Newbie problem. Putting 60v on 48v controller

Scoot 787

100 µW
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Dec 19, 2018
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New to this forum. I screw up my new 1000w scooter putting 60v thru my 48v controller. It works fine for about 15km with no problem although controller was a bit hot. The brushed motor that is rated for 48v 1000w has no problem handling the 60v and is quite cool to the touch. The 60v give the scooter a lot more top speed than on 48v. I connect three 4s and one 3s lipo in series to get the 60v. This morning, the scooter would not move, although the brake light, battery indicator and head light were all functioning properly. The controller is rated for 48v and 30A, but the capacitor inside it show 63v 220uf. I have attached some pictures of the controller. Is it possible for me to get the controller working again by changing to a 80v capacitor? If so, should the capacitance be at 220uf as well? Thanks in advance for all the input.
 

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Not sure whether I'm doing it correctly to check the capacitor. I connect power to my three 4s lipo (48v) again to check whether the scooter return to life, but it still won't move. Try to check each individual capacitor to see whether it has busted by checking the voltage. The big four IMG_20181219_210111.jpg63v capacitors is still holding voltage at around 42v. But the smaller 25v and 50v capacitor show nothing. Does that mean if I change the two smaller capacitor, I can get the controller to work again?
 
Scoot 787 said:
Not sure whether I'm doing it correctly to check the capacitor. I connect power to my three 4s lipo (48v) again to check whether the scooter return to life, but it still won't move. Try to check each individual capacitor to see whether it has busted by checking the voltage. The big four capacitors is still holding voltage at around 42v. But the smaller 25v and 50v capacitor show nothing. Does that mean if I change the two smaller capacitor, I can get the controller to work again?
No. The voltage being zero on those caps does not mean the capacitors are bad. Most likely you blew the housekeeping supply by overvolting it, and now there is no power supply to those capacitors. The HK supply is either a switcher or a linear IC, and may have a voltage limit which you exceeded.

Beyond that we'd need a schematic to tell you where to look for problems. Replacing the parts for a HK supply, or even replacing it with a new one entirely, isn't too hard - but you'd have to know what to look for. The only part I can see on the board is an LM339 which is a quad comparator, probably used for undervoltage lockout or something similar.

What is U2? If it says something like "7805" or "7812" or "LM317" it may be the HK regulator. They usually have a max input voltage of 35 - 40 volts.
 
Typically, the big green resistor (RX1) is meant to drop the voltage from the battery to something the 7812 / LM 317 / etc (TO220 part next to it) regulator can handle.

The resistor is sized for the particular voltage range of the battery the controller is expected to be used with.

If you use too high a voltage, the current thru the resistor is higher than it should be, and it can get so hot that it burns out, or even melts solder from teh board where it's mounted (and the solder can then short out other things). But I don't see the usual signs of overheating there, so the resistor is probably ok. (but there may be some discoloration of the color bands on the resistor, as it is not completely clear what they are...that can be poor quality manufacturing with poor tint choices or overheating causing color change).

However, the higher voltage also then reaches the 7812 / LM 317 / etc , and can burn it out, which would mean you don't get any voltage at the caps you mentioned.

You can replace the 7812 / LM 317 / etc with a new one, but you'll also want to change the RX1 to a higher resistance. To find the correct value, divide the new voltage by the old one, then multiply that result with the present resistor value (which appears to be brown brown black (11 ohm) or orange orange brown (330 ohm). If you disconnect one end of the resistor from the board, you can measure what it is with an ohmmeter.



However...sometimes 7812s fail shorted from input to output, and if that happened here, the high input voltage will reach the "control chip" and other very low voltage parts, and damage or destroy them. (then if those parts fail shorted, they draw so much current thru the 7812 from the source that the 7812 itself usually fails completely, opening the circuit--in the process the resistor usually gets hot enough to discolor, but not always).

You won't know if this has happened until you replace the 7812 and resistor, and retest.
 
billvon said:
The only part I can see on the board is an LM339 which is a quad comparator, probably used for undervoltage lockout or something similar.
SInce he said it's a brushed motor, that is likely to be the "controller chip", rather than using an MCU. I've had a few brushed controllers, including a 4QD unit, that used that sort of control.

http://www.4qdtec.com/pwmmod.html

https://www.google.com/search?q=lm339+brushed+motor+control&num=100&newwindow=1&sa=X&hl=en&prmd=ivns&tbm=isch&tbo=u&source=univ&ved=0ahUKEwj0xqOzpq3fAhUmilQKHXXLCZ8QsAQIHA
 
Is it possible for me to use the present controller and beef it up to take in 60v? What new components should I add in or is it a better idea just looking for a new 60v brushed controller?
 
Scoot 787 said:
Is it possible for me to use the present controller and beef it up to take in 60v? What new components should I add in or is it a better idea just looking for a new 60v brushed controller?
Maybe. But again, you'd need the schematic, whether from the manufacturer or from observation. If it's just the housekeeping supply that's not rated for that, you can sometimes deal with that by adding a 12V or so zener in series with the input.
 
Scoot 787 said:
Is it possible for me to use the present controller and beef it up to take in 60v? What new components should I add in or is it a better idea just looking for a new 60v brushed controller?
In my first post in this thread, it describes how to fix the low-voltage power supply for the higher voltage (assuming it's designed like others I've seen; can't know for certain without a schematic unless you reverse-engineer it or do the experiment).

Other than that, you can check the FETs and make sure they're capable of the voltages you need, and if not replace them with ones that are. I'd recommend at least a 20% margin on the voltage, vs the fully charged voltage of your batteries (15 x 4.2v = 63v).

Then you could replace your capacitors as well. They're only 63v, and your battery voltage at full charge is right there. Having some headroom is a good idea.

Most likely that is all that needs to be changed, as it is unlikely for the system to have any sort of high-voltage limit to prevent operation above that; it appears to be a very simple design. (it is still possible, however).

The LVC for the controller (if it has one) will be too low to protect your battery, so you will need to monitor and do that manually while riding unless you have a BMS of some type on it.
 
Let me see whether I got this correct since my electronic knowledge is close to none. Change the LM 317, replace resistor with a 60/48*330>412 ohm. Get 4 pieces of 80v capacitor to give me some headroom and I should be good for an upgrade using 60v lipo. I flew RC plane, but have never mess around with the internal working of the speed control. Never solder on small electronic board before, but I can give it a shot
 
Voltage ripple can cause voltage spikes that are higher than the resting voltage of the battery. I would not recommend using 15S, I think 14S is the most you should attempt.

Also, the wires between the battery and the controller should be short and fat.
 
Scoot 787 said:
Let me see whether I got this correct since my electronic knowledge is close to none. Change the LM 317, replace resistor with a 60/48*330>412 ohm. Get 4 pieces of 80v capacitor to give me some headroom and I should be good for an upgrade using 60v lipo.
What is the FETs' voltage spec? That needs to be high enough, too, or they'll pop (and often take other parts with them, like their gate drivers).

I recommend getting caps good for at least 105 degrees C, too, since it often gets hot inside those controllers. The more they're rated for, the longer they'll last. Whichever ones you get, watch out for their dimensions, because there are all sorts of sizes, and sometimes higher voltage ones are bigger (all other specs equal) and may not fit in the space you have (too tall or too fat).


Keep in mind that it's possible other things are already damaged, so it may not work correctly even at the original voltage once the regulator (LM317 / etc) is replaced. Then you'd have to you find out what those things are and fix them, too.

Also possible there are other things in the design that require changing, that we can't know about with out a schematic.
 
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