Understanding controllers

[jukos]

Hi!

I'm building my off road ebike that has gngelectric 48V 450W brushed motor. The controller is pulling peak 27Amps from my battery which is way too much. So what would be the right move to be able to run this motor lower peak power? Should I buy controller that is rated say peak max 15Amps or would this motor just burn that controller?

Thanks!

All the best
Jukka

 

[banbury frank]

Hi Amps X Volts = Watts to the motor most motors are 80% good at converting electrical energy to motive power so if you are using a 48 volt battery it will run at approx 50 volt X the amps drawn 50 X 27 = 1,300 WATTS LESS 20 % AROUND 1,000 WATTS

THIS IS WITH THE THROTTLE WIDE OPEN just don't open the throttle as much and the watts will drop to about 200 you only need the 1,000 wats to climb steep hills





How are you measuring the amps drawn

It also need a good size motor with heavy windings IE mass if you use a tiny motor and over volt it you will just waste the energy in heat and losses our motors weigh 6.5 kilos

Frank

 

[jukos]

Actually I haven't measured the amps yet, but my batterys BMS is shutting the battery down when throttle full open. I'm able to run slow speeds but giving full throttle it is obvious that amps are too high for my battery. So my question is how to limit the amps? Could I run the 450W motor with 350W controller or would that hurt the controller? So is it the controller or the motor that will decide the amps pulled from battery?

 

[banbury frank]

Hi the problem is the BMS not the controller you have a BMS for a small 250 watt motor

Answer Larger BMS

How old is the battery


Frank

 

[jukos]

I'm using two Kalkhoff pedelec Panasonic 26V 18Ah batteries in series. It is 52V, little overvolted. These are expensive high quality batteries so I'm little nervous using these. Single battery are used Panasonic 300W 26V motor so 450W 48V motor souldn't be too much for two batteries..in theory. Amps needed should be quite the same, but it seems that this 450W 48V motor is pulling much higher peak current that is too much for batteries I'm using. Is there any way to limit the motor?

 

[banbury frank]

Hi to limit the amps if you open the controller you can cut the current shunt

it will normally have 2 or 3 bridges please open the controller and photo the shunt it is where the power leads from the batter solder on the PCB we can cut them and you can always solder them back

Frank

 

[jukos]

Thanks Frank for your help. Here is some photos of the controller.

 

[banbury frank]

hi If you cut one off the links in the center above R23 lift the ends making a gap then try it if this don't work you can always solder back together

This will limit the amps the controller can draw


Frank

 

[jukos]

So do you mean that I'll pull one of the two wires off or pull the ends of two wires off? In other words, should I pull out the wire marked as red or pull the green 1&2 ends marked on the photo?

Thanks!

 

[flecc]

As an aside, a motor cannot hurt a controller. You can use a lower rated controller to reduce the motor consumption to what the battery can deliver comfortably.

 

[banbury frank]

Hi just cut one link in the center and lift up so it no longer makes contact



Frank

 

[jukos]

So I'll pull out that link I marked in red circle? Sorry for repeating my self but I need to be sure that I wont brake anything.

Thanks Flecc also for your reply.

 

[banbury frank]

Hi Cut one link in the center and lift a bit so it no longer makes contact

so if it don't work you can re solder

Frank

 

[jukos]

Ok, i'll try that. Thanks!

 

[jukos]

Yes! It worked just like it was supposed to! I measured 14 Amps peak which is good for my batteries. You can feel the lower power when driving hilly road, but this is good enough for me. And now I can drive without the risk of hurting my batteries.

Thanks again for your help!

Best regards
Jukka

 

[banbury frank]

Hi Good news

Frank