Smart Car of America Forum banner
1 - 20 of 22 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter · #1 ·
I'm looking at a used 2018 with 23,000 miles and the dealership tells me that the battery will be replaced before I buy it. It is currently at 40%. It's in-service date was in 2019.

Is that typical or does it indicate premature degradation? My concern is that if they replace the battery and there's an issue with the car causing the issue, then it may happen prematurely again.

The salesperson said that the 8 year warranty (from the in-service date) should still apply on the next battery, but he wasn't 100% sure.
 

·
Super Moderator
Joined
·
29,454 Posts
Mercedes-Benz dealership? What does Mercedes-Benz Canada have to say about a warranty? What is the reason for the original battery being at 40%? :)
 

·
Super Moderator
Joined
·
1,890 Posts
40% charge or 40% capacity? Very different issues. The 451's had a bricking issue if the 12v battery went dead and the car sat for awhile. That hasn't been a problem with the 453's AFAIK. And I am assuming that they are replacing the HV battery for around $10K and not the 12v battery for around $150? I can't believe that they would take such a hit on a used car that Mercedes basically ignores nowadays. AFAIK only rebuilt units are available and there is often a long wait time for them. With used car salesmen, I make sure my BS meter is turned on.

Len
 

·
Super Moderator
Joined
·
1,890 Posts
I moved this thread to the electric car forum where you will likely get more responses. Please keep us in the loop as to how things proceed. Good luck.

You know what - you never really said that you were talking about an electric version. I just assumed that. Please correct me if I'm wrong, because my answer would be very different and I'll move the thread back to where you had it. My apologies if I assumed incorrectly.

Len
 

·
Super Moderator
Joined
·
1,890 Posts
Yinzer - I totally agree with you, but keep in mind that he is getting his info from a used car salesman. :)

Len
 

·
Registered
Joined
·
3,327 Posts
@42smart The battery could have early degradation. For example, I believe charging to 80% is recommended under normal use or range degradation can occur. The previous owner may have charged it to 100% consistently and diminished it....

Tell them to "put it in writing". Either give you a receipt for the battery change or a promissory note of some sort...

Take that 80% into account in your purchase decision if that is enough range for your daily use....

Sent from my REVVL V+ 5G using Tapatalk
 

·
Super Moderator
Joined
·
1,890 Posts
Charging to 100% has no effect on the HV battery life IMO. I charge mine to 100% all the time and they are all still going strong In fact when the battery says it is charged to 100%, according to our test units, it only really goes to about 96% - maybe that's a safety factor built in? Don't make your life difficult - charge it to 100% and be on your way. :)

Here is a line from the read out from the test unit where SOC means State of Charge:

SOC : 99.0 %, realSOC: 95.2 %

Len
 

·
Super Moderator
Joined
·
1,890 Posts
What I'm trying to say is that there is a 4% or so built in safety factor from the factory, so that when you think you are at 100% you are only at 96% or so. It not a degradation - it's a "feature" I believe that has been there since the car left the assembly line.

Len
 

·
Registered
Joined
·
1,387 Posts
Charging to 100% has no effect on the HV battery life IMO. I charge mine to 100% all the time and they are all still going strong In fact when the battery says it is charged to 100%, according to our test units, it only really goes to about 96% - maybe that's a safety factor built in? Don't make your life difficult - charge it to 100% and be on your way. :)

Here is a line from the read out from the test unit where SOC means State of Charge:

SOC : 99.0 %, realSOC: 95.2 %

Len
When I download a report from my test unit, it reports 100% state of charge, and based on the cell voltages (about 4.15 volts) it is very close to the 4.15 to 4.2 volts which is the maximum "full" voltage for a NMC cell.

I agree that charging it to 100 percent is fine, as long as the car is used within a day or two. I still would not let the car sit unused for weeks at 100% SOC.
 

·
Registered
Joined
·
3,327 Posts
Toyota is said to limit cycle depth to 20% and max charge to 80%, (something like this, please excuse me if the range is off), in their hybrids because due to the gas engine they have the luxury to help protect the battery health.

Since EV (battery) manufacturers and hence EV manufacturers are playing catch-up with respect to range they make more of the total capacity available for use. This is at the expense of longevity. How much longer life one would get by keeping the battery between the recommended 20% and 80% vs charging to 100% I have no idea, I am just regurgitating what I saw when I peeked in some owners manuals. Pretty smart of smart to put 20-80 in the manual and hence the onus on the owner to take care of the battery, vs advertising an ED with what, 60 mi range. (Sorry if my range calculation is wrong, I forgot the range of the smart, then just remove 40%). Even less people would probably buy one.

I do notice a certain hypocrisy in my practice. For cell phones, cordless phones, and laptops I tend to leave them plugged in for as long as possible, then only unplug when I need to. Right now I have my cell phone connected to my charger which is connected to a long extension cord which I've run all the way to my bed where I am laying down typing this. (I wish my sleep cycle is different but that is a different topic....)

Sent from my REVVL V+ 5G using Tapatalk
 

·
Super Moderator
Joined
·
1,890 Posts
Mercedes does not recommend keeping the charge between 20 and 80%. They recommend not charging unless the battery is less than 80% and try not to let the charge go less than 20% if possible. One can assume from that that if it is okay to charge when the car is under 80% that charging it to over 80% is not going to be fatal. Once again I will say that when the car's state of charge reads 100% after it is "fully charged," that the car's real state of charge is only around 96%. I have been charging all three of my EV's to 100% for over six years and there is no discernible degradation that I have seen.

Len
 

·
Registered
Joined
·
107 Posts
Because i just read it yesterday in a service advise. MB and Smart propose for the 12V battery to charge before storage ob beyond 6, 12 or longer and check all several weeks of charge. For most cars they also propose to disconnect the 12V battery.

For HV battery the propose to charge the battery for storage if it is below 30% SoC up to 50%.
Best charge state for storage the propose 40% SoC. Which need to be checked after several weeks and recharged. Taking this into mind and align with the 12V discharge side effect which could kill the HV battery. They are not aware what the are requesting.
For exhibition or showroom the request permanent recharging and backup of 12V battery.

So still the most save condition would the HV battery on 40-50% and 12V disconnected after standby of BMS and Stacks CSE and fully charged 12V battery.

They also write, to fully charge the car short before start of trip.
Nice documents :)
 

·
Registered
Joined
·
107 Posts
Sorry they are proporty and copyrighted by Mercedes. I could not publish it. I maybe can tell the document numbers and you could search for them or ask your MB service center for a copy.
 
1 - 20 of 22 Posts
Top