Riding techniques

[howbeit]

Hi everyone,

Over the past week or so I found out about electric bikes by searching on the internet, and now I've bought parts that should be on their way.

I'm getting a MAC 500 kit with 38V 20ah battery from Paul (Cell Man). My CA V3 just arrived today (thanks Paul!).

With some luck, I should be hitting the road soon. So my question is this: Do you guys have any recommendations on riding with an electric bike? How often can one get away with using the throttle? Are there any warning signs before a motor dies from overwork?

I bought this system to commute and save on gas, and I do plan on pedaling the entire way if possible. I just want to make sure I'm always moving at a fast pace.

Thanks all, and look forward to being a part of this community.

 

[neptronix]

Depends on the winding of your motor, the amount you pedal, stop and go, hills, your weight, um.. yeah

You have a cycle analyst, so it's very likely that you'll learn what the system likes very quickly. You can't go wrong cruising along and pedaling as you would normally.

There are few signs that a motor will die for overwork, but a temp sensor in the motor is good to have. 36v on one of the 8T or 10T motors will be fine unless you are trying to climb extended length grades that even a car would have a hard time scaling.

 

[amberwolf]

Since you have the V3 CA, see if you can get him to install a temperature sensor in your motor, so you can connect it to the CA via the port for that, and then simply set the temperature limit in the CA to something appropriate (See the various motor cooling / temperature / overheating threads), and you will never have to worry about warning signs of overheating--the CA will limit and stop you before you get that bad.



As far as how much you can use the throttle--if you have selected your motor and controller and battery based on your needs and terrain, then they should be able to work continuously for you. If you did not determine what power level and how much energy you'll need before picking your equipment, then you'd either have to test the equipment under your conditions, or do the calculations and/or use a simulator like that at
http://ebikes.ca/simulator
to find out if it can handle your conditions.


Since we know nothing of your conditions, we can't say anything about how well your system will work for you.

 

[dogman dan]

It will take a lot of hill to give you problems with that setup.

Having a CA will help you avoid the main pitfall, which is letting the motor work too hard on hills. As you slow down, called stalling the motor, you will see the wattage really spike high on the CA. Soon you will see what speeds your motor "likes" going up hills, and which is pulling too much amps and turning it into excess heat. In general, below 15 mph you will make heat on a steep hill. But on a moderate hill or the flat, riding slow is ok. The CA will show you when you are maxing out your wattage.

The best ride style for me when commuting, has been to select a throttle setting see what speed that gets you, then pedal up 1-2 mph more. The CA will show you why this is good, the motor will work less hard, and your battery will last longer. No need too kill yourself pedaling till you puke. Just get your effort dialed in so you contribute to the wattage, but can continue that level of effort all day. In general, this method will take at least 100w off your CA reading, and keeps the motor in it's most efficient mode, avoiding stalling. For a short hill, a bit more pedaling effort will help a lot. But most of the ride you should be able to pedal easy, yet still help the motor a lot.

 

[John in CR]

People have gone overboard with this fixation on temperature sensors. Maybe if they paid more attention to the road and less to temp displays, they'd have less crashes and fewer close calls with cars. You got a complete kit from a reputable vendor, so it should be dead on reliable even if you ride around with no pedaling at all. Simply avoid situations where the motor inside is at low efficiency more than necessary, since whatever electricity isn't converted into work turns into waste heat.

At 0 rpm a motor has 0% efficiency, so all of the juice sent to it turns into heat. That means every start from a full stop begins at 0% efficiency, so whatever you can add at the pedals is the biggest help in the first revolution or two of the tire. In normal riding it's not a big deal, but if you get stuck in bumper to bumper traffic starting and stopping over and over many time or do a bunch of 50 or 100 yard sprints, you have reason for concern.

If you're a large person then acceleration is slower, so the motor spends more time at lower efficiency for a given power input, creating more heat. More weight means slower speeds on hills too, so lower efficiency and more heat.

Our motors all dissipate waste heat to the outside environment, and the higher the ambient temperature the slower heat can be transferred away. That means the performance limits of your system will be different on a hot day vs a cold one, since the motor can't reject heat as well.

Bogging the motor down on hills that are too steep can quickly cause a heat failure. I live in a mountainous area, and with my systems on a uphill grade as long as I'm able to maintain at least 1/2 of the maximum speed on flats, then the motor is running efficiently enough to avoid heat problems. YMMV

If you decide later to go to higher power with the same motor, then you'll need to pay closer attention, especially early on, since more power means high temps can happen faster. With a package deal just avoid getting bogged down on hills, along with repetitive full stop launches. It's a good idea to gain an understanding of what riding conditions make your own system run hotter along with what is normal operating temperatures for your motor. That's as simple as putting your hand on the cover when you stop, and if it's a geared hubbie check the axle too. With a geared hub the shell isn't directly connected to the motor itself so heat reaches the outer shell more slowly and the motor itself will be hotter. The axle has a direct metal connection to the heat source, and a failing bearing will show up as extra axle heat. Doing this isn't to check the absolute temperature of your motor, but instead to gain an understanding of your motor's operating conditions and what conditions create more heat. We're lucky that our systems are pretty darn efficient, so the waste heat results in a temperature range that won't burn your hand. Once you gain that understanding you can ride with impunity, and rarely check your motor for heat.

Unless your battery comes with multiple thermistors at different locations in the pack, it's a good idea to also check your battery for hotspots every once in a while.

Don't forget about good torque arms. That's a far more common point of failure than heat related failures of a stock kit, and the wheel can potentially separate from the bike, making it a high risk failure.

John

 

[d8veh]

If you want to pedal all the time, you need to think about the gearing. The MAC only takes a free-wheel gear set, which normally means 14T top gear. With a 42T or 44T chain-wheel on the front, it won't be comfortable pedalling over 15 mph. A 11T DNP free-wheel from Ebikes.ca will get you up to about 19mph. After that, you have to go up to a 48T, 52T or 53T on the front depending on what speed your motor is wound for.

 

[teklektik]

At 0 rpm a motor has 0% efficiency, so all of the juice sent to it turns into heat. That means every start from a full stop begins at 0% efficiency, so whatever you can add at the pedals is the biggest help in the first revolution or two of the tire. In normal riding it's not a big deal, but if you get stuck in bumper to bumper traffic starting and stopping over and over many time or do a bunch of 50 or 100 yard sprints, you have reason for concern.

If you're a large person then acceleration is slower, so the motor spends more time at lower efficiency for a given power input, creating more heat. More weight means slower speeds on hills too, so lower efficiency and more heat.

Bogging the motor down on hills that are too steep can quickly cause a heat failure. I live in a mountainous area, and with my systems on a uphill grade as long as I'm able to maintain at least 1/2 of the maximum speed on flats, then the motor is running efficiently enough to avoid heat problems.

What he said....

Here's a composite snap from Justin's simulator to help illustrate the point. The selected components are close enough to yours for this quick comparison...

 

[howbeit]

Thank you all for the good information. It sounds like stop and go will be the one thing to watch out for after the Cycle Analyst is completely set up. I am relieved to hear what some of you are saying regarding the kit though. It really doesn't sound like I should have a problem with the motor burning out.

The issue about the pedal possibly not keeping up with the motor is an interesting one though. I thought of that two days ago and ordered a lower tooth sprocket to hopefully deal with that problem. It might not, however, because I'm working with just a 3-gear internal hub. That issue might be the subject of a future post when I finally get things up and running.

 

[onlineaddy]

If you want to pedal all the time, you need to think about the gearing. The MAC only takes a free-wheel gear set, which normally means 14T top gear. With a 42T or 44T chain-wheel on the front, it won't be comfortable pedalling over 15 mph. A 11T DNP free-wheel from Ebikes.ca will get you up to about 19mph. After that, you have to go up to a 48T, 52T or 53T on the front depending on what speed your motor is wound for.

I'm getting an 8T Mac. Which of the 48T, 52T, and 53T would you recommend?

 

[neptronix]

The dnp 7 speed with 11t gear will very easily allow for pedaling at up to about 35mph on a 53T front chainring.
48T is adequate for going no faster than 30mph.

 

[onlineaddy]

The dnp 7 speed with 11t gear will very easily allow for pedaling at up to about 35mph on a 53T front chainring.
48T is adequate for going no faster than 30mph.

Thanks, neptronix. Sounds like the 48T is sufficient for my modest speed needs.

 

[Ykick]

"I'm working with just a 3-gear internal hub."

Ooops.....

 

[Ykick]

"I'm working with just a 3-gear internal hub."

Ooops.....

 

[amberwolf]

It might not, however, because I'm working with just a 3-gear internal hub.

If that MAC motor is a rear, then you won't be dealing with that 3-gear internal hub (IGH) anymore, becuase it will completely replace that wheel.

If it is a front motor, then you won't need to worry about freewheel/cluster changes on the rear, unless your IGH is setup to use them (the old ones I have are not--they use a single fixed sprocket).

Additionally, if that IGH is in stays/dropouts as narrow as some of the ones I have here with such hubs in them, the bike frame may be too narrow for your new MAC motor, with a full gear cluster on there--it may require using a single-speed freewheel, and/or stretching your bike's frame (if possible/advisable). Mine are more like 120mm, whereas IIRC the MAC rear hubs are 135mm. There are IGHs that have 130mm spacing, though, so if yours is like that, and your frame is steel, you should still be able to safely and easily fit the MAC in there.

 

[John in CR]

It sounds like stop and go will be the one thing to watch out for....

It probably won't even be an issue for you. After 4 years it only hit home for me recently. I did 10 mile ride into town a couple of months ago with the first 6 miles or so into the wind and generally up hill, gaining a couple hundred meters of altitude. I was hotdogging it the whole way. After I crested to the plateau where downtown starts, I checked the motor out of curiosity at a stoplight and was surprised at how it was only slightly barely warm. Then going thru downtown I got stuck in mega traffic with no way out even on a bike due to narrow streets and unsuitable sidewalks with high curbs. If I had functional pedals I would have just used them in the stop and move a couple of car lengths type traffic for much of it. When I did get space I went easy on the throttle because it was pointless to hurry. I got to my destination and the motor was scorching hot, far hotter than it had ever been.

It's just one of those things to be aware of, since it can sneak up on you. Running near recommended power, it's only the low efficiency operation where heat is a problem. As you get into multi-kw (low multi for geared hubbies, and mid multi-kw for DD hubbies), you run into situations where the motors can't reject enough heat at moderate efficiency. That's where guys start modding their motors for better cooling to raise the thresholds, though no amount of cooling will save a motor bogged down on a hill since the stator just turns into a heating element. I'm going to try to repeat my stuck in traffic ride with the motor ventilated. Since it occurred at relatively low power and in small spurts over 10-15 minutes, I think my mods will solve any stuck in traffic risk. Hell, I may even install a pedal chain on that ebike.

John

 

[Sunder]

I'm building a similar bike to you - 350w geared hub motor onto a hybrid bike. With such small assist, I will need to adapt my riding style to make the most of it.

I have geared it to a 48 front and 11 rear, which should be good for 50ish km/h. It however, can gear down to 28 front 36 rear, which I doubt I will use on the road, but you never know where I will take this. I'm intending to use it to haul a baby trailer, so I might need the lower gears.

My intended riding style will be to get the bike moving before I apply much power, though this is more for range extension than anything else. Also, to manually stop it applying power after about 40km/h - power required to increase speed increases exponentially due to wind resistance.

I expect the bike, including batteries to be about 20kg, which is about 15 less than my old 1kw steel framed mountain. My old bike used to do about 40ish km on my 10ah (12s lipo), with minimal pedalling, so I expect with both pedal first and speed limitations and an expectation of lots of pedalling, that I could go 60+ km between charge, but it largely depends of throttle discipline.

I'm hoping I will get enough time between now and the new year to finish the bike and will post photos when I can.

 

[dogman dan]

You could consider a front hub then, if you want to keep that IGH.

I saw nothing that would indicate a temp sensor would be required. Sure, I ran one on my commuter for quite some time, but only to gather data on 1000w riding of a brushless motor that wasn't avaliable at that time.

Bottom line, keep it going 15 mph up the steep hills, and you won't overheat. Many stops and starts won't overheat you, but you will see your wh/mi suffer some. I advise a slower winding for many stops. Not particularly super slow, just not the fastest avaliable winding.

 

[John in CR]

...Many stops and starts won't overheat you...

Really? Take a ride on a warm day for say 5 miles to get your motor up to normal operating temperature. Then do a 100 full stop moderate throttle powered starts over 1 mile, ie full stop every 50ft. That's many, and not outside the realm of possible conditions in heavy traffic congestion if someone hasn't been warned to avoid it. Maybe a little geared hubbie will survive it, but I doubt it, and I wouldn't risk a motor trying.

Think about it, every start from a full stop has a lot in common with bogging your bike down to a full stop.

John

 

[amberwolf]

When I was using the heavily modded Methods 18FET on the 9C rear 26", with peaks over 4.5KW, riding in typical stop/start traffic would heat it up a lot, to the point of very smelly phase wires and motor coils, where I often could not keep my fingers on the coils for long once stopped at the end of 2.5 miles, even with basic ventilation. If it were heavy stop/start traffic, it might have been significantly worse, especially on a longer trip.

However, the same setup on a trip with very few stops/starts but the same cruising speeds would not heat it up so much.

Even just a bog-standard 40A controller with 2KW peaks on the same motor could heat it up more than I liked in heavy stop/start traffic, but it did not come close to overheating it. I can imagine an unventilated situation with me hauling cargo in a traffic jam that might, though.


At least with standard typical ebike DD stuff (not counting geared motors), I am not sure if there is too big a worry. With more powerful controllers/batteries on typical ebike DD motors, under those heavy traffic conditions, then maybe there could be.

Either way, a temperature sensor with the V3 Cycle Analyst would not require the rider to do any monitoring at all, once it has been setup, it would simply allow the CA to cut power back as heat increased beyond whatever limits are set, until the cutoff is reached at which point it would cut power completely.

Personally, I'd also have an override switch for any cutout, becuase soemtimes you *have* to keep going no matter what you do to your equipment, or else get run over or hit or whatever. Not an every day thing most places, but it could happen, so having the option to get out of the way with power is a good thing. But having the built-in sensors and limits should keep stuff from being damaged under normal conditions in everyday riding, no matter how bad the traffic or hills might be.

 

[hjns]

Either way, a temperature sensor with the V3 Cycle Analyst would not require the rider to do any monitoring at all, once it has been setup, it would simply allow the CA to cut power back as heat increased beyond whatever limits are set, until the cutoff is reached at which point it would cut power completely.

Personally, I'd also have an override switch for any cutout, becuase soemtimes you *have* to keep going no matter what you do to your equipment, or else get run over or hit or whatever. Not an every day thing most places, but it could happen, so having the option to get out of the way with power is a good thing. But having the built-in sensors and limits should keep stuff from being damaged under normal conditions in everyday riding, no matter how bad the traffic or hills might be.

Yes, the CAv3 does that. And it does it so gradually, that I never have to worry about motor temp again. I am not sure whether one needs that override switch. I can imagine some circumstances where you would prefer to run the motor over it's limits and be gone from a place as soon as possible. However, if you got yourself in such a dangerous place with a motor ready to overheat, you really took too many risks from the start anyway.

Normally, when you run into a situation with a motor dangerously close to overheating, I would just suggest to wait for 10-15 minutes, and if possible have the motor turning unloaded. My temp charts show that my cromotor sheds at least 20oC of heat during that time, which of course will differ with different motors, different ambient temp, etc. However, it will bring the temp back to rideable realms.

 

[dogman dan]

Well John, I do always appreciate your making me write more specific and accurately. So how about this? No street in my town, which has no stop signs any more frequent than every 300 feet, will overheat any of the motors I have. Thank god I don't have traffic like you described. If so, it might be a poor place to ride an ebike very far.

Yes, they will get warmer if you are riding where stop signs come every 300', but not to the point of overheat. If a cargo bike was loaded heavy enough, and expecially if the stops were facing uphill, an overheat could be possible, or even likely. All my previous comments were intended to apply to the situation being dicussed. Obviously higher wattages can melt motors much quicker if the motor is being stalled a lot by starts and stops. It's how I melt a 9c motor once a year on average. But that is a dirt ride in thick sand, not a street ride. Perhaps I misunderstand, but he used the word "road" and never said, 3000w, off road, trail, cargo bike, trailer, rider weighs 300 pounds, or very steep hills.

I do recall a case whrere many stops overheated a motor. The many stops were done at the bottom of a bmx vert ramp. So lots of uphill starts and stops were done in that case.

 

[hjns]

Really? Take a ride on a warm day for say 5 miles to get your motor up to normal operating temperature. Then do a 100 full stop moderate throttle powered starts over 1 mile, ie full stop every 50ft. That's many, and not outside the realm of possible conditions in heavy traffic congestion if someone hasn't been warned to avoid it. Maybe a little geared hubbie will survive it, but I doubt it, and I wouldn't risk a motor trying.

Hi John,

I like this test. I have been looking at motor temps after 8 km (5 miles) of "normal" driving at ambient temps between -4oC and +1oC. Average power consumption is around 25Wh/km with average maximum power (aka over multiple commutes) of around 5kW. Starting motor winding temp is around +1oC (which is the overnight temp in my wintergarten where the bike is parked).

I find that after 3 days looking at motor temps after 8 km, motor winding temps are between 35oC and 45oC. It will be interesting to see how ambient temp will change this.

My riding techniques are really depending now on the capacity of my lipos. The cold weather decreases the capacity of my lipos severely, so that I can barely get 500Wh out of my 20S 13.5Ah (1kWh) pack. Within 15 minutes in the cold, I start hitting LVC (3.60V cell level) when accelerating.... And that time is probably a reflection of how long it takes for my pack to "cool down". After charging, I store the pack inside the house (approx 20oC), so in the cold weather it will catch a cold pretty fast...