Decisions! Cheaper kit or the not so cheap kit for my requirements?

[Flatcap_FPV]

Hi guys,
Just wanting a second, or third opinion please!

Quick run down on its purpose:
This isn't for a bicycle conversion and it will be used with No PAS, just throttle only.
I will be re-lacing the motor into a 20" wheel.
I intend running this using either VRLA Cyclic or VRLA high rate batteries at 48V (looking for Battery capacity over weight saving)

I'm a good 17 Stone (110kg?) and estimate final assembled weight of the vehicle to be in the region of 40-50Kg (inc batteries) Say around 150Kg all up weight!
I'm not looking for blistering speeds absolute max intended flat surface speed of 28-30Mph.
But something that will also cope well with a lot of hill work without having it running on the ragged edge all the time would be good!

The more expensive option does allow me to choose various motor winding options and is a 5:1 geared hub, the cheaper one is direct drive and probably luck of the draw on how it is wound!
Having a higher winding set may be a better option since i'm trying to find a good balance of torque and top end!

Ok, kinda sounds like i've already decided which i "should" buy, just wanting a little nudge in the right direction!

Both kits from ebay and seem to be without display (any suggestion on display to purchase along side these would be good too please )

Cheaper kit

Not so cheap kit

 

[vfr400]

You don't need a display or control panel if you're only going to use a throttle.

I don't understand what you're saying about the batteries. Lead batteries are rubbish for capacity. Don't forget that you can only use half the capacity, so you need double the amp-hours compared with lithium, and their life is only half what you get with lithium, which means you have to double the cost for comparisons. Weight is the worst thing for any electric vehicle, except a boat or tank. Put all that together and it's difficult to justify using lead batteries unless you get them free. Even if they were free, I would still rather pay for a lithium battery.

 

[KirstinS]

I do agree with vfr on this

30mph really is going some and will kill any pack fast

Plus your weight and hills climbing as stated make this harder still on the motor. Dd are utterly hopless at hill climbing too compared to geared - much better a flat speed

. To be honest, especially if totally set on using sla, I'd say go mid drive. That way you can be wiched up hills through low gears and also ha e a high top speed (gearing dependant )

 

[Flatcap_FPV]

Sorry, i should have worded that differently, my bad!
"max intended flat surface speed doesn't exceed 28mph"

I would however like to acheive a respectable cruising speed that wont make me a pain in the butt for motorists on country lanes!

I was going by the winding/speed chart on one of the listings:

6 turn high speed motor - 400rpm loaded at 36V, 520rpm loaded at 48V
8 turn standard motor - 320rpm loaded at 36V, 400rpm loaded at 48V
10 turn torque motor - 255rpm loaded at 36V, 320rpm loaded at 48V
12 turn low speed extra torque motor - 200rpm loaded at 36V, 250rpm loaded at 48V
Accepts disk brake and 7 speed freewheel with standard 135mm rear dropout.
As a guideline you can expect approximately the following real world speeds for the above windings on 12S LiFePO4 battery pack (approximately 38V under load) in a 26" rim on the flat, no pedaling with a rider plus bike weight of approximately 130kg total (286pounds):
6T - 45kph (36v), 65kph (48v)
8T – 39kph (36v) , 50kph (48v)
10T – 32kph (36v) , 40kph (48v)
12T – 25kph (36v) , 32kph (48v)
Spoke Radius - 172mm

I have now done the math myself and these may be exagerations!
They all roll in around -33% on those figures.... and i havent even factored for load difference yet!
Now i'm questioning if the winding info is true or BS too??

I have going spare a fairly large quantity of Yuasa Cyclic use and Yuasa High rate batteries unused around 12 months old... Maybe even enough for a tank!
Call me scrooge, but with 70% of my outlay cost going for nowt... I figured lemonade was ma'thing

My intention is for a fairly sturdy 2 at the front, recumbent type tricycle... not quite so recumbered and jacked up a bit!
Its use is, fair weather weekend.
Just a run down to the paper shop a 5.35mi round trip (only route) + 20% = expected 100% motor
If my knees arent giving me gip and i choose to pedal with light resistance (Physio type stuff) maybe safe to head for the next village over 9mi round trip

I wanted to avoid messing with a conventual mid drive motor with additional gears and motor mounting etc. (i work around EVs... that high pitch wine as they spool up under load goes through me like nails down a blackboard)

From what i understood the mid drive crank types to be PAS only and wouldnt work since the pedals will basically be decoration. Or is this yet more questionable info i have come across?

If it gets me a taste of the things to come... Winter time is for the Mk2

 

[Flatcap_FPV]

Ps. not having a display, isnt that like forgetting to turn the fuel tap from reserve tank?

I dont want bluetooth junk but a glorified petrol guage is good!
isnt it also a basic interface for the controller soft settings?

 

[Woosh]

Hi Flatcap,

most kits can do way more than 15mph if derestricted but 28mph is a big ask. Take a look at the motor simulator at ebikes.ca
https://www.ebikes.ca/tools/simulator.html?mass=140&hp=0&axis=mph
Look at the load plot. Determine the load according to your speed then deduce the motor torque, battery voltage and current from there.
For example, flat road, 28mph, 110kgs rider, 30kgs bike, no pedaling, you will need 859W at the motor wheel.
Your battery needs to be able to supply continuously 1.5 * the load, about 1.3kW, so something like 36V 21AH or 48V 17AH battery with top grade cells, not Yuasa batteries.

 

[vfr400]

A 36v 201 rpm motor will do exactly 15 mph in a 26" wheel at 36v without load. You can use that as a basis to calculate any motor's speed. A 400 rpm motor will spin up to 400/201 x 20/26 x 15 mph.

You will get good assistance up to about 85% of that speed, then the power ramps down to zero at max rpm.

The battery is 10% higher voltage than nominal when fully charged and 10% lower when empty. Motor speed changes in proportion to voltage, so you can multiply the equation above by (actual voltage)/(nominal voltage).

For a few gauge, you need a wattmeter. £8 on EBay. The GT type is easiest to waterproof.

 

[Woosh]

The battery is 10% higher voltage than nominal when fully charged and 10% lower when empty.

Lithium ion cells:
full: 4.1V, 50% charged: 3.6V, flat: 3.1V. They are safe limits.
its voltage is 13.7% higher when full, 13.7% lower when empty compared to what is on the label.

 

[vfr400]

Lithium ion cells:
full: 4.1V, 50% charged: 3.6V, flat: 3.1V. They are safe limits.
its voltage is 13.7% higher when full, 13.7% lower when empty compared to what is on the label.

If you want to be pedantic, you need to allow for voltage sag, and who runs their battery all the way down to 31V?

 

[Flatcap_FPV]

Hi Flatcap,

most kits can do way more than 15mph if derestricted but 28mph is a big ask. Take a look at the motor simulator at ebikes.ca
https://www.ebikes.ca/tools/simulator.html?mass=140&hp=0&axis=mph
Look at the load plot. Determine the load according to your speed then deduce the motor torque, battery voltage and current from there.
For example, flat road, 28mph, 110kgs rider, 30kgs bike, no pedaling, you will need 859W at the motor wheel.
Your battery needs to be able to supply continuously 1.5 * the load, about 1.3kW, so something like 36V 21AH or 48V 17AH battery with top grade cells, not Yuasa batteries.

Hi Woosh,
Thanks for the link to that simulator tool, that cuts down on a lot of math, much obliged.

Though it also raises further questions why you are so dead against sla batteries:
Based on the Mac 8T hub (though initiallay looking at 10T)
48V sla with an increased 0.3 Ohm internal, 21Ah adjusted capacity, (4s5p bank @ 12v6Ah assuming the smaller High rate 6AH batteries) 35A controller, 20" wheel, Semi-recumbent, auw 180kg (50kg batt, 110kg me, 20kg frame), 0w human power, 5.5% assumed gradient.
Shows a 12 mile range (Double my intended 0 human input usage), with a borderline voltage drop, a brisk 18.1mph top speed and 29mph theoretical top speed (which i can live with).
Heck, dropping to a 16" wheel (min size the hub can accept) gives 13 miles at a not too shabby 16mph with considerably less strain on the battery.

But if you would sleep eaisier, do you have any suggestions for bulk suppliers of life/lipo cells for battery building in uk/eu that you could point me at?
Afterall a lack of being able to find a supplier is why this project was on hold until a large supply of free batteries dropped in my lap!

Jeesh you're hung up on that 28mph.
My only requirement was that it cannot by law exceed that for my intended choice of registration.
Lets move it along now, lol!

The battery is 10% higher voltage than nominal when fully charged and 10% lower when empty.

Don't worry i got that was 'rule of thumb'.

Why has no one mentioned lihv 4.35v/cell yet?

 

[Flatcap_FPV]

To be honest, especially if totally set on using sla, I'd say go mid drive. That way you can be wiched up hills through low gears and also ha e a high top speed (gearing dependant )

In the process of ammending the list... This 1000w Bafang Mid Drive kit would be a better choice than the Mac motor, along with just crossing out the direct drive hub?

I can't find any generic mid drive motors that dont appear to be low quality kids buggy 'toy' motors!
Any suggestions on a motor of this tye with a reduction box, if i have space to fit a 2nd belt drive to opposite side (More work than i was planning for mk1 but it should at least be an option... right?)

 

[Woosh]

Jeesh you're hung up on that 28mph.

it's only because you use it as your target.
Typically, commuters who want to save a bit of time target 19-20mph when they derestrict their bikes.
I usually choose a geared hub motor for commuting.
My choice of winding is so that the maximum power output is centered around 15mph. When the motor goes faster than that RPM, the torque will drop gradually, thus protects the motor against overheating.

But if you would sleep eaisier, do you have any suggestions for bulk suppliers of life/lipo cells for battery building in uk/eu that you could point me at?

I usually look up price and specs at nkon.nl

 

[vfr400]

In the process of ammending the list... This 1000w Bafang Mid Drive kit would be a better choice than the Mac motor, along with just crossing out the direct drive hub?

I can't find any generic mid drive motors that dont appear to be low quality kids buggy 'toy' motors!
Any suggestions on a motor of this tye with a reduction box, if i have space to fit a 2nd belt drive to opposite side (More work than i was planning for mk1 but it should at least be an option... right?)

Every system has advantages and disadvantages. I can imagine that a BBSHD would be rather umpleasant hauling 200kg around. That's if your gears didn't break before you got to the end of the street. OK. That's a bit of an exaggeration, but you get the point.

You need to try some of these things before committing your cash.

 

[Flatcap_FPV]

Hi Woosh,
Righto, so its me just being awkward and working backwards then.
See, i'm not comuting, its nothing more than a project (Just because i can) that would have some light functional use.
I did my fair share of commuting on a bike 20 odd years back when i left school. My knees would not be happy with me trying that these days so need to rely more on powered, and assume very limited or no aid from me!

JEESO! had a luck on akon.nl... Inc shipping on brand new cells is near half what i was finding them (Like for like) elsewhere and there is bulk discount too! WOW

Every system has advantages and disadvantages. I can imagine that a BBSHD would be rather umpleasant hauling 200kg around. That's if your gears didn't break before you got to the end of the street. OK. That's a bit of an exaggeration, but you get the point.

You need to try some of these things before committing your cash.

Hey vfr400,
I get ya drift though, thats a lot of strain to expect of lightweight chains and sprockets.

Agreed, always best to try something first and get a feel of what im looking at/for... Being pretty rural can be a pain in the a$$ at times!
The only bikes i have come across up here are the ones sat on the shelf in Halfords, whilst having a bash on one would give some idea of what to expect i already know that a legal direct drive just wont have the guts needed.

In 10 years i haven't even seen a weekend country lane tour'de france group once (probably too hilly LOL)!

 

[Flatcap_FPV]

Ok, back to batteries...
So going down the "forking out on pristine cells" and keeping my initial battery outlay to the bare minimun. Looking at either prysmatic Lipo or 18650s. (I have 12x unused LiPo cells already to hand! )
Requirements unchanged. Range of 6mile (Total runtime), No human input, 160Kg - AUW with approx 20Kg excess load (For now we'll call this an approximation for real world factors?), 20" wheel and Mac 10T motor.

Lipo:
Cell 5Ah / 40A continiuos (80A burst) Confirmed not BS rating
10s-2s (36v packs just more practical for me as i already have charging equipt for up to 10s, however i could still make up as a single pack with dual discharge leads as a space saving measure)
2.3Kg (Exc leads, No bms req)
5Ah total capacity
135mm x 45mm x 210mm Assembled (Exc leads),
£121 Total cost (20 cells + balance leads)
40A(60A) controller,

Sony VTC5A 18650:
Cell 2.6A / 35A (err, i'm assuming that is burst rating?),
10s2p-2s (36v packs as above),
2.0Kg (inc x2 bms, exc leads),
5.2Ah total capacity,
200mm x 70mm x 80mm Assembled (Exc Leads),
£172 Total cost (40 cells + 2 bms)
30A(40A) controller,

Looking at the specs for the 2 battery types i would usually choose the LiPo pack over the 18650 cell packs, but only due to the extra discharge capability. Weight, capacity, size really has nothing in it and 0.2mi range difference doesnt seem worth the extra cost.
I have played around with motor winding, wheel size etc, but cant make the acheivable torque balance any better without loosing quite a lot of top end!

 

[vfr400]

I've used lipos extensively. I can summarise by saying that it's a lot of messing about and more expensive than you calculate. You have to allow for their shorter life and the chance of bricking them, which is much higher than you think. Don't forget that you have to make a case to put them in unless you're going to use hard-packs. Also, their quality isn't assured. You only need one duff cell and your whole pack can be in trouble. You have to test each pack thoroughly before assembling them into an ebike battery. Don't forget also that you need individual cell monitoring while riding. Finally, you need to be really neat with all your power and balance wires. If they short, you'll have a fireball.

A 2S 18650 battery isn't going to work. Whatever the current rating is, you need to divide it by two to get a battery that doesn't sag massively and overheat.

Having tried every type of battery over the years, I can't over-stress how much easier and cheaper it is in the long run just to buy a ready-made battery from a trusted supplier. A good battery is the most important component in your ebike. The only time I make my own batteries now is when I need a custom shape or size. It never works out cheaper to make your own than it does to buy a ready-made one.

 

[Flatcap_FPV]

Hmm, looking at the figures (from my perspective) i'm more suprised that you dont destroy 18650s more than you do, but then i suppose that explains the need for a cell/cell bms?

I'ts cool, lm used to polymer batteries, i have made enough for multirotor UAVs by now.
By nature defying gravity in the least efficient way possible pushes the upper limit of what current battery tech is capable of. First to hand off the shelf as an example, 1050kv 6s motor 84A draw around 90% throttle X 4 beleive me, battery sag and voltage drop is something i am used to managing on the fly HAHA! sry
Cant fault ya for the safety aspect though, i must say a cell going 'frrrrt' under my ass is preferable to one going 'KAWOOOSH' (I dont have that dilema usually )
The highest battery draw on that calculator was showing a 39A preak draw, which is still within the constant discharge capacity.
But hey, i conceed i'm coming at this totally the wrong way!
i'm looking Lb/thrust not Nm HAHAH... I'm used to needing huge burst power but little in the way of endurance relatively speaking.

I came across 72v 20Ah Pack+ charger, i have no experience with DHgate, never even heard of them for that matter. Must be another banggood or aliexpress-a-like.
Anyhow, £450ish (£7.05/Ah) - inc shipping & duty seems kinda reasonable, maybe worth a punt?

Any concerns or feedback on the website/product?

Risking them not being the best cells (though states premium cells) and needs a teardown within 6 months of being ragged about, i'm thinking winter project If i get 12-15Ah back on the rebuild... That works for me!

 

[vfr400]

There's no way in the world that 2S 18650s are going to give 39 amps for an ebike. Even if they could, the capacity would go down to from 5Ah to around 3.5Ah, which is going to last less than 6 minutes. That'll give a range of about 3 miles.

 

[Flatcap_FPV]

Sorry you've totally lost me with 2s?

The packs i was considering making would have been 10s regardless of battery chemistry, then 2 packs connected in series again to make up the 72v.
My only preference for building 10s packs over a single 20s pack was i would not need to buy extra charging equipt, that's all.

If you meant 2p... i see what you mean. To avoid excessive sag i half the rate of the cell, which would require double the cells in parallel.