Broken B250e

[hallcp]

Two scraps of information for you. Borrow a voltmeter and check the 12V battery voltage with the car off. It should be around 12V if not higher. If it's down to 10v or 11v then it's time to replace.

Second, the (original I presume) battery on my 2014 showed low voltage when I checked in 2019 so I replaced it. Watching voltage while turning on heat or headlights without the car fully turned on will load test the battery. Still should show 12-ish volts.

One other thought, someone on the list pointed out that when you "pre-heat" the car, perhaps by enabling it and clicking "un-lock", the 12V battery is used to produce the heat, not the big high voltage battery. Same if you turn the key one notch, but not two (mine still has a key, not a push-button). There's also that button on the dash to maintain climate control while the car is off. Same thing, it uses the 12V battery.

With the car fully awake, measuring battery voltage will only show you charging system's voltage (something over 13V, steady as a rock).

I am totally unclear if preconditioning while on charge is using the 12V or high voltage battery. I think the designer's intent was to try and avoid surprising an unwary mechanic with high-voltage when he thought the car was off.

Finally, I think almost all modern cars go completely haywire when the 12V battery finally fails. The car can show all kinds of crazy symptoms.

 

[FordAnglia]

So with that being said, would you consider replacing the 12v battery as maintenance item? If so, what interval? We haven't replaced ours yet (purchased in Sep'17 a 2015 model). I'm simply trying to prolong our use of this car, knowing how problematic they can be. We have been going strong on the new drive unit (14k miles and 18 months)

We don't have enough data to predict a B250e 12V battery fail, and replace it beforehand. To blindly replace the battery based on the date code, or vehicle miles seems wasteful to me.

A better plan would be to use a roadside service (AAA for example) to replace a defective battery. Often they have the replacement battery on their truck and also take credit card payments. Their tools can measure the health of the battery before pulling it out of the vehicle, and monitor charging performance (as an ICE car with alternator issues will result in a dead battery)

Peter,

 

[Deena Waite-Bettencourt]

I purchased 2 B250e Mercedes here in FL. One had 14K miles the other 27K. I loved both cars but they both had a warning light co upposed to have the highest level of ev trained techs) totaled both cars saying they could not get parts.
I am now fighting with them about the second car that has been sitting there for 4 months while they are trying to figure out what was wrong. I have reached out to Mercedes and they just are throwing the whole issue back on the dealership.
Exhaused.

 

[Electric Benzo]

I purchased 2 B250e Mercedes here in FL. One had 14K miles the other 27K. I loved both cars but they both had a warning light co upposed to have the highest level of ev trained techs) totaled both cars saying they could not get parts.
I am now fighting with them about the second car that has been sitting there for 4 months while they are trying to figure out what was wrong. I have reached out to Mercedes and they just are throwing the whole issue back on the dealership.
Exhaused.

I feel for you because I am in the same predicament where I purchased my B250e here in Virginia, “as is” was able to drive it for a month before it completely stopped on me. I am now paying for a car that I cannot drive. Such a waste! I do not fall under the lemon law because I purchased the vehicle as is from the dealership. Lesson learned!

 

[BusyB]

I had issues from the first day I purchased my B Drive from a dealer in 2015. It was in and out of service for a year. There were continually error messages that would cause the car to be inoperable. Finally I requested a replacement car under the lemon law. They couldn't find a replacement anywhere in the US. I requested that they replace the complete wiring harness. They complied. Problem fixed. Everything has been fine since, and we love our little car.

 

[Bill Walker (Camaro3097)]

I bought an electric drive (2015) and got about ten months out of it. Few weeks ago I took it to electrified garage in ocala, FL to have it checked. Turns out coolant and sludge are in the motor and they are rebuilding it now. At a cost of 6k to fix and I owe 19k on it. I hope the rebuild goes well and I can at least get a few more years out of it until it’s paid off. Other than that it’s my favorite car to drive hands down.

 

[asavage]

My advice: don't join Tony's private forum on FB. He won't participate elsewhere due to criticisms on his ongoing business . . . problems. He only works on the Tesla parts of the B250e, and you'll get excellent advice from the Tesla and RAV4 EV communities that won't involve having to deal with a person who can't figure out how to use email, return a VM, or honor a business commitment.

Alex, who works for Tony, has done some excellent YT videos, and so far nothing he has said publicly has been bad advice, but . . . that alone doesn't make QCC a good first choice for repair.

$6k for a Tesla LDU ("Large Drive Unit") reseal and light repair is about the going rate, give or take. Be sure and ask about getting a "coolant delete" for the rotor cooling at the same time, to eliminate the rotor seal leakage problem in the future. I know of at least three firms selling a replacement cooling manifold to do this, and Tesla Remans (Rev U+) have this done by Tesla, they've given up on trying to keep them from leaking.

If you have a rotor seal coolant leak and you're unlucky -- as a lot of used early Model S owners are discovering -- the coolant ruins the stator windings' HV isolation resistance to the extent that they can't be "dried out" and used, and since the stator is bonded to one half of the gearcase . . . expensive. Re-Volt in Arizona says they have a process to dry low-Iso stators out; I have no feedback on their success rate. One fellow has THREE low-Iso stator/gearcases, beyond repair.

If you have ANY EV check warnings, pull (or have pulled) the LDU speed sensor and check for Blue Drops of Death: G48 coolant in the reluctor cavity. The longer a stator sits in wet conditions, the less chance of salvaging it, and on the B250e and RAV4 EV, there are not a lot of used gearcases around to use for parts -- and Tesla won't sell parts.

--

For completeness, there's another way that water gets into the LDU, on the inverter side instead of the motor side: the HV cables into the LDU have vertically-mounted cable glands, and esp. in places where road "salt" is used, they corrode badly, and allow rainwater etc. to enter the inverter side. A new post just today, with pictures is here.



Not only does this allow water into the inverter side, it can also lower the HV system's HV Isolation. Fortunately, these cables can be purchased (though IDK if they're available new for the B250e).

 

[jjo]

I'm part of the FB forum and I don't think it's Tony's private forum, it's managed by someone else. Nevertheless, he treats it like it existed to support his business.

 

[nrkmann]

I bought an electric drive (2015) and got about ten months out of it. Few weeks ago I took it to electrified garage in ocala, FL to have it checked. Turns out coolant and sludge are in the motor and they are rebuilding it now. At a cost of 6k to fix and I owe 19k on it. I hope the rebuild goes well and I can at least get a few more years out of it until it’s paid off. Other than that it’s my favorite car to drive hands down.

I would get a detailed description of what they are doing. Usually this is a transmission problem not a motor problem. Usually cleaning out the sludge is replacing the seals and the two motor bearings unless there has been sludge intrusion into the battery. See oiher posts on this Forum and there are som good YouTube videos on this. This is a Tesla Model S motor run backwards because it is flip-flopped compared to the original Tesla S.

Search YouTube: mercedes b class electric transmission problems

 

[Hussain]

2 years ago we took delivery of a new B250e. It's been just fine, apart from the limited mileage but 3 weeks ago it stopped working; would switch on but wouldn't move. Since that time it's been in the MB workshop and they appear to have been struggling to diagnose the problem. Today we received notice that they've decided it needs a new drive unit, which they don't have either here in the UK or in Germany. So they've ordered one -I guess from Tesla? - and to date they don't know how long it's going to take to arrive. Given the car is discontinued, does anyone have any thoughts on how easy and how quickly it's likely to take to get over here and fitted? We're borderline demanding a refund.

H.

Better get the refund ,these all drive unit have manufacturing defect ,people reported they change the drive unit 4 times and still not sure about the 5th one

 

[Brittnie]

May I ask what happened with you b250 e ? What issues and do you have it still ?

 

[laurentm]

Hi everybody, I have found this site in Poland, they repair the motor. I think it's much cheaper than buying a new one.

https://sts.parts/en/articles/repair-of-mercedes-benz-b250-ed-with-tesla-electric-motor