36v Vs 48v

[anon4]

that depends on your current configuration and what you want to achieve.
As NealH has already pointed out, don't just connect a 48V battery to a 36V system without checking.
Provided that your system can support dual voltage, then the 48V will give 30% more power and also can achieve higher derestricted speed. However, there is no free lunch, even if you only occasionally need the higher performance. Typically, motors can tolerate higher current but higher current produces higher magnetic flux, when the flux reaches the limit that the rotor can take (magnetic saturation), the extra voltage does not produce extra power, just more heat.
I sell both SWX02 in 36V and in 48V. They are built differently. The 36V has winding code 13, the 48V has winding code 16. You get much more torque at low speed for climbing with the 48V version.

It's my modified Carrera Vulcan, I have a dual voltage controller in there already. How do I tell if it would benefit from extra voltage? It's a bigger motor with sturdy wiring so I'm sure it can take it but if it's not wound for it well... There are no winding codes on the casing.

 

[Woosh]

It's a bigger motor with sturdy wiring so I'm sure it can take it but if it's not wound for it well... There are no winding codes on the casing.

please post a picture.

 

[anon4]

please post a picture.

Can be seen here, I'll get a closeup when I get home https://drive.google.com/file/d/1lBmfvuyAtNAabkE71cOkXMBw6Jss9IeL/view?usp=drivesdk

 

[Woosh]

what the current noload speed is with your 36V battery?

 

[anon4]

what the current noload speed is with your 36V battery?

Couldn't say for sure as the Speedo is wrong, haven't had a chance to calibrate it. It's around 20mph I would say though give or take 1

 

[Woosh]

here is an estimate in optimal conditions using the motor simulation tool. It's slightly optimistic being based on the Bafang BPM which has a larger motor core than yours.
The larger motor core has higher saturation. Your motor may saturate at around 45-50NM so climbing performance may not be as good as the chart suggests.

https://www.ebikes.ca/tools/simulator.html?bopen=true&batt=B3614_PF&batt_b=B4814_EZ&motor=MBPM&motor_b=MBPM&axis=mph

 

[anon4]

here is an estimate in optimal conditions using the motor simulation tool. It's slightly optimistic being based on the Bafang BPM which has a larger motor core than yours.
The larger motor core has higher saturation. Your motor may saturate at around 45-50NM so climbing performance may not be as good as the chart suggests.

https://www.ebikes.ca/tools/simulator.html?bopen=true&batt=B3614_PF&batt_b=B4814_EZ&motor=MBPM&motor_b=MBPM&axis=mph

Thanks for that. It's advertised at 50nm torque on halfords

 

[Wisper Bikes]

Comments on this thread suggests that a 48V system is superior to a 36v.

If that’s the case why are most systems on the market 36V?

 

[Woosh]

Comments on this thread suggests that a 48V system is superior to a 36v.

If that’s the case why are most systems on the market 36V?

it's a trade off between maximum torque and weight/cost. A system designed to peak out at 21mph will be optimally used at two third of its max speed, in this case 15mph, and is therefore more than enough to climb hills at 10mph and assist at up to 15mph.
However, there is an important number of customers who need higher hill climbing performance because of their weight or challenging terrain.

 

[anon4]

it's a trade off between maximum torque and weight/cost. A system designed to peak out at 21mph will be optimally used at two third of its max speed, in this case 15mph, and is therefore more than enough to climb hills at 10mph and assist at up to 15mph.
However, there is an important number of customers who need higher hill climbing performance because of their weight or challenging terrain.

You forgot laziness and towing, both of which are me also I think a lot of vendors were lead to believe that 36v was the max legal, which I've since heard isn't true as long as it stays below the speed limit

 

[anotherkiwi]

Comments on this thread suggests that a 48V system is superior to a 36v.

If that’s the case why are most systems on the market 36V?

- Batteries are cheaper so the entry level price point is easier to sell
- Remember that the first generation pedelecs were often 24v so the 36v "standard" is already a 50% increase in performance from then
- There is some ambiguity in the wording of EN15194 around whether maximum volts is 48v or nominative maximum volts is 48v
- ... your other reason goes here

 

[Woosh]

- Batteries are cheaper so the entry level price point is easier to sell

the 48V charger costs $1-$2 more but the batteries are sold by WH. All things equal except the voltage, the motor costs about $10-$15 more due to smaller volume and more expensive copper charge.

 

[anotherkiwi]

the 48V charger costs $1-$2 more but the batteries are sold by WH. All things equal except the voltage, the motor costs about $10-$15 more due to smaller volume and more expensive copper charge.

At luna cycle a 17.5 Ah battery is $100 more expensive in the 48v version. Normal, there are 3 more cells in each series chain...

If you sell 36v and 48v batteries that have equal Wh then the 48v battery will have fewer parallel groups. You must use cells with higher discharge and lower capacity to have a 48v battery with equal Wh that also performs as well as a 36v one on very steep terrain.

 

[Woosh]

If you sell 36v and 48v batteries that have equal Wh then the 48v battery will have fewer parallel groups.

that's correct. 36V batteries are 10S5P, 48V batteries are 13S4P using the same BMS. The main thing is the 48V motor is produced with higher magnetic saturation threshold and at the same power, heat loss is slightly better too, in the same way that 220V system is more efficient than 110V system.

 

[Wisper Bikes]

What a great thread! I also understand that the higher Voltage means that the current can be reduced, minimising pressure on cables and connections. Is this the case or am I missing something?

 

[anotherkiwi]

What a great thread! I also understand that the higher Voltage means that the current can be reduced, minimising pressure on cables and connections. Is this the case or am I missing something?

Reducing current will help the controller run cooler.
36v @ 15A = 540W
48v @ 12A = 576W so a little more power, less heat in theory

There is a bit of calculation to be done to get the right compromise:

I want to run my GSM at 44.4v because I need more RPM at the pedal to stop back EMF (I spin too fast...). I don't really need any more power than I have now. My 36v controller can't handle 15 A x 44.4v, it gets too hot and the thermal cutoff kicks in as soon as I am in assistance level 4 or 7.5 Amps! That means when I am pulling >330W there is a huge amount being lost as heat with the extra voltage. The same controller is fine up to 610W @ 36v

I have noticed that the motor runs smoother at 44.4v and is a lot quieter. The sensation of spinning faster and not going over assistance level 3 is no real problem as long as you are in the correct gear for the slope. As I was working at the time I didn't do any serious hill testing last time I ran at higher voltage. At the moment I am waiting for a weather window to continue testing.

I have a suspicion that I won't need much more than 250W on the trike:
- the motor is used to climb hills, at the moment I can climb hills I can't climb on an upright. At 6 km/h... If the motor allows me to double that speed or even increase to 10 km/h that is fine for me (on those types of hill - think >15% gradient )
- the motor is used to accelerate to 25 km/h in stop and go traffic, I can pedal easily to >35 km/h on the flat on the upright and the trike is wicked faster

A 48v capable 10 or 11 Amp controller will suit me fine. It has to be 48v for the 63v caps inside, my 36v one has managed with 49.8v hot off the charger but that just squeaks under the 50v rating of the caps, I don't want to tempt the devil...