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I replaced my OE battery after 4.5 years of use with a date code making it about 6.5 years old. I replaced it because of all of the bricking reports we've had, nearly all being blamed on the 12v battery going bad. My readings on the old battery were sometimes down around 12.1v or 12.0v. I knew the time was coming, so I just did it. So the old battery has been sitting on the shelf for six months and still read 12.3v. I decided to charge it up and see what happened. So I charged it and it went to about 12.75v. Now after almost a week it has settled in at 12.65v.

So this seems to tell me that the old battery still had a fair amount of life left. Do you agree? I do still sleep a little better at night though knowing there is a new battery in there. I may not be as quick to replace the battery in my other Smart though.

Question - how long will a battery last sitting on the shelf just in case I need it?

Len
2014 EV Coupe 21,000 miles
2014 EV Cabriolet 20,500 miles
 

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You did good. Give the battery to an ICE owner where there are no serious risks but just a car that gets hard to start on cold mornings etc. Let them squeeze all the remaining life out of it!

With the Smart battery down in that hole it is really hard to deal with especially if it fails and you need a quick replacement.

On the other hand I've been disconnecting mine during periods on non-use and trickle charging. This factory-original battery dated 5/2015 likes this treatment as well as ~daily driving so it has been maintaining at least 12.5v when I go to use the car. At home I do not lock the car so there is no security drain (a guess) and when waiting in the car for whatever reason I leave the key ON to maximize dc-dc charging. So far this is working out and proving a somewhat perverse methodology. 8^)
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Question - how long will a battery last sitting on the shelf just in case I need it?
Len
As long as you keep the battery at a 100% state of charge at all times, it will last indefinitely. Generally assuming it is stores at a reasonable temperature, a lead acid battery only degrade with charge-discharge cycles, or sitting at a partial SOC.

I still have the original battery on my 2015 - it's probably at least 6 years old. The car is used frequently enough that I am gong to catch a dead 12V battery before it triggers the bricking process.

And should the worst happen, the DIY procedure for resurrecting a main battery in the event of such a bricking is maturing - as long as that guy in the Ukraine or other BMS hackers stay in business.
 

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2017 453 Passion ED/EQ
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I do still sleep a little better at night
That is KEY, and much more important than what I used to think. As I get older, (in my late 60's now) i am finally realizing piece of mind is much more valuable than I ever had thought, less worry = more happy. So what if you might have removed the battery a little sooner than later, if you feel better because you did it, then you made the right decision. (y)
 

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Discussion Starter #5
Thanks for the replies. I'll try to remember to check the "on the shelf" battery every few months to see how it's doing. It used to be my practice to only replace the battery in my ICE cars when it told me it was going bad. I probably could do the same with the EV because it does get used often, but if I replaced it a year or more sooner than I should have, I'm okay with that. I hope the cars last longer than two 12v batteries, but two will get me close to ten years and I'd be happy with that.

Len
2014 EV Coupe 21,000 miles
2014 EV Cabriolet 20,500 miles
 

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Also worth noting that the battery sitting disconnected on a shelf (with exactly zero load on it) isn't really the same as the same battery installed in a car with a small but non-zero parasitic load to keep the car running (listening for the key fob, powering the always-on modules, etc). If a battery is weak and sulfated and you charge it all the way up, I can easily imagine that it would stay "looking fully charged" on the shelf yet still be a risk in the car.

Did you replace it "too early"? Maybe, but probably not by more than 25%. You don't want to make this into a contest where you tie the world record for "how close can I drive to that bridge abutment?" in terms of risk. If you wasted 25% of the battery life, you already saved more money by doing your own desiccant change once or even just doing the battery install DIY. You did alright.
 

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...a battery can read 12 point whatever...and still have no balls to carry a load...
...that's how a battery is measured...under a load...

Jetfuel...halfway charged...
 

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But the EV load is nowhere near the load of cranking an ICE. So the EV is able to get away with what is essentially a weak battery month after month giving the owner a false sense of security until it blows up in his face (dies, actually!).

Someone who can please measure the 'onrush current' when turning key ON in a SmartEV please do so. I'm looking for one of those old car dash ammeters that read '30A-0-30A' with the needle @12 o'clock when disconnected - where have they all gone?? Much simpler than trying to use a modern digital multi-range.
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We have a Prius in the household with a relatively tiny AGM battery, somewhat similar to a smart ED as starting doesn't really mean using the energy from the 12 V to start. Toyota set instructions on testing as after a drive or charging, turn off car/stop charging. Turn on high beams for 30 seconds to remove surface charge. Measure voltage at battery terminals. Probably closest to true test of an AGM. I realize that there is question as to whether the OEM smart battery is AGM or flooded. Those capacitance testers are for the most part quite reliable in testing the wet/flooded batteries. Take it to a local parts store if you're truly curious...
 

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I replaced my OE battery after 4.5 years of use with a date code making it about 6.5 years old. I replaced it because of all of the bricking reports we've had, nearly all being blamed on the 12v battery going bad. My readings on the old battery were sometimes down around 12.1v or 12.0v. I knew the time was coming, so I just did it. So the old battery has been sitting on the shelf for six months and still read 12.3v. I decided to charge it up and see what happened. So I charged it and it went to about 12.75v. Now after almost a week it has settled in at 12.65v.

So this seems to tell me that the old battery still had a fair amount of life left. Do you agree? I do still sleep a little better at night though knowing there is a new battery in there. I may not be as quick to replace the battery in my other Smart though.

Question - how long will a battery last sitting on the shelf just in case I need it?

Len
2014 EV Coupe 21,000 miles
2014 EV Cabriolet 20,500 miles
My 08 with 90k+ miles still had original battery in it until I had to store it over the winter while we went south (electricity not available for trickle charge).
 

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My 08 with 90k+ miles still had original battery in it until I had to store it over the winter while we went south (electricity not available for trickle charge).
I have an 08 that is still running on original battery at about 67K! At this point I knock on wood for that statement!
 

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Discussion Starter #13
BIG difference with an EV vs. an ICE. In an ICE, I'd go until the battery gave itself up. That would often be ten years or more. In an EV if the 12v battery goes and especially if the car is left unattended with a dead 12v battery, there is a good possibility that the HV battery bricks itself making the car a paperweight. A replacement HV battery runs you around $10K if you can even find one. That's why EV owners should be a little aggressive as to when to change their 12v batteries.

Len
 

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2017 453 Passion ED/EQ
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p23. Online version of 2018 Operator's Manual smart electric drive, "replacing the 12 V battery within the prescribed interval, at the latest every three years." My 2017 car manual does not have this, hmm, M/B knew something needed to be addressed
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I realize that there is question as to whether the OEM smart battery is AGM or flooded.
The M/B Battery for 453 ED/EQ smarts, p/n 453-982-02-00, is a 12V - L2 EFB 60aH 510A battery.

A quick google search of EFB batteries yields: "An enhanced flooded battery (EFB) is an entry level battery for cars that support start-stop technology. EFBs are wet-filled and similar to standard flooded batteries. ... This means the battery recovers more quickly, as its application needs to handle heavy-duty, cyclic, start-stop applications." (sauce: What are AGM and EFB batteries and why would you need one | RAC WA ) :geek:
 

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I finally changed my battery this past July at inspection. The OE that was in it was from when I bought it new in '09, so yeah it was 11 yrs old! I had it regularly tested in the Fall ,before it starts to get cold, to make sure I wouldn't have trouble starting in the Winter. I think it was because of my lengthy drive to and from work that it lasted so long. Not that it was giving me any trouble, but it gave me peace of mind to replace it.
 
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