Conversion kits and the law

[RossG]

I've often wondered though does that extra 33% of speed, torque etc. result in 33% more wear on your motor ?
After all when you buy a car you may have a choice of a 1.2ltr or you could have the 1.5ltr for a bit more oomph, the extra power comes from the larger engine. In the case of a ebike you can do all sorts of things to make it go faster increase torque and so on, but at the end of the day it's still the same motor you're just driving it harder.
I know in most cases a 36v ebike motor will run quite happily at 48v but is it not more efficient running at a lower voltage as far as wear and tear are concerned.

 

[Woosh]

when you run a motor outside its optimal environment, the probability of wrecking it increases much more that just the percentage of boost.
it's still a fairly low probability though.
The most likely outcome is stripping the internal gearbox and clutch and burning the Hall sensors.

 

[bagss2]

Hi folks,

I'm a complete newbie reading this thread and many others on the forum, in order to try and get my head around the electrickery side of things.

I have a used bike currently/hopefully winging its way to me, my first step on the ladder. It's a manufactured 24v bike (front-hub brushless motor) with a 24v 8.4ah battery.

From advice received by knowledgable members in another thread, I am resigned to 1. the inevitable need for me to replace the battery and 2. that the current battery spec is 'a bit bobbins'.

My question is therefore: Can I consider a 36v 10ah or 36v 12.8ah battery to replace my 24v (these options are available as 'straight swap' via Yose Power, alongside 24v 10ah / 24v 16ah) - or will doing so fry the bike?


Cheers, Baggers.

 

[Darthpaul]

I’ve got a 36v 250w rear hub paired to a 48v battery and can confirm when on the work stand it maxs out at 23mph. Stick my 15st lump on it and I’m sure it’ll struggle to get to that on the road! But I can get up a local 7% hill at 15mph without even getting out the saddle, which is mainly why I picked up a 48v batt so I knew I at least wouldn’t struggle on the inclines.

 

[Benjahmin]

Hi folks,

I'm a complete newbie reading this thread and many others on the forum, in order to try and get my head around the electrickery side of things.

I have a used bike currently/hopefully winging its way to me, my first step on the ladder. It's a manufactured 24v bike (front-hub brushless motor) with a 24v 8.4ah battery.

From advice received by knowledgable members in another thread, I am resigned to 1. the inevitable need for me to replace the battery and 2. that the current battery spec is 'a bit bobbins'.

My question is therefore: Can I consider a 36v 10ah or 36v 12.8ah battery to replace my 24v (these options are available as 'straight swap' via Yose Power, alongside 24v 10ah / 24v 16ah) - or will doing so fry the bike?


Cheers, Baggers.

The motor would probably be OK, the controller may not be. The main weakness would be the inrush capacitors and their rated voltage. A fully charged 36v battery is actually around 42v, so the capacitors need to be rated above this voltage otherwise they will release the magic blue smoke.

 

[RossG]

when you run a motor outside its optimal environment, the probability of wrecking it increases much more that just the percentage of boost.
it's still a fairly low probability though.
The most likely outcome is stripping the internal gearbox and clutch and burning the Hall sensors.

There's a modification for my car available via firmware that increases torque and overall engine performance. However reading online from what I can gather many who have taken that path have reported clutch problems as a result. Think I'll give that mod a miss.

 

[Nealh]

A 24v /7s bike will need a new 36v/10s controller as you are asking for 50% more power, I don't know what the capacitors are rated at but 50v would be the minimum for 36v. My 24v Swizzbee can handle 8s/ 33.6v.
On a side note any 36v bike can run at 12s if you limit the voltage to 12s x 4.15 or 49.8v total pack voltage.

 

[bagss2]

The motor would probably be OK, the controller may not be. The main weakness would be the inrush capacitors and their rated voltage. A fully charged 36v battery is actually around 42v, so the capacitors need to be rated above this voltage otherwise they will release the magic blue smoke.

Thank you for this.

So is a replacement controller readily available?

Presumably, to swap ovee, it needs to be the same physical size as the original, rated 36v and for a brushless motor?

Is the wiring to/from these things fairly interchangeable/plug'n'play? I've seen them online but never to this point understood what's what...

The bar-mounted control on the bike is one of the old-school '980' ones, with a few LED lights but no LCD screen. Presumably this needs factoring in also?


Cheers, Baggers.

 

[bagss2]

A 24v /7s bike will need a new 36v/10s controller as you are asking for 50% more power, I don't know what the capacitors are rated at but 50v would be the minimum for 36v. My 24v Swizzbee can handle 8s/ 33.6v.
On a side note any 36v bike can run at 12s if you limit the voltage to 12s x 4.15 or 49.8v total pack voltage.

Thanks for this reply.

Please forgive my ignorance - but what are these 's' numbers of which you speak?


Cheers, Baggers.

 

[Nealh]

24v is 7 cells or cell groups in series or 7s , 24v will charge to 29.4v maximum.
With lithium each cell is 4.2v maximum charge 7 x 4.2v = 29.4v.

36v is 10 cells or cell groups in series or 10s, 36v will charge to 42v maximium.
10 x 4.2v = 42v max charge.

12s is an in between voltage and not 100% 48v , with 12s you have to stop the charge at 49.8v or 4.15 per cell to work with a 36v controller.
48v is 13s or 13 cells in series and 13 x 4.2v = 54.6v max charge.

 

[bagss2]

24v is 7 cells or cell groups in series or 7s , 24v will charge to 29.4v maximum.
With lithium each cell is 4.2v maximum charge 7 x 4.2v = 29.4v.

36v is 10 cells or cell groups in series or 10s, 36v will charge to 42v maximium.
10 x 4.2v = 42v max charge.

12s is an in between voltage and not 100% 48v , with 12s you have to stop the charge at 49.8v or 4.15 per cell to work with a 36v controller.
48v is 13s or 13 cells in series and 13 x 4.2v = 54.6v max charge.

Thank you Neath - really helpful explanation.

So from a 24v base, 36v is a helpful real-world upgrade, subject to a 36v controller that can handle 42v?

Re. battery 'ah' figures, do these simply mean more range the higher you go? Or do ah figures have further implications?


Cheers, Baggers.

 

[Nealh]

All 36v controllers can handle 42v, as 36v is the nominal battery voltage. The min usable voltage for a36v battery is about 32v and the max is 42v.

The Ah is the capacity and simply as you have said is about the range the higher the Ah the more range. Sometimes batteries are quoted in Wh terms which is simply the voltage X Ah and is a more meaningful figure to quote range. One divides the general category they fit into by the total battery Wh to get an idea of range they should expect.
Typically a really fit rider can use about 7 or 8 wh per mile, a regular rider who is reasonably fit might use 12-14wh per mile and an unfit rider about 20wh per mile.

 

[bagss2]

All 36v controllers can handle 42v, as 36v is the nominal battery voltage. The min usable voltage for a36v battery is about 32v and the max is 42v.

The Ah is the capacity and simply as you have said is about the range the higher the Ah the more range. Sometimes batteries are quoted in Wh terms which is simply the voltage X Ah and is a more meaningful figure to quote range. One divides the general category they fit into by the total battery Wh to get an idea of range they should expect.
Typically a really fit rider can use about 7 or 8 wh per mile, a regular rider who is reasonably fit might use 12-14wh per mile and an unfit rider about 20wh per mile.

More great info! Thank you!

Now potentially the daftest question of all:

With a 36v battery and a 250w motor, naturally I assume a 36v-250w controller is in order. What effect would a 36v-350w controller have?


Cheers, Baggers.

 

[Nealh]

The 250w /350w rating take no notice of, what is important is the current they supply.
Most 250w controllers are about 7a nominal , 15a max.
All controllers no matter what the so called 'w' rating is vary.
17 or 20a is acceptable for a 250w hub and will give you more power/torque.

My new small Bafang 250w G370 hub is due for delivery today and I will be marrying it with a 22a KT controller.

 

[WheezyRider]

The 250w /350w rating take no notice of, what is important is the current they supply.
Most 250w controllers are about 7a nominal , 15a max.
All controllers no matter what the so called 'w' rating is vary.
17 or 20a is acceptable for a 250w hub and will give you more power/torque.

My new small Bafang 250w G370 hub is due for delivery today and I will be marrying it with a 22a KT controller.

Bafang G370, nice I've heard good things about them. Are you going for a fast wind model?

Ok, getting this thread back on track...what have we learned?

1) EN15194 does not apply to kits, hopefully they are ok so long as they comply with the basics of the UK 2015 act (15.5 mph +/- 10% limit, 250W continuous output motor and PAS post 2016) as the EU rules only apply to bikes sold commercially, not DIY systems.

2) DoT says they are not happy about derestriction, but they don't clarify what level of barrier to derestriction is acceptable - given that systems are produced for mass markets with different legislation. Furthermore, derestriction does not appear to be addressed specifically by any UK legislation.

3)It seems ok to be able to use a higher voltage for a kit bike than the motor is specified for.

Is that a good summary?

 

[Nealh]

I want torque so have the 201rpm G370, at 22a it should manage 19mph . My Big Bear kit 201 BPM topped 19.5 at 20a.

 

[WheezyRider]

I want torque so have the 201rpm G370, at 22a it should manage 19mph . My Big Bear kit 201 BPM topped 19.5 at 20a.

What sort of tyres are you running? I'm using 40-622 Schwalbe Almotion on the rear of my main bike with a generic Bafang 250W 36V and with the larger circumference of the 40 width, compared to narrower tyres, it will just about hit 20mph derestricted (off road of course ). I find the wider tyre saves my backside too on our pot hole covered streets. Then the rolling resistance of the Almotion is incredible for a wide tyre. It is a bit pricey though for a tyre.

 

[flecc]

derestriction does not appear to be addressed specifically by any UK legislation.

The DfT had a consultation with interested parties including us, before the 2015 amendment. Here's their statement following that:

Summary of Government response to consultation

2.The Department for Transport has considered the responses to this consultation and supports recommendations to harmonise power limits (from 200 Watts to 250 Watts) with similar provisions in place across Europe. This will provide consumers with access to a wider range of electrically assisted cycles.

Extracts from intentions:

The DfT and Police are aware that electric bikes currently sold and used in the UK are fitted with 250W motors, they do not intend to become involved in prosecuting those that sell or ride them. The use of an "Off Road Button" however is strictly forbidden now and is specifically mentioned in documents appertaining to new and existing guidelines.

"Grandfather rights" will apply to all bikes sold before the new regulations come into force. So any changes will not be retrospective.

Note the sentence I've highighted in bold, that means dongles too. Their term "Off Road Button" they've said refers to any assist speed restriction defeat device.
.

 

[WheezyRider]

The DfT had a consultation with interested parties including us, before the 2015 amendment. Here's their statement following that:

Summary of Government response to consultation

2.The Department for Transport has considered the responses to this consultation and supports recommendations to harmonise power limits (from 200 Watts to 250 Watts) with similar provisions in place across Europe. This will provide consumers with access to a wider range of electrically assisted cycles.

Extracts from intentions:

The DfT and Police are aware that electric bikes currently sold and used in the UK are fitted with 250W motors, they do not intend to become involved in prosecuting those that sell or ride them. The use of an "Off Road Button" however is strictly forbidden now and is specifically mentioned in documents appertaining to new and existing guidelines.

"Grandfather rights" will apply to all bikes sold before the new regulations come into force. So any changes will not be retrospective.

Note the sentence I've highighted in bold, that means dongles too. Their term "Off Road Button" they've said refers to any assist speed restriction defeat device.
.

That's really interesting Flecc. Obviously, a bit red button marked "off road", or "go faster dongle" is illegal, but an LCD screen that can be programmed for different wheel sizes or legislations seems a grey area. Nowadays, you even have Blue tooth phone programming of controllers (way above my head!) - as usual the tech is way ahead of the law.

 

[flecc]

That's really interesting Flecc. Obviously, a bit red button marked "off road", or "go faster dongle" is illegal, but an LCD screen that can be programmed for different wheel sizes or legislations seems a grey area. Nowadays, you even have Blue tooth phone programming of controllers (way above my head!) - as usual the tech is way ahead of the law.

I've always maintained that such LCDs are technically illegal since the speed alteration is under the riders control, which is strictly forbidden. But in pedelec law the "blind eye of the law" often prevails where expedient.
.