shotgun_banjo

I parked my car this morming besides a brand new GLE450 and it reminded me of my 450 as it was the same colour and interior. After 8 hours I went back and I saw a guy standing besides it looking pissed. He then asked me if I can give a boost and I just looked at him and literally said "oh you are f*cked!" I asked him what he is seeing on the dash and long and behold it was the 48v battery malfunction. Car is dead with only 4k clicks on the motor. I told him we cant boast it and it needs to be towed. Now here is the problem. We where at the 4th floor of a parkade with only 6'6" of headroom and the only way down is a tight spiralling ramp. The car literally needs to be dragged hundreds of feet and who knows what will break. Curiosity of me went "why not try to boost it as I never get a chance to do it with my 450 before" so I told the guy we can try but it might damage the vehicle if I boast it and he said he does not care as long as it runs and gets out of the parkade. Long story short, it did not work.

That scenario is why I decided to get rid of the V167 and go back to the old fashion X166. As much as I miss the fancy interior I kinda sleep a little better at night not worrying when will the car become a brick. Not sure what happened to the 450 but 45 minutes of trying to help out the guy was more than enough and I was hungry.

TonyF61

Brand new!!!! What a shame; I thought we were past that issue. Guess not. Well it was very kind of you to try to help out the poor soul.

stktyz33

Why would a jump start damage the vehicle exactly? The manual has proper procedure to do it. Having that said, it's not necessarily a charge issue.

chassis

This is how it is with MB ownership. Especially with 48V vehicles.

Bad reliability. The word is out. MB ranked 29 out of 30 in the most recent Consumer Reports reliability survey. The cars are nice looking pieces of rubbish.

mikapen

That's a relevant question. I can't think of any damage that could happen if you do it properly.

shotgun_banjo

I guy has no clue about his vehicle. I myself have not done it on a 48v system so a disclaimer must be said en all. The most expensive vehicle I jumped is a $68k BMW so doing one for a +$100k needs that kinda disclaimer in a way.

jkaetz

I feel like there is a lot of FUD surrounding jumpstarting/boosting. A running vehicle will typically be providing 14.7 volts to the electrical system. If that voltage is applied to a good but discharged battery (< 10 volts) it will begin to charge it. Jump cables typically won't provide enough current to start a car with a 100% discharged battery but they will provide plenty to start charging it. Once the discharged battery gains some capacity then the cables + the battery can usually provide enough current to run the starter. I've seen it stated that when the 2nd car starts and gets its alternator going the two alternators can be providing too much power but I'm not sure if I believe that as the systems would be connected in parallel and the voltage output would not be added together, only the current providing capacity would be added. Additionally, IMO, the batteries in both vehicles should act like large capacitors and smooth out any voltage spikes. The recommendation I've seen to combat this is to use the running car to charge the dead one for 5 - 10 minutes then shut down the running car, keep the cables connected and see if the two batteries together can start the dead car. The simplest solution is of course one of the small lithium battery jump starters but I doubt most people carry these around. Finally all of this is moot if the starter is 48v.

mikapen

I agree with your post, especially the summary that I quoted.

However, I think (hope?) that a dead (not defective) 48 volt battery would respond in the same way, through the 12- 48v converter.
And therefore be able to start the engine after an appropriate soak time.

Unless there's a complete battery failure, but that would be true of a 12-volt only system, wouldn't it?

I carry one of those 2500A jump starters, it works great on 12v batteries, but I can't really test it on my 48 volt system until I have a problem 😕.

I don't have access to my owner's manual right now, but I don't remember mention of a different jump start procedure for cars with 48v.

mikapen

Duplicate post.

jaxslk

From my 2022 manual :