Using UK 13amp plug appliance wire to connect controller to battery?

[afia2k8]

Hi,

Sorry if this question sounds silly but I'm still learning about ebikes.

I got a 250w motor kit with this kt controller rated 7amps, max 15 amps. The plan is to use 2x power tool batteries in series - Each rated 20v 4ah, which will give me 4p10s = 40v 4ah (each cell is actually 3.7v 2000mah) and (potentially add another 2x batteries in parallel to make it 40v 8ah in the future). Will it be ok to use the wire I salvage from a standard 3 pin UK plug socket (usually has a 13amp max fuse) to connect the controller to the batteries? Or best to buy a 10 awg wire? I can't seem to find out what awg size the uk plug sockets are. Thank you.

Link for kt controller: https://www.aliexpress.com/item/33044427896.html

 

[Bikes4two]

Hi,

Sorry if this question sounds silly but I'm still learning about ebikes.

I got a 250w motor kit with this kt controller rated 7amps, max 15 amps. The plan is to use 2x power tool batteries in series - Each rated 20v 4ah, which will give me 4p10s = 40v 4ah (each cell is actually 3.7v 2000mah) and (potentially add another 2x batteries in parallel to make it 40v 8ah in the future). Will it be ok to use the wire I salvage from a standard 3 pin UK plug socket (usually has a 13amp max fuse) to connect the controller to the batteries? Or best to buy a 10 awg wire? I can't seem to find out what awg size the uk plug sockets are. Thank you.

Link for kt controller: https://www.aliexpress.com/item/33044427896.html

A UK 13A plug can be fitted with different sized flex/cable depending on what it was being used for and the fuses to go in the plug top range from 3A to 13A so before one can even consider the suitability of the flex you've recoverd, you need to know the size of it is - what was it used for - a washing machine, tumbel drier, bedside table lamp etc.?

 

[Nealh]

I would use silicone awg for the flexibility and no cracking of the outer sheath, but 10awg is a bit strong. 14awg is plenty for up to 30/32a.

 

[afia2k8]

A UK 13A plug can be fitted with different sized flex/cable depending on what it was being used for and the fuses to go in the plug top range from 3A to 13A so before one can even consider the suitability of the flex you've recoverd, you need to know the size of it is - what was it used for - a washing machine, tumbel drier, bedside table lamp etc.?

Apologies. I've attached a picture. The left grey cable was taken from a fridge freeze. The right black from a microwave. The middle is 10 awg.

I would use silicone awg for the flexibility and no cracking of the outer sheath, but 10awg is a bit strong. 14awg is plenty for up to 30/32a.

Thank you. By silicone do you mean the outer sheath? Does it matter if core is solid or stranded? Also can I mix 14awg cable with my already attached 10awg xt90 connector?

Thank you both.

 

[sjpt]

Do you know the sustained output current of those batteries? Just a single pair in series may not be able to provide the 7amps continuous of that controller.
I think a single one will be 2p5s, so 2p10s for the series pair.; you'll only get the 4p10s when you add your second pair.
(I have got mild Covid so my brain's a bit blurry ... excuse me if I'm wrong)

p.s. I expect you recovered the wire from the plug, not the mains wiring from the plug socket?

 

[Nealh]

Yes silicone covered multi stranded, it is more flexible for ebike use, twin and earth house wire or white goods flex is not really appropriate as in time the outer sheath may crack. Solid core is highly likely to break with bending and movement also not so good for soldering as there are no strands for the solder to suck in to.

 

[matthewslack]

Apologies. I've attached a picture. The left grey cable was taken from a fridge freeze. The right black from a microwave. The middle is 10 awg.



Thank you. By silicone do you mean the outer sheath? Does it matter if core is solid or stranded? Also can I mix 14awg cable with my already attached 10awg xt90 connector?

Thank you both.

Most mains wiring is rather small, because it is low current at high voltage. Ebikes need more current and so a thicker wire.

But you don't need much length, so I buy a few metres of the ideal cable each time, because it is usually a small part of the project cost.

Sometimes I use a three core cable, because it is already here, rather than order two core and wait. For example, the yellow or blue 'arctic' cables, available up to 6mm2 conductors .

 

[afia2k8]

Do you know the sustained output current of those batteries? Just a single pair in series may not be able to provide the 7amps continuous of that controller.
I think a single one will be 2p5s, so 2p10s for the series pair.; you'll only get the 4p10s when you add your second pair.
(I have got mild Covid so my brain's a bit blurry ... excuse me if I'm wrong)

p.s. I expect you recovered the wire from the plug, not the mains wiring from the plug socket?

You're right. 2x batteries in series will indeed be 2p10 (total 20 cells and 36v4ah). That should be enough to get me to town and back on my16 inch brompton. It's mostly to assist with the hills. How do I check the batteries' continuous discharge rate? These are the power tool batteries I have: https://service.kompernass.com/documents/326390_BG.pdf
A disassembly youtube video showing the custom cells of the batteries:

The batteries have BMS and cell balancing, but no low voltage cut off (it's on the power tools circuit). I assume low voltage cut off will be handled by my Controller?

Yes sorry, it's wire from appliance plug. Looks like it's best to use 14 awg wire or lower. Hope you get well soon! I've had covid recently too, i'm better but still coughing here and there.

Yes silicone covered multi stranded, it is more flexible for ebike use, twin and earth house wire or white goods flex is not really appropriate as in time the outer sheath may crack. Solid core is highly likely to break with bending and movement also not so good for soldering as there are no strands for the solder to suck in to.

Most mains wiring is rather small, because it is low current at high voltage. Ebikes need more current and so a thicker wire.

Buf you don't need much length, so I buy a few metres of the ideal cable each time, because it is usually a small part of the project cost.

Sometimes I use a three core cable, because if is already here, rather than order two for and wait. For example, the yellow or blue 'arctic' cables, available up to 6mm2 conductors .

Thanks guys! Looks like a 14 awg or lower wire will suffice. I'll just get a 1 metre stranded black and red off ebay.
What do you mean 3 core cable and arctic cables? You've lost me there. Do you have a link?

 

[Nealh]

3 core is better known as twin and earth type.
Artic Blue & Yellow is the heavier duty stuff used for 240v & 110v for temporary exterior power supply.

 

[sjpt]

How do I check the batteries' continuous discharge rate?

Sadly, with difficulty. Even though it's an important figure for ebike batteries it very often isn't quoted. I can't see it quoted in your battery specs. It doesn't mention the cells used either.

Mainly an issue for people who buy cheap direct drive kits that need high currents, and cheap batteries to go with them that can't provide the current. Your current needs are much lower than that, but that battery isn't designed for ebikes. It's quoted charging rate is 3.5amp, and I think discharge rates are usually quite a bit higher so it will probably be OK. Nealh can probably give you a better idea.

 

[Nealh]

Most decent well know branded power tool cells are of high rate discharge, one reason the Sam 30q was developed for this reason. Even a decent drill needs a lot of torque/power to drive home say a 4" screw so the cells need to be able to deliver. One would assume they are min 10a and could be more, without knowing the actual cell used one won't know the current rating or whether they will be much kop.

 

[matthewslack]

You're right. 2x batteries in series will indeed be 2p10 (total 20 cells and 36v4ah). That should be enough to get me to town and back on my16 inch brompton. It's mostly to assist with the hills. How do I check the batteries' continuous discharge rate? These are the power tool batteries I have: https://service.kompernass.com/documents/326390_BG.pdf
A disassembly youtube video showing the custom cells of the batteries:

The batteries have BMS and cell balancing, but no low voltage cut off (it's on the power tools circuit). I assume low voltage cut off will be handled by my Controller?

Yes sorry, it's wire from appliance plug. Looks like it's best to use 14 awg wire or lower. Hope you get well soon! I've had covid recently too, i'm better but still coughing here and there.







Thanks guys! Looks like a 14 awg or lower wire will suffice. I'll just get a 1 metre stranded black and red off ebay.
What do you mean 3 core cable and arctic cables? You've lost me there. Do you have a link?

Just ebay search arctic cable and you'll see it. But it's always 3 core, just I always have some around, so for prototyping does the job.

 

[afia2k8]

Most decent well know branded power tool cells are of high rate discharge, one reason the Sam 30q was developed for this reason. Even a decent drill needs a lot of torque/power to drive home say a 4" screw so the cells need to be able to deliver. One would assume they are min 10a and could be more, without knowing the actual cell used one won't know the current rating or whether they will be much kop.

Someone did a test of the Parkside cells here. The ones I have are newer though. From the graph it looks like 15amp continuous discharge will be ok? From what people said it is "Looking through the comparator, it seems the closest “Major Brand” cell to this is the Samsung INR18650-20Q. It seems they are almost, but not quite, identical chemistry inside. The discharge curves at 5A, 10A, and 20A are almost identical. The 20Q doesn’t voltage sag as much at the beginning of the curve, but drops off a bit earlier at the end (lower capacity, even though they’re rated the same). The comparator doesn’t have a discharge curve for the 20Q at 30A, but the Parkside cell didn’t do well with that test. "

Test/review of Parkside INR18650E 2000mAh (Blue)

Parkside INR18650E 2000mAh (Blue) Official specifications: Capacity: 2000mAh Nominal voltage: 3.7V Type: LiIon Voltage for 5: 20V The batteries has been removed from a unused Parkside 2.0 PAP 20 A1 battery pack. The marks from the spot...

budgetlightforum.com

Is there a way I can test the continuous discharge rate? I have a multimeter.

Additionally, will having 4x packs at 4p10s 36v8ah be less stressful on the cells than only having 2p10s at 36v4ah? Thank you.

 

[matthewslack]

Is there a way I can test the continuous discharge rate? I have a multimeter.

Additionally, will having 4x packs at 4p10s 36v8ah be less stressful on the cells than only having 2p10s at 36v4ah? Thank you.

Second bit first: yes, the current is split over twice as many cells, so only half the current per cell.

First bit: you need more than just a multimeter to measure high currents. Usual method is to use a 'shunt', which is a special low value but accurate resistor, and then measure the small voltage across the shunt, and convert that into current. Look up 'current measuring shunt', and there are no doubt YouTube videos about it.

 

[Nealh]

One can wire in a watt meter inline, use it not only for current but also wh's used.

 

[Nealh]

What range are you after ?
And do you typically know what current you expect to use mostly?

 

[afia2k8]

What range are you after ?
And do you typically know what current you expect to use mostly?

If possible, 3 miles throttle only should be enough. It's mostly to help me overcome hills on my commute whilst keeping the Brompton light. Then I could leave another pair of total 36v4ah at work for the commute back.

I've linked the controller in the initial post. It says rated 7amps with max 15amps. For a 16 inch akm74s 250w motor. Thank you.

 

[Nealh]

With the parksides at 7a discharge one will get about 3.2ah from a pair and if planning on maxing them out about 2 ah total.
At a modest 2a discharge then one might see 3.8ah to give maybe up to 15 miles in assisted range if ones wh per mile usage is sub 9wh.

My smallest battery is 12s2p using Lg Hg2 's for 6 ah/264wh typically I can eke out 30 miles.

 

[afia2k8]

With the parksides at 7a discharge one will get about 3.2ah from a pair and if planning on maxing them out about 2 ah total.
At a modest 2a discharge then one might see 3.8ah to give maybe up to 15 miles in assisted range if ones wh per mile usage is sub 9wh.

My smallest battery is 12s2p using Lg Hg2 's for 6 ah/264wh typically I can eke out 30 miles.

Wow, didn't expect to get that much assisted range! That's pretty good. What do you reckon if throttle only? So the pair of 2x batteries won't have any problems meeting the 15amp max continuous discharge rate?

Once the motor kit arrives from China I'll update everyone with the actual figures. Thank you.

 

[Nealh]

For the pair nominal wh will be approx.4ah/144wh
With throttle use one will draw 7a from each pack so one might see approx. 3.2ah/115wh from a pair. With throttle use wh per mile is going to be high so one would say about 20wh + pm or maybe 6 miles for the pair but depends how bad they do actually sag as the voltage lowers. Graphs are one thing but real world usage is another.