2012 i-MiEV (not clone) Charges HV Battery But No Auxiliary 12V Charging

[martinwinlow]

Hello, all.

I got a petrol-head friend to buy an 80k miles non-functional i-MiEV a few weeks back here in the UK. It was just up the road from him (500 miles away from me!) and he has expressed an interest in 'getting into EVs' for years so this seemed like a golden opportunity. He won it on eBay for £500! Original assessment was: dash comes on with key but no 'ready' light, 'high voltage' warning on (yellow !+car), no 12V dc-dc conversion nor AC charging - DC charging not tried. Also interior lights not working and although the radio appeared to have power, there was no sound.

The car had been sitting around for quite some time, apparently, maybe a year or more. SOC was around 40% from dash.

Anyway, I happened to visit him shortly after he purchased it and we got Hobdrive working from him with his android phone and a OBDLink LX.

Original DTCs:



As you can see, the P1A15 error is present along with a few others including a seised brake vacuum pump. So, we dealt with the P1A15 first as I am quite familiar with it (I've done 2 resistor-bodge repairs already on different clones). That was successful and the car would then drive OK but still no AC charging and no dc-dc converting to charge the 12V aux battery, etc...




So, the P0A09 DTC led us to investigate the interior light issue and fuse 13 (below steering wheel fuse box) was found to be blown. After replacement:




So, now the car AC charges...


15 mins later...

... but still no dc-dc conversion to charge the 12V battery.

Anyone got any thoughts?

MW

 

[MickeyS70]

So, now the car AC charges...

... but still no dc-dc conversion to charge the 12V battery.

Anyone got any thoughts?

MW

I take it you don’t measure the 14.4V OBC voltage across the battery terminals with the car in READY then?

Might not be obvious now but certainly worth in the long run, get a new 12V aux and fully charge it externally before swapping it.

There is a thread that deals with the OBCs DC/DC circuit but that’s more @kiev ’s field of expertise and he’ll guide you if necessary:

https://myimiev.com/threads/the-troubleshooting-and-repair-for-on-board-charger-obc-thread.4079/

It looks like there is also an issue with the HV battery’s calibration as HobDrive shows a SoC of merely 53% with the cells almost fully charged (balancing looks good though)?

 

[martinwinlow]

Hi MickeyS70... Thank you for your help.

Forgive me but I assumed the voltage Hobdrive provides (CM Voltage) was the 12V battery voltage...?

We had discussed replacing the 12V battery and I think that would be sensible (especially given how finicketry the clones can be if that battery is sub-optimal).

I'll check out the OBC thread a bit more... it is quite long!).

As for HV battery calibration; is this something that running the car down to turtle mode would resolve or is it a MUT3 job (I have one - but here, not 500 miles away where the car is)?

 

[MickeyS70]

Forgive me but I assumed the voltage Hobdrive provides (CM Voltage) was the 12V battery voltage...?

Yes, but you won’t find it in the BMU screens you posted; it’s displayed in General/Charge and should show above 14V DC when READY. What value are you getting?

As for HV battery calibration; is this something that running the car down to turtle mode would resolve or is it a MUT3 job (I have one - but here, not 500 miles away where the car is)?

No need for MUT3, HobDrive has a similar function called ‘Capacity Measure’

 

[martinwinlow]

(balancing looks good though)?

Yes, even under a foot flat to floor there was very little cell voltage variation, <10mV...

My friend reports: "The battery voltage was reading correctly. It never showed 14v. And dipped down to 11.4v with the coolant circulating. I had to put my battery pack on to keep it going"... 12V battery reading taken via multimeter directly at the battery.

I think the battery pack he's referring to is a jump-starter pack - which may just be confusing things as far as the car is concerned. I have recommended replacing 12V battery with a new one before proceeding further anyway.

 

[martinwinlow]

An update: 1/ New 12V battery makes no difference (tho I have forgotten to tell him to clear the DTCs in case it makes a difference...)
2/ He has opened up the OBC...



Nothing obvious... I have suggested checking both visible fuses...

3/ Anything else he can have a look at?

MW

 

[kiev]

So the car will AC charge now, so it is not an OBC issue.

 

[martinwinlow]

What about the fuse in the MCU (under the little access cover)? With no AC charging and no DCDC i would bet that fuse is blown.

Hi Kiev, Thanks, but as per Post#1 (and the thread title!), it does now run and AC charge (which was fixed apparently by replacing Fuse 13 in the cabin, as you say - interior lights also - we have not yet tried DC charging) - it's just the 12V battery charging that is missing and we still have the one remaining P0A09 DTC (and he's also got the brake vacuum pump working, too - albeit briefly as it has seized again. It has an outstanding replacement recall for the vacuum pump but as we can't drive it far (see below) we're going to try to source a working used pump for now and he'll get the recall done in due course, the dealer is not far away)...




The other thing that has come to light is that there is quite a high drain on the 12V battery such that it goes from fully charged (bear in mind this is a new 12V battery, now) to flat in about 30 minutes whilst 'Ready' and drains so fast when actually driving that the car will not go very far (not even 100m) before it shuts down.

I have suggested that we wait until my friend has a DC current meter so he can check the current flow from the 12V battery and compare it with 'normal'. I have also suggested he partially remove the DC-DC converter from the sub-frame so he can examine the inside from the bottom to see if there is anything obvious wrong with it. I'm also going to have another look at the OBC thread to see if there is anything else we can check for...

 

[MickeyS70]

Hi Kiev, Thanks, but as per Post#1, it does now run and AC charge (which was fixed apparently by replacing Fuse 13 in the cabin, as you say - interior lights also - we have not yet tried DC charging) - it's just the 12V battery charging that is missing and we still have the one remaining P0A09 DTC (and he's also got the brake vacuum pump working, too - albeit briefly as it has seized again. It has an outstanding replacement recall for the vacuum pump but as we can't drive it far (see below) we're going to try to source a working used pump for now and he'll get the recall done in due course, the dealer is not far away)...

Maybe it’s the brake vacuum pump that’s draining your 12Vaux and blew a fusable link somewhere between the OBC and the battery?

The other thing that has come to light is that there is quite a high drain on the 12V battery such that it goes from fully charged (bear in mind this is a new 12V battery, now) to flat in about 30 minutes whilst 'Ready' and drains so fast when actually driving that the car will not go very far (not even 100m) before it shuts down.

‘Quite high’ is a bit of an understatement if a 40Ah battery is drained in 30min, unless of course it’s not fully charged to begin with, did ye fully charge the new one externally?

I have suggested that we wait until my friend has a DC current meter so he can check the current flow from the 12V battery and compare it with 'normal'.

Make sure he uses an clamp Amp meter..

I have also suggested he partially remove the DC-DC converter from the sub-frame so he can examine the inside from the bottom to see if there is anything obvious wrong with it.

I would temporarily disconnect the OBC’s DC/DC section and measure it’s output voltage ‘load free’,

 

[martinwinlow]

Thank you:
"Maybe it’s the brake vacuum pump that’s draining your 12Vaux and blew a fusable link somewhere between the OBC and the battery?" Not, as the vacuum pump worked for a while without fixing any fuses before stopping again - tho I take your point re the possibility of it draining the 12V battery whilst 'stalled'. It has occurred that this pump failure may have caused the problem with the DC-Dc converter in the first place. I'll suggest Ade try disconnecting it if that doesn't prevent the car from driving... I may have located a used pump...

"‘Quite high’ is a bit of an understatement if a 40Ah battery is drained in 30min, unless of course it’s not fully charged to begin with, did ye fully charge the new one externally?" I agree! And yes it was fully charged and he has done this more than once, I believe. He has it disconnected when not tinkering...

"Make sure he uses an clamp Amp meter.." I have bought him one as an early Christmas present - not yet delivered, tho...

"I would temporarily disconnect the OBC’s DC/DC section and measure it’s output voltage ‘load free’," Ah, I thought abut that but worried that that might fry something (like running an ICEVs alternator with nothing connected to it can... apparently... or is that a myth?!).

 

[kiev]

Pulling down a 12V battery in 30 minutes is an important clue that was left out of the problem statement.

That might explain the DTC and why the DCDC "appears" not to be working--it can't keep up with a drain like that.

There is a 125A fuse on the pcb inline with the output of the DCDC--never seen it blown before but this may be the first?

There is a dedicated thread for the DCDC converter troubleshooting and repair, [can be found here: https://myimiev.com/threads/my-troubleshooting-repair-list.5619/ ]

There is a big black connector on the Output of the DCDC, it is difficult to disconnect but it would isolate the Output from the 12V battery. Won't hurt the DCDC but it might throw a different code.

 

[martinwinlow]

Pulling down a 12V battery in 30 minutes is an important clue that was left out of the problem statement.

That might explain the DTC and why the DCDC "appears" not to be working--it can't keep up with a drain like that.

There is a 125A fuse on the pcb inline with the output of the DCDC--never seen it blown before but this may be the first?

There is a dedicated thread for the DCDC converter troubleshooting and repair, [can be found here: https://myimiev.com/threads/my-troubleshooting-repair-list.5619/ ]

There is a big black connector on the Output of the DCDC, it is difficult to disconnect but it would isolate the Output from the 12V battery. Won't hurt the DCDC but it might throw a different code.

I'll ask Friend to give that a go ...

 

[kiev]

There is an input fuse in the upper left corner, and the 125A output fuse in the lower right corner. Never heard a report of either to fail that i can recall. The 4 FETS on the heatsink pad, top center, have been reported to fail, but may have happened during troubleshooting (be careful when using probes while operating).

 

[martinwinlow]

There is an input fuse in the upper left corner, and the 125A output fuse in the lower right corner. Never heard a report of either to fail that i can recall. The 4 FETS on the heatsink pad, top center, have been reported to fail, but may have happened during troubleshooting (be careful when using probes while operating).

Friend is away for a while. More upon his return...

 

[martinwinlow]

Friend is back...

He has opened the OBC box and removed the bottom cover which reveals...
1/ Quite a lot of water..


2/ Nothing especially 'blown' looking...


3/ A very wet-looking inside of the bottom lid but no black splodges...


I have suggested letting it dry out very thoroughly over at least 72 hours and try it again... as well as checking both fuses for continuity.

Any other helpful suggestions? MW