Thursday, 22 May 2014

LVC-HVC Wiring

Ok so the LVC/HVC cut off boards have two white plugs at the top of each board (one board for each parallel bank in the traction pack)

They are labelled as shown in the image below

Online manual for these boards below

Only found this manual recently (thanks again Steve)

I “just” need to connect all the HVC/LVC board connections in a chain connect the HVC part to the charger and connect the 6 solder connections at the top (can’t quite see them in the photo above) in line with the throttle cable, between the Throttle Position Sensor (TPS) and the Soliton Jr’s Throttle input.

So this bank holiday weekend 3rd/4th/5th May 2014 I spent several hours joining all the 3 packs HVC/LVC loom cables together, I have soldered them all up as I have not got any inline 6 way connectors handy although if I need to remove the pack again (I sincerely hope not any time soon) I would have to cut these cables, so I do need to buy some inline 6 way connectors for this purpose.
As the front 3rd of the Traction Pack is a good 2 meters further forward than the other two boxes I had to run a long 6 way cable under the car to join the front battery box HVC/LVC loom, I threaded this 6 way through another second hand inner tube and fastened this under the car using many zip-ties.

Once the HVC/LVC loom was complete I wired the Throttle and Controller as shown in the picture above (to the solder terminals hidden behind the white plugs at the top) this is so the LVC cut off can cut the throttle.

It is very difficult to test the LVC in the real world without running the pack to near flat, I did test the board on the bench with a variable PSU attached to fake a cell voltage and sure enough when the cell voltage drops to 3.00v the Throttle signal line drops to 0v (cutting the throttle)

I then set about connecting the HVC to the chargers BMS pin, I ran 4 wires out of the charger box, 5v, Gnd, BMS & EOC. After much fiddling about testing this I discovered that it only seems to work if I leave the BMS & EOC pins connected together (otherwise the charger never starts at all) and then connect the HVC “sig” line to these via a low value resistor (I was advised to add a resistor inline to avoid the Methtek boards drawing to much current) I am not sure the resistor is even necessary but I put one in just in case I ended up having to use two 51 Ohm resistors wired in parallel as that was all I had to hand that worked it seemed if the resistor was even 100 Ohms the signal would just not get through or was not detected on the far side of the current limiting resistor.

So to summarise:-

1) Connected 5v from the control board in the EMW charger and fed this directly into the HVC 5v pin.
2) Connected Gnd from the control board in the EMW charger and fed this directly into the HVC Gnd pin.
3) Connected the BMS/EOC pins from the control board in the EMW charger together.
4) Connected the HVC “Sig” line on the Methtek board (HVC/LVC chain) to the BMS/EOC via two 51 Ohm resistors in parallel.
5) Connected the “Throttle” 3 Pin soldered connections to the throttle.
6) Connected the “Controller” 3 Pin soldered connections to the controller.

I have just realised after writing this up (This is why it is a very good idea to write things up) that I have not fed the LVC part of the HVC.LVC chain with 5V or Gnd!  As this would be active when the car is running (unlike the HVC part which is only active when the car is charging) I would need to source this 5V & Gnd from the Soliton controller! (Update After speaking with Steve the + 5v & Gnd

Shit I had better check this when I get home tonight as I may very well not have a functional LVC!
Anyway I did test the HVC side of the HVC/LVC cut out extensively in the car by using a variable resistor to work out what value of current limiting resistor I would need, and testing it by starting a charge and then shorting the HVC “Sig” line to ground to see if the charger stopped and sure enough if I connected it directly it worked.

My initial guess of a 1K resistor did not work so I put in the variable and dropped the resistance until it started working, checked the resistance and it was way low I eventually settled on the two 51 Ohms in parallel which should give around 25 Ohms resistance and burn around ½ watt power (2 x ¼ watt resistors) I could be completely wrong here as my electronics is still decidedly rusty!

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