Help! Crystalyte controller woes

[NickF23]

Well its a gorgeous day here in Brighton (UK) and I thought it might be time to try out my new rewired bike. I just had to fix a new throttle and then everything would be up and running.

BOOM.I'm not totally sure what happaned next, I think I connected all/the wrong throttle wires together, or and something else happened at the same time. The battery fuse had blown. With the controller opened up I can't see anything looking obviously damaged.

There is continuity between the positive and negative inputs and also between the positve and the yellow phase wire (see pic). If I measure the resistance of the first two fets its almost 0 unlike the other 4 which measure either 120 ohms or 1400 ohms between the far pins.

Do I have a shot at fixing it? I have a half decent multimeter and a less than have decent understanding of electronics and am ok-ish at soldering.






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[fechter]

It sounds like you blew a FET. If you have zero ohms from the yellow phase wire to the positive battery wire, it will tell you which one.

Measure the ohms from each phase wire to each battery wire (6 combinations). Any zeros indicate a shorted FET.

You can replace the FETs. You might consider replacing all of them with better ones.

Typically, the gate resistor also blows when you short a FET.

The gate lead is the one with the skinny trace. You can use an ohmmeter to measure the gate resistors. Typically 10 ohms. When they blow, it will be greater than 10 ohms.

You can also sometimes blow the gate driver chip (IR2101). I would recommend replacing the FETs and gate resistors first and see if everything works. The IR2101's are challenging to replace because they're tiny surface mounted things.

When replacing blown gate resistors, I just leave the blown one installed and bridge a leaded 10 ohm resistor across it.

 

[NickF23]

Thanks Fetcher.

Both the negative and the positive have a clear path to the yellow phase wire. All the rest seem ok. Only one of the gate resistors i showing higher resistance (1600omms) the others all show 100 omms. Strangly the one with the higher resistance is not next to the damaged fets but at the other end by the negative battery cable and the shunt.

The fets read irf3205 which come up as 55 volt. No surprise as its a 48 volt controller. If I replaced all six with better/ higher voltage fet would I be able to run at higher voltage?

 

[fechter]

I've never seen that controller up close, so just guessing, but if you upgrade the FETs, and the main capacitors have enough rating, you should be able to bump it up to 72v.

Even if you keep it at 48v, better FETs would give you more current capacity. Then you could tweak the shunt for a higher current limit (if you want more power). FETs with lower on resistance will be more efficient too, with less heating.

Check the big transistor opposite the FETs. See what the number / voltage rating of that one is. It's probably the voltage regulator.

 

[NickF23]

It says F 325 then below e13005

 

[fechter]

I'd guess that's a MJE13005, which is rated for 400v, 2W.
So as long as the caps have a high enough rating, changing the FETs should get you up to 72V or so.

 

[NickF23]

Hmmm, that sounds like it might be worth some expermimentation. I've got a dead controller now, so nothing much to loose. What Fets shall I try to get. I'va had a read around some of the other threads and was thinking maybe the irfs4710? Do you know if its signifacant my gate resistors are 100 ohms rather than 10 omhs?