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Discussion Starter #1
My wife has a 2015 Smart ForTwo that says "Malfunction" when we plug it into our charging station. She hadn't been driving due to the pandemic. Accessories/lights etc. seem fine so I think the 12V is fine.

Is the car toast? I can't even find a price online to swap out the high-voltage battery if it's fried; the car is probably only worth $3000 and I heard that the full lithium battery costs more than the car (can anyone confirm?)

I've plugged it into the low-voltage wall charger now to see if it manages to charge overnight, but the dashboard now just says "Charge HV Battery Now" and doesn't give any indication that it's actually charging....

The Mercedes-Benz dealerships around me are pretty crappy -- most of them won't even service their own Smart brand; there's only one super far away that we can take it to for maintenance, but if it's totaled I don't think it makes sense to tow it a long way to a dealer...
 

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Don’t assume 12v is fine unless you have checked it properly. It might have enough for the accessories but not enough to allow the car to start or take a charge.

It’s also worth trying to disconnect the 12v battery for a short while before trying again, if the voltage is confirmed good.

Basically if in doubt, blame the 12v battery. It’s almost always the source of all problems in an EV. Only then should you worry about it being something more serious.
 

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Discussion Starter #4
Thanks -- I'll check the 12V then as well. The manual made me nervous as it says in one place not to leave the car unplugged and not charged for more than 2 weeks.... so I'm wondering if the HV battery will die permanently in this case.
 

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The warning in the manual relates to the 12v going flat and not having the capacity to engage the contactors to allow the HV battery to charge. A feature of the Smart is that the 12v isn't charged from the HV unless the car is running (as in ready to engage a gear and drive, not just Aux on). Most EVs charge the 12v from the HV if it isn't run for a while, for example the LEAF does every 24 hours.
Leaving the HV battery alone for a period of time is unlikely to kill it entirely. Do you have any idea of roughly what level of charge it was left at?
If you have jumpleads you can use another car to lift the 12v temporarily to see if the HV will charge. Don't bother running the other car, just connect the 12v systems in parallel.
Good luck.
 

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Something similar happened to me when I came back from a long 3 week vacation last year. It was a MB B-250e, but same issue.. dead.. then I used my wife's CRV to jump it and it was fine. I replaced the 12v battery and have been good to go ever since.
 

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Discussion Starter #7
Thanks so much for the advice here! I went out and bought a 12V charger (Noco Genius 2) and pulled out the 12V to charge it. The Noco reports that the 12V was indeed very low, so I'll let it charge overnight, reattach, and then hope for the best!

I also tried the suggestion from dk6780 to connect the 12v systems, but that didn't work. I guess it's possible that one of the cable connections wasn't good, but I decided it was nice to just charge the 12V completely and then see if that allows HV charging again. Fingers crossed! Will let y'all know how it goes.
 

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The warning in the manual relates to the 12v going flat and not having the capacity to engage the contactors to allow the HV battery to charge. A feature of the Smart is that the 12v isn't charged from the HV unless the car is running (as in ready to engage a gear and drive, not just Aux on). Most EVs charge the 12v from the HV if it isn't run for a while, for example the LEAF does every 24 hours.
Leaving the HV battery alone for a period of time is unlikely to kill it entirely. Do you have any idea of roughly what level of charge it was left at?
If you have jumpleads you can use another car to lift the 12v temporarily to see if the HV will charge. Don't bother running the other car, just connect the 12v systems in parallel.
Good luck.
To answer this question: I think that 8 weeks ago the car was at around 80% charge. So that's about 56 days without power.
 

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It sounds like the 12v is the problem, and the HV battery will not have been damaged if left at that level of charge. Hopefully a long gentle recharge will let the 12v recover.
 

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If it’s not already been said, the 12v battery may have been damaged so won’t retain charge. You might want to replace it in any case so you don’t get stranded.
 

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Discussion Starter #11
I charged the 12v, but it still refuses to charge the HV battery. I think it's bricked, which seems to happen to lots of Smart ForTwos out there, and Mercedes doesn't care and only offers to sell a $10k replacement. The dealer was absolutely worthless on the phone today; they don't want to support Smart.
 

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I charged the 12v, but it still refuses to charge the HV battery. I think it's bricked, which seems to happen to lots of Smart ForTwos out there, and Mercedes doesn't care and only offers to sell a $10k replacement. The dealer was absolutely worthless on the phone today; they don't want to support Smart.
That’s odd, as they’re still selling them. But of course this is the US.

What voltage reading are you getting from the 12 volt battery?
 

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Discussion Starter #14
That’s odd, as they’re still selling them. But of course this is the US.

What voltage reading are you getting from the 12 volt battery?
It's reading 12.41V now (currently it's attacher, back in the car). I assume 12.41 is a good enough charge, right?
 

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Discussion Starter #16
The warning in the manual relates to the 12v going flat and not having the capacity to engage the contactors to allow the HV battery to charge. A feature of the Smart is that the 12v isn't charged from the HV unless the car is running (as in ready to engage a gear and drive, not just Aux on). Most EVs charge the 12v from the HV if it isn't run for a while, for example the LEAF does every 24 hours.
Leaving the HV battery alone for a period of time is unlikely to kill it entirely. Do you have any idea of roughly what level of charge it was left at?
If you have jumpleads you can use another car to lift the 12v temporarily to see if the HV will charge. Don't bother running the other car, just connect the 12v systems in parallel.
Good luck.
Do you think the 12.41V I'm reading in my battery after charging is high enough? I mean, it's over 12 so it seems like enough to me, but I'm not an expert. I still get the error "charge HV battery now" but plugging the car into either the travel/wall charger or the charging station doesn't start the charging process.
 

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It's still low, you'd expect 12.6v. However, the no load voltage is not the best test as a damaged battery will show a reasonable no load voltage but dip significantly when subject to load.
Given that the car is still refusing to charge and you have no support from Smart/MB I can only suggest replacing the 12v.
 

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Discussion Starter #18
It's still low, you'd expect 12.6v. However, the no load voltage is not the best test as a damaged battery will show a reasonable no load voltage but dip significantly when subject to load.
Given that the car is still refusing to charge and you have no support from Smart/MB I can only suggest replacing the 12v.
Thanks again for the advice. I bought a new one at the local AutoZone, verified the voltage of the new battery, and installed.. and had the same issue. Pretty sure it's really the HV battery, which other Smart Fortwo owners seem to be complaining about a lot; seems like it's extra-prone to bricking. In any case I'll try to tow it to the dealer so they can confirm it's busted.
 

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Discussion Starter #19
FYI here's more info on how the Smart FortTwo EV is flawed and will self-destruct quickly:


Note that I double-checked the manual. It actually says in one spot that if you will leave the car without power for an extended time, you must ensure that the temperature is between -4F and 104F to avoid "irreversible damage". But actually you get irreversible damage just for leaving it unplugged for 1 month.

If anyone else runs into this, let me know; I've sent a note to a legal team and I'm looking into either class-action or a simple small-claims case.
 

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I wonder if it would be worth disconnecting the HV battery from the control electronics overnight also, in case you can get the electronics to 'forget' there is a problem?

(Take the 12v off first.)
 
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