Hi. First ebike conversion.

[Woosh]

the 48V TSDZ2 has a wider range of torque, so when you climb a typical 10% hill for example, you can maintain easily 30% more speed than you would with a 36V TSDZ2, the higher speed preserves the motor yield, less battery is wasted in heat.
I have had the 36V TSDZ2 nearly a year before I decided to sell only the 48V TSDZ2.
The same argument goes for my 48V SWX02 rear hub motor. Both have excellent customers feedback.

 

[sjpt]

I have both 36 and 48 versions I can say for sure the 48 has more than a 30% advantage on range in eco mode , in real world use the 48 does far more miles than a 36 which does one days ride then requires a recharge but the 48 does 2 days ride on the same route with out a charge the motor zips up to the cut out speed far quicker so the assist is for a shorter time = more range

What are the battery capacities of the two?

 

[Deleted member 25121]

And also how do the maximum current ratings of the controllers and batteries compare?

 

[peter.c]

The 36v is 13.0 468W the 48 is 13.5 648W both cheaper packs from psw power
The peak watts on both motors are considerably less than a bafang bbs motor my amp meter showed 12 peak amp for the 36v and the 48v showed 15 amps both run normally around 6- 8 amps or less the 48v backs off max very quickly both standard no remap the standard 48v is programed to run smoother

Remember the tdz only will provide assist in proportion to the human effort given, unlike the bbs motors that's the difference between torque and cadence sensors

My bbs01 in the trike was the etm version of the bafang 250watt it draws 20/22 amps, and the bafang bbs02 750watt I had in my previous specialized used 25 amps.Both of which required high spec /cost battery packs to avoid sag but both produce a much higher constant output as standard, and once tinkerd /remapped much high watt s across the range

 

[vfr400]

The 36v is 13.0 468W the 48 is 13.5 648W

I'm no expert, but I think that might have something to do with the difference in range, when one has nearly 50% more charge in it than the other.

The correctness police say that it's 468 watt-hours and 648 watt-hours capacity in each battery, not watts - just so nobody reading gets confused. The 13.0 and 15.5 are amp-hours, which can't be directly compared because the voltage changes them.

 

[Deleted member 25121]

my amp meter showed 12 peak amp for the 36v and the 48v showed 15 amps

So the 48V version can provide 25% more current which corresponds to around 25% more torque, was that using the same motor? I wonder if the 36V controller and battery pack could be set to provide 15A or would the motor not draw that current at 36V?
I notice that Woosh didn't answer our earlier questions about battery capacities and maximum currents...

 

[Backpeddle]

So the 48V version can provide 25% more current which corresponds to around 25% more torque, was that using the same motor? I wonder if the 36V controller and battery pack could be set to provide 15A or would the motor not draw that current at 36V?
I notice that Woosh didn't answer our earlier questions about battery capacities and maximum currents..

The 48v does not directly provide more current, the difference is in the power P = I x V. as V is higher the power is greater. However it has been reported else where that the current drawn by a 48v motor is a bit less than a 36v motor. I believe this means that the motor will heat up less and hence losses are less. No one has quantified this, this would be the real advantage, the bigger capacity of a 48v battery is not really relevant it does not mean its more efficient just got more gas in the tank.
It would be more useful if someone could compare a 11.6ah 48v battery and a 15.5ah 36v battery, which have about the same capacity. Much of the comparison between the two motor voltages here and elsewhere shed no light on the efficiency, only that it goes a bit quicker because it has more power and goes a bit further because the battery has got more capacity (cells).

 

[peter.c]

I agree its all anecdotal but in the end its personal choice and experience, I will now buy 48v tsdz2 and not 36 it has a small cost advantage, but I get one days use with one and two days on the other

 

[sjpt]

They don't have a TSDZ2 as far as I can see, but you should get a very good idea of the effects of voltage, controller amp, etc on power, efficiency, overheat etc for a given motor at the Motor Simulator. For example, set up to compare BBS02 at 36v and 48v below; I didn't do anything to set up appropriate controllers.

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

 

[Deleted member 25121]

The 48v does not directly provide more current, the difference is in the power P = I x V. as V is higher the power is greater.

I think I'm right in saying than according to a certain Mr Ohm, V=IR, where R is the resistance of the motor windings. For a given motor, if V increases then I (the current) will also increase.

 

[Woosh]

I think I'm right in saying than according to a certain Mr Ohm, V=IR, where R is the resistance of the motor windings. For a given motor, if V increases then I (the current) will also increase.

the motor is not a resistive load, I think of it as a coil, instead of 'R', it's a combination of ohmic resistance and inductance. For inductance, I usually think of it as a bucket. The current flows in, filling it up, when the current is cut, the bucket is tipped over, pouring out its energy. High inductance = larger bucket.
When you increase the battery voltage, you increase the diameter of the hose, making filling faster without increasing heat loss in the ohmic part.

 

[vfr400]

I think I'm right in saying than according to a certain Mr Ohm, V=IR, where R is the resistance of the motor windings. For a given motor, if V increases then I (the current) will also increase.

The current is regulated by the controller, so it doesn't go up with the voltage, but the torque does. It's easier to think about it in terms of energy. The energy is going into the motor in pulses. The pulse has a width (time) and a height (voltage). The energy in each pulse is the width times the height. The current is the width times the frequency, both of which are controlled by the controller. When the voltage goes up, you get more energy in each pulse. If the controller is sending them at the same frequency and width, you get more power too.

 

[Deleted member 25121]

the motor is not a resistive load, I think of it as a coil, instead of 'R', it's a combination of ohmic resistance and inductance. For inductance, I usually think of it as a bucket. The current flows in, filling it up, when the current is cut, the bucket is tipped over, pouring out its energy. High inductance = larger bucket.
When you increase the battery voltage, you increase the diameter of the hose, making filling faster without increasing heat loss in the ohmic part.

I was simplifying things for him, V=IZ is a better representation for an inductive load such as a motor where Z is the impedance of the winding.

You lost be with the plumbing analogy, I tend to work the other way around and equate water flow, height and restriction to electrical terms.

I've tweaked the link provided by sjpt (thanks sjpt) to compare motor characteristics using 48V LiFe battery with those from a 36V LiFe battery for example. Move the cursors to just before the point where the back EMF using the 36V motor comes into effect so that a fair comparison can be made (ie to a speed of 11.3km/h, I didn't play with the gearing, the indicated speed has no relevance to the discussion).

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

www.ebikes.ca

look at the Mtr Amps (motor winding phase currents) and Batt Amps (current drawn from the battery) parameters. The battery amps is being current limited by the controller but the motor current is higher, as the link says "At low speeds when controller is PWM current limited, it is possible for the motor current to be several times greater than the current drawn from the pack."
With the cursors at this point:
1. The 36V system is more efficient
2. The 48V system is providing more current to the motor
3. The 48V system is providing more power

 

[Deleted member 25121]

The current is regulated by the controller, so it doesn't go up with the voltage, but the torque does. It's easier to think about it in terms of energy. The energy is going into the motor in pulses. The pulse has a width (time) and a height (voltage). The energy in each pulse is the width times the height. The current is the width times the frequency, both of which are controlled by the controller. When the voltage goes up, you get more energy in each pulse. If the controller is sending them at the same frequency and width, you get more power too.

Yes, I understand all of that, the current supplied is being pulse width modulated. I wonder how this relates to the difference in Mtr Amps (motor winding phase currents) shown in my previous posting?

 

[Deleted member 25121]

here is a modified comparison based on your selection, I want to show that 48V is more efficient at climbing. You need to match motor output to load to simulate the bike.

climbing a 15% gradient showing the 48V system is not only faster (therefore more comfortable) but also more efficient.

36V climbs 15% gradient at 7.7mph, 76.3% yield
48V climbs 15% gradient at 10.3mph, 76.6% yield

https://www.ebikes.ca/tools/simulator.html?bopen=true&motor=MBBS02&mid=true&gear=1&motor_b=MBBS02&mid_b=true&gear_b=1&batt=B3610_LiF&batt_b=B4810_LiF&cont=C20&grade=15&grade_b=15&axis=mph

Very interesting, those are the speeds at which the efficiency of the motor starts to drop off because of the effects of back EMF. The advantage of the 48V system is that there're 12V more headroom before the back EMF bites so the motor speed is higher at 95rpm vs 71rpm.

I see this as the big advantage of 48V over 36V.

It's interesting that the battery current is 19.2A in both cases, this suggests that the 48V battery is supplying 33% more power to give a 25% increase in speed. Indicated efficiencies are both around 77%.

The 48V system is certainly faster at climbing and will feel more responsive but I'm not sure that it's any more efficient?

 

[Woosh]

The 48V system is certainly faster at climbing and will feel more responsive but I'm not sure that it's any more efficient?

the load is proportional to speed cubed, that accounts for 33% more supply versus 25% more speed. In my link, you get 0.3% more efficiency for the 48V.

 

[Deleted member 25121]

the load is proportional to speed cubed, that accounts for 33% more supply versus 25% more speed. In my link, you get 0.3% more efficiency for the 48V.

I would say that a 0.3% improvement in efficiency is negligible, the benefit of 48V vs 36V with typical hub motors is more to do with high rpm I feel.

As an aside, I wonder why Bosch still use 36V motors and batteries, is it because their motor technology is somehow different (unlikely), because it's not such an important issue with crank motors and associated gears or because they want highest amp-hours for a given battery pack size?

What are your thoughts on this?

 

[vfr400]

Yes, I understand all of that, the current supplied is being pulse width modulated. I wonder how this relates to the difference in Mtr Amps (motor winding phase currents) shown in my previous posting?

In practical terms, it's irrelevant. You should think in terms of energy coming out of the battery and going into the motor. It's easier to figure out what's happening at the battery end. I've always thought of phase currents as something we don't need to be interested in because they change so quickly with time and go in both directions. When you talk about the maximum phase current, it's a spike. The actual average phase current is very low. Look at the phase wires in your motor cable. I've used 30 amp controllers with them. If the phase current really was three times the battery current, that would be 90 amps and they'd melt.

 

[vfr400]

I would say that a 0.3% improvement in efficiency is negligible, the benefit of 48V vs 36V with typical hub motors is more to do with high rpm I feel.

As an aside, I wonder why Bosch still use 36V motors and batteries, is it because their motor technology is somehow different (unlikely), because it's not such an important issue with crank motors and associated gears or because they want highest amp-hours for a given battery pack size?

What are your thoughts on this?

The Bosch motor is actually a 24v one. If you connect a conventional ebike controller directly to the phase wires, it runs twice as fast. Bosch are doing something interesting with their control system. Have a look at Adweb's tests.

Bosch Active Line 3

Here, I share technical solutions that arised during the development of my solar-bike.

www.avdweb.nl

 

[Deleted member 25121]

In practical terms, it's irrelevant. You should think in terms of energy coming out of the battery and going into the motor. It's easier to figure out what's happening at the battery end. I've always thought of phase currents as something we don't need to be interested in because they change so quickly with time and go in both directions. When you talk about the maximum phase current, it's a spike. The actual average phase current is very low. Look at the phase wires in your motor cable. I've used 30 amp controllers with them. If the phase current really was three times the battery current, that would be 90 amps and they'd melt.

I'm not sure that Mtr Amps (motor winding phase currents) represent the peak currents, perhaps they represent average current in some way.

Here's something that's been puzzling me for a while - if rpm is low so that the controller is current limiting then what actually limits the current? The FETs switch the field coils between the 0v and 36/48V so does the controller turn them off as soon as it detects the current limit through the shunt? What then about the inrush currents?

Your description in term of average energy being applied makes a lot of sense, and is the way I approach things, but I'm struggling to see how the control electronics work when they are current limiting.