Elmweaver said:
Well you know looking at the pictures first thought that came to my mind was it looks like 3 more NIMH batteries could be added to the pack and still fit. So that would be a 27.6 volt pack?
Might not over heat the motor and who knows might even bump up the speed a 1-2mph. Of course charging it might be a problem.
EDIT: Ya, good idea with the 20A controller that might work, I was wondering how to get a 24V 10A one that would work with this bike and whether that would help me extend my range while still keeping my ultimate top speed.
Yeah, could probably squeeze quite a few more "F" cells in that pack.
Well the best way to think of voltage and amps is like this. If had a large 300 lb crate on wheels. Say you had a basketball gym to roll this around on. Humans can run about 20 MPH in burst, so you start to push this heavy thing and say get up to 8 MPH. Well, you get your buddy to help, and now you can push it 12 MPH. You get a third buddy to help and now you can push this crate 16 MPH. Now, let's go on the extreme, I have 6 guys to push this heavy crate. Now, because I have 6 guys, this doesn't mean that adding a new guy increases the speed by 4 MPH every time. If it did, then that means 6 guys should be able to push this crate 32 MPH across that gym floor. We know that isn't possible. The best they could do if they all reached top speed is push that crate 20 MPH at most. Now even if we had a 100 people pushing this crate, it only means it will reach 20 MPH top speed.
But, what if we were pushing it up a steep hill. Who is more likely to push the crate up a steel hill at 20 MPH? 2 guys or 100 guys?
So apply this to voltage and amps. Think of the voltage as the "top" speed and the amps as "the number of guys pushing". If you have a 24 volt controller that has a 10 AMP limit, this means that under ideal conditions (flat ride area, no wind, etc) the bike could do for example 20 MPH. But when you factor in road to tire resistance, air resistance, wind, rider weight, etc. Then you soon discover that more amps is needed to move against the increased resistance.
A 10 amp controller would basically give you 10 X 24 = 240 watts of power maximum that the motor can use. The controller in these bikes we have are rated at 30 amps. So this means (if necessary), the controller can send up to 30 X 24 = 720 watts of power to that motor. Why so much power? Well to get the bike rolling from a dead stop,to climb steep hills, etc.
So does using less amps give you more range? Well yes and no. Since the maximum amount of power has been cut down by 480 watts, the bike will have very slow acceleration. Any steep inclines will probably bring the bike to a stop because it won't have enough power to move the bike forward. But on the flip side, if you ease up on the 30 amp controller and do the same "slow" acceleration as the 10 amp controller, you are basically using the same amount of power and thus getting the same low power usage.
What does this mean for travel distance? Well, in a straight head to head race on a level track, it will mean nothing. The 30 amp bike will accelerate faster than the 10 amp bike, but once they reach top speed they will both be using the same amount of power. They will get the same range, maybe the 10 amp bike will get an extra 100 feet of distance because it started out on a slower acceleration, but that would be it.
Basically, (for the same reason that free energy machines don't exist) energy in and energy out will always balance. So those (2) 24 volt batteries can hot rod around for a short distance or give you extended range if you cut down on power usage with gentle acceleration.
This is one major advantage that electric vehicles have over gas vehicles. Bigger engines in a gas vehicle means less gas mileage. Big power controllers in electric vehicles mean the same mileage no matter what. It all depends on how much power you are willing to spend in one time. If you hot rod around in an electric vehicle, you get less mileage. But that same vehicle can get great mileage if you are easier on the acceleration. Conversely, gas vehicles have a certain RPM range that the engine must turn before it reaches "maximum" efficiency but an electric motor is always in "maximum" efficiency no matter what RPM range you choose (within reason of course)
For electric systems, it all comes down to power (watts) is what really matters. The controller I have in my 24 volt e-bike will push out over 720 watts of power. It means it can do a solid 17 MPH no matter if I weight 100 lbs or 300 lbs. What I plan on doing later is changing it for a higher top speed. That's why I'm going to try a 36 volt controller at 20 amps. That means the max power it will send out is 36X20 = 720 watts of power. So it's identical to what the first controller was doing. The only difference is, I've sacrificed amps for volts. So now the motor will have a higher top speed, but will have less amps in which to "reach" that top speed. So maybe the bike will have a top speed 25 MPH. The difference will be in range. To keep the bike moving at 25 MPH will take more power (watts) than it did to keep the bike moving at 17 MPH. This means that if the controller was only spending 200 watts of power to keep the bike moving at 17 MPH, it make take 400 watts of power to keep it moving at 25 MPH. So basically I go faster, but I probably reduce my mileage by almost a third.
In the end, the motor will have power levels within it's acceptable operating range. It's a 450 watt motor with 900 watt peak, so in theory it shouldn't melt on me going faster since the total power going to it will only be raised by a small factor.
This is similar to when I was running 60 volts through a 36 volt controller by at quite a bit of reduced amps to keep it from melting. That same controller, I did try a 60 volt run at the maximum amps the controller could handle and it melted of course, was way too much for it. Heat (resistance) is always the enemy of all electronics
