Help Needed urgently please (range extender problem - have i blown my pre-charge circuit?)

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Joined
Feb 3, 2018
Messages
6
Hello all,
bit of a desperate plea for help I'm afraid.

I've been working on a range extender for my leaf - The packs are fully built and balance charging as we speak.
This morning I have spliced two high voltage cables to the HV cable between the battery and inverter (No extra battery anywhere near the car yet) this seemed to work fine and when the car was turned on I got a reading of 360volts between the ends of these two cables as expected.

I was then trying to work out how to get the RLY P (yellow cable on the data connector) to control a gigavac relay that will eventually be used to turn the extra pack on and off in sync with the main pack relays.

It was at this point that I've done something obviously rather stupid as the car now will not start.

I connected the yellow cable (again a spliced connection) to the gigavac relay in the boot, and from the relay on to what I assumed would be ground (i.e. the chassis). clearly this is the wrong thing to do and I can now see that there appears to be a RLY P ground wire.

On turning the car on it seems to have less charge than it did earlier in the day by about 10% and will only respond as though started up without the brake pedal depressed. It does not accept charge.

I've read a few forum pages and the common theme seems to be a blown pre-charge resistor - I think???

Will what I have done above have caused the same? can you think of anything else that I can check to see what damage I've done?

Best Wishes and with much gratitude,
Andrew
 
First of all, I don't have an answer for you but I'm doing the same thing you're doing, so this is very informative. Your mistake is a learning opportunity for the rest.

What you almost certainly did is temporarily overloading the relay driver. Considering relays are fairly badly behaved in general, they will have engineered this with a PTC fuse or some kind of self-resetting mechanism for overload. The relays are normally open, so when you overloaded the driver, the relay coil voltage sagged and possibly the main pack relay has opened. The RLY P and RLY N signals opening unexpectedly is a critical fault, so the car will NOT restart after that happening. The car thinks the relays have failed short.

This explanation does not account for the charge level of the traction battery seeming to have dropped dramatically. 10% of your SoC is a LOT of energy, about 2kWh. You'll have noticed something vaporizing from that amount of energy being expended. I think either this is a red herring or my explanation is fundamentally flawed.

I think you should be able to see a RLY P failure in your DTCs when connecting to your car with LeafSpy. I don't know if this can be cleared, but other people have messed up much worse than this and got their packs working, so I wouldn't worry too much. Try clearing it and seeing if it works. If you cannot clear it, I believe the maker of LeafSpy has helped people like Leaf XPack clear them anyway with a modified clearing routine. That programmer is awesome.

If the problem persists or reappears immediately after clearing, you have most likely damaged the RLY P driver circuit, and you will have to remove the... I think VCM from your car, open it up (do NOT damage the weathersealing!) and replace most likely just a fuse, maybe some MOSFETs. I am not familiar with these parts, maybe there is an easier to service fuse box, so thoroughly study the service manual before doing anything. Don't take my word. I am currently just as experienced as you are.
 
Thanks for the reply. I'm hoping that you are right. I have come to the conclusion through plenty of research over the last few days that I've done one of three things - damaged the pre charge circuit (worst case scenario as I will then have to break open the main pack to replace the resistor), shorted something within the vcm as you suggest (more expensive but less labour intensive) or simply created an error code that has confused the car completely. There was certainly no electrical burning that would account for such a capacity loss so I really don't understand that, hopefully a red herring as you say.
OBD2 reader arrives tomorrow so I will finally be able to check what's happening on leaf spy and then work through the problem.
The annoying thing is that I was simply testing out whether the power from the rly p wire would activate my pack relay. I now realise that the data connector must ground through the vcm and not onto the chassis at all. So hopefully if I can repair whatever I've done I can, then try again using the yellow and black wires.
I'll keep you posted and let you know if it works.
 
Wow, what a relief!
OBD2 reader finally arrived at 7:30pm and I've just plugged it in to the leaf.
only had 2 error codes:

P31E7 000B EV/HEV Restart Inhibition EVC-310
P0AA6 0008 EV/HEV Hybrid Batt Volt Sys Isolation EVC-157

cleared DTCs and the leaf is back to the way it was. Suddenly has 28% charge again instead of 21% (really can't explain this but who cares?)

Tomorrow is going to be the big day where I finish wiring everything up and (hopefully) take it for a test drive with the new pack installed.

I'll start a new thread if it works to show what I've been up to.

Best wishes,

Andrew
 
Good to know that the VCM output drivers are correctly designed to account for this kind of stuff. You never know with automotive stuff.
 
So things haven't gone quite to plan. For one glorious moment I seemed to have control of the extra pack relay controlled via the leaf itself with a separate breaker switch on the dash.

Unfortunately on restart I now have errors:

P0AA4 0009 EV/HEV QNRH Hybrid Batt Negative Contactor EVC - 151
C118C 0109 ABS EV/HEV System BRC-126
C1A6E 0109 Brake EV/HEV System BR-146
C1A70 0109 Brake Control System BR-160

All of the C codes appear to be related to the regenerative braking system however the P0AA4 seems a little more concerning and may represent a main contactor that is persistently shut (perhaps opening and closing briefly while the new relay was turning on and off - enough to weld itself shut). With a little coaxing and use of leaf spy I can clear all error codes and get the car moving and charging but on turning the car on again the errors re-appear.

I need to find a day to troubleshoot this as it may simply be that I have created a short at the data connector by accident or even overloaded the VCM. Hopefully have some answers by Sunday. If not then I'll need to drop the main pack and check the main contactor.

Talking of which - does anyone know anyone who might have a spare contactor that I could buy from them in the UK? I can source one from America but it won't arrive until 1st March and I'm achingly close to getting this all working.

I'm now beginning to wonder whether I need to use a small relay that sits in the positive wire of the main relay controller so that there Is no fluctuation in power signal to the main pack relays, (and no chance of shorting) I can then use this relay to deliver power to the new pack relay i.e. from the leaf's 12v battery. Lots to think about.

Just hope it's something that is easily rectified otherwise it's going to be a fairly embarrassing visit to the dealership to get the VCM replaced.

I'll keep you updated if I have any breakthroughs. All I can say at the moment is... don't do what I've done so far - because it clearly doesn't work :)
 
A weird constellation of errors like this usually points to some issue with the 12V system, i.e. too much power being drawn and some subsystems not properly initializing. BCM is situated in the rear of the car, so it could well be a vestige of your initial fault.

Having a wire short somewhere also could be the source, but that is possibly even more concerning: those splices need to be super-secure to survive the torture of enduring years under a car. If something went wrong there, you may need to redo them.
 
Checked insulation across high voltage splices and all seems to be ok. Removed all new connections at the data connector and checked for any short circuits there - all seems ok. Still getting the same error set. When the errors are cleared the car drives absolutely normally.

I am noticing that when I measure the voltage at the new splice ends I find that there is an initial drop to 20volts then a very brief spike to 100volts before going back down to 20volts and then diminishing slowly to 0v over a few more seconds.

I've ordered a new battery junction box from America and I'm coming to the realisation that the safest way that I can ensure that all things are working properly is to open up the battery, see(hear) that the contactors are doing what they are meant to do while I finish integrating the new pack and then once I'm happy with everything i can then replace the main pack. If I still get the same error codes then it makes them far more likely to be sensor problems which can be sorted at a later date when everything is bedded in.

It'll be a couple of weeks before the JB arrives so I'll update then.

Best wishes,
Andrew
 
That voltage spiking to 100V and then down is probably a combination of the Leaf RLY N/P and precharge relay switching in a certain order every time the pack is connected/disconnected. This guy has the sequences on video:

https://www.youtube.com/watch?v=d0IozEyeGSk

So that is nominal, nothing particularly wrong I don't think.

Be very careful when opening (and more importantly: closing) the main battery. It's gasket sealed all around for a good reason. At least one person had his Leaf flame out due to water getting into the main pack. Caulking is not enough, you need a compliant gasket around the pack to properly weatherseal it.
 
Finally had a few days to have another go at integrating the extra pack. Mux thanks for your input, I saw your recent videos and had actually came to the same conclusion that mosfets were the only way to safely integrate new relays without the leaf realising - so thank you for proving that it works first :) - my circuits are slightly different but do the same job. Now need to properly balance the packs and see exactly how much extra range I can get. I think possibly making the pack up to 100s 10p might allow the 18650s to start helping the leaf earlier in the range as at present (due to different chemistry) they only really make a difference beyond about 35% residual. It would also stress the new 18650s less - especially as some of them must be over 10 years old. No temperature issues at the moment. All staying nice and cool without any active thermal management. As for the persistent error code (negative contactor stuck closed) I have concluded that this is a sensor issue as the signals from the vcm are as expected and I can hear the leaf's relays working as they should too - so for the time being we're just resetting the codes each time and it's become part of the routine and at least it makes the car unstealable. There have been no new error codes since install. When I get chance I'll upload some photos and some real world range figures but for now thanks for all the help to everyone who replied to the above and to anyone who is wondering "can it be done" the answer is YES, absolutely.
 
I've done some spreadsheeting on changing the amount of series cells, and it doesn't matter. I've gone through all combinations of NCA and NMC cells with 94-102S, and you can never get more than approx. 40% of nominal capacity out of the extender pack before VLBW. There is basically still well over half of the extender pack left after the car already says it's empty. In practice, it's even more pronounced; I get my VLBW at about 130km these days, and can drive it down to about 250km. I mean, for now it makes estimating range very simple: just multiply whatever the car says it can do by 2.

So don't even bother. Just keep the same series amount of cells, it will be best for cycle life anyway. I'm currently working on the electronics that will fix the displayed range, this will be done and tested before the summer holidays.

Edit: also, it's probably informative to tell you that I have had the contactor failure DTC once as well, when replacing my MOSFET driver solution with a new custom board (as shown in my last video). A firmware bug caused the contactors to not close at the correct time. I was really ragequitty at the time but persisted, reflashed corrected firmware, cleared DTCs and waited a bit, and it all went away. I don't think I actually damaged anything, there must be some sensor that actually does the contactor-welded-closed-measurement that is sensitive to something else causing stray DTCs. Same goes for the isolation DTC, it intermittently shows even though I've gone through the entire service manual procedure of narrowing down where it could come from. Some of these sensors are just a little bit too sensitive it seems.
 
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