Please clear up my 12 volt battery question - Smart Car Forums
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post #1 of 7 (permalink) Old 05-04-2019, 05:43 PM Thread Starter
 
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Please clear up my 12 volt battery question

I just bought a new Smart electric (2016 with 4k miles) on it and I am paranoid about the battery life and care. Actually If I read correctly if the 12 volt battery goes dead it can kill the traction battery. Is that correct. Didn't make sense as what happens when you need to replace the 12 v battery. Other question is I live in Donna, Texas just a couple of miles from the Mexican border so summers are very hot. Usually 100 to 105 every day. I don't drive very much. Usually only a couple of times a week to the store and a few other places as I am retired and an old fart. What is the best thing I can do to extend my traction battery life. Just open to suggestions. Thanks in advance.
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post #2 of 7 (permalink) Old 05-04-2019, 08:50 PM
 
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I ran my 12V battery down once due to leaving lights on, recharged it, and everything was fine. I'm sure that for many other people, this has happened too. You can remove and replace the 12V battery and nothing bad will happen.

We are working on various hypotheses for recent reports of HV battery packs being bricked after several months of storage. The common denominator was that the 12V battery was also dead - or in one case it was deliberately removed from the car to be kept indoors for winter storage. The hypothesis is that a dead 12V battery might be bricking the HV pack, but, even then, only if the 12V battery sits dead for a long time period - months. But it might be something else that is causing the problem.

Somebody at MB knows what the problem is, but they are not talking.

So, out of an abundance of caution, If you are storing your car for more than 3 weeks, I would recommend connecting a maintenance charger (trickle charger) to the 12V battery.

But unrelated to this, in warm temperatures, you should also NOT store the car plugged in for charging. It should be stored in a shady place with an indicated SOC of 60-80 percent or so for minimizing any time-related capacity degradation of the pack. You should keep the pack at a less than full state and in the shade as much as possible during regular use too - especially in hot weather.

So in your case where you are using it only a couple times a week, keep it about 60 percent, and do only partial charges whenever you don't need the full range. But, every 10 charges or so, you should charge it full, as charging full is needed to be sure all cells stay balanced (i.e. charged to same voltage).
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post #3 of 7 (permalink) Old 05-05-2019, 06:10 AM Thread Starter
 
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Thanks for the input. I think what worries me is so much talk about it. I guess it's true in any forum.I have driven only Toyota's for over 20 years. In that time I have never done one thing to any of them other than oil changes and routine maintenance. They were 100% reliable but you can still go on the Toyota forums and see all the problems people have. As always people post what is wrong but seldom how good a car is. I don't expect my Smart to even be close to what a Toyota is but just hope I don't have a catastrophic battery failure. I know the total amount of Smart electrics is small but still hoping that eventually someone other than Mercedes will come out with a traction battery that doen't cost a fortune. You can buy Prius and several other electrics now for somewhat a reasonable price. Just hope I don't end up with a brick as I am 70 and hope the car might last as long as I do. I guess if it gets bricked I can make it in to a front yard planter for my flowers.
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post #4 of 7 (permalink) Old 05-05-2019, 09:55 AM
 
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An aftermarket battery pack for the Smart is very, very unlikely. You have to realize that everything on the Smart - from the battery management syatem to simply turning on the headlights, is software driven, and all of that software is the copyrighted property of Mercedes Benz.

It wold probably be easier for an ev homebuilder to simply tear out all the MB-made stuff except the motor and mechanical drivetrain, maybe modify the onboard charger so it does not rely on MB's software, build a whole new battery pack with a commercially available BMS and put another commercially made (Sevcon or Chinese) inverter/controller to drive the motor, than it would to try to make a copy of the existing battery pack - which uses custom cells of dimensions not available commercially. Such a homemade Smart drive syatem could have more range too as there is room under the car for a bigger battery.
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post #5 of 7 (permalink) Old 05-05-2019, 10:06 AM Thread Starter
 
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Originally Posted by Yinzer View Post
An aftermarket battery pack for the Smart is very, very unlikely. You have to realize that everything on the Smart - from the battery management syatem to simply turning on the headlights, is software driven, and all of that software is the copyrighted property of Mercedes Benz.

It wold probably be easier for an ev homebuilder to simply tear out all the MB-made stuff except the motor and mechanical drivetrain, maybe modify the onboard charger so it does not rely on MB's software, build a whole new battery pack with a commercially available BMS and put another commercially made (Sevcon or Chinese) inverter/controller to drive the motor, than it would to try to make a copy of the existing battery pack - which uses custom cells of dimensions not available commercially. Such a homemade Smart drive syatem could have more range too as there is room under the car for a bigger battery.

I think your right and that sucks, especially for someone like me that wants to keep a car for a long time. I guess if I still have it when the batteries die maybe I can part it out if there is still any value in it.
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post #6 of 7 (permalink) Old 05-05-2019, 07:50 PM
 
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You should not think of this problem as being "when the battery pack dies". If you use and charge the car even only once a month, you won't encounter whatever the very specific combination of conditions is that is bricking the battery pack, and the battery pack will last a long time and only very slowly degrade.

I am at the 4-year point in my car and my pack diagnostics shows no more than 1 percent/year loss of capacity.
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post #7 of 7 (permalink) Old 05-18-2019, 11:44 AM
 
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Just purchased a 2015 Smart for Two Electric drive, after 5 days of limited driving and charging nightly, I had to replace the 12V battery ( it was the original battery and 4 years old) but my question is actually about the radio. Just before I had to replace the battery, the radio stopped working totally and after I replaced the battery the radio appears to be working and I can change channels etc. but no sound! I'm at wits end trying to figure it out. Any Ideas??

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