Conversion of a Bultaco Sherpa

[Elektrosherpa]

Thanks for the info.
I guess I will just take the controller and go to an electric workshop and have the crimping done there,
rather than buying a 25/35/50 mm² crimping tool for 100 Euro, just to do 5 -10 crimps with it...

Meanwhile I have started planning the positioning of all the small components.

Another question arose from this:
Most wiring plans include a ~200 A fuse somewhere- do I need one, too,
additional to the fat 150 A fuse on top of the Kelly controller?


AND 2nd:
As clearly visible in the picture above, the tag on the controller says "350A".
So why do they put a 150A fuse on it???


Here is a first "design idea" what the bike might look like in the end:



(I hope Senor Bultó 's spirit will not haunt me for changing the name "Bultaco" to "Eltaco" and "Sherpa T" to "Sherpa E" )

 

[SlowCo]

(I hope Senor Bultó 's spirit will not haunt me for changing the name "Bultaco" to "Eltaco" and "Sherpa T" to "Sherpa E" )

:lol:
No, he would approve of it I'm sure!

 

[_GonZo_]

(I hope Senor Bultó 's spirit will not haunt me for changing the name "Bultaco" to "Eltaco" and "Sherpa T" to "Sherpa E" )

The Spanish original brand name is based on a surname; "Bultó"
"Eltaco" in spanish does not sound good at all. In Spain it will mean something like "The frock". Not sure about North and south American countries, but probably it sounds bad as well. So maybe better to reconsider it. :lol:

No problem about "Sherpa E"

 

[Elektrosherpa]

Dont worry-this "name" was just a result from playing around with picture editing.
Probably I will leave the Bultaco logo...

 

[SlowCo]

Bultaco-Eléctrico

E-Sherpa

Sh-E-rpa

 

[Elektrosherpa]

Because nobody replied until now, I want to repeat my question from above:

Most wiring plans include a ~200 A fuse somewhere- do I need one, too,
additional to the fat 150 A fuse on top of the Kelly controller?

 

[rsnoiser]

Hello, no need for two fuses in series.

Great build!

 

[j bjork]

If you can it would be better to move the fuse as close to the battery as possible.
That way you will have wiring etc after the fuse, and protected in case of damage.

Now you are only protected if something happens in or on the controller, or in the motor and wiring between the motor and controller.
However, if you have a bms that cuts at overcurrent it matters less.

 

[JimVonBaden]

Because nobody replied until now, I want to repeat my question from above:

Most wiring plans include a ~200 A fuse somewhere- do I need one, too,
additional to the fat 150 A fuse on top of the Kelly controller?

I added a 250 amp breaker so that I could isolate the battery when not in use, and when removing and installing the battery.

 

[Elektrosherpa]

Thanks for the replies

But I am still not sure how I can introduce those suggestions into my wiring.

To make my ideas clear, I have modified the wiring plan from the Kelly Controller Manual according to my purposes:



- deleted what I dont need (red)
- added a switch and a DC-DC Converter to provide 12V for lights etc.

The fuse in the red box seems to be the one which sits on the controller?
I think the cables from battery to controller won't be longer than ~30 cm (12") .

So would you add another fuse in this scheme, and if yes-where ???

 

[JimVonBaden]

The highlighted fuse is built into the Kelly Controller.


Mine is where it says Battery Disconnect:

 

[rsnoiser]

JimVonBaden is right, the main fuse is on top of the controller. You can move it next to the battery if you want. On my mini dirtbike who use a KBL Kelly Controller, the main fuse is between the battery (+) and the main contactor.

 

[Elektrosherpa]

The highlighted fuse is built into the Kelly Controller.


Mine is where it says Battery Disconnect:

So you added another 200 A fuse, additional to the 150 A one on the controller?
But (according to your wiring scheme) no fuse in front of the converter ("inverter") ?

And:
Why Kelly put a 150 A fuse on the KLS7245N controller?
Its data sheet says: "maximum continous current 100 A", but "30 seconds current 350 A" !
Wouldnt it make sense to have a 350 A fuse, rather than a 150 A one ?

 

[rsnoiser]

It’s probably a time delayed fuse. It can accept more than its nominal value for a limited time before blows. I dont know the datasheet of your fuse but perhaps you can send a mail to Kelly to have the answer.
An example of a time delay fuse:
https://www.farnell.com/datasheets/683342.pdf

 

[Elektrosherpa]

In the meantime, I have made a sprocket/chain protection from steel sheet metal,



mounted the controller to its final position
(originally I had planned to have it sit directly ON the motor brackets, but now it is hanging some cm above, so that as well the motor as the controller can be disassembled independently),

and made the right side cover from 3mm aluminium.



At the left side, there will be a similar cover. Between the two covers will be space for some of the electric stuff.
In the end, I will either put the original side covers on, or I use some blue decorative film to come close to the design which I showed earlier.

The controller will also get some kind of cover on top, to protect the wires (btw: in the picture above you can see the excess cable length-at about half of them will be cut off)

 

[JimVonBaden]

The highlighted fuse is built into the Kelly Controller.


Mine is where it says Battery Disconnect:

So you added another 200 A fuse, additional to the 150 A one on the controller?
But (according to your wiring scheme) no fuse in front of the converter ("inverter") ?

And:
Why Kelly put a 150 A fuse on the KLS7245N controller?
Its data sheet says: "maximum continous current 100 A", but "30 seconds current 350 A" !
Wouldnt it make sense to have a 350 A fuse, rather than a 150 A one ?

Not a fuse, a circuit breaker, switchable. Mainly as a backup, but also as a battery disconnect.

 

[kuoppis]

Fuses are more complicated than you may think. They wont blow at the amperage they are rated at. Too big fuse and it will never blow on short circuit if you battery cant provide the current. To get deeper into fuses you need to find time/current graph for your fuse.
Here is an example. This is for Cooper-Bussman high speed LMT fuses.


160A fuse will not blow even at 200A and can handle 300A for 60 seconds. It takes more than 400A to blow under a second.
Lets say you put a 315A fuse. Can your battery provide 1000A for a second to safely blow the fuse on a short circuit situation before the wires melt?

It is harder to choose a fuse on these EV applications since you wont be pulling constant power like in industry where the motor could be on for 24/7.
Thats why cables on EV are also smaller. 25mm2 copper cable constant current carrying capacity is somewhere 100-150A depending on insulation and ambient temperature.

Most people install too big fuse. Luckily we have controllers and BMS which will blow before the wires melt.

 

[Elektrosherpa]

Fuses are more complicated than you may think. They wont blow at the amperage they are rated at.
...
160A fuse will not blow even at 200A and can handle 300A for 60 seconds. It takes more than 400A to blow under a second.
...
Thats why cables on EV are also smaller. 25mm2 copper cable constant current carrying capacity is somewhere 100-150A depending on insulation and ambient temperature.
...

Thanks for these clarifications.
I haven't been thinking of the fact, that these are MELTING fuses. I know that in domestic AC installations, melting fuses are used for applications where a short over-tension must be tolerated (e.g. for the high starting current of machines).

Thanks too for the mentioning of cable dimensions. This would have been my next question:
In most lists, I find the information that for high currents enormous cable cross sections are required (for example: For a 300 A fuse, a 70 mm² cable is required) - but nobody seems to use such cables in EVs. Even the motor cables of the QS138 are not larger than (estimated) 7 mm diameter (= ~35 mm²)

So if I understand that right, I can use 25 or maximum 35 mm² cables without any problem?

 

[kuoppis]

Fuses are more complicated than you may think. They wont blow at the amperage they are rated at.
...
160A fuse will not blow even at 200A and can handle 300A for 60 seconds. It takes more than 400A to blow under a second.
...
Thats why cables on EV are also smaller. 25mm2 copper cable constant current carrying capacity is somewhere 100-150A depending on insulation and ambient temperature.
...

Thanks for these clarifications.
I haven't been thinking of the fact, that these are MELTING fuses. I know that in domestic AC installations, melting fuses are used for applications where a short over-tension must be tolerated (e.g. for the high starting current of machines).

Thanks too for the mentioning of cable dimensions. This would have been my next question:
In most lists, I find the information that for high currents enormous cable cross sections are required (for example: For a 300 A fuse, a 70 mm² cable is required) - but nobody seems to use such cables in EVs. Even the motor cables of the QS138 are not larger than (estimated) 7 mm diameter (= ~35 mm²)

So if I understand that right, I can use 25 or maximum 35 mm² cables without any problem?

Yes. For short durations like full acceleration smaller cross sections could be used. It wastes a little power and heats up but its acceptable since you wont be pushing full power through it constantly so the cables have time to cooldown. Industrial electric motors take starting current something like 6,5-8 times the nominal current and those cables are fine.
I would go same size cables as the motor has.

On battery size the amperage is even lower since the controller acts similiar to buck converter. And if im not mistaken that kelly is rated at 350A phase and 100A battery current.

 

[Elektrosherpa]

Not a fuse, a circuit breaker, switchable. Mainly as a backup, but also as a battery disconnect.

So battery PLUS is interrupted by the contactor, and battery MINUS by the switch?
Makes sense to me.
I ordered a battery switch for this purpose.
Maybe it will fit to the place where the fuel cock had been...

 

[Elektrosherpa]

Seems I can put most of the bigger electric parts underneath the fuel tank-even without modifying it:


(The blue and grey lines outline the fuel tank, seat and side cover)

The frame triangle is still free, for more components (and/or the charger)

And I finished the rear part.
Found some nice small turn signals,to put on the license plate base.

The rear light is only 0.75 W, the turn signals too.

I need a solid base for the license plate, because in France, license plates must be riveted to the vehicle...

 

[Elektrosherpa]

I am preparing the main contactor, and I am a little confused:
In the internet, found 2 pictures of my contactor with the diode, and they show exactly opposite orientations...

I put it this way now:

Is that right, or does the diode have to be the other way round?

 

[Elektrosherpa]

Nobody here can tell me which way the diode ????

 

[kuoppis]

Nobody here can tell me which way the diode ????

That is the correct way on the picture. Other way around and it would be a short.

 

[Elektrosherpa]

Thanks

In the meantime, I have shortened the motor cables.

Main contactor + DC-DC-converter both fit under the fuel tank, and are completely invisible: