bbs02 steep hill best practices?

what are the general best practices rules for riding on steep hills? i am using pedal assist so i am always pedaling.

e.g., should i ride in lowest gear and use the lowest assist setting (setting 1 of 9)?

obviously riding in highest gear with the highest assist setting is bad since the motor won't keep up and will instead generate a lot of heat. but is it better to use a higher assist so that i get up the hill a little faster to give the controller more time to cool down?

i tried riding up a steep hill today. it's pretty short (only 0.21 miles) but it goes up around 100 ft and grade starts at around 7% and goes up to 25% so it's really steep. i was pedaling as hard as i can and i was riding up zig zag so that it was flatter than taking the full impact of the grade and i made it up but it didn't feel like the motor was doing much at assist 1 gear 1. my mph was in the 4-5mph range. since i was riding in a zig zag pattern it felt like on the flat parts i was getting some assist but when turning direction to head up a bit, it was all me (no assist kicking in). at the top, i put my hand to the bbs02 and it was slightly warm but barely.

i don't care about speed, i just want to make it up using less effort if possible (i was huffing and puffing).

my bike is a breezer uptown commuter bike with a shimano nexus 8 speed rear internal gear hub. i believe that my front is a 46T (it's whatever the default is on the bbs02). i realize that i can change to a smaller chainring but was wondering if it's still possible to work with the current chainring.

the route is http://www.mapmyride.com/routes/fullscreen/743835909/ (click show elevation chart on the bottom graph part to see the grades).

RVD said:

what are the general best practices rules for riding on steep hills? i am using pedal assist so i am always pedaling.

e.g., should i ride in lowest gear and use the lowest assist setting (setting 1 of 9)?

Click to expand...

I would personally ride in lowest gear and level 9. Level 1 will cause the motor to stall very easily, which will be worse than using plenty of watts to keep the motor turning at a good speed.

Also, you'll probably find that your controller is programmed to drop the current down to a certain percentage (usually 60% from Bafang factory) of the PAS level power.
It's labelled as ' Keep Current(%) ' in Bafang's programming software.
This happens once the motor has been running for a few seconds after you start to pedal. Therefore PAS 1 ends up producing very little power once you are on the hill and tends to stall, unless you pedal like your arse is on fire.

With a 48v battery, 25A controller and ' Keep Current(%) ' at 60%, you still only have 720 watts to play with in PAS 9. Therefore there is plenty of controller protection, which is why I think Bafang programmed them this way.
Program ' Keep Current(%) ' beyond this and I reckon yer looking at cooking the controller if you get the gearing wrong on steep hills.

Only way to find out how your controller is programmed is with a cable and Bafang's software. Both easily obtainable and just as easy to use.

ok, i may try that. i will say that at assist 1, it was almost as if i was just pedaling on my own so you're probably right.

would it be safer to try assist level 4 or 5 instead of 9? i only go up that hill around 4-5 mph and i'm fine with that as long as i don't have to work so darn hard to get up it.

Good question and discussion. I just ride for pleasure and a little exercise, so don't care about speed and usually just use PAS level 1. On those steep hills that get over 15% grade I use low gear, but instead of increasing the PAS level I grab a little throttle override. That way I can control the assist to keep the motor happy while applying a reasonable amount of pedal power.

I'm pretty new to the bbs02 (just installed it this past week and have less than 3 miles on it). Does the throttle give more power than the assist setting? i.e., if I'm in assist 1 going up a big hill and it feels like the motor isn't helping, I can use the throttle and get some more help in addition to PAS?

I was under the impression that the throttle was basically there if I don't want to pedal at all (which isn't me because i actually want the exercise).

I ride hils s lot, mostly woods. For super steep ones i use pas 5 or 5 and throtle and pedaling. Normaly i ride in 3 of 5, pedal plus throtle on bad terrain. It never overheated even if i coulnd touch it of heat.
Most important is to use correct gears. I have 46 34t.. climbs everything if i help wiht pedalling

thanks for the info. does your bbs02 ever feel hot to the touch? i know it's not the best way to check heat but i don't have a thermometer installed. with my other bikes, i can sort of tell how hard the bike worked by putting my hand on the controller (if it's too hot to keep my hand there, i know that it's not good).

I don't know enough about bikes to know about gear ratios but I was told that my low gear is the equivalent of a 38 tooth.

my front chainring is the standard size that came shipped with my bbs02. i believe that is 46?

RVD.

"I don't know enough about bikes to know about gear ratios but I was told that my low gear is the equivalent of a 38 tooth."

I think they meant you have a 38" low gear. It refers to the equivalent diameter of your tire, as if you were riding than early bicycle.

http://www.historywebsite.co.uk/Museum/Transport/bicycles/Earlybicycle.jpg

Some conventions die hard.

The PAS settings are only to get to a certain speed.
The speed is dependent of the gear you are in, you can see the PAS levels as RPMs.
The PAS will help you until it reached it's set RPM for PAS assist level.

As an example, if you are on PAS 1 and the bike is in third gear. (speeds depend on your gears ratio and wheel size)
PAS 1 : 2mph
PAS 2 : 4mph
PAS 3 : 6mph
etc...
PAS 9 : max speed.

I suggest you use the gear that makes a straight chain line with the front chainring. for me it's about third or fourth speed on the rear. This will cause the less stress on the chain.
Then on a flat terrain, determine the ideal speed for the hill you are climbing and use this PAS. It will help you during ascent by trying to keep this speed.

If by "best practices" you mean easiest on the motor/controller/battery...your lowest gear, and wide open throttle. This will put the least strain on them, for the shortest time.

RVD asked:

Does the throttle give more power than the assist setting? i.e., if I'm in assist 1 going up a big hill and it feels like the motor isn't helping, I can use the throttle and get some more help in addition to PAS?

Click to expand...

Yes. The throttle will give full power no matter what your PAS setting.

Like many here, I normally just use PAS setting 1 and only use the throttle occasionally, such as when crossing a wide street, going up a steep hill, or just needing to give my tired legs a break on a long ride. However, the throttle is very responsive and is capable of giving your drive line a very destructive jerk.

To avoid extra wear and tear on the drive line I only use the throttle after I have first pedaled until the PAS system has ramped up the motor speed. Then I keep pedaling as the throttle quickly and smoothly increases the power. Takes a little experimenting, but I believe it's worth it.

This might also be a good time to repeat how a backwards nudge on the pedals will stop the PAS over-run immediately. This facilitates quick smooth shifting without having to tap an e-brake or install a special cut-out in the shifting mechanism.

fwiw, i live in the Pacific Northwest so it has been raining a lot. i haven't been able to take my bike out for the last few months due to weather, coming home late at night, icy streets, etc. but today all of the stars aligned...i didn't have to go to work, the sun was out, and the temperature was above freezing. so i took the bike out and tested it on the big steep hill. i was on 1st gear with assist set to 9 and it worked! i actually made it up the hill. i was pedaling the entire time but it wasn't too hard and i think the bike would have made it even without me pedaling if i really wanted to. it was struggling a little bit but not much.

what a world of difference from hub motors (both direct drive and geared).

RVD said:

what are the general best practices rules for riding on steep hills? i am using pedal assist so i am always pedaling.
i don't care about speed, i just want to make it up using less effort if possible (i was huffing and puffing).
my bike is a breezer uptown commuter bike with a shimano nexus 8 speed rear internal gear hub. i believe that my front is a 46T (it's whatever the default is on the bbs02). i realize that i can change to a smaller chainring but was wondering if it's still possible to work with the current chainring.

Click to expand...

Looking at the Breezer site, if your Nexus has an 18t cog as shown stock, then I would change it to a 22t or 23t (easy to do and dirt cheap, probably will have to add a link or two) .. that will drop your gear inches in 1st to under 30 .. that will make a big difference .. and your top gear will be just short of 90 g/i, which will still be fast for a situp bike and a BBS02..

Thanks for the update RVD. The bike I set up for my sister two years ago is using the Nexus 8, so is essentially the same as yours. On every ride from her house she has a couple of good climbs in both directions that approach 20% grade. My advice to her was to always use 1st gear when going up steep hills and set the PAS at whatever was comfortable and/or use throttle override when necessary. She's in Newport, Oregon, so doesn't normally ride this time of year, but the last time I asked her what she was using for the hill climb she said she wasn't using the throttle, just 1st gear and PAS level 3 or 4, because she liked to pedal hard. Just for the record, this is my youngest sibling, only 62, still working full time, and likes to commute on her bike when the weather is good.

Oh yeah, I did change out my rear cog on my Nexus 8 to a 22T to assist with the climbing. I did have to also get a new chain for the additional length.

I can't wait until the weather gets better so that I can commute to work on this bike.

My car lease (Nissan Leaf of course) is up in March so the car goes back to the dealership and then I commute on my bike full time. Once it starts getting wet and cold again in Oct or so I'll see what's out there for another car (Chevy Bolt or if I can convince the wife...Tesla).

I melted the nylon gear with a 32 tooth Raceface chainring and stock controller settings in my BBS02 (old mosfets). The only thing you can do is install a temperature gauge and keep it below 110F. (see Electric-Fat bike web site)

Well, it's March so my Nissan Leaf is gone and I'm riding my bike full time to/from work. I ride up this massive hill every day coming home and the BBS02 has been performing beautifully!

The bike is kept relatively light because I'm using 12s1p turnigy lipo (44v 5ah). I'm using 3 X 4s 5ah batteries. My commute is only about 7 miles and according to my watt meter I use around 2.5ah each way. I charge at work and at home.

This massive hill performs well at 1st gear on assist setting 9. I barely even have to pedal and I am pretty confident that the bike can haul me up with just the throttle if I wanted to.

I even tried going up on 2nd gear and although I do have to help out, I'm able to do it fairly easily.

There was one trip (my first one last week) when I didn't shift properly so I pedaled all the way up at assist 9 on gear 8 (my highest gear) and it really sucked. I was pedaling like crazy with all of my strength but the crank was barely moving. I am surprised that I didn't end up damaging the controller/motor. I was really confused as I went into 1st gear but I guess the gears were under too much load so it didn't shift. My gears are internal hub so there's no visual and I didn't have enough experience on this bike to know what 1st should feel like.

Anyway, I am definitely happy and impressed with this bike. BBS02 is working well. I might move up to 52v at some point but don't really see a reason to do so. I have plenty of power at 44v.

I generally climb long steep hills (and there are plenty around Vancouver) in the lowest gear needed to maintain high crank RPMs (80+), in top PAS mode using the throttle to keep it at or below 750W while I pedal as necessary to avoid needing to downshift. It takes a bit of getting to know the hill itself and being in the right gear at the bottom. I would rather pedal than use granny gear as the chain line is just horrible in that gear.

I bought two BBS02s in December 2014 (old mosfets). I geared them down with a 32t and 34t chainring. Both failed within 6 months. I cannot stress this enough: You must gear the bike down with either a 32t, 34t of 36 tooth Raceface Narrow wide chainring. You MUST install a temperature gauge and keep it around 110 degrees F. If you don't, you will melt the plastic gear or fry the controller and possibly burn up the armature. Don't loan the bike to someone you do not trust to keep it below 120 degrees. Once you install the temp gauge, you will be surprised by how quickly the temperature goes to 120 degrees when climbing or using too high a gear on level ground.

If you don't want to do these things, then buy a BBSHD. I have subjected the BBSHD to 10x the abuse and so far no problems.

I don't have a temperature gauge but when i put my hand to the motor just after climbing the hill it's barely warm (i can definitely keep my hand there forever).

i have an internal gear hub so the chain line is not an issue for me.

i didn't change out the front chainring but i did change out the back chainring to a 22T and that seems to help a lot. top speed (where i can still pedal) on flats is around 25mph which is plenty for this bike since it's just a commuter that can climb big hills and is mostly ridden on public bike paths with other cyclists, joggers, walkers, etc.

QUOTE
"i tried riding up a steep hill today. it's pretty short (only 0.21 miles) but it goes up around 100 ft and grade starts at around 7% and goes up to 25% so it's really steep."

First off you have no clue what a 25% incline is, your going "up about 100 feet in .21 miles, or 1108 feet, for an average grade of just over 9%.

If your weight is anyway near average the BBS02 will climb that hill without you having to pedal at all, and it won't get hot. I know I live on English Mountain Road which has a average grade exactly like your road only it's much longer, and some bits of it are steeper than the average.

Put your bike in first gear, assist level about 4 or 5 of 9, if you want to help a bit, and is about as fast as I care to pedal, and put in a higher level if you want, which is too fast for me to pedal if you don't.

The reason your doing all the work in assist level 1 is your going , what did you say 5 MPH, well that's as fast as PAS 1 goes.

Someone mentioned that the throttle overrides PAS with full power, well that is not true in all cases, it does ONLY if programmed to do so, which the vast majority are not, if you have no throttle in assist level "0" then throttle does NOT give full power in any assist level other than max assist.

RVD said:

I don't have a temperature gauge but when i put my hand to the motor just after climbing the hill it's barely warm (i can definitely keep my hand there forever).

i have an internal gear hub so the chain line is not an issue for me.

i didn't change out the front chainring but i did change out the back chainring to a 22T and that seems to help a lot. top speed (where i can still pedal) on flats is around 25mph which is plenty for this bike since it's just a commuter that can climb big hills and is mostly ridden on public bike paths with other cyclists, joggers, walkers, etc.

Click to expand...

So which is it BBS02, or geared hub ? the thread title says BBSO2

Both

It is a very bad idea to go up steep inclines with the bbs02 in a low PAS level (I don't like to call it an assist level, as that is not how it works). The motor will not be turning fast enough (in a low PAS level) for it to operate efficently and also the controller is working very hard, to drive the motor at a low rpm (where phase current is high).
Frankly, if a high PAS level is too fast for you to pedal, you'd be better off selecting the lowest gear possible and using the throttle to spin the cranks to a fast pace, and not pedal at all The lowest pas level is not a low assistance, it is just slower and can still provide enough power, to put the motor itself and the controller, to be put under considerable stress.
In my experience, the people that think they are going easy on the kit by using a low PAS level, would often be those thst were blowing controllers, sometimes repeatedly. The guys that thought they were using the kits harder would typically have less problems with blown controllers, as they would generally keep the motor spinning fast, where it is less stressed. We've sold lots of kits, so this is real experience, not just an opinion.
The controllers in the bbs02 are now much more reliable, due to the better mosfets used, and i think the firmware has improved also. Even still, it is always best to keep the crank rpm fast and the gearing as low as possible when the motor is working hard on a steep incline.
I'm sorry if that doesn't suit your riding style, but these are basic facts, it's a middle motor and the entire point of these motors is to use the gears to make best use of the motor, not to use the motor in a way where efficiency is low and the system is strained. If i could, I'd make the motors too weak at low rpm to do any damage and force users, to use the gears properly, that way reliabilty would be improved IMPO.

Alan B said:

Both

Click to expand...

If you have a Nexus 3 or Sturmey Archer 3-speed you might need more than a 22t sprocket. The Bikesmith has 25t and I think 27t sprockets available. The biggest the factories go is the 22t you have already. On my Nexus 3 for off-roading I ran as big as a 34t with extra offset to fix the chainline, but this was with a BBSHD using an offset chainwheel too.