Dumb question?

[ecowheelz]

This might be a dumb question, but if you undervolt a 48V controller with 36-40V, will there be any negative impact other than lower top speed??? We've overvolted kits... but never undervolted...

Just trying to make a recommendation for a customer. He wants the option to upgrade to 48V later and we thought starting out with the 48V controller might be a good choice. But he plans on starting out with 36V. We're talking a Crystalyte Roadrunner (408?)...

 

[Lyen]

This might be a dumb question, but if you undervolt a 48V controller with 36-40V, will there be any negative impact other than lower top speed??? We've overvolted kits... but never undervolted...

Just trying to make a recommendation for a customer. He wants the option to upgrade to 48V later and we thought starting out with the 48V controller might be a good choice. But he plans on starting out with 36V. We're talking a Crystalyte Roadrunner (408?)...

A 36V battery on a 48v controller will not work if the 48V controller has a low voltage cutoff (LVC) which usually cuts at around 42V, and that is too high and cannot be reprogrammed. But some 48V controllers do not necessarily have LVCs like that, so you may want to confirm with whom you have acquired the inventory from.

 

[dogman dan]

Depends on the controller. What you need is a controller with a LVC for a 36v battery, that can handle 48v. The one that comes to mind immediately to me is the sensorless controller sold by High Tech Bikes, or the similar( maybe identical) one in WE kits.

I found my BR36 motor would run ok on 24v sla's. It had a lvc right around 24v. It ran fine on 2,3,or 4 sla's. My aotema sensorless controllers from High Tech
Bikes can be run at 24v, but the performance is very poor, and no hills can be climbed at all. But the WE type controller works fine at 36 or 48v.

I belive the controllers Justin is selling at Ebikes-ca are similar in lvc. They can go 36v or 48v.

I belive the Ebikekit controllers , intended for 36v, can handle 48v. It better, I just bought a 48v ping :lol:

Thats the list of controllers I know of that go 36v or 48v. I'm sure there are others, maybe ampedbikes, but I don't know for sure.

 

[ecowheelz]

OK... that answers my question. After speaking to the manufacturer I found out the controllers have 40.8V LVC...

Might be better for this customer to go with an E-BikeKit if he wants more flexibility. Otherwise, he'll have to make a choice between a 36V or 48V Crystalyte...

THANKS EVERYONE!

 

[Lyen]

OK... that answers my question. After speaking to the manufacturer I found out the controllers have 40.8V LVC...

Might be better for this customer to go with an E-BikeKit if he wants more flexibility. Otherwise, he'll have to make a choice between a 36V or 48V Crystalyte...

THANKS EVERYONE!

Can you take a picture of the circuit board and the enclosure of the 48v controller? This way we might be able to help you determine the resistor values to control the LVC circuitry so you or your customer can choose the type of batteries at will.

 

[dogman dan]

Great deal on ebikekits on the for sale section.

 

[ecowheelz]

There's been some talk about sensorless kits recently and I wanted to clarify the pros and cons. We're considering the CUTE motors from BMSBATTERY or possibly the Bafang BPM for conversions at our shop. But I'm not totally clear on the pros and cons of going sensorless.

Obviously, sensorless means less wiring and a cleaner install. But I've also read it causes delays from a dead stop. Are there any other issues to be aware of? What are your thoughts on sensored vs. sensorless setups???

 

[Drunkskunk]

My understanding is the sensorless don't start as cleanly, and don't run as smooth or as efficent as the sensored, but then there's no complication of the sensors either.

The project I had been planning with 2 of those Cute motors was going to use one of each, with the Sensored motor being the primary drive for clean starts and smooth running, and the sensorless being a part time assist.

 

[TPA]

My understanding is the sensorless don't start as cleanly, and don't run as smooth or as efficent as the sensored

Isn't this a function of the sophistication of the controller. The controllers the RC guys use are sensorless. I think the software in the controller plays a big role, if in fact the controller is software changeable.

 

[dogman dan]

Sensored works a lot better for gearmotors that freewheel. So if those motors you are talking about are gearmotors, you should use sensored controllers.

For dd motors that only want 20 amp controllers, I find the sensorless one sold by high tech bikes pretty nice. I wouldn't call it rough starting at all.

 

[johnrobholmes]

sensorless cannot start up from zero speed reliably under load (when considering ebikes and three phase motors). That is why they are considered pedal first. Even the best RC controllers do much better if you are rolling a bit. Sensorless can have a higher commutation efficiency if they are quality.

Sensored, better for zero speed starting- hands down. I hate the extra hassle of wiring and increased cause for failure, however. The failure from improper wiring (customer caused) is much more likely too.


I would choose sensorless any day, unless it was for a bike with no pedals. Even better, a hybrid controller that would start sensored and switch once the bike is rolling. You could also have a sensorless failure mode in case a sensor failed.

 

[John in CR]

Are there any reasonably priced high voltage, high current (say 72V50-60A) sensorless controllers available that work well?

 

[johnrobholmes]

I have had great success with the shenzen controllers, but I don't know where they hit the max commutation frequency. I have only tried them on lower voltages.

 

[Knuckles]

You can add a sensorless module to a sensored controlller and operate both at the same time.
If you loose a hall sensor the motor still operates fine.

 

[HTB_Terry]

Knuckles, I would not have thought connecting the sensorless module at the same time as the sensors would work, but maybe it is operating as a wired-OR since the LM339 comparitor (on the sensorless card) has an open collector output. I was planning on adding a digital mux chip to switch between the two. The outputs are around 9-12V as I remember.

In my opinion, there is only one slight downside to sensorless setup. If you bog down the motor on a steep hill and drop below about 5mph, the controller might loose "sync", meaning it can't determine motor position. The motor will then start stuttering. You should never operate any DD hub motor in this condition (it will over heat quick), so I don't see this as much of a disadvantage. I don't think pushing the bike forward 1 inch, or refraining from rolling backwards when starting off is a disadvantage either. I am not super heavy so I dont have to push it forward at all, the Aotema controller pulses the motor at startup causing the wheel to move backwards about 1 mm. With me standing with half my weight on the seat offers no problem for the motor/controller to do it's take off jig.

Theoretically, sensorless motors are more efficient because there are inefficiencies in the sensors due to variations in the rise time of the outputs and the physical placement in the motor. A slight offset can cause the motor to "fire" at the wrong time, wasting power. A sensorless controller is constantly monitoring the motors position so is more precise in that regard.

Sensoless has a huge reliability advantage. That's why the major motor companies (Aotema, Bafang, Tongxin, etc) offer sensorless models and want companies to switch over. It's easier to manufacture also. Some companies don't offer it yet so it depends on what motor you want.

 

[liveforphysics]

The difference is minimal, but basically a sensorless one just shoves the pulses through the motor,while the sensor one has a sensor to find out where the rotor is, and adjusts the pulses to it's rotation. basically,a sensorless one is cheaper and snappier.

Sensorless actually monitors BEMF voltage on the set of un-powered windings (there is always 1 unpowered set on a 3-phase motor). By observing where the voltage peaks occur, it can know at which point the magnet passed by that coil, and calculate to form a timing sequence to know when to energize the next phase. To start, it must send a preset program of cycles for a second or so to attempt to get the rotor in motion. With no rotor in motion, it can't sense BEMF, and it's just as likely to be half jerking your rotor backwards as it is forwards. When abrupt rotor speed changes occur, the controller can loose sync, and struggle to find a correct sequence again.

Sensored makes loads of sense for all E-bike appliations IMO, but hubmotor and RC powered.

 

[ecowheelz]

Would a higher wattage motor get less range than a lower wattage motor??? For example, we're considering the CUTE motors from BMSBATTERY. Would a 36V/10AH battery get less range from a 350W motor vs. a 250W motor??? Or will the wattage ratings have little or no effect on range???

 

[Knuckles]

Knuckles, I would not have thought connecting the sensorless module at the same time as the sensors would work, but maybe it is operating as a wired-OR since the LM339 comparitor (on the sensorless card) has an open collector output. I was planning on adding a digital mux chip to switch between the two. The outputs are around 9-12V as I remember.

I thought the same. But I did test the sensorless module WITH the hall sensors connected and everything seemed to work.
My testing was limited, however, as I got bored with sensorless.
More extensive testing of the cheap module (only $10 from Keywin) is still on my TODO list.
But it worked fine with/without the hall sensors connected.

So ... Nice pet project for anyone interested.

-K

 

[dogman dan]

Range would be better on the slower motor because of wind resistance and it's huge impact on range. But if both motors go about the same speed, they will have pretty similar range, since it simply takes a certain wattage to get to a certain speed.

In my testing, a 350 watt gearmotor gets about the same range at 20 mph as a 700 watt direct drive motor when it is run at the same speed. There is a small difference, with the 350 watt motor going about 5% further, but not enough to make me want to be limited to 350 watts. I definitely prefer 700 because I have to climb hills.

Only when comparing brushed motors to brushless motors have I observed a large difference in range on the same battery if the motors are used at the same speed.

The thing to do of course, is buy one of each and test em.

 

[Mark_A_W]

My friend's Bafang BPM Climber with a http://www.lsdzs.com/ sensorless controller is indistinguishable from a sensored controller setup. It starts fine from stall, it never misses a beat.

http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=12582&start=30

 

[full-throttle]

Sensored works a lot better for gearmotors that freewheel. So if those motors you are talking about are gearmotors, you should use sensored controllers.

sensorless cannot start up from zero speed reliably under load

Both of the above are good examples of 'facts vs personal opinions'. I think what you are trying to say is: not every motor would run smoothly with a given sensorless controller.

There are great s/less geared motors and s/less controllers out there and it will only get better over time.

 

[ecowheelz]

Definitely plan on testing several motors (all geared). I just thought there might be a 'common sense' rule to motor wattage and range. It would make sense that a higher wattage motor would pull more power -- therefore have less range than a smaller motor with the same battery. But we have a variety of products with different motor sizes (same battery) and they're rated at the same range. Is this a manufacturer discrepancy -- or does the motor wattage not affect the range?

Guess we'll know for sure when we test... but I thought someone might have a definite answer based on electrical theory (I'm no electrical engineer )

 

[Drunkskunk]

assuming the low wattage and high wattage motor are ment for the same speed range, and same quality construction, then in theory there is no diffrence.

It takes a fixed amount of power in watts to move a person on a bike at a certian speed. that amount is independant of the motor. The amount of power the motor uses will be that amount pluss the % of efficancy loss. (20% more power for a motor that runs 80% efficent)
So if John Doe needs 200 Watts to push him along at a constant 15mph on flat ground, an 80% efficent motor will need 240 watts to do so, regardless of the motor's size.

But thats constant speed running. On acceleration, an electric motor will generaly suck down as many watts as you feed it. While it's upper limit is a factor if its internal resistance, when it comes to ebike motors, that upper limit is high enough to be ignored. essentualy, the only limiting factor is the Controller's Amp limit. a 48 volt, 20Amp controller will limit the motor to ~1000 watts peak. So if John Doe tries to ride up a ski slope, his controller will limit him to a max of ~1000 watts. it makes no diffrence which motor he uses.


So whats the point of a bigger motor?
Heat. A 750 watt motor is going to be able to sustain 750 watts of heat for as long as you want. A 350 watt motor will cook its self quickly at 750 watts.

 

[ecowheelz]

So assuming both motors (250W and 350W) top out at 18-20 mph, they should have a comparable range? I assume the larger motor will provide more torque and handle load / inclines better? If so, it seems like the larger motor is the way to go...

In the Spring we plan on starting a "Create Your Own E-Bike" campaign at our shop. We'll have 5-6 standard bicycles to choose from and several kit options. We plan on creating an "Economy" setup for price concious customers who are OK with 15mph. For this, we'll use a 250W or 350W geared hub motor at 24V (SLA or LiFePo4). Then we'll do a "Standard" 350W setup at 36V for more speed and a slighly higher price tag. Of course, we'll be offering higher-power setups too. But these will be the two main options for 90% of our customers.

If a 350W motor performs OK at 24V, we'd obviously prefer to offer the higher powered motor. Guess we won't really know for sure until we do some testing...

 

[999zip999]

Here's the way I see it 24v is a euro. motor for flat terrain. 36v is a good general motor with 12ah. batt. plus. in the 350w. is a good med. long range combo. You will be peddling up all hills in a lower gear. 48v will give you the speed, with 500w, now this wil seperate the motors true power and speed do to the non confroming watts ratings and quality of the motor. You must wacth the amps. on the controller you buy! Would like to see the comparisons on the difforances (spell check) can't find it. ha.ha. With a true mileage. The big crstalytes are monters fast prowerful heavy lots of battery draw and must have a battery that can handle the draw. So what is the perfect motor? and combo? With a good price and service!