Failed pre-charge resistor on the MLEC board (again)

[phil hochstetler]

Last week I had my second failure of the MLEC board in my Red Think City.  I have about 9100 miles on it in 14 months.   I lost the first resistor in early Sept 2013 and now 4 months later it failed again.  A free trip to Hawthorne Auto in Portland and fixed in a day or two.  No cost except the inconvenience, but a couple of things come to mind.

Have others seen this failure rate?

What happens after the 36 month warranty date expires?  It looks to me to cost between $300 to $900 depending on whether the resistor can be replaced or the board need to be replaced.

Is the MLEC board a EnerDel board or part of the Think's car design?  Who is responsible for coming up with a solid fix that does not keep failing.  If the pre-charge resistor is failing, it must be undersized for the job.  Why not just put in a higher wattage one? or a PTC resettable fuse in series or instead of?  This does not seem to be rocket science here.

I don't know about you but in 22 months (when my warranty is up), I'm going to come up with a fix of my own if no one else does.

I heard that EnerDel sent out someone to trouble shoot the problem but could not reproduce the problem and and spent 2 days but concluded it was Think's problem, not theirs.  Huh?

Comments?

Phil H.

[Ken Brown]

I think you're absolutely right, Phil.  That's an alarming failure rate.  Plus, since it's a well-known pattern of a specific component failing I really hope there will be a more permanent and robust solution!

[Mike Overton]

Phil,

Do you think we could get schematics?  Or a failed board?   That would at least be a start.

Mike

[Myles Twete]

Phil, you should have attended the workshop.  I'm at 18 months and over 18000 miles without any battery or PCS or MLEC issue.  Perhaps I'm lucky.  Info from Enerdel?  You've gotta be kidding.  Ain't gonna happen.  Given that, and given the finger pointing between Enerdel and THINK on the root cause for recurring MLEC failures, I agree that we need to work on a solution.  I'm happy to help diagnose this with you and others.  Let's do lunch again.

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[Ben Wrightsman]

 

Over 4,418 of these MLECs exist in over 62 vehicle applications with now just over 5million miles on the road without a failure.   This is not an MLEC or a battery issue, it is a known vehicle issue that was induced during a specific recent “update” and is not within the battery to be fixed or remedied.  Unfortunately the update now causes the battery precharge circuit to fail over time.  It is likely to continue until the update to the vehicle is 100% complete.

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[Steve Bigelow]

Good info. What do you mean by "until the update is 100% complete"?

I've had the" fast mode " update for several months. Is it not complete yet?

[Myles Twete]

As I suggested, Enerdel & THINK aren’t helpful here at all.

If only we knew the failure scenarios, we might avoid the problems by adopting strict behavior.

From the information we learned from THINK reps about a year ago, here’s what I’ve surmised (could be totally wrong)

·         Turn key to START too soon

o   MLEC precharge resistor gets bypassed (not torching it) quickly, but now there’s a huge inrush to the bulk capacitor in the PCU, which could torch either the capacitor, a fuse or PCB traces.

o   Mitigation: Don’t turn key all the way to START without pausing at ON

·         Turn key ON with LOTS OF LOADS in place

o   Normally transient and decaying bulk-cap charge current thru pre-charge resistor spikes higher & decays to a static level that eventually takes out the resistor

o   Mitigation: Turn key to START before it’s too late and precharge resistor smokes

·         Turn key to ACC from ON with LOTS of LOADS still in place

o   Load path may switch back to the precharge resistor path---if loads are too high for too long, the resistor smokes

o   Mitigation: Don’t leave lights or heater on with key only at ACC position for long---if needing heat or lights, keep switch in ON position

 

It’d be a shame if even 1, let alone 10 more of these cars have to go into the shop to fix a preventable problem.

I’m at nearly 19,000 miles now without issue.  I follow the mitigations above.

 

-Myles Twete, Portland, Or.

[Ben Wrightsman]

The recent PTC heater and software updates allow more than just the PCU to be on during precharge which is NOT how the vehicle system/battery was designed to work.  Ex. like on any fueled car when you turn the key to start EVERYTHING except the ignition and starter go off momentarily.  The precharge was designed for certain loads and sequences.  Updates have changed those and are overloading the precharge circuit.  The stackup of tolerances and variation w pcu's and other tweaks vehicle to vehicle are why some are ok right now.  I appreciate the "arent helpful" but that is not the case.  We dont have access to vehicle software.  Mods to the pack would be pretty intrusive and require more than software, that plus void factory warranty if not completed by Think.    Sorry for being useless.  I will say we are still supporting and have been servicing packs as requested but remember we were only the supplier.  

[Bill Dvorak]

Not sure I understand the last two posts. Start and position II with the green vehicle light on are ok. Everything else is suspect?

 I just got the new FW and I love the acceleration improvement. Also the E mode seems more aggressive? Anyway the car is great but now I am worried about the resistor. 

Bill

Sent from my iPhone

[Ken Brown]

Ben, thanks.  That information is helpful.  I'm pretty sure that's the most complete description of the actual problem mechanism that we've heard.  It's been frustrating not to have specific enough information to really understand the problem.

If there isn't a reliable solution from Think before the warranty runs out, I think a lot of us would be interested in a fix to the pack even though it would be, as you say, pretty intrusive.  But it sounds like the correct fix is on the Think side of the circuits, and I hope that can be addressed quickly with a reliable fix.

In the meantime, does anyone know if the problem can occur if the car is always started with all accessories off?  It sounds like that's what the software should be ensuring, but is that all it takes or are there other dangerous loads than user-controllable accessories?  And is it still a good idea also to pause in the ON position before turning to START, as Myles described and many of us have been doing?

Thanks,

Ken

[Myles Twete]

Almost 19000 miles now...lucky or doing something right...

[Johnny]

I think I was one of the first owners to describe a "power limit" when you turn the key on to start "too fast" to Patrick Bouchard from Think tech support.  I could repeat the problem almost every time by turning the key through the "on" position to start.  About 1 week after I sent them the email, we all received the "turn off all 12v accessories prior to starting car" email.    Now I turn the key "on" and pause a second, then turn to "start" and have not had a power limit since.

I believe I have heard about a service center that had tried to replace only the burnt resistor to fix the problem and eventually they had to replace the complete board to fix the problem.  It is not just a resistor problem.  I think it is a software "bug" which does not have a delay from when the "on" is detected to when the "start" is detected or it is missing a permissive for when the car can successfully "start".  Either way we have to remember to turn off high loads, (mainly) the heater / AC load to keep it from frying the board.

Johnny

 
On Wednesday, December 18, 2013 5:08:18 PM UTC-8, phil hochstetler wrote:

[hirs...@yahoo.com]

Well, I just now joined this group (didn't know it was here!)  Most of you I recognize from either the Yahoo Th!nk group or the Facebook group.  This thread about the MLEC problems has very little more info than the other groups.  I have not had mine fail yet (touch wood!), but there are several now around the country waiting for support that doesn't seem will ever come.  Is there any solid knowledge here of how to access, remove, and troubleshoot the board?  Anyone know of a schematic diagram?

Cheers, -Hirsch

[Myles Twete]

Sure...remove battery pack from car, remove top cover, remove MLEC and if you're lucky all you have to replace is the p recharge resistor.

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[eivind...@hotmail.com]

Holding a burnt precharge resistor in my hand and want to replace.   But what to buy?  There is nothing about name, type, resistance to be seen on the resistor.
Even googling for several days is without result.

Does anybody know anything about this resistor?  Name? Type? Resistance? 

Eivind

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[Steve Bigelow]

It's a 47 ohm, 3.5 watt. Lots of discussion on that here. Replace with 4.5 watt or higher.

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[John Mayer]

Actually, I would warn against installing a higher power/energy rated resistor, in a similar way that fuses should not be replaced with higher amperage rated fuses.  I understand that you want to reduce the chance of exceeding the rating, but when the failure mode occurs the energy dissipated in that resistor is way, way beyond the rating of any resistor you could reasonably attach to the board.  By using a higher rated resistor, more energy is dissipated in the resistor before it causes an open circuit.  More energy dissipated means more heat, larger fireball, more chance of irreparable damage to the MLEC circuit board, (damage to the Li-ion cells?) which means no amount of new resistors will make your car run again.

The part used by Enerdel is supplied by HVR Advanced Power Components, 47 Ohm U-2115 series which is rated at 3.5 Watts average power and 700 Joules single impulse energy.  I'm sure you can find an equivalent from Digikey, Mouser, Newark or similar.

Everyone one who subscribes to this group should know that the best way to avoid the problem of burnt precharge resistor is to always turn the blower off before starting or turning off the car.  Please spread the word and see the exhaustive explanation posted in this forum last month.

Based on the date format of your email I'm assuming you're not in the Portland, Oregon area-- if you are you should certainly bring it to Hawthorne Auto Clinic.  Please be careful when working on the high voltage battery.  There are safety features in place, but battery voltage is potentially fatal.  Specifically, if you only have the MLEC out of the battery, be mindful of the wires to the white connectors on the top edge of the board, and make sure no 12V power is supplied to the traction battery (i.e. disconnect the car's 12V battery) before and during any access to the battery.  (And potentially lethal energy can be stored in the PCU capacitors (and on the cables to the traction battery for 5 minutes after shutdown.)  Basically, be careful.

Best of luck,

John

[Gilles ROY]

Hi everyone, hi John !
I am new to this group, and I live in France. Sorry if my English is not always correct.
A friend of mine in Belgium recently bought a 2011 Think, and is worried about what we read here about the pre-charge resistor and the MLEC failure.
I understand the failure can possibly occur if the Think software has been updated. Is that right ?
If so, how could my friend know wether his car got the new software or not ?
Thank you for your help !
Gilles

[hirs...@yahoo.com]

Gilles, the MLEC precharge failure risk is equal with every software version.
Cheers, -Hirsch

[Gilles ROY]

Thank you Hirsch for this answer... though it hurts a little ;-)
I was thinking the software would matter because of what I had read above from ben.wrightsman (12.2013) :

« ( ... ) This is not an MLEC or a battery issue, it is a known vehicle issue that was induced during a specific recent “update” and is not within the battery to be fixed or remedied. Unfortunately the update now causes the battery precharge circuit to fail over time. It is likely to continue until the update to the vehicle is 100% complete. »

Did you get any other clues to get rid of this problem, or any place where to find the perfect How To document explaining "How to replace the failed resistor on my Think" ? ( Lets dream sometimes... )

Are you in the US ? Did you ever have any problem with your car yet ?

[Myles Twete]

While Ben was not entirely unbiased (being an Enerdel designer) on the issue, he's right.

It is absolutely true that the battery pack and MLEC isn't the place to fix the problem except perhaps to have never put the dang resistor on the MLEC in the first place---it should've been anticipated in the design that the MLEC was at risk by putting that precharge resistor on the board.  Timing is everything.  The precharge resistor needs to tolerate high capacitor influx currents (that's its job) for a short time---and only a short time.  By sizing it at 5watts or so, the designer would know that it's suitable for its purpose: "precharge" quickly.

 

But good engineering doesn't end there.  You have to consider the what-ifs.  What if the heater is left ON when the power switch is turned ON?  What if the heater or other HV loads turn ON, then OFF or vice versa at critical times?  What if those things are left ON?  This stuff either needs to be analyzed or tested or there's risk.  And if there's risk, it needs mitigation.  Enerdel likely had absolutely no say in how THINK was to manage the power & energy that went into that resistor.  They could have, however, decided to not locate that resistor on the MLEC and perhaps made it easier to replace without having to pull the entire battery pack.

 

It's an awkward thing that resistor being on that board, in the pack and under the car...just sayin'.

 

-MT

 

 

 

 

 

-----Original Message-----
From: 2011-think-ev...@googlegroups.com [mailto:2011-think-ev...@googlegroups.com] On Behalf Of Gilles ROY
Sent: Sunday, May 17, 2015 1:26 AM
To: 2011-think-ev...@googlegroups.com
Subject: Re: Failed pre-charge resistor on the MLEC board (again)

 

Thank you Hirsch for this answer... though it hurts a little ;-) I was thinking the software would matter because of what I had read above from ben.wrightsman (12.2013) :

--

[Gilles ROY]

So, was Ben also right saying : it is a known vehicle issue that was induced during a specific recent “update”  ?

[Myles Twete]

Well, you should always expect someone who works for a battery company to defend their batteries, so there’s that.

And yes, SW is a factor---still, did it get worse with a SW update---maybe yes, maybe no.  People were blowing these resistors before the “update” that is for sure.  A coworker of mine blew his MLEC pre-charge resistor the day he drove his brand new car out of the lot in Oct 2012---well before that “update” to the SW.

Enerdel probably shouldn’t have located this resistor on a PCB when it made little sense to do so and added risk. They also made this completely inaccessible to replace without pulling the pack.   Then they left it up to “THINK” to ensure against blowing the resistor.  After all that, when THINK failed to appreciate the importance of ensuring the limiting of the time that high current could appear thru this resistor, damage proliferated.

Some of us have been very diligent and cautious and haven’t had problems.  Others haven’t been so lucky…

 

Just my opinion of course…

-MT

 

From: 2011-think-ev...@googlegroups.com [mailto:2011-think-ev...@googlegroups.com] On Behalf Of Gilles ROY
Sent: Sunday, May 17, 2015 11:43 PM
To: 2011-think-ev...@googlegroups.com
Subject: Re: Failed pre-charge resistor on the MLEC board (again)

 

So, was Ben also right saying : it is a known vehicle issue that was induced during a specific recent “update”  ?

 

--

[Gilles ROY]

We'd better be cautious then…

Thank you very much for your answer !

[Rick Brown]

Just checking Myles, but when I drove my Think off the lot in October 2012 the heater update, and associated software update, had already been done. Do you know which software update Ben is referring to? Is it the one with the heater upgrade, or the last "high speed" one? Thanks.

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[Myles Twete]

I couldn’t tell you---it’s a black box.

The update I got to fix my failed charging issue was simply labeled as something like “fixes charging issues”.  No explanation of the details of what was fixed (let alone what was disabled---“proximity” button functionality) or what side effects might come out of it.

 

If I’m to hazard a guess, I’d say that the SW update that got installed when the heater was changed out could have changed pre-charge timing or some other factor that perhaps Ben was referring to.  If Ben’s still tuned in to this group, maybe he would elaborate.

Who knows…

 

-Myles

 

From: 2011-think-ev...@googlegroups.com [mailto:2011-think-ev...@googlegroups.com] On Behalf Of Rick Brown
Sent: Tuesday, May 19, 2015 1:17 PM
To: 2011-think-ev...@googlegroups.com
Subject: Re: Failed pre-charge resistor on the MLEC board (again)

 

Just checking Myles, but when I drove my Think off the lot in October 2012 the heater update, and associated software update, had already been done. Do you know which software update Ben is referring to? Is it the one with the heater upgrade, or the last "high speed" one? Thanks.

On Monday, May 18, 2015 at 11:25:54 PM UTC-7, Myles Twete wrote:

Well, you should always expect someone who works for a battery company to defend their batteries, so there’s that.

And yes, SW is a factor---still, did it get worse with a SW update---maybe yes, maybe no.  People were blowing these resistors before the “update” that is for sure.  A coworker of mine blew his MLEC pre-charge resistor the day he drove his brand new car out of the lot in Oct 2012---well before that “update” to the SW.

Enerdel probably shouldn’t have located this resistor on a PCB when it made little sense to do so and added risk. They also made this completely inaccessible to replace without pulling the pack.   Then they left it up to “THINK” to ensure against blowing the resistor.  After all that, when THINK failed to appreciate the importance of ensuring the limiting of the time that high current could appear thru this resistor, damage proliferated.

Some of us have been very diligent and cautious and haven’t had problems.  Others haven’t been so lucky…

 

Just my opinion of course…

-MT

 

From: 2011-think-ev...@googlegroups.com [mailto:2011-think-ev...@googlegroups.com] On Behalf Of Gilles ROY
Sent: Sunday, May 17, 2015 11:43 PM
To: 2011-think-ev...@googlegroups.com
Subject: Re: Failed pre-charge resistor on the MLEC board (again)

 

So, was Ben also right saying : it is a known vehicle issue that was induced during a specific recent “update”  ?

 

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[jeff spooner]

Just wondering of the prospects of making an access door in the vehicle, above the battery, to access the problem resistor?  When I got tired of dropping the fuel tank to work on the fuel pump in my '90 Isuzu Amigo,  I cut an approx. 1 foot square access hole & made a cover.  I know metal dust/chips/shavings & sparks are not good for batteries/electronics, and I have no clue how big an area is needed to work on this.  Just thought I'd throw this out there.  Meanwhile my red Th!nk is approaching 12k miles, no issues, here in upstate NY.

Jeff S.

[Jim Houser]

Our first 2 failed pre-charge resistors on the MLEC boards were in the summer of 2012, shortly after the first cars arrived, and long before we were performing any updates.

Jim

Jim Houser
Hawthorne Auto Clinic, Inc.
4307 SE Hawthorne Blvd.
Portland, OR 97215
503-234-2119
503-234-4230, fax
www.hawthorneauto.com
j...@hawthorneauto.com

[Johnny]

I have a work around with pictures at the Yahoo group site. I also just fried my precharge resistor and am working on fixing it right now.  The workaround to keep the precharge from frying can be done through the radio opening by adding 2 relays, a time delay "on" relay and a 40A single pole power relay.  It is powered from the sunroof fuse (not used) so when the key is turned to "On" position, (not the accessory position)  the timer starts counting for 20-30 seconds.  When car is then started within the time, the heater / ac blower is off.  I did the heater fix before I started the MLEC fix.  As long as you "Start" the car within 20 seconds, your good and will not blow the board.

see text:

https://groups.yahoo.com/neo/groups/think_ev/conversations/topics/11178?reverse=1

See Pictures with comments:

https://groups.yahoo.com/neo/groups/think_ev/photos/albums/1019683942

Cost about 30$ and one hour to wire it in, but will save your MLEC board when you accidently turn key on quickly to roll up a window with the heater on or a unfamiliar driver is driving the car and does not know it will "Brick" the car with a careless restart and the heater on.

Johnny 

[Paul Steele]

Hi Hawthorne Auto Clinic,

I would like to have this fix on my vehicle if you think it is practical to do. I've been diligent but also lucky so far in switching every thing off when I park and double checking before starting but sooner or later I or my spouse are going to slip up. The cost of a couple of hours of shop time and parts would be a good long term investment to me.

Thanks, Paul

[ron.s...@duke-energy.com]

I would like to have the pictures and work around from Phil using the 2 relays but it says I am not a member. Mine just blew the MLEC for the 3rd time and was able to get a rebuilt board but want to try to keep it from happening again using the relay method. How can I become a member and get to the links?

[ron.s...@duke-energy.com]

Sorry I meant Johnnie

[hirs...@yahoo.com]

I own the Yahoo group.  I can't send you an invite or just add you because Google doesn't show me your full email address.  You need to have a Yahoo registration to access the group photos and files.  You can find and apply to the group here:   https://groups.yahoo.com/neo/groups/think_ev/info

[Joseph Lundgren]

Why is this group even private anymore? Seems like more of a hassle than it's worth.

--Joe

--

[Steve Bigelow]

Keeps the spammers off. Trust me -- you don't want it wide open for anyone to post.