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More ebike questions

Posted: Oct 13 2017 1:10am
by s4turn
So finally have put together my ebike.
Still need to place the pas sensor (trying to come up with a bracket)
And get brake cutoffs


So my questions ! :)
1. I got the bike up to around 40km/h, is this normal for a 29” q128c 48v (201 rpm 36v motor) ?
Feels a little slow? I Might just be getting use to it.

2. I have schwalbe cruiser road tires, hardly used, brand new tread, should I be buying specific ebike tires ?

3. I have 2 torque arms, not a lot of space on the axel to place the 2nd arm, is one fine ?

4. Got some small reed sensors on the way for my existing brakes. should I buy bigger brakes? Avid/sram db1 brakes with 160mm rotors

5. Was going to shorten the cables or do people just hide them in a bag?

Re: More ebike questions

Posted: Oct 13 2017 2:56am
by d8veh
The speed seems about right. The assistance goes to about 30 mph, but it reduces as your speed increases. If you want faster with a small motor like that, you need to think about reducing resistance. You don't say what bike you have. I'm assuming 29" wheels means an MTB.

One torque arm should be enough, provided that it's properly anchored.

I'd prefer at least a 180mm hydraulic disc brake on the front for speeds in the low 20s.

Re: More ebike questions

Posted: Oct 13 2017 3:12am
by s4turn
yeah its a GT Karakoram MTB, has lock out forks, but not exactly the lightest bike I dont think :D

Any recommendations on brakes or is upgrading to bigger rotors sufficient?

Re: More ebike questions

Posted: Oct 13 2017 4:52am
by motomech
Don't fix things if they aren't broke.

Still need to place the pas sensor (trying to come up with a bracket)
The "ring" that came w/ your PAS sensor is malleable and can be shaped to fit the round contour of the underside of your bottom bracket and epoxied there. Usually the sensor needs to be turned around(Use the existing screw holes). W/ the bike upside down, hold the bracket close to the disc and test by cranking the bike by hand. The sensor needs to be close to the disc. If you don't want to pull the crank to install the disc, Ebike CA sells a 2-piece disc that snaps together;
SAM_1133.JPG
1. I got the bike up to around 40km/h, is this normal for a 29” q128c 48v (201 rpm 36v motor) ?
Feels a little slow? I Might just be getting use to it.
Yeah, you should have gone w/. the "260" motor.
2. I have schwalbe cruiser road tires, hardly used, brand new tread, should I be buying specific ebike tires ?
Some of us go w/ wider tires for stability, which requires wider rims, but at your top speed, it's not necessary. If you start to experience flats, you might consider the flat-resistant tires. I like the Forte Gothams and the Forte extra thick tubes.
3. I have 2 torque arms, not a lot of space on the axel to place the 2nd arm, is one fine ?
I perfer two pr.s of TA's for piece of mind. One side is usually easy while the other can be tricky. Sometimes the axle piece of the genaric TA can be used and a "link" piece that bolts to the brk. caliper can be fab'ed;
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100_0106.JPG (83.34 KiB) Viewed 1785 times
On my other bike, I used this special shaped TA from Ebike CA(Grin);
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100_0066.JPG (66.38 KiB) Viewed 1785 times
4. Got some small reed sensors on the way for my existing brakes.
I epoxy mine to the lever bracket and stick a sm. magnet on the lever w/ double-sided sticky tape;
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100_0087.JPG (93.72 KiB) Viewed 1785 times
should I buy bigger brakes? Avid/sram db1 brakes with 160mm rotors
Can you stop the bike? Both of my bikes have 160 mm brk.s and I weigh 250 lb.s and have no problem stopping on a dime. If you don't know if your brk.s are strong enough or not when riding, then I'm guessing you don't have much riding experience. You should practice hard stops in a parking lot. A good rider can actually do "brakies", lifting the rear tire off the ground, although it's not something you actually want to do in a panic stop. Only after you are good on the brk.s and they don't feel stroung enough, should you think about larger ones.
EBC makes Ebike brk. pads that last a little longer.
Was going to shorten the cables or do people just hide them in a bag?
People do both. I shorten my cables which requires soldering skills, a bunch of connectors, etc. And after I shorten them, I hide them in a bag. Where is your batt. now? Your bike has a big open frame w/ lot's of space, You might as well use it and install one of the frame bag types.
its a GT Karakoram MTB, has lock out forks, but not exactly the lightest bike I dont think...
Weight on an ebike doesn't matter much unless you are carrying it up and down stairs.

Re: More ebike questions

Posted: Oct 13 2017 6:06am
by dogman dan
One TA should be ok. two if you run higher power than around 1000w

Re: More ebike questions

Posted: Oct 13 2017 9:53pm
by s4turn
Well that was short lived
Was riding up a hill, lost all power. Had 2bars battery left

Now nothing powers up
Rechecked all connectors.
Getting voltage reading on battery. It’s down to 35v so charging it up.

I would expect at least the display to turn on..

Any tips with troubleshooting here ? About to get my multimeter out..

Re: More ebike questions

Posted: Oct 13 2017 11:36pm
by s4turn
battery seems to be stuck at 35v... and can see a voltage reading of 25v to the display controls
checked voltage with battery on charger and its 41v, without charger its 35v, charger on its own is 54v

Will try and leave it a few hours

Can only assume my battery is faulty? or is there a potential controller problem here?
I have no spare parts to quick troubleshoot with. all connections are using higo plugs

Re: More ebike questions

Posted: Oct 14 2017 12:31am
by motomech
If it's a 48 V battery(you haven't told us what it is), it should never read below 41 to 42 Volts and should match the charger fully charged.
What is the batt. and charger exactly, where and when did you buy it?

Re: More ebike questions

Posted: Oct 14 2017 1:06am
by s4turn
Yes it is a 48v battery, using Panasonic cells
48v 14.5ah, got it from BMS Battery

I just reset the BMS, by unplugging it for over a minute, system now powers on.

battery only showing 2 out of 4 bars on display, reads 49.6v
when i plug the battery into the charger its a solid green light.

I assume it means its not charging?

Re: More ebike questions

Posted: Oct 14 2017 6:08am
by s4turn
update, changed p5 setting to real time voltage monitoring and now I can see full bars in the battery meter

my problem now, is why did it even switch off today and only work when i reset the BMS? what would normally cause this?
do I need to reduce the amount of current?

currently my current settings are set to max
my controller is 18a (48v)

Re: More ebike questions

Posted: Oct 14 2017 1:40pm
by wturber
If I understand you correctly, you were going uphill with two bars showing on your display. That suggests a fair degree of battery discharge when this happened. The batteries were at half capacity or less - maybe more. I have no way of knowing how what the "two bars" really means or how reliable it is. Watt and amp meters are much better for that. But if the battery was on the low side, then it is likely that the increased load of going uphill caused the battery voltage to sag below either the controller cut-off or the battery's BMS cut-off or both. Given that the battery's BMS needed to be reset, it seems pretty clear that the BMS was involved. Given that, yes, you might want to configure your controller to either draw less than its maximum amperage or have a higher low voltage cut-off point. These changes would probably make it less likely that the BMS would see a voltage drop and shutdown battery use. You might still get a cut-out if the battery is very low. But I think it will be momentary and will allow the system to still deliver power. A cut-out would be a clear indication to look for a place to charge or to baby the throttle on the way home.

We don't know what kind of amperage your battery can deliver, what its stated of charge was, or what kind of load was being put on the batteries. So this is all a bit of a guess. Getting a watt/power meter (or Cycle Analyst) as well as your reconfiguration to show better voltage numbers should be helpful in figuring out what is actually going on.

Re: More ebike questions

Posted: Oct 14 2017 7:05pm
by s4turn
sorry to clear this up

using the s-lcd3
ive adjusted the p5? setting to display real time voltage, which now shows correct bars on display
limited the current (C5) -4a which seems to have fixed the issue of the entire system cutting out

I have an 18a controller, I thought a motor like the q128c people were running higher current into?
mines set at 14a

it usually cuts out when going uphill and really pushing the bike
i have to reset the bms to get the thing going again

Re: More ebike questions

Posted: Oct 14 2017 7:39pm
by wturber
s4turn wrote: I have an 18a controller, I thought a motor like the q128c people were running higher current into?
mines set at 14a

it usually cuts out when going uphill and really pushing the bike
i have to reset the bms to get the thing going again
A stronger battery that can deliver more amps should allow you to send more current (after re-setting your C5 setting for 100% output) without having the controller and or BMS cut out. But failing that, limiting what the controller will draw seems like a good solution to me.

Re: More ebike questions

Posted: Oct 15 2017 11:52pm
by s4turn
still the same issue tonight :(

Re: More ebike questions

Posted: Oct 16 2017 12:54pm
by wturber
s4turn wrote:still the same issue tonight :(
I dunno. Per spec, that battery should be able to deliver up to 50 amps continuous assuming it is using NCR18650PF cells. Not sure why you are having this problem. I can only suggest getting a watt meter to help you observe what is happening with current draw and voltage drop.

Re: More ebike questions

Posted: Oct 16 2017 2:42pm
by s4turn
I dont have the PAS sensor connected currently, would that make any difference?
is there any settings I need to adjust for that?

Im using the throttle currently


last night I took it for a ride and noticed the battery voltage was at 46.4v or so
I have the p5 setting is set to 0

I noticed it dropped down to 42v after about 10 minutes of riding and then all power was lost
I can only get this working when resetting the BMS

would this be the low voltage cutoff? switching the system off?

Re: More ebike questions

Posted: Oct 16 2017 3:44pm
by wturber
If you are starting off with your battery at around 46 volts, then it is less than halfway charged. It may be nearly empty already. Freshly charged it should be reading 53-54 volts.

Re: More ebike questions

Posted: Oct 16 2017 4:04pm
by s4turn
battery wont charge past 47.4v

this is the BMS I have:
https://bmsbattery.com/bmspcm/810-7s-10 ... esults=101

im starting to think I have a bad cell somewhere

Re: More ebike questions

Posted: Oct 16 2017 8:08pm
by wturber
s4turn wrote:battery wont charge past 47.4v

this is the BMS I have:
https://bmsbattery.com/bmspcm/810-7s-10 ... esults=101

im starting to think I have a bad cell somewhere
Then there is something wrong with your battery or your charger. Also, your 18a controller probably pulls more the 18a for a short time. It might surpass the limits of that BMS. But I'd attend to the batter/charger question first.

Re: More ebike questions

Posted: Oct 16 2017 8:57pm
by s4turn
i tested the battery charger and can confirm its putting out 54v

Re: More ebike questions

Posted: Oct 16 2017 10:02pm
by docw009
You're showing a non-balancing BMS. Did you buy it separately?

If it were mine, I'd send a note back to BMS battery if I had purchased it as a complete battery. I'd want to open it up but that might void any warranty, so I'd want their OK. Further tests would consist of walking my volt meter up the balance cable connector and seeing what voltages are on the 13 cell groups.

Re: More ebike questions

Posted: Oct 16 2017 10:22pm
by s4turn
Yes I did get it as a complete set, the only thing separate was the motor.
The set included controller, display, pas, battery etc were all sold together

Re: More ebike questions

Posted: Oct 19 2017 12:17am
by s4turn
Update, BMS battery asked me to check each cell on the battery

tested the following: see picture for each terminal
1. 46.5v
2. 33.5v
3. 47.1v

With charger plugged in:
1. 47.1
2. 47.1
3. 54v

tested each of the cells (13s)
each shows 3.6v
plugged charger in and shows full charge (green light)

I can only assume my BMS is bad ?

Re: More ebike questions

Posted: Oct 19 2017 5:12am
by d8veh
As a temporary measure, while waiting for a BMS, you could move the charge negative wire to the same output point as the discharge one on the BMS, or even to the negative from the cell-pack to bypass the charge controls. The balancing will still work and the charger will charge it to the correct voltage, so there's no significant risk

Before doing that, be sure that you have 13 cell voltages the same and check them from time to time during a trial charge with the battery open. I say that because it's often the first or last group that is anomolous and it's voltage is found between either ground ab the B1 pin or the cell-pack positive and the B12 pin when there's a 13 pin connector.

Re: More ebike questions

Posted: Oct 20 2017 4:42pm
by s4turn
might try that if the BMS takes any longer

its on a 2 to 7 day shipping, ordered it a couple of days ago, im hoping next week I get it
got a spare charger coming too.

I've also ordered 2 more PAS sensors $4 or something, they have different mounting brackets
https://bmsbattery.com/ebike-kit/705-du ... results=67

and this

https://bmsbattery.com/home/837-dual-ha ... results=67