Rookie Question #4: Low Gear Battery Usage

[Catalyzt]

I'm calling this Rookie Question #4, because I'm sure I've asked at least three previous Rookie Questions.

This one is: On a torque-sensing mid-drive, assuming you are at the highest assistance level possible, do you use less noticeably battery at high cadence, low gear and low speed on steep hills compared to being in high gear, and medium-high cadence, and higher speed on a moderate grade?

Here is why I ask: After I have been grinding up 10-11% grade climbs for a few miles at high cadence and low gear, mostly in HIGH or NORM and in low gear, I am finding that my indicated range drops less than expected in "HIGH."

When I am pushing harder in "HIGH," and going fast on a more moderate grade-- say, winding through mild upgrades on canyon roads, which is a lot of fun-- it seems like the range drops much faster. So I'm trying to avoid doing that on longer rides to preserve range. Is that a good strategy?

The other variable is just what the cycle computer is telling me, which is not accurate. (Shimano E6100.) Its estimates are all over the place. I start out with 92 miles of range for ECO, this drops to 45 miles or something after a 4.5 mile 850 foot climb... but then after descending the other side and plowing through the flat lands with the motor off or on ECO, range for ECO increases to 104 or 105 miles. I understand why the computer does this, but it's really not that helpful! Maybe when I am grinding up those long hills, it simply hasn't yet processed the energy usage of the climb yet.

Thanks! I am planning to push more towards the edge of my range on Monday, pretty sure I'll get home with a decent cushion of range, but wish I really knew how many electrons I was using in what situations.

 

[AHicks]

I'm calling this Rookie Question #4, because I'm sure I've asked at least three previous Rookie Questions.

This one is: On a torque-sensing mid-drive, assuming you are at the highest assistance level possible, do you use less noticeably battery at high cadence, low gear and low speed on steep hills compared to being in high gear, and medium-high cadence, and higher speed on a moderate grade?

Here is why I ask: After I have been grinding up 10-11% grade climbs for a few miles at high cadence and low gear, mostly in HIGH or NORM and in low gear, I am finding that my indicated range drops less than expected in "HIGH."

When I am pushing harder in "HIGH," and going fast on a more moderate grade-- say, winding through mild upgrades on canyon roads, which is a lot of fun-- it seems like the range drops much faster. So I'm trying to avoid doing that on longer rides to preserve range. Is that a good strategy?

The other variable is just what the cycle computer is telling me, which is not accurate. (Shimano E6100.) Its estimates are all over the place. I start out with 92 miles of range for ECO, this drops to 45 miles or something after a 4.5 mile 850 foot climb... but then after descending the other side and plowing through the flat lands with the motor off or on ECO, range for ECO increases to 104 or 105 miles. I understand why the computer does this, but it's really not that helpful! Maybe when I am grinding up those long hills, it simply hasn't yet processed the energy usage of the climb yet.

Thanks! I am planning to push more towards the edge of my range on Monday, pretty sure I'll get home with a decent cushion of range, but wish I really knew how many electrons I was using in what situations.

The only way to know (that I know of) is with a display able to show you watts (in use) in real time. That's telling you exactly that, allowing you to play with/experiment your gear and PAS settings to see/monitor exactly what you have going on at any given moment. -Al

 

[RunForTheHills]

The Grin motor simulator has the Bafang mid drives in it if you use the show more option and you can select the gearing use to compare two different setups. Note that in the lower gear the motor will never overheat on an 11% grade, but it will in the higher gear.

https://ebikes.ca/tools/simulator.h...mid_b=true&gear_b=1&tr=15&grade=11&grade_b=11

 

[PedalUma]

I'm calling this Rookie Question #4, because I'm sure I've asked at least three previous Rookie Questions.

This one is: On a torque-sensing mid-drive, assuming you are at the highest assistance level possible, do you use less noticeably battery at high cadence, low gear and low speed on steep hills compared to being in high gear, and medium-high cadence, and higher speed on a moderate grade?

Here is why I ask: After I have been grinding up 10-11% grade climbs for a few miles at high cadence and low gear, mostly in HIGH or NORM and in low gear, I am finding that my indicated range drops less than expected in "HIGH."

When I am pushing harder in "HIGH," and going fast on a more moderate grade-- say, winding through mild upgrades on canyon roads, which is a lot of fun-- it seems like the range drops much faster. So I'm trying to avoid doing that on longer rides to preserve range. Is that a good strategy?

The other variable is just what the cycle computer is telling me, which is not accurate. (Shimano E6100.) Its estimates are all over the place. I start out with 92 miles of range for ECO, this drops to 45 miles or something after a 4.5 mile 850 foot climb... but then after descending the other side and plowing through the flat lands with the motor off or on ECO, range for ECO increases to 104 or 105 miles. I understand why the computer does this, but it's really not that helpful! Maybe when I am grinding up those long hills, it simply hasn't yet processed the energy usage of the climb yet.

Thanks! I am planning to push more towards the edge of my range on Monday, pretty sure I'll get home with a decent cushion of range, but wish I really knew how many electrons I was using in what situations.

Good question. Yes. Using a low gear and high cadence while climbing a mountain while using a high level of assistance will save battery capacity and range. It will also save stress on your drivetrain. I live in a place with big hills and high winds and do many miles along side other riders. I also use the smallest batteries I can to save weight, so I need to milk the most out of a charge. If you can, drop the power level one notch as soon as you can, while keeping cadence high. Get aero on the flats. I am the 'Domestique' of my riding group. That is the domestic servant who rides out front so the others can draft. Isn't it funny, the leader is the servant!
Light cashmere breaths and has a texture that is super aero. Things like a rough shark's skin, a golf ball with dimples, and a bird with feathers use this principle. Is cashmere an unfair cheat to get the most miles out of a battery?

 

[m@Robertson]

@PedalUma beat me to it. Here's a slightly different take on the same phenom:

Low rpms (cadence) tells the bike to pour on the amps to let you get your cadence up. So... higher draw on the battery. hi rpms (cadence) needs lower amps as the motor senses you are already hauling ass based on the cadence. So lower draw. You can watch this happen if you are on flat ground and go up an incline. Watch the wattage climb when you are doing nothing different other than pedaling harder and your cadence and bike is slowing down. Even a decent cadence sensor (KT, Bafang HD) will ramp up power faced with decreasing speed and crankarm rpms.

Lower draw and also lower temperature. Its 95 in the shade today and my cargo bike was parked in front of Costco in the sun (couldn't be helped). Pack temp at ride inception was 105 Fahrenheit (hint: Put a cheap wired sensor on your pack). I used my Luna/Bafang 860C display - which is my favorite as it can be set to show simultaneous real time watts and amps - to help me get that temperature down. Hi cadence in a lower gear was a full amp lower draw than lower cadence in a higher gear. It was flat land so I was just shifting back/forth PAS and gears on a constant level surface.

Edit: Pack temp got to 96.8 by the time I got home.

 

[Catalyzt]

Thanks, guys, great info and just in time-- hopefully, the big ride is today.

It's misting right now-- so long as it doesn't actually rain, this will actually give me a bit more traction, e.g. some of the light, slippery, sandy stuff will firm up.

If it actually rains, definitely will abort. But I've been fixated on climbing the first hill really fast mostly just because it's a benchmark, just to push myself and the bike and see what it could do, always try to do that 850 feet in 20 minutes or less. Today, I'm going to gear down and shoot for more like 23-- and yes, drop from HIGH to NORM or even ECO whenever I can stand it.

A lot of days, I do want to get a fast start for other reasons: because I'm starting late to avoid the heat. I don't mind riding the last stretch on the way home in full dark with lights, but I don't want to be in Brand Park after dark-- I just don't know it as well as Griffith Park or the Hollywood Hills, it's an intermediate-level trail, and I want to have good natural light. But it's cool today, so slowing down a bit shouldn't be an issue.

Just hope the rain holds off!

 

[PedalUma]

Thanks, guys, great info and just in time-- hopefully, the big ride is today.

It's misting right now-- so long as it doesn't actually rain, this will actually give me a bit more traction, e.g. some of the light, slippery, sandy stuff will firm up.

If it actually rains, definitely will abort. But I've been fixated on climbing the first hill really fast mostly just because it's a benchmark, just to push myself and the bike and see what it could do, always try to do that 850 feet in 20 minutes or less. Today, I'm going to gear down and shoot for more like 23-- and yes, drop from HIGH to NORM or even ECO whenever I can stand it.

A lot of days, I do want to get a fast start for other reasons: because I'm starting late to avoid the heat. I don't mind riding the last stretch on the way home in full dark with lights, but I don't want to be in Brand Park after dark-- I just don't know it as well as Griffith Park or the Hollywood Hills, it's an intermediate-level trail, and I want to have good natural light. But it's cool today, so slowing down a bit shouldn't be an issue.

Just hope the rain holds off!

I hope the ride went well. If you got rain you are lucky. We are dry as a bone in Coastal Northern California.

HOW to PEDAL:
Yes, you will want a fast cadence with a torque sensor bike. Most American's think of riding a bike as a pounding down motion, as if they were using mallets on a kettle drum. Wrong! I have to admit that kettle drums are cool though.
What you want to focus on is the sweeping back and pulling up on the pedals. Professional musicians practice everyday even it they are already super stars, the same with pro athletes. You need to practice how to pedal and you will suddenly have a huge boost in power and range. Practice only using power to sweep the pedals back and up. I recommend doing this in a low gear with a high cadence. When you get it pedaling will feel like swimming almost effortlessly. You are going to be fast and go on longer rides than you could have imagined. It is also better for your drivetrain, motor and your knees.

 

[Catalyzt]

I hope the ride went well. If you got rain you are lucky. We are dry as a bone in Coastal Northern California.

HOW to PEDAL:
Yes, you will want a fast cadence with a torque sensor bike. Most American's think of riding a bike as a pounding down motion, as if they were using mallets on a kettle drum. Wrong! I have to admit that kettle drums are cool though.
What you want to focus on is the sweeping back and pulling up on the pedals. Professional musicians practice everyday even it they are already super stars, the same with pro athletes. You need to practice how to pedal and you will suddenly have a huge boost in power and range. Practice only using power to sweep the pedals back and up. I recommend doing this in a low gear with a high cadence. When you get it pedaling will feel like swimming almost effortlessly. You are going to be fast and go on longer rides than you could have imagined. It is also better for your drivetrain, motor and your knees.

This is really interesting... but this does seem to presuppose being clipped in, or you can't get any meaningful power past 6:00 or so.

Is that correct? I don't know a thing about being clipped in. I've resisted it because of my experience using old-style foot-clips in the 70s-- they were such a pain in the ass for traffic riding, we only did it because we thought we looked bad ass, and I had many near accidents because I had to stop abruptly and couldn't get my feet on the ground fast enough.

If you can stand another rookie question... how does all that work? Are MTBs always clipped in? What if I have to jump off the bike in a hurry... something that happens relatively frequently, because I ride surface streets with traffic lights a lot, and also my hill-climbing technique still needs tons of work.

Bear in mind, I'm on blood thinners. My goal is not to fall at all, ever, not even once.

 

[Catalyzt]

And BTW, this generally went well. I finished the ride two weeks ago with an estimated range of 28/19/14 (ECO/NORM/HIGH) and I finished this ride with 29/20/14 and two out of five bars remaining (probably just about to drop to one bar)-- almost identical, despite ascending another 380 feet at approx. 9% grade and traveling and 1.25 miles.

Note also the descent was about ten degrees colder, and I was far more exhausted, so I did pretty good.

The summit is about another two miles and 530 feet of vertical, so it can be done on this bike. I just have to pick the right day (one that's cool enough), hydrate properly, and have an emergency recharge plan (have my wife meet me at a brewery in Atwater with the charger if it looks like I won't make it!)

But I should do it soon, before battery health declines as a result of normal wear and tear, because if I have unexpected wind, unexpected exhaustion or other factors, it could be close. Assuming that the range indicator is, somehow, connected to some kind of voltmeter, I know what I need to see: My ECO range start at 93, drop into the low 30s at the top of the Hollywood Hills, and then increase to 103 at the bottom of the valley in Glendale. If it's better than that, I have much more cushion. If it's less than that, it may be very tight.