Another day, another newbie

[Nick_Piliens]

Hello fellow bike enthusiasts!
A newbie here looking for some advice.

About myself- have been bike mechanic for 10+ years in various bike stores and hobby frame builder (not any more).

Due to my commute being around 8 miles one way I am looking to build my first ebike that I would mainly use for commute, but would also occasionaly do some light offroad/exploring rides. For this build I will be using Boardman Team 29er, that I have owned for a while and think it would make a great base for an ebike.

So what do I need help with, you ask? Components. Although I have extensive experience in cycling industry, I lack knowledge of ebike components (what to look out for, what works, what doesn't)

On some other thread here I read that someone has used 36v battery (legal on road) with additional plug in booster battery that gets around 48/52v( for off road). And I would like to do exactly that. (Have a little experience with soldering in the past)
In terms of motor I was looking at 500-1000w rear hubs (preferred with cassette for 11 gear setup which I only saw options for 500w ones, but would ideally go for 750/1000) that I would then fit with 250w sticker ( yes, I'm a bit cheeky)
In terms of controller and display I would like to be aware of the motor temperature, and adjust max speed. I would also only use pedal assist instead of hand throttle.
So I guess I'm after a bike that could perform when needed, but still kinda be semilegal in case sh*t goes pearshape. (Haven't had a single road accident in my life, but don't want to get in legal trouble if do - reference to recent incident with pedestrian and ebike collision)

So if you have any recommendations to what components I should use/avoid your help will be appreciated.

Thanks in advance.

 

[sjpt]

Most of the high power hubs are direct drive; heavy, pretty inefficient for everything but high speed on the flat, and hopeless on hills. Also very large and very obviously not 250w. The legal 250w ones (or very similar 350w ones from Yose) will probably do much better. They still generate from 400-600w for peak use (eg hills).

Voltage up so 48v nominal is ok legally; it is some more generic low voltage law not e-bike specific that then comes into play ... I don't know exact voltage. It is the nominal 250w and 15.5mph max assisted speed that are important for legal e-bikes.

And on/off road switches still leave it illegal on the road even if switched to a lower power. And illegal off the road unless on private land not accessible to the public (eg not bridleways/public tracks) and with landowners permission. I've never heard of anybody being had up for an illegal e-bike off road thought.

 

[scott gaza]

HI There is no point in getting two battery's for a power hungry d/d hub as its size is a dead giveaway to its illegality! You would be better served with a smaller geared hub and dialing down top speed as when required. I expect you will have trouble finding a 29" wheel so expect to build you're own.

 

[KirstinS]

A rear 500w bpm would be a beast of motor. Far superior to those cheapo ebay DD hubs

I am one person who has a bike which can take a booster battery.

But only because I could not fit a mid drive to that bike (shaft drive and alfine hub) . A bbs01 can output 600w. It's legal unless you up the speed cutoff. But you can change this in LCD settings

Better off road too for the hardtail you are converting as you can use the gears or rather the motor runs through the gears

Also no hassle of building wheels and better weight distribution too

 

[Nealh]

You will regret the D/D hub choice, they are cheap because they are simple but for your use will under perform compared to a geared drive.
Ideally best used for fast riding and not slow stop start or off road use.

Why mess with a booster battery if you don't need to ?

Buy a 48v hub or mid drive and a 48v battery as you are starting from scratch.
No motor has an internal temp sensor or lcd motor temp reading, some LCD's read ambient air temp.

 

[Nick_Piliens]

Thank you guys so much. That gives a lot of clarity.
As an option I was looking at this since it comes in 28", has cassette option and is geared. Would that be a good option for this little project of mine? : (if there are better hub-only options please suggest - don't mind building the wheel myself)
https://www.amazon.co.uk/Bafang-Conversion-Wheel-Electric-Display/dp/B07JVK4TR3/ref=sr_1_fkmr3_2?dchild=1&keywords=bike+conversion+kit+48v+500w+rear+wheel+pasand+bafang&qid=1583269505&sr=8-2-fkmr3&th=1&psc=1

Would this be a decent build quality battery to go with it?:
https://www.amazon.co.uk/Electric-Bicycles-Battery-Lithium-500W-1000W/dp/B07SJFWHSH/ref=sr_1_fkmr0_2?dchild=1&keywords=bafang+48v+lithium+e-bike+bbshd+bbso2b&qid=1583270148&sr=8-2-fkmr0&th=1&psc=1

Another question I had was if this setup could deal with 52v battery relatively safely? If so would the difference in power outweigh the added weight (i have no idea, just assuming bigger voltage one is heavier)?

Once started looking into batteries I noticed quite a large amplitude of prices example-
289£ - https://www.amazon.co.uk/676WH-Hailong-Battery-Ebike-Shark/dp/B07WG14MGF/ref=sr_1_2?dchild=1&keywords=free+duty+52v+13ah+676wh&qid=1583269897&sr=8-2
428£ - https://www.amazon.co.uk/dp/B07VHPM3WX/ref=cm_sw_r_fm_apa_i_iHSxEbKT8FWRD?fbclid=IwAR3FbCOOICcyVKccTFlv1NTYatXJJ5zEam1xjEUFlyi24D6j9ryxJsadOgM&th=1&psc=1
Does this difference come from a genuine difference in quality/longevity or is it just marketing?

Thanks again!

 

[scott gaza]

Good choice looks like a bpm2 hub kit you could get it a bit cheaper going direct @ bms or topbikekit. and for the best battery speak to Jimmy at BGA reworking. there you can have a bespoke battery made with the cells of your choice.

 

[Nealh]

Bafang are one of the best when it comes to hubs, the best feature is it's unloaded/ speed of 240/205rpm which makes it a good hill climber and for off road use and v.good torque of 48nm. It will likely top out at 24 /25mph @ 48v.
When it come to lacing the motor a 2x is th max you will want for nipple/spoke entry angle and a good dish to centralise the rim in the D/O's, all which will be a piece of cake for someone with your knowhow.

In the first battery link the 52v Sam 29E is the best battery in terms of the cells used and is proven top cell for life cycle, though if you are going to beast the bike in max assist mode all the time then the battery will take a bit of hit in it's longevity.
The Sam 35E although a newer cell with greater capacity, it doesn't have a better cycle life in fact in cycle ageing tests it is worse. Vendors list the battery specs but aren't bothered about the shortness of user life, the two batteries will be good but won't stand up to constant max power or speed without some performance loss over the longer term . It all boils down to how long you want the battery to last 2, 4 or 6 years for example.

 

[Nick_Piliens]

So just to double check it would be the 17.5ah Samsung cell battery that you recommend, correct?

Would I be able to get away with 52v (assuming I select display thats 52v compatible) or would it seriously sacrifice the reliability of the motor? Since Samsung cells have been specified in both 48 and 52v (at 17.5ah).
Also wondering if the difference in performance would be significant enough to even consider it, what are your thoughts on this?

Also do different ah batteries have significant weight difference? Like 13ah of 17.5ah for example.

Thanks a lot!

 

[Nealh]

Beg my parden but this answer will be a bit long …..

The 13ah battery will use the Sam 26F cell or a derivative they are for very low powered set ups and after 18 months or so deteriorate quite fast loosing a lot of capacity. The cells used are only 5.2a max current so are for low power only.

All cells have a max current draw and cells have a C rating at which they might be capable of sustaining current for about 30 seconds or for occasional use without causing damage, once you climb above that 1C rating cell damage can occur as heat builds up. All cells are usually safe to use at the 1C rating, 1C = the cell current draw where no damage occurs and most lower powered cells below 10a rating only at max 1.5c 2600mah = 2.6a draw, 2900 = 2.9a draw & 3500 = 3.5a draw etc , etc.
Cells at 10a rating have a higher 2C rating and the even higher 20/30a current rated cells have even higher C rating of 3 - 8 x C, these cells aren't usually high capacity mah rated cells and tend to be 2500/2600 mah.

In a battery that has 5 cells in parallel (5P) so eg, Sam 29E is 2900mah x 5 gives 14.5ah/14500mah capacity, the safe current draw is 14.5a from the controller. The cells will cope with 1.5C rating which is 21.5a current draw but only for short spells of use other wise as I found out damage (heat) will occur with prolonged spells of riding, in my case I was using 30mph + for many minutes of riding and cooked the cells a bit causing the loss of capacity. As mentioned I have mollycoddled them in later life to still give good use but it is a compromise I will be very happy with two more years use out of them.

The Sam 35E is similar to the 29E and a bit so so, it has a 2.5c rating of about 8a max current but at that level it suffers damage. It is better kept to 5a max per cell for occasional use which is near the 1.5C rating. Although the 35E in a 5P will have 17.5a/1C rating it's max C rating for longevity should be max 26a current draw for occasional use, all quite complicated until you can get your head around the figures. In all independent testing carried out the larger mah cells (under 10a rating) do give extra range form there capacity but after a few hundred cycles lose more capacity then the slightly lower mah cells and the difference can be as much as 10 - 15% in capacity over a few years.

There is a tipping point in 18650 cells where the cell mah has a limit and 3500mah is that limit, LG claim 3600 mah but the capacity is actually no better then other 3500mah cells. 2900/3000 mah is the best capacity limit for 18650 cells though the slightly higher ones can deliver the extra capacity if the rider uses lower power. Any cell can't deliver all the capacity stated at the max current draw of the cell, you have to except one or the other so it is a compromise. You have to accept either the max capacity at a low/lower current draw and eke out the range/mileage or max out the current for torque/power and except range will be about half. If you want range then use the PAS in the lowest assist level you are happy with and then use higher assist just occasionally for the hills or when the terrain gets tough, not using PAS when going down hill and even in some cases on level terrain if you have the fitness.

I haven't experience of using the 35E but have with the 29E and 29E is a good cell if you don't chuck more then 20amps at it for occasional max power. In the most part my 29E's (two batteries x 36v) only see 4 -5a max current which is plenty for my use even when towing a heavy trailer. If you derestrict the speed limit then the cells in both cases will be worked hard, it all depends on the application for use.

My 29E batteries are now in to year six and I can still get 30- 40 miles range using a Bafang Cst hub and a 20a controller, the batteries suffered about 4-5 years ago when I tried to use them with a derestricted mid drive that pulled (I believe) more current then thought, the cells suffered from I believe now heat damage causing higher internal cell resistance which led to loss of some cell capacity and a lot of voltage sag. Before that bit of abuse the batteries would see me 50-55 miles range, for my use now I get 30 -40 miles using PAS 1 or 2 and is ample for my local commute/errand & trailer towing, if I use PAS 3 I get only about 16 -18 miles use and the voltage sags quite badly due to high IR.

In a nut shell over a similar cycle the 35E will have about 5 - 8 % less capacity then 29E given a full 700 odd cycles, at the 150 cycles stage 35E loses 3% more capacity then the 29E, 29E retains 95.5% & 35E retains 92.5%.
At end of a full 700cycles 29E retains a tad over 90% capacity , the 35E will by the looks of things be below 90%.

This independant cycle graph uses a 2.5a charge rate and a 1a discharge rate for cycle testing, the voltage charge/discharge range is 4.1v max to 3.3v min.
See how poor the Sanyo/Panny is against the best the LG. The Sam 30Q is pretty disappointing.




The 35E should be fine the numbers are small.

It is a toss up on how you use the batteries vs current draw and speed.

I did say it will be a bit long ............

 

[scott gaza]

the exact same kit @ https://www.ebay.co.uk/itm/48V-500W-BAFANG-Electric-Bike-Rear-Hub-Wheel-Motor-Conversion-Kit-w-Display-/352540518911 for £125 less. The Sam 35E cells are on the 48v 17.5 ah battery nothing else in stock. PS: weight is down to cells used 48g per cell

 

[Nealh]

You don't have to worry about getting away with 14s/52v using a 48v controller as a 48v/13s controller can cope with the 52v max charge voltage of 58.8v, the 48v controller uses 60v capacitors so you are safe and the 14s voltage will soon drop to a more comfortable voltage of 56v.
52v over 48v isn't great deal more % wise though you will notice maybe a little more torque if you experience 48v first, the difference is a tad over 7.5%.

The most noticeable torque/speed difference noticeable is between using 24v/36v where it is 50% greater and 36v/48v where it is 33% greater.

 

[Nealh]

the exact same kit @ https://www.ebay.co.uk/itm/48V-500W-BAFANG for £125 less. The Sam 35E cells are on the 48v 17.5 ah battery nothing else in stock. PS: weight is down to cells used 48g per cell

Link no work to product.

 

[Fat Rat]

Hi welcome
I bet you didn't prepare for all that info

 

[Nealh]

Don't forget any kit from China will incur vat/import duty based on the stated value inc p&p and a handling charge.