Electric Starter

Discussion in 'Electric Bicycles' started by matt4x4, Jun 4, 2014.

  1. matt4x4

    matt4x4 New Member

    I was roaming the junk yard, found a starter laying there off a V6 Minivan. I searched the web, found 6cyl normally pulls ~175 amps. I took the solenoid off, but kept the gears. Hooked it up to a 14.4V Dewalt 2.4Ah battery, it spins both ways depending on the wire to terminal setup. I got some 14AWG wire for grounding to the case, used one strand, it gets hot, tied two strands together and it heats up, 3 strands together equals ~#9AWG and its normal. Bought some #8AWG off of ebay which is the same size as the wire that came with the starter.

    I was thinking I could pulse the voltage, wire up a computer fan to cool the motor, maybe figure out how to drill holes on the case to help the cooling.

    The switch, I can easily buy 50A DC toggle switches around here, but I am thinking I need more like 100A DC switches so they dont "weld" closed, for safety reasons. Maybe put in some fuses, find an old circuit breaker rated for 100A, but those are meant for AC.

    I will see where this leads, I might downsize the starter to a 4cyl (130-150A), or even 3cyl (110-120A) perhaps even a motor cycle starter (85A), then if the amp draw and heat is a no-go, its onward to the 24-36V cordless mower motor.

    Oh and yeah, I am going to buy one of those amp-voltmeter guages off of ebay, looks like most of them are coming outta China. I tried a el-cheapo Motormaster MultiMeter, but 10A range is no good. Plus it literally vapourized the tip of the probe, hopefully the clerk wont notice it, I sanded it down a little bit.

  2. matt4x4

    matt4x4 New Member

    I think I am off on my numbers.

    • 4 cylinder gas engine -typically draws up to 160 amps
    • 4 cylinder diesel -typically draws up to 350 amps.
    • 6 cylinder gas engine -typically draws up to 210 amps.
    • 6 cylinder diesel -typically draws up to 450 amps.
    • 8 cylinder gas -typically draws up to 250 amps.
    • 8 cylinder diesel -typically draws up to 650 amps.

    I got that off some web search, along with this.

    Starting Systems
    An import motorcycle’s starter uses about 1000 watts of power every time you press the button, an air-cooled Harley-Davidson almost double that. Given a 12 volt battery, the import starter therefore sucks up about 85 amps of current (1000 / 12 = 83), and the Harley 150~175 amps. Turn the equation around and you can see that electrical power is the product of volts x amps (12 x 83.3 = 1000). The interesting thing is, the starter doesn't care in what combination it gets the two -- i.e. more current and less voltage or more voltage and less current -- as long as it gets the total 1000W. Understanding this basic fact is the key to diagnosing starter trouble.

    That gets me to thinking, if I go 24V which I read you can do safely to most motors. That would half the current draw. Mount it up to my bicycle with a chain to the wheel. It just comes down to the size of battery pack I need for my needs, and how much heat is produced in the starter motor. Some great deals going on at HobbyKing. Some 5Ah 20C for $25, I still dont quite understand the C-rating deal I assume I go 5Ah x 20C = 100A/60minutes = 1.67A/minute, would last 3 minutes. But what does the starter amp draw mean in terms of time. I guess its per hour, so 6cyl gas 200A/hour and that is connected to the engine, meaning the rating would be totally different connected to my bicycle. I will just keep plugging along, I think the amp/volter meter guage will help.

    Of note when the geared adapter plate is on, with the solenoid off, the shaft spins freely one way, and theres drag the other way. This is not the case with just the starter motor, both ways theres drag. I will keep the gears on, because I want to be able to pedal freely without drag. The solenoid shoves the geared shaft out to connect to motor, and it acts as a low voltage switch for the huge current draw. So when I power up the motor, either way that shaft does not come out, the solenoid does that. However when I manually spin it, its somehow internally geared to come out. Interesting. I will find someone to weld on a motorcycle sprocket. That is my only real hurdle now. Might be a huge battery pack I am riding around with, but can always downgrade the starter.

    Last edited: Jun 4, 2014
  3. matt4x4

    matt4x4 New Member

    Trying to find why a starter heats up. I cant feel no heat on mine, when running 14.4V. Perhaps the wires heat up inside due to too much amperage, so increasing the voltage will decrease the amp draw, if that idea actually works. With my limited knowledge I think it would work. I have added some cheap temprature sensors to my list. When I run the motor for a period of time, I can hear the motor change, probably RPM slowing down due to the battery draw, it only has like 2Ah maybe 3, but cant find no C-rate on these Dewalts. I know that battery itself was heating up, every time I run the motor for a minute, I put the battery back on the charger and it wont charge right away, cuz its too hot, I can feel it too. Probably drawing too much power out of it. Just justifies going to 22.2V (6S) which equals 90A on a 12V 170A starter, or even maybe 29.6V (8S) could reduce the amp draw down to a reasonable 67A, then perhaps I can pump more Amps through with battery to up the motor wattage. Who knows, perhaps I am way out in left field here, maybe Endless Sphere would have been a better platform. Guess I will keep expirimenting away.
  4. matt4x4

    matt4x4 New Member

    What do you think about four 3S lipos from HobbyKing 11.1V 5Ah 20C Turnigy $25, plus an extra $33 for S&H.
    A 3-6S 10A 80W charger from HobbyKing, or perhaps the HK B6 AC/DC 50W for $20.
    Two digital temprature sensors for $6 each.
    Turnigy 130A Watt Meter and Power Analyzer. 0-60V, Watts, Wh, Ah. $24.
    UWrench welder rental $25/hour. + Consumables. - Probably just weld on some Alum Plate at the intersection under the seat, both sides, as well as the chain stay rear wheel hub area. Bolt on some metal to make a rack

    No more breaking a sweat riding up slopes. Good thing is, if it dont work too well, can re-use all these parts for a electric bike kit, probably from ebikes.ca, just be out $50 cash.

    How long does it take to recharge a 3S battery, on a 50W (5A) charger?
    What is the formula to obtain the time for charging?
  5. professor

    professor Active Member

    A starter motor will not work.
    It is just the wrong application.