Run 48v bike on 36v
- Thread starter Andreas_t
- Start date
Voltron
1 MW
It depends on the controller. Sometimes it will work, but other times it will think the battery is too low and cut out. Its safer than the other way, running 48v on a 36v, as that can lead to the battery getting drained too far sometimes.
Jon NCal
1 kW
The controller may have a low voltage cutoff of around 42 volts. Sometimes there is a jumper or switch to change that setting.
Thanx alot för the help guys! I found two Pictures of the gear and it seem like there is a cut off at 39 volts. Anyone can identify the controller and knows if it is possible to remove the cut off from this model?
The motor is Dapu and maby also the controller is the same brand?
Regards!
The motor is Dapu and maby also the controller is the same brand?
Regards!
Attachments
You definitely don't want to remove it; that will kill the battery. Reducing it is the key.Andreas_t said:
In general there will be a voltage divider going to either a comparator or an A/D input on a processor. To fix that you have to change the divider ratio so that the cutoff voltage decreases from about 39V to about 30V. Usually it's a one resistor change - but figuring out where the resistor is and what to change it to requires an EE background.
billvon said:
Thanx! Is this true even if there is a BMS on the battery, correct?
I sIf I manage to get the resistor changed to lower the cut off limit, will I face any other issues? Will the BMS be a problem? What will the difference in Power and speed be compared to a 48 volt system?
Regards!
Yes. BMS is separate and should not be the primary means to discontinue discharge when the battery is dead.Andreas_t said:
I am assuming you are swapping the battery completely (including the BMS) right? You're not just removing some cells from the top of an existing battery, are you? That would be bad.
Top wheel speed, assuming a "normal controller" i.e. no phase advance, will be reduced by 25%. Actual speed reduction will likely be less, since drag goes down at lower speeds.
billvon said:
If I mange to change the cut off limit the plan is to use the 36 volt battery that I already have.
Top wheel speed, assuming a "normal controller" i.e. no phase advance, will be reduced by 25%. Actual speed reduction will likely be less, since drag goes down at lower speeds.
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Good to know. Probably the speed will be enough anyway
Just to clarify the background of this project. I have an option to buy a 25km/h 250 W bike with a 36 volt battery at good price. I also have an option to buy the kit in the pic above at a good price. The kit is 48V 500W. This is why I am trying to figure out if there is a way to make this work out. The plan B would be to convert the fully functioning 36 volt battery to a 48 volt.
Regards!
wturber
1 MW
Andreas_t said:
I run a 48v system using 36v batteries by using a boost converter. The particular boost converter I use is relatively inexpensive and will supply about 1150 watts of power at 54V. There are some details of what I did in the link in my signature.
Thanx for the idea! I actually red the whole thread about your conversion. Its a really nice idea but unfortunately there is not space on my bike since i want an OEM-look.
I have decided to take the economic punch and convert the original 36 v battery to a 48v dito.
Regards!
I have decided to take the economic punch and convert the original 36 v battery to a 48v dito.
Regards!
docw009
1 MW
You might get a controller that can run 36V/48V if you want to mix batteries. That's what I do.
Not worthwhile or easy to actually convert a 36V battery to 48V. I tried it once. If you were going to buy the cells and frankenstein a battery, it's better to make a 12 volt battery with its own BMS.
A 36V bike goes faster on 48V, and a 48V bike goes slower on 36V. I don't ride at max speeds, but for a given effort in pedal assist at lower speeds you might find the speed changes about 2mph while the difference is max speeds is about 4 mph.
Not worthwhile or easy to actually convert a 36V battery to 48V. I tried it once. If you were going to buy the cells and frankenstein a battery, it's better to make a 12 volt battery with its own BMS.
A 36V bike goes faster on 48V, and a 48V bike goes slower on 36V. I don't ride at max speeds, but for a given effort in pedal assist at lower speeds you might find the speed changes about 2mph while the difference is max speeds is about 4 mph.
eCue
10 kW
The Chinese kt controllers that comes packaged with the lcd5 or lcd3 display have adjustable voltage cut off points plus 30 more useful features. I use a 9 fret 36/48v 22A max version rated for the 351 - 500w motors.
docw009
1 MW
The OP is looking at a kit with the SW900 display. Programming manual says the LCD can be set for 24/36/48, but it will need a controller that doesn't have a hard LVC limit. Could be easy to change. Could take some EE detective work.
markz
100 TW
ebay seller Sunwin sells controllers with a Low Voltage Cutoff "jumpered" on the pcb. There is lettering right on the pcb. I've desolered a few back to 48V lvc.
wturber
1 MW
eCue said:
My 48V KT controller would only let me roll the cuttoff voltage from 40v down to 39v. A controller with a 36/48v option seems like a good choice here.
