I got an AmpedBike 26" front wheel drive kit a while ago. When I got it I bench tested it, and it worked fine.I got a mountain bike to use it on and when I got it all put together and wired up it didn't work. I tested components until I ascertained it was the controller. When I opened up the controller I found a big resistor was cooked beyond recognition. The color bands were no longer identifiable so I don't know what resistance it was. Is there a way to get a schematic to find out or is there some other way to find out what the value of that resistor is? Is it critical, can I just put a resistor in and pray? If all else fails, what controller can I use to replace it? Any and all help will be greatly appreciated, Thank you
Repair or replace AmpedBike controller
- Thread starter Limabean
- Start date
What value does the resistor read with your multimeter, with one end unsoldered from the board? (it's pretty likely it's not failed, it's normal for that resistor to get very hot due to the...er...minimal design of that part of the controller. 
).
The usual reason for a controller not working when wired up is a mis-connection/miswiring or if using connectors, a pin that has backed out of a connector, preventing a connection. Another can be if the "keyswitch/ignition" wire (sometimes called "door lock" or other things) is not connected to the battery positive, since this gives power to that resistor that then goes to the LVPS.
The resistor is essential to drop the voltage from the battery to the LVPS of the controller that takes the battery voltage and converts it to 12v and 5v to run the controller brain, gate drives, throttle, hall sensors, etc., as that LVPS doesn't usually handle more than around 30v at it's input. So it has to be the right resistance such that the current drawn by the LVPS causes a voltage across it equal to or greater than the difference between the input limit of the LVPS and the highest (full) voltage your battery will ever have on it. It also has to be physically large enough to dissipate the several watts or more of heat that are generated by this. The higher the battery voltage, the more heat this is (and typically the higher the resistance has to be).
Somewhere around here there are some threads discussing this part of controller design and/or repair, generically, that have some values for various controllers vs different voltage battery packs, but I couldn't find them in a quick search.
). The usual reason for a controller not working when wired up is a mis-connection/miswiring or if using connectors, a pin that has backed out of a connector, preventing a connection. Another can be if the "keyswitch/ignition" wire (sometimes called "door lock" or other things) is not connected to the battery positive, since this gives power to that resistor that then goes to the LVPS.
The resistor is essential to drop the voltage from the battery to the LVPS of the controller that takes the battery voltage and converts it to 12v and 5v to run the controller brain, gate drives, throttle, hall sensors, etc., as that LVPS doesn't usually handle more than around 30v at it's input. So it has to be the right resistance such that the current drawn by the LVPS causes a voltage across it equal to or greater than the difference between the input limit of the LVPS and the highest (full) voltage your battery will ever have on it. It also has to be physically large enough to dissipate the several watts or more of heat that are generated by this. The higher the battery voltage, the more heat this is (and typically the higher the resistance has to be).
Somewhere around here there are some threads discussing this part of controller design and/or repair, generically, that have some values for various controllers vs different voltage battery packs, but I couldn't find them in a quick search.
If you need to replace the controller, then it depends on what you need the system to do for you and what battery you have, and which motor, as to what controller would replace it.
If the controller has markings on it for it's voltage range and current limit, then you can start with those as limits for what the new one must match. The next step is deciding what features you want (display? PAS? Throttle? Programmability? etc), and eliminating any controllers that don't have those.
If you don't know what you want or need, the KT series of controller/display kits are a good place to start, as they come in a variety of capabilites, and have at least some customizability via the display settings, and if you need more there is OpenSource FirmWare available (threads here on ES about that) which you can install on them.
If the controller has markings on it for it's voltage range and current limit, then you can start with those as limits for what the new one must match. The next step is deciding what features you want (display? PAS? Throttle? Programmability? etc), and eliminating any controllers that don't have those.
If you don't know what you want or need, the KT series of controller/display kits are a good place to start, as they come in a variety of capabilites, and have at least some customizability via the display settings, and if you need more there is OpenSource FirmWare available (threads here on ES about that) which you can install on them.
motomech
10 MW
Jeeze, On my first ebike, I installed an Amped frt. geared motor kit. That was something like 12 years ago! The controller died on that too.
In the suceeding years, I killed a bunch of controllers and I found it seldom works to try and repair them. Soldering one thing will often kill something else, besides newer controllers have displays, have a softer start and just generaly work better.
I just replaced the controller on my Bafang SXW02 rear motored build to a 22 Amper (over the 17A that I was using) and since I didn't want to wait for the slow-boat from China, used this one;
It's a rebranded KT and I had to go with a 5-wire display as the old one had a 4-wire and I used this one:
Just a simple LED with a 3-speed limiter. I don't care about a bunch of info and three speeds is enough for a 22 MPH ebike. Took me a little while to figure out I had to turn the display on AND activate the mode button before the bike would move.
I also got a new cable just to make it easier to connect the Hall wires;
It's for a rear mount, so it will be a little long for the frt., so a shorter cable would be nice, but if not avail., it could be looped or shortened.
If your Amped kit is a geared motor, a 22A controller is perfect for it.
The only thing this controller doesn't have is cruise, but I'm ok w/that.
P.S. The Amped motor (which is actually a MXUS F07) was great. Eventually, the axle bearings got loose and I gave it to a kid in the neighborhood. The last time I saw him (a couple of years ago), he was still using it.
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