Monday, 23 September 2013

EMW Charger testing the final chapter (I hope) (Update: NOT!)

I had already completed my low voltage (12v) tests and so far had discovered a reverse orientated IC blowing a 2n2222 and possibly the IC as well, replaced the IC and transistor and carried on testing with a lot of help and guidance form Valery I found a wrong value resistor out by a factor of 10 (27K instead of 2.7K that it should have been) replaced this and completed the low voltage tests with a fair amount of confidence that it was working as expected.

So I proceeded to HV testing and things were looking good, Connecting my 75v DC 45AH battery to the AC inputs went well, All measurements checked out fine.

Apart from the spark upon connection which scared the S#!t out of me (even though I was expecting it)
Moved on to the full AC test and this also went well (initially), Input voltage was around 288V (correct for 240Vac I think, RMS?) as shown on the LCD panel, Input current was set at 10A in and out as in the notes, Output voltage was still at zero as expected.

Started the charger and the dummy load lamps (2x60w incandescent bulbs in series) lit up as it entered the CV stage with an audible click then I got the duty screen, however when the values started to change the display problem (not clearing screen as values change) reared its ugly head again, I had been working around this with clrscreen statements.

As I could not see the readings without this being fixed I pulled the plug (Bad Idea?) and disconnected the load as in the instructions.

I need to fix the display refresh issue before I can move on.

When I plugged in AC power a second time the dummy load lit immediately!

And trying to repeat the test it responded differently, it just showed the Type 1 & 2 screens and then says charging complete without showing the duty screen, I tried disconnecting the dummy load and powering on this tripped my circuit breaker!

I then tried switching it back on (load connected again and it lit up again) and seeing if I could cancel the charge somehow, whilst going through the menus I heard a snap and saw a whiff of smoke, powered off immediately.

Smell check narrowed it down to the driver board I think (defiantly not control board) no obvious burn signs, so I guess it is back to low voltage testing again?

Low voltage test failed, now it won’t even power up, the only life I get is two flashing lights on Arduino red green in quick succession and nothing else LCD is blank. (Shit!)

Removed driver board quickly and checked over the board with my nose trying to identify which component had fried and my top lip revealed that U4 was red hot, so I am guessing this is fried and possibly the A3120 as well (Valery mentioned when these go they tend to go together)

SO I have 2 problems to solve now:-

Sort the display refresh issue so I can see the readings on the screen and repair the damage to U4 the DC-DC convertor that now seems to run very hot (I am guessing this is fugged) and probably replace the A3120 that is connected to U4, I may also need to remove and test the supporting components and replace as necessary.

Placed an order at Digikey for a replacement DC-DC (U4) and a few other bits for the next charger build, enough to get free delivery.
AC Input showing inrush resistors in series with live and neutral
 Output Diode package in white, Input Diode Bridge in black
 Driver board showing connections (removed from HV board for clarity of photo) 
 HV power stage board showing white inductor connection and black +ve -ve inputs
 same HV board from slightly different angle showing sense wire connection
  same HV board showing other inductor connection in white hall effect sensor and output terminal
Controller board in situ

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