BBS02 500w with 48v battery?

I have a Biktrix Stunner (http://www.biktrix.com/collections/bikes/products/biktrix-stunner) with a 500w BBS02 motor, powered by a 36v 11.4ah battery. The bike is totally awesome. It tops out at about 26mph with the throttle fully open and a pedaling pretty fast.
I would like to speed the bike up a little bit.
I'm looking at upgrading the front chain wheel to the 52T version (http://lunacycle.com/motors/bafang-mid-drive-and-parts/bafang-bbs02-chainwheel-44-46-48-or-52-tooth) because a larger chain wheel should allow me to pedal more slowly at top speed, and maybe speed the bike up a little bit.
Somebody also recommended that I put a 48v or 52v battery on the bike. Wouldn't that fry the controller? I could lower the max amperage in the firmware. Would that make this a safe proposition? I don't want to replace the whole motor at this point, since I just got the bike about a month ago.
I don't really understand how the formula for how the motor's wattage, the battery's voltage, and the amperage result in a specific top speed. If anybody here can explain this to me, that would help! I tried to find it in the forums, but didn't have much luck. I apologize in advance if I didn't do a good enough job searching for the information.

Nada

Hi Oliver, as I mentioned earlier in our email conversations, the Stunner is equipped with a 36V500W motor. You should not use a 48V or higher battery with it. It will blow the motor and/or controller. The controller will probably go first.

The best way to get increase speed is gearing. The larger the chainring and smaller the rear cassette, more speed you'll get but proportionally lower torque too. If you do put a larger chainring on the front, you need to make sure that when you ride, you start off with the lowest gear in the rear and work your way up to the highest gear. Starting off with the highest gear will put a lot of strain on the motor.

Roshan has been great! Dealing with biktrix has been an incredible pleasure start to finish, and Roshan continues to be on top of every question I ask. He has told me exactly what he's saying here over email. Thank you Roshan!
I posted this question here, because other people I talked to about the gearing have recommended that I get the controller on the motor changed, and put a bigger battery on it.
I'm an analytical person. If I'm going to do something, I want to understand the workings behind it.
I would love the bike to be just a little faster (I'd be happy with 30mph).
I understand the workings/physics behind the gearing. That makes complete sense. I ordered the 52T chain ring, and will try that out when it arrives next week.
I still don't understand if it is technically possible to put a 48v or 52v battery on a 500w motor, and if it is, what it changes.
My lack of understanding stems from the fact that it's been a long time since physics class, and I don't know how wattage (w), voltage (v), and amperage (a) relate to each other in this scenario. I understand that w = v * a. So a 500w motor, at 36v runs at 14 amps. But I imagine that the amperage is controlled by the firmware, no? So if I left the motor alone, but put a 48v battery in there (and changed the controller), I'd have 500w = 48v * 10 amps. So if I lowered the amps in the firmware, then everything should work, no?
I sincerely don't know if that is right, so please correct me if it isn't.
And if it is right, does that mean the motor now goes faster? What in this relationship of w, v & a determines how fast the motor will spin? And what defines the upper limit of how fast the motor can spin?

Roshan, I hope you don't mind me having this conversation here even after we've talked. You have been amazing to deal with, and I would buy a bike from you again in a heartbeat. I'm also telling everybody I work with how great the Stunner is. It's a beautiful, fun, comfortable, affordable, and fast bike. I'd just like to see if I can get it to be a little bit faster. Right now I'm spending almost all of my time in 7th gear. I will do more downshifting as I come to a stop going forward. Previously I lowered the PAS level when I came to a stop, and then slowly go up level by level as the bike picks up speed while I pedal and slowly open the throttle. It sounds like you are saying that's not the right approach, and that I should also downshift. I'll gladly follow that advice.

Nada

Sorry tomjasz, you seem annoyed. Not sure if I'm reading that right.
I don't actually have the facts. I still don't understand how w, v, and a relate to one another and what the decision criteria looks like in pairing a motor with a battery.
I also am not second guessing Roshan or trying to prove him wrong. Not sure where you are getting that.
In my mind, trying to learn something one doesn't understand, and asking questions isn't tying to prove somebody else wrong. I am simply open about the fact that I don't know how this all works, and I'm trying to learn from a bunch of smart people that know a lot more about this than I do.
Isn't that what forum's like this are for? So people who know more can teach people who know less? I'm not looking for anybody to tell me what to do or what not to do. I can make that decision once I understand how things work.
I am not even saying that I am going to put a different battery on the motor. I am merely trying to understand the workings of the whole system to understand if it's possible. Even if it were possible, my next question would be "how much faster would it be?"
You seem to be wanting to shut the conversation down (at least that's how I read your reply). Feel free to disengage, no hard feeling from me.
I'll stick around in hopes that somebody can explain things to me.
So back to the topic: If I replace the 46T chainwheel currently on the bike with a 52T one, and I change my shifting behavior to stay in a lower gear when I accelerate from stop, am I still putting more strain on the motor, or should I be fine then?
Also, am I currently doing something wrong with the 46T chainwheel by being in 7th gear most of the time, even when accelerating from a complete stop, even when I am in the lowest PAS mode and I then shift up?

I put a 48 tooth chain ring up from 44 tooth on my
Mountain bike so I could pedal still at higher speeds. Mostly in high gear on the road.

Your controller and battery need to be compatible with the same voltage.

48 volt systems go faster than 36.

52 volts is how much you can stress a 48 volt controller without blowing it, usually.

Nada

Nada

i give up.

I actually spent about 3 months researching what bike to buy before I bought one. I also spent about 6 hours last night reading various posts on electricbike.com, electric-fatbike.com, here, and a few other websites. It's a little hard to piece it all together, which is why I asked the question here.
I don't understand why somebody who gets annoyed at the conversation is even participating in it.
Like I said, I am not second guessing Roshan. I am looking to learn. I don't think I should continue to email him and ask him all these questions. He's been great, but his job was to sell me a bike, not to answer all my questions. This being a community of volunteers, if somebody can answer my question, great.
Also, where do you get the idea that I don't take the advice? I've not bought a bigger battery, and I've not put a different controller on the bike. I've not even decided, much less said, that I would do those things. I've simply asked if it is possible, so I can learn. Some people have said that it is possible, if you change the controller. That's all.
And even if it were possible, I just bought a bike for @ $1700. I don't think I'd spend another $700 to upgrade the battery and controller. At that point I'd rather sell the bike, and buy one that provides the higher speed.
Also, nobody told me up front that I shouldn't keep the bike in 7th gear. I've owned a hub motor ebike without PAS before, and there it didn't matter what gear I was in. Now that you have explained it, it's completely logical that it isn't a good idea to keep the bike in 7th gear all the time. Maybe I should have deduced that on my own before. I didn't. Given that I don't even understand how wattage, voltage and amperage relate to one another in the context of the bike, I'm not sure how I could have deduced that.
I'm glad you did the numbers. I'd like to see the numbers, as that's exactly the learning experience I'm looking for.
Thank you also for the links! I actually read the second one yesterday, but I have to admit I didn't really get all of it. I'm going to read the other two now, and maybe that'll complete the picture.
Thank you also on the advice around the BBSHD on a 52v battery. Has anybody put that combination on a cruiser style bike yet?

Great, we're getting somewhere!
I will change my behavior to use the gears more. That's valuable information I didn't have before. I knew i had to change it for the 52T chain wheel, but I don't have that yet.
I don't expect the motor to last forever either. It'll break at some point, and I'm sure my next bike will have a BBSHD motor with the biggest battery I can throw at that. Speed is fun!
I hope I can find a cruiser style bike with that configuration.

Let me try to come at it from a different angle:
How fast might this bike go with either of the following configurations:

BBS02 750w and a 52v battery
BBSHD and a 52v battery

I have no sense for how much more speed each level up provides.

Subscribe this channel...

https://www.youtube.com/watch?v=5NQAZSzJdrc

https://www.youtube.com/watch?v=RbiNoNmqUpg&list=PL59mIOWSOm9rFcoO_dR0gSrRoVr7qhZKm

oscholz said:

Great, we're getting somewhere!
I will change my behavior to use the gears more. That's valuable information I didn't have before. I knew i had to change it for the 52T chain wheel, but I don't have that yet.
I don't expect the motor to last forever either. It'll break at some point, and I'm sure my next bike will have a BBSHD motor with the biggest battery I can throw at that. Speed is fun!
I hope I can find a cruiser style bike with that configuration.

Let me try to come at it from a different angle:
How fast might this bike go with either of the following configurations:

BBS02 750w and a 52v battery
BBSHD and a 52v battery

I have no sense for how much more speed each level up provides.

Click to expand...

Subscribe this channel...

https://www.youtube.com/watch?v=5NQAZSzJdrc

https://www.youtube.com/watch?v=RbiNoNm ... RoVr7qhZKm

Wow, thanks for sharing! That gives me a great idea.
That's quite a bit faster than I'd be comfortable with.

Hi Oliver, I just replied to your email. I'm just posting it here for completeness so everyone else can pitch in too:

Hi Oliver,

Absolutely no problem asking the question on ES. There are some folks there that may know more than I do even!

On the bike motor, or any electric motor, W=V*A, but that said, the input W is not always equal to output W because there is a bunch of loss due to efficiency and heat. On the Bafang motors, in best case its about 80% efficient. This means if the motor draws about 36V x 25A (900W), the output in best case is just about .8 * 900W = 720W. That's the peak output. You can increase the output watts by either increasing V or A or efficiency. Of course the hardest factor to improve on is the efficiency. So that leaves you with just V and A to play with. Now, each motor is wound with a particular gauge of copper wire inside it. The thickness of the wire determines how many Amps it can take without burning. On the motor that's on your bike, the wire thickness is optimized for 36V. So you could go a little higher - 38V , 42V perhaps but anything more than that will burn through the copper mass. Also, think of the voltage as the size of a pipe and the current (A) as the amount of water flowing through it. Smaller the pipe with larger volume of water going through it will eventually lead to a pipe burst. This is why you don't want to pump more than 25A through at 36V.

On that note, you should ride the bike like you would ride a standard car or a motorcycle -> use the gears of the bike as leverage for the motor -> Start off with gears 1-3 and work your way up to gear 7. The levels on the motor itself doesn't matter as much as the gearing of the bike. Remember that electric motors are most efficient at high RPM. That's why you want to start off on the lowest gear.

On your motor, you will see a stamp - with serial number and model info BBS02 or BBS01 - check it out. Either way, don't use a 48V battery on that motor. It will burn.

Hope that helps!

Cheers,
Roshan

Click to expand...

oscholz said:

.......
Also, nobody told me up front that I shouldn't keep the bike in 7th gear. I've owned a hub motor ebike without PAS before, and there it didn't matter what gear I was in. Now that you have explained it, it's completely logical that it isn't a good idea to keep the bike in 7th gear all the time. .........t?

Click to expand...

I was going to help explain and clarify some of the points here,.......
.....but that comment has made me realise that it's probably wasted effort !

Thanks! It's super clear to me now.
Thank you for being patient with me and explaining a bunch of stuff.
I now understand how things work. Needless to say, I won't be putting a bigger battery or motor on my existing bike. I will try the 52T chain ring, but if it doesn't feel right, I will take that off again, too.
I might buy a faster bike down the road. Something with a BBSHD and a 52v battery. I don't think those are available on a cruiser style bike yet. Maybe I'll go with the biktrix Juggernaut. Can't go wrong with Roshan.
I've also changed my behavior around accelerating from a complete stop. I now shift into first gear every time. I really had no idea that I was doing it wrong. I think the bikes should come with a set of instructions on that. It's kind of like a manual car. If nobody explained that to people, I think some people wouldn't naturally know to always start in 1st gear.

Sorry that some people here seem rude,do not take it personal as it is probably
A mental defect on their part. Welcome to the forum and keep reading and learning. We are a diverse group and give it time. God bless.

Thank you for the kind words and welcome!
I don't take things personally. We all have days where we aren't our best selves.
I actually got something out of a couple of his posts, for the short duration they were up. He had a few good articles that I missed in my research.

roshan said:

The best way to get increase speed is gearing. The larger the chainring and smaller the rear cassette, more speed you'll get but proportionally lower torque too. If you do put a larger chainring on the front, you need to make sure that when you ride, you start off with the lowest gear in the rear and work your way up to the highest gear. Starting off with the highest gear will put a lot of strain on the motor.

Click to expand...

Sorry but this is not true; and I don't know why on Earth this myth of bigger chainring = higher top speed keeps perpetuated. Your absolute top speed is ultimately limited by the amount of power that your motor can deliver, period. If you want to go faster without adding more power then you'll need to reduce your aerodynamic drag, not changing chainrings... if your top speed is already 30, then its 30, wether you achieve that with a 48-17T or a 44-13T... My bike tops out at 32 mph on 48-15T, shifting to 48-13T or 48-11T actually makes me go SLOWER... so if you want a gutless middrive, then by all means, get a 80T chainring.

Gearing all it does is trades RPM for torque, or the other way around; and power is the ability to deliver torque at any given RPM. There is no magic in a 60T chainring that will gain you an extra 30 mph top speed: if your top speed is already 30 mph, no amount of chainring teeth in the world are going to change that; if you want more top speed get a higher voltage battery (as in, get more POWER) or reduce your aerodynamic drag. (as in, become thinner, use thinner wheels, use a recumbent bike...etc)

Gearing allows the motor powerband to match your current drivetrain rotational RPMs... thats all gearing does. Gearing != perpetual motion machine.

G.

https://www.youtube.com/watch?v=YJ4JuUFLJkg
This seems to show that a larger chain ring (ok, comically large) does increase top speed. There are a bunch of other videos around high speed bicycles, with larger front chain rings.
This also seems true given the fact that in a higher gear you go faster, and higher gears have bigger front chain rings, paired with smaller rear rings.
It's a sub $20 test for me. I'll report back here in a few days what I find.
I realize I'll be giving up a little torque. I'm ok with that, given that I don't need the lower gears for much anyway, other than accelerating from a complete stop.

oscholz said:

https://www.youtube.com/watch?v=YJ4JuUFLJkg
This seems to show that a larger chain ring (ok, comically large) does increase top speed. There are a bunch of other videos around high speed bicycles, with larger front chain rings.
This also seems true given the fact that in a higher gear you go faster, and higher gears have bigger front chain rings, paired with smaller rear rings.
It's a sub $20 test for me. I'll report back here in a few days what I find.
I realize I'll be giving up a little torque. I'm ok with that, given that I don't need the lower gears for much anyway, other than accelerating from a complete stop.

Click to expand...

Like Chalo would say to me, a load of hogwash... read upon power. (Like I had to read about chain stretch and get clued in) If you are already aerodynamically drag limited, no amount of chainring teeth is going to increase top speed; but since at the moment you don't seem to understand the concept of aerodynamically drag limited then you won't understand what I am talking about. A 1-2 mph increase in top speed due to gearing is because the motor has more power in that part of the RPM power band, so it will pull the gear, or because the headwind is less, a couple mph difference can have a huge difference in top speed; and either one of those are still bound by the you need MORE POWER laws of physics. Once you're past your top speed, a higher chainring all will do is make you SLOWER... or you just think you've discovered the perpetual motion machine?, you just keep adding bigger chainrings and bike just goes infinitely faster? Wow, man, make sure you patent that idea.

So, don't try to claim statements like that, misleading people into believing what is simply NOT TRUE, and just because you saw a video on the internet? haha, must be true, you saw it. Let me reiterate, AGAIN, if you are NOT aerodynamically limited changing gearing will get your MAX SPEED closer to your absolute TOP SPEED. If you want more TOP SPEED then you need power (or be more efficient at using the one you have (and changing a chainring is NOT either one of those) its as simple as that.

G.

Wow, what is it about this forum?
I find your aggressive tone uncalled for. Second person reacting like this to a simple question.
I already ordered the chain ring, and I'll report back here if I reach faster than 26mph top speeds with it or not. I still think the logic of a larger chain ring holds up, since in the same situation on my mountain bike, I switch the front gear to a larger chain ring, I go faster. Same position on the bike, same everything. Yeah, I have to apply more power. So maybe the motor isn't capable of that. But I'm also pedaling along with the bike. So I imagine I'll go a little faster. But imagining things doesn't count. Results do. So we'll see.

Oscholz, do not get into a pissing match with idiots. they have more experience than you and will just bring you down to their level. Good luck in your endevour.