That was nice!

[DannyC]

A cheeky 2 & one-half day escape from the enemy was enjoyed by yours truly in the company of Stormbird of this parish.
Just a stretch of the legs and a test of the batteries you understand.
We stayed at a National Trust site (Houghton Mill/Waterclose Meadows) and triked into Cambridge and back and enjoyed a beer sitting in the sunshine on the side of the river Cam looking at some of the old college boat-houses.

The weather was "mixed", with some rainy periods but also some lovely sunshine.
Paul kept getting away from me as his gearing was better and his top-speed at his preferred cadence was higher.
Remarkably, nothing broke on either of our machines and we live to fight another day.

 

[stormbird]

Yes I was there !

Heston Station house a sort of Bistro cafe we sat outside and enjoyed the sunshine [ IIRC twice ].

Little dessert after the main course , just to see what it was like you understand

We found [ we were told ] the last pub in Cambridge on the river Cam , wanting something light I selected battered Halloumi in a chilli and Peri-peri sauce for some reason Dan suppressed the inner carnivore and ordered the same ...

On the face of it quite innocuous I had only had one piece when Dan said through the tears ' don't eat the red rings ' it took 1.5 pints for Dan and 2 bottles of beer for me to quench the heat and get the feeling back in our mouths .... most enjoyable

In truth my gearing was no better than Dans , Dan was still running his ' get me home @ any cost gearing ' low enough that should he have an electrical failure he could pedal very slowly back to the ferry with his camping gear when we were in the Netherlands last year. His is rather awkward to change as neither the Bafang nor the Nuvinci have a large choice of sprocket/teeth options , it looks like he needs a UK non-camping set and a Netherlands camping set , to stay at his speed I needed to use my lower front ring and the cadence is to high for more than about 30 minutes for me , the moment I changed up I started pulling away from Dan and he could not spin faster and the motor had reached it's fixed limit [ well that is what I though he said ? , I may not have understood correctly it's all magic [ well till you let the smoke out that is ! ] ]

Paul

 

[maddox]

I have a twin chainring on my BBS02b, the normal 44T and the "climb mountains" 34T. Manual change over tough.

But everybody can fit it.

 

[DannyC]

I have 2 rings on the Bafang too 53T & 34 with a 34T 36T sprocket on the N380 CVT Hub. Changeover is via a standard shifter mounted on an outrigger.
Even in the 53T and the top gearing in the N380 it max's out at 10.8MPH.
The Bafang is capped at 72 RPM of the front rings. So with my gearing being so low I was never likely to keep up with Paul.
We did manage to bimble along nicely though.
The 10AH battery managed to propel me along for about 18 miles before it gave up the ghost and I had to switch to the other one.
That was at MAX output (level 6 of 6), that's just how poor my leg strength has become.

 

[Popshot]

That's crazy low gearing. Using a more typical rear end I've never topped out below 25mph on any assisted set up. Sounds like you need an igh jackshaft but that's adding even more weight. Is the nuvinci worth the low speed?

 

[maddox]

The low RPM on the Bafang is strange. My BBS02b 750W caps out on 135 rpm (test in very low gear tough), what is idiotic to follow.

 

[DannyC]

I changed the big 36T sprocket on the Nuvinci for a more modest 20T one and the speed difference is clearly noticeable.
At everything on MAX (Bafang & Nuvinci) I had 20MPH on the flat (where 15.xMPH is the legal limit).
Remember the previous gearing was "escape from disaster" gearing with no e-assist and me towing a ruddy trailer and needing to be able to get back from Holland to the ferry.
My Bafang is a BBS01 not a BBS02 so maybe the BBS02 runs faster?

 

[stormbird]

The BBS01 low rpm is discussed here Changing rpm way above my head however noted by others.

As Dan says this was a bale out option to self assist back to the ferry if needed , NOT intended for UK non trailer use.

Paul

 

[Dale Rider]

So 78-83rpm load speed Danny.
Max speed about 26mph. Looks useful if set up right.
My 'electric' is a 250 watt unit running at half power setting easily doing 22mph, (with favourable conditions), so I don't need to push it hard at all to get a good lick of speed.

 

[maddox]

250W vs 750W.

In effect, the mechanicals are the same for both motors. But the electronics, battery voltage and size of rotor are the difference. That explains, together with the settings, the end RPM.

I geared Grey Ghost so , with a cadance of 130 rpm (only achivable with SPD's or simular), I have an end speed of 45km/h. But that's not something I do on regular roads, nor bikepaths. There I limit my top speed to 25km/h, and in a lot of cases, not even that.

 

[DannyC]

250W vs 750W.

In effect, the mechanicals are the same for both motors. But the electronics, battery voltage and size of rotor are the difference. That explains, together with the settings, the end RPM.

I geared Grey Ghost so , with a cadance of 130 rpm (only achivable with SPD's or simular), I have an end speed of 45km/h. But that's not something I do on regular roads, nor bikepaths. There I limit my top speed to 25km/h, and in a lot of cases, not even that.

Thanks for the above two posts Maddox, and for your post Paul.

My BBS01 is a 350W model. But somehow that printing got rubbed off.
If I put no appreciable load on it I could probably test the max RPM's with a tachometer and a white bit of tape on the chainring.
I know you can reprogram them to alter several parameters, but I don't really want to step outside of the factory specifications.
I do have it set to cut off at 40kph (25MPH) and not 15MPG as per UK law.

 

[Dale Rider]

Based on 80rpm from Banf: 53T to 36T sprockets: M.A. N380=3.8 to 1: 20" wheel drive.
I calculate a speed of 26.6mph potential.
How old are the batteries?
Whats the voltage (36V)? (Will be 37~39 charged, ok)
And the discharge rate (C).
I'm guessing 10S.
You could have a battery pack for a 250watt motor but driving a 350watter. Not knowing the windings and motor spec is probably (most) where the problem lies.
Think we are all thinking this, so will setting fiddling work?? Only to a degree but not ultimately correcting the inbalance of supply to demand.
In my 10 years of model brushless flying, I carefully select an ESC to motor and batteries to give a defined performance.
Just bragging, my electric flying gear is very fast, ie 35,000 revs stuff, on the peak, matching IC nitro powered motors of the same class., doing over 100mph, not that that stuff will help you.
But I do have a pedigree on the stuff.

 

[DannyC]

Based on 80rpm from Banf: 53T to 36T sprockets: M.A. N380=3.8 to 1: 20" wheel drive.
I calculate a speed of 26.6mph potential.
How old are the batteries?
Whats the voltage (36V)? (Will be 37~39 charged, ok)
And the discharge rate (C).
I'm guessing 10S.
You could have a battery pack for a 250watt motor but driving a 350watter. Not knowing the windings and motor spec is probably (most) where the problem lies.
Think we are all thinking this, so will setting fiddling work?? Only to a degree but not ultimately correcting the inbalance of supply to demand.
In my 10 years of model brushless flying, I carefully select an ESC to motor and batteries to give a defined performance.
Just bragging, my electric flying gear is very fast, ie 35,000 revs stuff, on the peak, matching IC nitro powered motors of the same class., doing over 100mph, not that that stuff will help you.
But I do have a pedigree on the stuff.

Well, these original 36v 10AH battery packs were once driving a 500W hub motor on the other trike.
They have probably had <200 cycles [pun intended] .
My excel spreadsheet says a top speed of 23.97MPH if we assume lossless transmission (no such thing) and the N380 wound all the way to the top gearing possible.

With the 36T sprocket on the back this was reduced to around 11.8 MPH (as anticipated).

It's OK, I am content to bimble along at 10MPH or so and I have no real need to do >20mph as it spoils the view and the appreciation of the scenery when your eyes are streaming.
I do have 2 15AH battery packs (never used) but they would need a new rack making for them and ICBA.

 

[stormbird]

Unsure what you tables are showing ?
One has 4 rows 1.87 - 1.90 the other has 3 rows 1.88 to 1.90 ?

Can we assume you comfortable cadence is 60 rpm ? or is that really your max for a short while ?

Where does the motors maximum efficiency lie ?

So if :-
36T gives 10.8 mph @ 60 rpm
28T gives 15 mph @ 60 rpm [ assumption from figures given ]
20T gives 20 mph @ 60 rpm [ to fast to be of much use ? ]

I have no speedo [ a curse and a blessing ] I reckon my comfortable cruise speed to be about 10.5 to 11.5 mph just above your max available last week.

You are hampered further by a greater trike weight than mine so comparisons are NOT in your favour

Paul

 

[Popshot]

What's the bms rating of the batteries?

 

[DannyC]

Paul,
In answer to your questions.....

One has 4 rows 1.87 - 1.90 the other has 3 rows 1.88 to 1.90 ?

No significance in this, I just carved up the N380's gearing ("X" * 0.5 to "X" * 1.9) into 0.1 steps when creating the spreadsheet. It is just a scrolling difference when looking at the big output table.

28T gives 15 mph @ 60 rpm [ assumption from figures given ]

A 28T sprocket with a 53T chainring will give about 12.84MPH at 60 Cadence, 15MPH @ a cadence of 72.
Popshot, in answer to yours.....

What's the bms rating of the batteries?

I have no idea, all I know is that they are 10AH packs and each one on "MAX Draw" (I assume it is the full 350W of the motor) will take me about 18 miles.
Where would I find the BMS rating of the battery packs, I don't recall seeing a rating plate on them.

 

[Popshot]

Usually printed on the bms itself which will probably be about a fat credit card sized thing wrapped up inside the casing. If you have a means of measuring the current when in use a 350w should pull 10amps at 36v. Whether it does will depend on the controller and the bms. Given it's a bafang the controller is integral and likely to be correct for the job so it will ask the battery for 10a at full draw. If the bms is 10a or higher it will be supplied that. If the bms is rated lower then it will only get that lower figure so the motor will make less than 350w.

 

[DannyC]

Usually printed on the bms itself which will probably be about a fat credit card sized thing wrapped up inside the casing. If you have a means of measuring the current when in use a 350w should pull 10amps at 36v. Whether it does will depend on the controller and the bms. Given it's a bafang the controller is integral and likely to be correct for the job so it will ask the battery for 10a at full draw. If the bms is 10a or higher it will be supplied that. If the bms is rated lower then it will only get that lower figure so the motor will make less than 350w.

I could stick a wattage-meter shunt in the power line going to the bafang, I have got one somewhere.

 

[DannyC]

I had a look at the tech specs for the BAFANG motors.

Both of mine are the BBS01 36v 350W so their "Under Load" RPM is a max of 75.
I have searched for info on where the "sweet-spot" is for the motor (RPM/Watts) but not found it yet.
Assuming 75 RPM is where they intend it to sit most happily I would see the following Speed(s) at varying cadences.

This would all be in the top-ring 53T, for towing a loaded trailer (camping) I would stay in the lower ring (32T)
Which would give the following Gear-Inches and Speeds. Note the max speed is still more than adequate for any inter-site travel.

 

[Dale Rider]

BMS = battery management system.
Charging and cell balance management.
The BMS ensures that all of the individual cells in your battery are operating and balancing cohesively, it also ensures that your cells are protected from issues such as under and over-discharge, temperature instability, cell and current imbalances.

ESC =
An Electronic Speed Controller (ESC) is a purpose-built device designed for controlling the speed of an electric motor. Using a specialised combination of hardware and firmware, ESCs drive motors to a commanded speed. They maintain motor speed under various circumstances, such as the dynamic load of a propeller.

Think I'd look at the ESC, if possible and get the ID numbers to get the specs online.