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I have a 2014 Smart ED I purchased in May of 2014 with around 1800 miles on it. I tried to drive it yesterday but the doors were locked and the remote key would not unlock them. I used the key the old fashioned way to get in and found all power was off. I found the 12 volt battery (why is there one anyway) and attached a trickle charger overnight. Now when I turn on the key I get a couple a weird message on the dash. "HV System Workshop" . Also the red battery light is on.
Do I have a defective 12 volt battery? I know if you only drive a gas engine auto on short trips your battery will eventually give out. is that the same with the Smart ED? If so thats crazy since thats the purpose of a Smart ED- short intown trips.:shrug:
 

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Either a faulty 12V battery or an issue with the dc to dc converter that charges the 12V battery from the HV pack.
 

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Discussion Starter #3
Thanks Huronlad. So I assume I need to take it to the dealer? So the HV battery pack charges the 12 volt battery? it isn't just charged by driving?
 

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The car is under warranty, make smart fix it.

As I understand it and I stand to be corrected as I do not own an ED.

The 12V should be topped up when the car is being charged by the 120Vac or 240Vac source. When driving the car and using 12V accessories the HV pack will top up the 12V battery as needed.

If the dealer replaces your battery and if the dead 12V battery happens again, I would expect the problem to be the dc to dc converter.
 

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Putting a 12V lead acid battery in an EV seems like bad engineering. In my opinion, the 12V loads should be driven directly by the DC-DC converter.
 

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If something happens to the HV pack then you have no power to power anything, important things like the SAM and warning lights.
 

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If something happens to the HV pack then you have no power to power anything, important things like the SAM and warning lights.
You're right. If the HV battery were to be abducted by space aliens, then the warning lights wouldn't work. On the other hand, if the HV battery were drained to a level that it couldn't drive the car, it could still drive the DC-DC converter. The realistic failure mode would be the DC-DC converter itself, not the HV battery, though DC-DC converters are very reliable. If that's a legitimate concern, I'd rather have two DC-DC converters in parallel than just one and a 12V battery.
 

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There have already been reports of a couple owners with HV pack problems. The dc to dc converter likely costs more than a battery by all means let put two of them in there. The SAM is fairly voltage sensitive, relying on a reduced voltage from the converter may not be as reliable as just putting a $20 12V battery in the thing.

By law the 12V battery likely has to be there for redundancy.
 

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There have already been reports of a couple owners with HV pack problems.
I'm willing to bet that every single Smart ED HV battery that needed replacing was still capable of powering a DC-DC converter. 100V would have been more than enough.

The dc to dc converter likely costs more than a battery by all means let put two of them in there.
300W DC-DC converters with 100V to 370V input as typically used in EV conversions (with all the certifications needed for automotive use) cost $100 to $200 in single unit pricing. That's about the same as the cost of a typical small lead acid battery like the one in our Smart EDs. Unlike the very heavy lead-acid battery, a 300W DC-DC converter weighs about 1 kilogram (and takes up much less space than a lead acid battery).

The SAM is fairly voltage sensitive, relying on a reduced voltage from the converter may not be as reliable as just putting a $20 12V battery in the thing.
Lead acid batteries output a very wide range of voltage depending on their state of charge. A nominally 12V (six cell) lead acid battery can produce anything from 14.5V down to less than 6V. A nominally 12V (four cell) LiFePO4 battery would be better for voltage sensitive equipment, dropping from 13.6V to 13.2V over nearly its entire state of charge range, finally dropping to about 10V as discharge is virtually complete. A DC-DC converter would be optimal for voltage sensitive equipment, maintaining a solid (for example) 13.5V whether the HV battery is fully charged, discharged to the point where the car refuses to drive, discharged to the point where it couldn't spin the motor even with the wheels jacked up in the air, and even with 2/3 of the cells shorted out and producing only 100V overall the DC-DC converter would still be outputting a solid 13.5V.

As for reliability, lead acid batteries are one of the least reliable components found in any automobile. Who has ever driven a car for ten years and not had to replace the battery (at least once)? DC-DC converters, on the other hand, are highly (not perfectly) reliable.

It would not add much to the cost to build a 300W DC-DC converter that internally had two 150W units in parallel with a CANbus connection that would signal when one of the internal units had failed. It could signal a fault via the CANbus but still provide more than enough power for all safety related 12V equipment.

By law the 12V battery likely has to be there for redundancy.
That may be. Laws rarely keep up with technology. Taxis in London are still required by law to carry hay to feed the horse pulling the taxi (not enforced, but still on the books).
 

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150W will never run the the necessary 12V systems. A 12V battery is the cheapest and easiest solution to the problem.
 

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150W will never run the the necessary 12V systems.
Fine. Whatever size DC-DC converter is needed is still a tiny fraction of the size and weight of a lead acid battery. The cheapest and easiest solution is sometimes the best solution, but not in this case.

A 12V battery is the cheapest and easiest solution to the problem.
... and the heaviest and least reliable solution, which is why lead acid batteries are not used for the HV battery. At least some of the EV manufacturers are now using Lithium 12V batteries rather than lead acid 12V batteries. The home-brew EV conversion all (or virtually all) dispense with the 12V battery altogether and rely on the DC-DC converter. I've never heard of one having any problems relying on the DC-DC converter.
 

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Putting a 12V lead acid battery in an EV seems like bad engineering.
As with most things in life, there is a good reason for the way things are: The 12V battery is necessary to provide power to boot the controller. When parked the HV traction battery is disconnected for safety reasons. As such, the HV battery cannot provide power to boot on the on-board controller. The 12V battery provides the power to boot the controller and provides reserve power for the 12V accessories when the HV battery is disconnected. If the 12V battery is dead, the ED cannot boot the controller so the HV battery never gets connected. So a dead 12V battery means a dead ED.

In my opinion, the 12V loads should be driven directly by the DC-DC converter.
The 12V accessories in the ED are driven directly from the HV battery when the ED is in the "ready" mode. The DC/DC charges the 12V battery and provides power to the 12V accessories exactly like the alternator in an ICE car does.
 

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As with most things in life, there is a good reason for the way things are: The 12V battery is necessary to provide power to boot the controller. When parked the HV traction battery is disconnected for safety reasons. As such, the HV battery cannot provide power to boot on the on-board controller. The 12V battery provides the power to boot the controller and provides reserve power for the 12V accessories when the HV battery is disconnected. If the 12V battery is dead, the ED cannot boot the controller so the HV battery never gets connected. So a dead 12V battery means a dead ED.
That makes sense. It would also make sense, in my opinion, to have the motor controller disconnected from the HV battery for safety reasons while parked, but leave the DC-DC controller connected to the HV battery at all times.

Anyway, I hope that the 453 ED will at least upgrade the 12V battery to from lead acid to lithium.
 

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Bought my ED about same time as last year. It sat for about 2 weeks in garage and was dead when I went to use it. I fully expected the wife had left a light on or something to drain battery. Not the case. Jump start worked and I drove it around block and back into garage. Turned off and on again fine. Next day, dead again. Jump start wouldn't work again as propulsion system wouldn't come online, so had to have it towed. Big battery showed over 80% charge.

Just got word test on car fine, but battery would only put out 10v and change, so battery replaced under warranty. Never had that happen on new car and I have leased quite a few over the years. Perhaps MB isn't installing the best 12v batteries or perhaps they had a bad run. Either way, even 2 (that we know about) out of 2k EDs sold seems like a lot.
 

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But this isn't new technology failing. These are just the regular old 12V car batteries. But yeah, that's what warranty is there for. Odd that the battery failed though.
 

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Perhaps MB isn't installing the best 12v batteries or perhaps they had a bad run. Either way, even 2 (that we know about) out of 2k EDs sold seems like a lot.
Odd that the battery failed though.
Lead acid batteries have never been highly reliable. That we know about 2 failures out of 2000 means there are probably additional failures that we don't know about.
 
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