Going 30mph on a 48v 10ah LiFePo4 battery on a Bafang motor

[kmxtornado]

Is this reasonable to expect? Perhaps 25mph at least? I'm convinced my second e-bike setup will be a Bafang BPM or Q128 (b/c I love stealth) or at least something from the BMSbattery website. I'd like to take advantage of the sale that's gong on for the 48v 10ah LiFePo4 batteries. There's so many choices of kits to match it with.

- Overvolt a 36v kit? In which case, should I be looking at the 500w one I assume with the lowest RPM for hill climbing?
http://www.bmsbattery.com/103-36v

- Or perhaps don't overvolt at all and should match the battery with a 48v kit? 350w or 500w? What's the difference btw the last two on here? and which would you recommend for me?
http://www.bmsbattery.com/105-48v

WOT speed will be on flats only. I believe I can discipline myself enough to keep off the throttle too much on the hills. The bike can climb by itself w/o the e-power. But of course electricity always helps. Hahah. All thoughts welcomed.

 

[johnrobholmes]

You can get there comfortably on the large bpm, but not for long with a 128 sized stealthy motor. 20mph yes, 25mph spurts, and 30mph short bursts. But you will be dealing with much heat and enough power to strip the gears.

A steady 30mph hub would be a 9c or Puma or large BPM

 

[kmxtornado]

Bursts would be good. Which kit from the above list would you recommend? There's so many to choose from. A bit overwhelmed.

 

[DAND214]

Short and sweet, NOT THE NEW Q128!

No power like the old ones. New one went a whole 6 miles before it melted down.

The gears are differant, mags are weaker, just not like the year old ones.

And don't think about support, such as gears. I have tried, asked the supplier, asked the manufacturer. No help at all and I sent a dozen emails to ANANDA and thought I had succeded in gett help. The first contact said he would take care of it!!! Yeh he sure did, sent it to another guy and he said, sorry no cando.

Other than that they are a nice small stealthy hub, but don't expect to do 30mph for long if at all.

BUY a MAC.

Dan

 

[neptronix]

Get a MAC or BMC style motor bro... you'll never look back and say to yourself and say 'gosh, i wish i would have got motor X, this thing is pathetic!'
Unless we are talking about one of the very large DD motors like the croationmotor, X5, or magic pie.

2-3 pounds over one of those weak sauce geared hubs and you'll have something that can do 30mph up a multi-mile long hill
And you'll actually be able to replace the parts when it craps out, unlike those where you get to buy a new one..

...i finally killed my MAC after dumping 4kW into it a few times & using it at 2300w quite frequently doing about 35-38mph.. all it needed was a $30 set of gears and a cover plate.. lol.

Also.. that 48v bmsbattery lifepo4 batt you're looking at, it's made up of headway cells which are big and heavy, also sag pretty bad at 2C ( 20 amps ). You may regret that purchase down the line, it is definitely one of the least desirable options out there.

 

[kmxtornado]

Thanks for the warnings. Definitely no Q128. Although none of this is what I wanted to hear, I'm glad you guys were up front with me about it so I'm not wasting money. I'm really in love with the mini motors. I understand there's a limit and I'm not trying to be naive and unreasonable about it. Have a reached the max limit of my HTB Mini Might? It goes 20mph tops and maybe 21-22mph with pedaling. It takes hills with pedaling just fine. No strain. No sweat. But that also means no flat bursts either. It literally goes 20mph tops and perhaps 17-18mph with super strong headwind like we've been having in the Bay Area the past week or so.

1. What do you imagine would happen if I switch my 36v 10ah LiFePo4 battery with the "not so great, but still" 48v 10ah BMS LiFePo4 battery? Anything worth spending $336 (with shipping) on?

2. Is the MAC 500 the second smallest motor apart from the Mini Mights and Bafangs?
3. How does the MAC 500 physical size compare to the MAC 1000?
4. What can I expect out of either if I don't buy a new battery and just reuse my existing HTB 36v 10ah LiFePo4 battery here?
https://hightekbikes.com/shop/index...oducts_id=20&zenid=36uk0batfffcv5e5e4ns088au4

Neptronix. BMS battery no good eh? I believe you, so I continued my research here on the boards. How about this one?
http://www.conhismotor.com/ProductShow.asp?id=144

 

[dogman dan]

Bear in mind, your 10 ah batteries are perfect for tiny motors that go 20 mph. So if you upgrade to the faster mac, you will need a bigger battery too. So start shopping for a 48v 15 ah. I'd say for now, get the 48v 15 ah battery, and add about 4 mph to your speed with the motor you have now. Then later on, you can get the fast version of the mac. Alternative, get the 48v A123 battery, which can be smaller because it has a good c rate.

No free lunch. You want 30 mph, you'll have to invest in a bigger motor, and a bigger battery to run it, just like the rest of us did.

Bms battery has great prices, but they never made my recomended vendor list.

 

[kmxtornado]

The only difference btw a 48v 10ah and one that's 15ah is the range, right? I suspect you may be recommending the 15ah b/c with more power comes more usage and with more usage comes a decrease in range, correct? If not, please clarify. Thanks!

 

[Scottyf]

Correct. Speed will stay the same. Range will increase.
Cells will also not be stressed as much as the C rate you discharge at is shared across more cells.

 

[kmxtornado]

Is there anything btw the HTB Mini Might and the MAC 500 in terms of size? I'm looking for something small and am willing to deal with the limits of performance that a smaller motor will have. I can't believe the MAC 500 would be the next step up. It looks like the MAC 500 is quite a high performance model.

If I got the MAC 500 and used my existing 36v 10ah battery, can I expect to go any faster than I do now? I'm not sure how the logic works. From a layperson's POV, I just see that the motor is more capable and heavier but the power (battery) going to it if remained the same, wouldn't do anything. For some reason I think I'm wrong. Enlighten me.

 

[wesnewell]

You need to find the rpm specs for the motors to compare them. As an example, I've got a 500W motor rated at 380 rpm @ 48v and a 1000W motor rated at 470 rpm @ 48v. Using the same 14s lipo pack and same controller on each motor, the 500W motor will do 25mph, while the 1000W motor will do over 30mph. The 1000w motor is a little heavier because of different windings and larger magnets. The design of the motor windings and magnets determines its rpm and torque at a certain voltage. These are dd hub motors. On geared hub motors, the gears also play a part of the final rpm. So in that case, you need the final rpm value, not just the motor rpm.

 

[neptronix]

All MAC motors are the same diameter ( about 7 in. ) and i believe they are the biggest geared motors you can buy.
I run ~2300w on mine, no problem.

They do make a 350w version, it's a bit narrower, a pound lighter, but still as wide around. It should be able to handle about a thousand watts in reality, which is enough for what you're trying to do.

 

[Racer_X]

Neptronix Is it not Cellman's 350w motor 134mm Diameter?
the Bafang BPM 500w motor is actually 180mm Diameter, and according to your measurements the 500w motor is 7 inches which is 177.79mm.
We round cellmans to 180mm which I would imagine it is the same size? Maybe cellman gears fit this Bafang BPM?
just food for thought.

 

[neptronix]

You're talking about the MXUS 350w motor. I'm talking about the MAC 350w motor. Two different beasts.

The MXUS motor can't take a lot of additional power.. it also does not have replacement parts available for it, nor is it designed to be serviceable. It's a good motor if you're willing to deal with a 500w nominal limit.. you need quite a bit more power to go 30mph, especially if you're trying to climb a hill etc.

http://emissions-free.com

 

[kmxtornado]

All MAC motors are the same diameter ( about 7 in. ) and i believe they are the biggest geared motors you can buy.
I run ~2300w on mine, no problem.

They do make a 350w version, it's a bit narrower, a pound lighter, but still as wide around. It should be able to handle about a thousand watts in reality, which is enough for what you're trying to do.

If the MAC's are the biggest geared and the Mini Might is the smallest, is there no in between size motors that might be more powerful than a Mini Might but smaller than a MAC?

 

[dogman dan]

Bottom line is this. Laws of phyics means it's likely that traveling 30mph is going to take at least 800-1000w. So take your 1c capable el cheapo lifepo4 pack from bms battery. 48v at 1c is 10 amps. 10 amps x 56v ( actual volts at top of charge) = 560 w. 560w is going to get you to around 23-25 mph. That's pretty set in stone for upright bikes.

So, to get 30 mph out of that battery, you'll need to discharge at a higher c rate. Bye bye to any cell in that pack that is not perfect. Soon after, bye bye to that cell group.

So get a 48v 15 ah battery, and now 56v x 15 amps for a 1c discharge is 840 watts. That's a lot closer to a 30 mph wattage. For the moments you may need more wattage, you have a lot more headroom for a short discharge at 1.5c.

So it's not just simply range, if you are going to choose a low c rate battery, you need a big one to run a bigger motor.

 

[kmxtornado]

Understood. Thanks for penciling that out.

To help with my budget, I'm trying to phase this second build out. I was trying to determine: If I were to only get either an upgraded battery OR an upgraded kit (and use the existing battery), which I should do. The 48v 15ah battery would give me an extra 5mph tops. The only reason that would be worth the extra bucks is I'd be able to put the existing 36v 10ah battery into my mini foldable scooter. Technically, that money spent on a 48v 15ah battery would be benefiting two bikes - not just one. At least that's what I'm telling myself to justify the cost.

Using the existing 36v 10ah HTB battery on a new MAC 500 motor would give me....zilch? A bigger motor means nothing if it's not matched with a bigger battery, right (since increasing the capacity does nothing for performance unless it's realized...with more power/battery)?

 

[TonyReynolds]

I have the 500W 8T MAC motor (rear) from cell_man. I regularly run up to 1650 watts through it no problem, at up to 32mph off a 52V 11.5 Ah A123 battery that will run 10c. I paid more for the battery because I wanted a triangle configuration and the high-discharge, forgiving nature of the A123 cells. That limited me to 11.5 Ah, but I plan on doubling my capacity with another 52V 11.5Ah battery, this time in a rectangular configuration.

This motor is powerful enough for my needs. It has a selector switch for three speed ranges, and I've never used it on setting III. I truly don't know what the top end is, but tucked on a flat, with higher gearing I could probably do 35mph. My normal speed is 25-28mph.

I initially wanted to go low budget, having seen the listings on eBay and the like, but ended up with a more realistic, albeit more expensive system. You get what you pay for and I figured that the extra outlay in reality wasn't that much extra and was only about 150% over the less expensive offerings. If I'd bought cheaper and they failed, I'd be out the money. I want a system that is scaleable and that will last... YMMV!

 

[dogman dan]

Pretty simple, you upgrade the motor first, you'll kill your existing battery. So you have to keep the little motor paired up with the little battery.

Get a bigger, and or higher c rate battery now, then get the motor later. Once you go 48v, take it easy on the little motor so you don't fry it too quick. Watch the long hills or even just really long rides at 1000w.

 

[kmxtornado]

If I used a 48v 10ah battery, would I lose any hill climbing ability compared to my 36v 10ah or would it actually make it better?

 

[wesnewell]

If you increase voltage on the same controller, or a controller with the same amp output, then you increase power and speed capabilities. If you just need more power, then you can keep the same voltage and just change the amp output of the controller.

 

[kmxtornado]

That makes sense. I suppose that's why the HTB recommended the 20a controller upgrade which I ended up going with vs the stock 15a one. Thanks for the clarification.

 

[kmxtornado]

And is this any good?

http://www.joyfay.com/us/48v-10ah-lifepo4-battery-pack-free-bms-6a-charger-new.html

 

[NeezyDeezy]

I wouldn't be able to tolerate a 20lb 10ah battery.

 

[kmxtornado]

Good point. I'm not so much about range though. I literally pedal about 95% of the time or more so no biggy for me. It's the voltage I'm looking for. But there's definitely a big jump in size and weight of batteries when switching from a 36v to a 48v for sure.