Broken battery charger

[northernlights]

My B-class refused to start, so I brought it in to the dealer. Apparently the "charging unit" went bad and needs to be replaced to the tune of $10k! I'm looking around to see if I can find a second hand unit, or some alternative that is functionally equivalent that might be cheaper (i.e perhaps a tesla unit is compatible?). Does anyone know anything about the charging unit? Even what it is called so I can google more precisely? This is the internal piece that takes the AC voltage fed in to the charge port and converts it to DC to charge the battery.

 

[JeffRay]

Northern Lights,

Sorry to hear about this, sounds like they want to replace the entire battery plus charging unit. Perhaps you can pm Tony Williams as he is the resident charging expert and a member. Also, there is HallCap, aka Charles, who seems to be able to come up with schematics at will so you can identify the particular part.

There seem to be a number of retired B250es who are being used as "hanger-queens" for parts if you want to procure the part cheaply. You will still need someone who is skilled and has the experience to replace the part for you. You are in canada if I recall correctly so it would mean possibly shipping the car to the west coast unless you feel you can do it yourself as you have made some modifications on yours already and are more skilled than the rest of us.

 

[FordAnglia]

My B-class refused to start, so I brought it in to the dealer. Apparently the "charging unit" went bad and needs to be replaced to the tune of $10k!

Sorry to hear of your troubles. The quote doesn't make sense to me, perhaps I missed something?
"Refused to Start" - Is the instrument cluster dark? Or, does it light up? What battery level (driving range) is displayed?

"Charging unit" - You are correct that this module conditions the incoming AC during charging. It is located under the rear deck floor, and is made by M-B (and not by Tesla)

As you may know, there are two battery systems in most (if not all) EVs. The high-voltage battery stores energy to drive the vehicle, but the 12V Battery is much like an ICE vehicle. It is used to "start" the EV drive train, and also power the normal automotive electrical devices (exterior lights, headlights, media, instrumentation, etc.) This is a conventional lead-acid battery. An EV can even be jump-started if the 12V battery fails (but the high voltage battery has a charge)

Under normal operation the 12V battery is charged from the high-voltage battery through a DC-DC converter, when the EV is turned-on. 12V Battery failure is the number one cause of Tesla vehicle failures, and presumably this applies to all other EV platforms. Any competent auto repair shop can test the 12V battery for state-of-charge, charging and discharging current, and at the very least read the manufacturing date and remaining warranty from the label. Failure of the DC-DC converter (or a safety trip) is possible, in which case the 12V battery would discharge and stop the vehicle from being operated, even if the high-voltage battery is charged.

I'm new to the B250e, so I haven't explored where the 12V battery lives in the vehicle, and what size is used (might be quite small as it does not need to crank over an ICE, but does power the heated rear window, seat heaters, etc.)

There are many safety features on any EV, it is possible that one (or more) have tripped to prevent the vehicle from being driven. I'd want a more thorough investigation before jumping in and replacing a module on hearsay.

Please keep us informed of your progress.

Peter,

 

[northernlights]

Thanks for the replies. I've learned a bit more since my original post. The issue is the onboard vehicle charger (MB part # 242982062180) has died. I'm able to find this part for $5k from various MB parts suppliers, and I can find a Tesla unit (part # 6009278-00-F) that seems to be functionally equivalent for about $1k on eBay. One of the eBay listings even mentions that it is compatible with the B-Class. Unfortunately it also mentions that after installing it, the unit needs to be programmed by the dealer to work with the cars battery - apparently it is paired somehow. My dealer is clueless about this, but said he'd be willing to TRY to program it for $2k with no guarantee that is will work. I'll reach out to Tony as Jeff suggested (thanks for the tip) to see if someone who knows more about how this all works can help educated me. I'll post an update when I have one.

 

[JeffRay]

Northernlights,

So I am at my MB dealer, charging my unit which is a weekly chore. At least it is free vs. parking at commercial lot for more than 2 hours and paying a $20 charge fee ($54 last time total). AND, I entered a raffle and won $250 worth of MB accessories. Woo hoo.

So at the workstation was a schematic of parts from mboemonline.com. There, I found the battery charger part, see below, listed for $4799. It is a good site as it has schematics for our car.

https://www.mboemonline.com/oem-par...yaWMtZHJpdmUmeT0yMDE1JnQ9YmFzZSZlPWVsZWN0cmlj

 

[FordAnglia]

So at the workstation was a schematic of parts from mboemonline.com. There, I found the battery charger part, see below, listed for $4799. It is a good site as it has schematics for our car.

https://www.mboemonline.com/oem-par...yaWMtZHJpdmUmeT0yMDE1JnQ9YmFzZSZlPWVsZWN0cmlj

Jeff et al.,

Thanks for posting the link to find replacement parts. I poked around and there are several fuses (item 6) listed, too.

Before replacing the battery charger module I'd take a look at fuses that may have blown. Easy to check with a DMM.

The theory is an electrical surge could blow a fuse (to protect the equipment) and be the only issue for repair. If there is a real fault the replacement fuse will blow too, at not much cost compared to the replacement module.

Note that the lower amperage fuse was discontinued, possible due to nuisance tripping? I recall these was an issue on the BMW MiniE charger for similar reasons.

6
FuseFuse
000000-008239
BATTERY CHARGER, 35 AMP
$5.46

6
FuseFuse
000000-008240
BATTERY CHARGER, 40 AMP
$2.41

6
FuseFuse
000000-008241
BATTERY CHARGER, 50 AMP
$2.54
ADD TO CART

6
FuseFuse
2429820036
BATTERY CHARGER, 20 AMP
Discontinued

Peter,

 

[northernlights]

Just an update. I bought a refurbished Tesla Gen 1 10kW on board vehicle charger on eBay for $650 and brought it to the dealership so they could swap out the broken charger for this unit. Unfortunately after working on it they told me it was incompatible because it had different plug connectors. I brought the car home and decided to work on it myself. I pulled the bad charger out and opened it up. It was exactly the same as the replacement unit I bought on the inside, but had different electrical connectors on the outside. So, I swapped the internals and put it back in the car. Now I need to get it back to the dealership to get it programmed. I'm hopeful that this will work - I'll post an update when it is done.

Oh - Also I was able to determine what the problem with the original unit was - there was a small spot of soot on the inside of theon board vehicle charger housing cover indicating something had overheated. I identified the location on that was right below this spot on the cover and sure enough found that one of the surface mount ferrite beads on the control board had exploded. Replacing it would cost about 25 cents and some delicate surface mount soldering, which I may do later, but for now I am just going to use the replacement charger I bought on eBay.

 

[JeffRay]

NL,

Very handy of you. Go for it and let us know how it works out. Love the fact you are willing to try to fix instead of simply replacing at MSRP.

 

[barsaec]

Awesome job. Good luck with the reprogramming.

 

[FordAnglia]

Oh - Also I was able to determine what the problem with the original unit was - there was a small spot of soot on the inside of the on board vehicle charger housing cover indicating something had overheated. I identified the location on that was right below this spot on the cover and sure enough found that one of the surface mount ferrite beads on the control board had exploded. Replacing it would cost about 25 cents and some delicate surface mount soldering, which I may do later, but for now I am just going to use the replacement charger I bought on eBay.

Congrats on a successful repair! Can you post PIX of the MB and Tesla-style connectors, and more importantly the charred component?

Thanks In Advance,

Peter,

 

[northernlights]

Photos of the Mercedes Charger, the damage component and the replacement Tesla charger are at https://photos.app.goo.gl/XuKYn61gkeJNxFTt7. You can view the activity stream for annotations, but basically what they show is: the first few pictures show the charger with the angled bracket on the right side that the orange HV wires connect to. This bracket doesn't exist on the Tesla charger (the wires have different connectors and plug directly into the side of the box). The next picture shown the Inside of the box the lid with the the sooty spot indicating the area where overheating occurred. The next photos are of the circuitboard and a closeup of the area under the sooty spot - the element labeled FB2 is clearly the culprit as it appears to have burnt up. In the last picture you can see the internals of the box are connected to the housing by the thick brass bars on the right. By unscrewing the screws that attach these bars to the internals, I was able to swap the internals and keep the Mercedes Benz housing that has the angled bracket so it can still interface with the car.

 

[FordAnglia]

Photos of the Mercedes Charger, the damage component and the replacement Tesla charger

Thanks for sharing your PIX.

The next photos are of the circuitboard and a closeup of the area under the sooty spot - the element labeled FB2 is clearly the culprit as it appears to have burnt up.

Understatement - FB2 certainly took one for the team!

The problem going forwards is whether FB2 was the weak link, and another component failed, and that overloaded FB2.
BTW, FB2 is quite small compared to other power electronics parts in your PIX, and likely in a low power circuit path.
A ferrite bead (assuming that's the meaning of 'FB') typically has a power limit rating, rather than an over-voltage limit rating typical of semiconductor devices. I recall you said this problem started with a utility power surge while charging, and leads me to thinking this was an over-voltage event.

Appreciate updates as you dig further.

Peter,

 

[northernlights]

I'll keep you posted - at this point I just need to get it back to the dealership to have the new charger programmed. I may never know whether FB2 is the only damaged part or not as I have swapped the internals of the entire charging unit with the Tesla unit. I though about trying to replace the ferrite bead, but since I had already purchased a replacement charger and replacing FB2 would require some seriously challenging surface mount soldering (including stripping off the conformal coating on the circuitboard and repairing the pads that it is soldered to), I'll probably sell the old charger on eBay for parts rather than try to fix it.

 

[northernlights]

Update:

Well I putt the refurbished Tesla charger in and towed it to the dealership to get it programmed to work with my car, however they tell me that after three hours of trying they were unable to get it programmed. I don't know anything about what they tried or what the issues were, but my experience with the dealership has me convinced they don't know or care much about servicing this vehicle. Without any other options apparent I expect I will be selling the car as-is for pennies soon.

 

[JeffRay]

NL,

This is bad news. If you are serious about scrapping it, may I respectfully suggest that you sell your parts online to other B owners on eBay as parts are hard to come by. For example, having hard time getting OEM rear tail headlamp for my 2017. eBay has one for $250. My mechanic also had to source parts for front end, headlamp and fender. Was unable to get OEM left front quarterpanel so he intends to bend the steel back.

You seem pretty handy and can be helpful to other B owners. How about it?

 

[FordAnglia]

Unfortunately it also mentions that after installing it, the unit needs to be programmed by the dealer to work with the cars battery - apparently it is paired somehow. My dealer is clueless about this, but said he'd be willing to TRY to program it for $2k with no guarantee that is will work.

Would it be possible to transfer the memory device(s) between the two units? (that presumably contain the data required to "pair" the new charger unit to the existing high-voltage battery)

Peter,

 

[northernlights]

I was thinking the same thing, but as far as I can tell the elements that need to be programmed are on the same board that had the part failure. I did make an attempt to repair the damage on the board - I scraped away what was left of the burnt up ferrite bead and put a short in its place. I then swapped this "repaired" board into the new charger that I had installed, but alas it didn't work - I got a different error message "Stop shut off engine" when trying to turn on the car. Alas, it seems my board repair was unsuccessful.

 

[FordAnglia]

I was thinking the same thing, but as far as I can tell the elements that need to be programmed are on the same board that had the part failure.

Tesla Motors approach to vehicle maintenance is OTA (Over The Air) software updates. I think they were the first car company to do so.
It doesn't look like the B250e has this feature. I would therefore expect the dealer's service bay to have some sort of hardwired connection to do this.
Is that what your dealer was trying to do? Or, was it much more "low-level", where they were attempting to update just the module you have replaced?

Before writing-off your B250e, perhaps M-B corporate (in the USA) can step in?

I did make an attempt to repair the damage on the board - I scraped away what was left of the burnt up ferrite bead and put a short in its place. I then swapped this "repaired" board into the new charger that I had installed, but alas it didn't work - I got a different error message "Stop shut off engine" when trying to turn on the car. Alas, it seems my board repair was unsuccessful.

Bravo for having a go! I'm not too surprised at the outcome. Optimistically, there may be a single component fault (the FB being collateral damage)
It would require access to the board level schematics, possibly also to a bench fixture, and electronic test equipment. I don't think we'll get any of that as end users. Pity.

Peter,

 

[solardell]

I was presented with a bill to replace the charger for $9,800. This after last month the electric motor went bad with the whining sound. That repair was $8,500. Off to the scrap yard the car went the salvage yard giving me $3.300 to take it away.

I did the exercise of calculating my total cost of ownership per mile driven (48,476 miles) and it came to $1.05/mile. ;( Lessen learned, don't own this vehicle without warrant coverage!!!

 

[JeffRay]

Solardell,

This IS the worst case scenario. Not sure I would have replaced the battery like you did. My experience with cars is when it starts misbehaving, get rid of it as the chances for worst case increase.

While you had a lemon of sorts and the car is otherwise mostly trouble free, it is a cautionary tale to buy any limited issue used car out of warranty. Despite your unfortunate incidence, I would still buy mine off lease at a negotiated price around $15K but only if I can get an extended warranty that covers the battery and the electricals. If not, downsize to my two older ICE cars and wait and see.

Right now, with the lock-down, am driving only to the grocery store. Have to talk to my insurance company about that.