Thursday, August 14, 2014

eBike Burn-out?

People tell me that all e bikes burn out (melt down). This is not true, the reason most burn out is simply that most people just over power their equipment. If one would use a programmable controller you could keep your equipment from overheating. Get one with heat sensors. It may not be able to sense the heat in the coils, but the machine can compensate for the difference between the inside and the outside.

Heat is the biggest reason electric bicycles do not last long!

Heat is the nemesis of motors and controllers. More heat is created by low voltage than high voltage.  Amperage creates friction, at high voltage there is less amps pumping through the wires. The lower the gear the less stress is placed on the motor. So if you’re motor is overheating get a low gear. If your motor is not big enough you will need lower gears. The smaller wattage the motor the lower the gear is needed.

The majority of the heat that can damage the motor and controller comes from the amps of current. By choosing a system that has higher volts, you can achieve the same amount of power with fewer amps.

 Heat only occurs when the motor R.P.M.s are not EQUAL to the peak efficiency R.P.M.s (see the label). This is "by definition" because the point at which the motor runs "best" is the place that it runs "coolest".

So the thing to look for in an E-bike is one that uses at least 48volts and a motor of the largest wattage you can afford. Driving up our 8% grade hill with a total combined weight of 300lbs will be easier on the motor than 400lbs.

You should use MTB gears with at least 24 sprockets on the front and 34 sprockets on the rear. 350 watts will drive 300lbs up an 8% grade at about 5-6 mph. use a speedometer!  Try it out and feel the motor to see if it is overheating.

500 watts will do the job at about 8-9 mph with the bikes gears to keep the motor cool by making sure it is running fast enough. If you hear your motor bog down when climbing a hill it is over heating!

Another big source of heat is when the driver twists the accelerator all the way up and pumps too many amps through the motor, pushing past the peak efficiency wattage (see the label on the motor). The best way to avoid this is to have an amp meter like the Cycle-analyst; and a programmable controller.

Power does not change when it goes through gears, all gears do is slow the power down so it can push the wheel easier creating less heat in the motor.

 Read more of this here: Electric

The power that you need (or want) is further complicated because the true limit of the power you can put through a motor is how much heat it can survive. If you take a given motor and begin raising the volts, you will get some extra power, and also the motor will spin faster than it did at a lower voltage. If you begin raising the maximum amps, the acceleration will get faster, but…adding more amps will cause most of the heat that will kill a motor (and sometimes the controller).

Factory power ratings are rarely accurate. Legitimate sellers under-rate their kits, because so many buyers will overheat their E-bike and want to have the motor and controller replaced due to heat damage. Then, there are the other retailers…the ones that don’t answer their customer service lines…they claim their kit will put out thousands of watts and will climb anything!…and then when you melt something, they refuse to help you.

Here’s a tip about raising the power that you can use on all these kits. If you are running on fairly flat land, you can run much higher amps for some very impressive acceleration. You will draw the max amps setting for only a few seconds while the bike is speeding up, and once your top-speed stabilizes…the amps draw slides back down to a low setting that only needs to maintain your speed, and that gives the motor and controller a chance to cool down before the next acceleration.

But here’s the worst-case-scenario…you loan your E-bike to a friend who doesn’t understand this and then they ride it up a very long and steep uphill at full-throttle. With no cooling-off phase, the motor and controller overheat, and your friend has to do the “walk of shame” back to your place. This is where you should have limited the max amps the kit can provide (a Cycle Analyst E-bike computer is an easy way to adjust the amps the controller can draw).

The popular MAC is generally regarded as capable of performing very well when using 25A, but…if you live in a very flat region you could actually use more. One of the reasons the MAC has grown in popularity is because it’s one of the few kits where you can order it with a temp sensor installed inside the motor from the factory ( is the other seller with temp sensors). If you have a Cycle Analyst (the best E-bike computer on the market), you can easily adjust how many amps the controller can use, so you can adjust it to get the max power possible…without

The secret to making an oversized motor legal is simply to use a programmable controller to keep the power going into the motor at a legal limit. 745Watts for most of the country.

And using an oversized motor at a lower than maximum wattage will keep it from burning out. But it could still burn out your tires, and pop your chain. Unless you set your controller to take it easy on the acceleration.

The controller can also keep your battery from draining too low. And limit the speed of the vehicle.
Brushless motors could be the best kind of motor to use on an EV because they will out last any other kind of motor, but they have less slow speed torque than brashed motors.

Brushless motors will not work at all with out a good controller. So unless you want to build a hot rod that will burn out the power system, don't be a cheapskate. Get a controller that will handle 12 volts even if your not going to use a 12 volt system. The lower the speed the lower the voltage, and believe me that when climbing steep hills with cargo you will need all the help you can get.

For a long time in high current/power, the motor might over heat & even burnt. A thermic Probe should be installed in hub motors so that the controller will turn off when it's 120°C (248°f) inside of motor.

If 3 to 7 years life span is long for a big hub motor, then forget them.(For Life expectancy, hub motors could work 5000 hrs without damage in Lab. In real life it depends on the motor's usage (e.g. hitting bumps and water getting in).
Stronger configuration like wider lamination, more cooper wire/phase wire and thicker cross-sectional area, bear more current in usage.

You can make a good heavy-duty motor like the brushed Mars 909 last twenty years if you do not over power them with a cheap controller.

Brushed motors have more slow speed torque than brushless motors?
What a motor controller does:

If you want to make sure your controller won't fry, you need to over-spec your motor controller. ie: If you have a 500W motor, get a controller capable of handling 1500W. The larger controllers will have more power Mosfets (the electronics actually handling the power to the motor) and more heat-sinking. 

This shouldn't cost you any more than about $200. People selling quality upgraded controllers will also usually advertise having replaced "no-name Mosfets" with quality Mosfets with a "low RDS" (ask them about this, if they don't know don't what RDS is don't buy from them, if they do know they'll be able to solve your problem).

Also make sure your motor controller is mounted on your bike in such a way as to get some airflow to cool it down (ie: don't hide it inside a bag/pannier as it won't have any air flow).

No comments: