CORRECTED BY THE IDLE SPEED CONTROL VALVE, WHICH MEANS MORE FUEL...

    And if you think the system will run whatever you want no matter how powerful it is even with a tiny alternator and do so as long as you have fuel; you're horribly mistaken. It just doesn't work like that.

    AGAIN WHERE DID YOU GET THIS FROM??? OBVIOUSLY IT CAN ONLY PROVIDE THE ALTERNATORS MAX OUTPUT LESS WHAT THE CAR IS USING. BUT THAT IS ALWAYS WAY MORE THAN A MOBILITY CHARGER!!! SO I DONT GET YOUR OBJECTION! THE FACT IS IT WORKS, AND WORKS VERY VERY WELL!

    I PLUG IN MY CHAIR INSIDE MY VAN AND WATCH THE AMPS SLOWLY DROP FROM AROUND A 100 TO 2 OR 3 AS I GET TO MY DESTINATION. THATS AROUND 90 PERCENT CHARGED (AT 14.4V MEASURED) IN SAY HALF HOUR OR SO EVERY DAY FOR 13 YEARS IN 3 VEHICLES AND 7 DIFFERENT POWERCHAIRS...

    You are pulling from the battery itself when you've maxed out the alternator's capabilities. And once the battery drops to low, the engine will die because the exciter voltage is no longer stable.

    THERES A BIG HOLE IN YOUR LOGIC AGAIN. IF YOU CONNECT A DEAD BATTERY (12V) TO A FULLY CHARGED BATTERY (12.7V) THEY WILL CHARGE AND DISCHARGE EACH OTHER. UNTIL THEY ARE THE SAME LEVEL. LETS SAY 12.35V. NEITHER CAN OR WILL GET LOWER... AT WHICH POINT THE ENGINE WILL STILL START AND THE ALTERNATOR WILL STILL CHARGE. WHEN YOU START THE ENGINE BOTH WILL CHARGE AND WILL DO SO AT MAX ALTERNATOR OUTPUT UNTIL 14.4V IS REACHED. IF THE ENGINE IS ALREADY RUNNING THEN THEY CANNOT GET TO EVEN THAT 12.35 FIGURE (50 PERCENT CHARGED) SINCE THERE IS 100 AMPS (OR WHATEVER YOUR ALTERNATOR PUTS OUT) GOING IN...

    Cool chair, but needs to be eased up on the charging requirements for more general real-world use.

    THANKS BUT YOU ARE VERY WRONG IN YOUR BATTERY, PHYSICS, CHARGING KNOWLEDGE. I ENCOURAGE YOU TO GO TO MY PAGES AND READ. AND POST IN MY FORUM IF YOU HAVE ANY QUESTIONS.
    I ONLY POSTED HERE TO SHOW YOU GUYS WHAT I WAS DOING AND SO YOU COULD UNDERSTAND WHATS POSSIBLE. ONLY TO GET INTO AN ARGUMENT ABOUT ALTERNATORS AND BATTERIES (WHICH I KNOW A LOT ABOUT!) THAT IS OFF TOPIC. SO I AM OUT OF HERE.

    BURGERMAN

  6. #16
    Remember that this is EXACTLY the same as connecting another discharged car battery to your running car via jump leads... And that seems to work pretty well too!

  7. #17
    >>> Anyhow; most vehicles today won't sustain 100A constant draw for even an hour... At least not while not screaming down the road. They should have a much slower (20A-ish) feed option.

    Unless you have all your lights, spots, heater, air con, sterio, heated glass and mirrors on it will not need more than 20 amps when "screaming" down the road. Even if you do turn everything on there will still be some left to charge the chair. The chair does not "need" 100 amps, thats just the initial inrush current until the violtage rises a little and then the batteries naturally draw less from the supply. So after ten mins they probably only draw 20 to 30 amps anyway...



    >>> I don't need the chair to be charged in an hour if it lasts for 30+ miles on a charge. I can take it charged, and recharge it overnight or while I'm taking a break or whatever.

    The more often you give the batteries a boost, the higher the average state of charge. Deep cycling and specifically the depth of discharge is the thing that murders your deep cycle batteries. Off road, sand and hills etc rapidly depletes them even if you have 30 milers range. So its ALWAYS a good idea to keep them topped up at every oppertunity you get. Like as you drive to an airfield, on your way to the shopping centre or beach. etc.

    >>> Especially if we're out at a track or trail where a tow-truck is unlikely even able to get to me. I want my charging systems to be as protected as possible. A dead battery here can actually kill a person (which is one reason why we have at least two in all of the vehicles).

    Which the alternator has to charge? !!!
    But with your chair you have FOUR batteries. Dead truck? Start it from the powerchairs Odyssey batteries!!! Its exactly the same as fitting batteries to your truck! What part of this dont you get?


    >>> Plus, don't forget, your 100A alternator also has to run the entire vehicle, it's toys, etc. while trying to charge your chair. Some modern toyed up rigs can draw a sustained 70A or more just to run the engine, lights and the stock entertainment setup.

    My digital clamp meter says 15 engine, 5 max average for music, and about 30 with air con, fans etc running. Leaving about 50 exess to charge the chair. When after 10 mins it only draws about half that... Ohms law.

    So again not an issue. Its just the same as jump starting your truck and driving off with flat batteries...

    >>> Pulling 10-20A off the charging system at any given time is not too much for any stock system. But 10 times that very much can be. At the very least, it will drastically shorten the life of your alternator.

    An alternator rated at 130 amps, running the van and the chair will only be at full or close to full output for around ten mins. And only then if you drove your chair so far it will not move. The batteries only draw full salternator output if REALLY discharged. And then not for long. Alternator brush wear may be increased marginally. But not beyond its rated power.

    I doubt its detectable. Most alternators fail due to diodes, bearings, corrosion etc before brushes wear out anyway.

    And nobody is FORCING you to do this. You can charge it via the hyperion (lithium or lead) at any current or voltage you wish.

  8. #18
    Hey still have the permobil trax?

  9. #19
    Senior Member SuprSi's Avatar
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    Yay, I'm also into RC planes with big lithium batteries and fast chargers. I've been curious to see how long it would take for someone to build a decent power chair with lithium batteries (and brushless motors?). I personally don't need a power chair but a lot of my friends can benefit hugely. And this is just interesting to me.

    One thing i'm wandering about is how you get that amount of current to the charger while you're driving. Do you just limit the charger input to 10A or run heavy guage wires back from the car battery?

    Just to back you up:

    SirGCal.. You don't seem to understand how lead acid batteries work. A full charged 12v battery with nothing connected will sit at 12.6-12.7v. NOT 12. To charge the battery requires a CC/CV charging regime (constant currant-constant voltage). This means a flat 12v battery would take whatever currant is offered to it during the 'Bulk' phase of charge, while the voltage raises to generally 14.4V, at which point the voltage is kept constant while the current ramps down. This is the 'Absorbtion' phase. On a car usually it will just keep the voltage at 14.4V, but smart chargers will go onto a 'Float' phase which just keeps the voltage at 13.5Vish to keep the battery from self-discharging. You can go as high as 15V on most non-sealed wet batteries without damaging them, it will cause the battery to gas and loose water so you shouldn't go this high for too long, but it can be beneficial, reversing sulphation, preventing stratification and helping to ballance out the cells.

    I thought you were correct about requiring >2000rpm for the alternator to supply its rated capacity, but I've never looked into it like Buegerman has. Even if the demand exceeds the alternators rating, all that will happen is the voltage would dip and the difference in currant would be supplied by the battery. Not the end of the world because the maximum 100A demand to charge your chair is only at the start of the charge, for 15 mins or so.
    T11 Asia A after near-fatal bike crash.. Just happy to still be here

    No, I didn't loose my mind... It got scared and ran away!!

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