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Discussion Starter · #1 ·
Got a couple of questions about the 12v battery in our Smart EV's.

I replaced the battery on one of them 15 months ago. The old battery was the original and was six years old. It read 12.5v when I removed it. It has been sitting on the shelf now for those 15 months and still reads 12.53v. So how much confidence should I have in the old battery if I should need it in a pinch? BTW the new battery I installed reads about 12.56v if it hasn't been used for a day or two.

So I'm getting a little concerned about my oldest battery which is now 7 years old even though the car has only been on the road for the last four years. It sat on the dealer lot for almost three years. That battery reads about 12.57v after sitting a few days and has given me no symptoms of there being any issues. The car is driven at least weekly.

If I buy a new battery just to have it on hand, how long is the shelf life, i.e. how long can I safely keep it on the shelf until I can't wait any longer to install it?

With ICE cars I'd wait until the battery told me there was an issue. I'd often go ten plus years with their batteries, but there was no chance of the car bricking itself like might happen with the EV's.

Len
2014 EV Coupe 22,000 miles - with the new battery
2014 EV Cabriolet 23,000 miles with the original seven year old battery
2015 EV Coupe 21,000 miles with a three year old battery
 

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Discussion Starter · #3 ·
Load tester - is there a DIY version or do I need to go to a repair shop or one of the McParts stores to get that done?

Len
 

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Most “chain” auto parts stores will do a load test.

Because the smart battery is in the vehicle rather than under the hood (in our contagion world) they may request that you remove it and/or loan you the tool?
 

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Discussion Starter · #6 ·
Is this the Harbor Freight one you have?


With three batteries to keep tabs on, it probably makes sense to have one at my finger tips rather than drive to one of the McParts stores with the footwell taken apart.

Len
 

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Is this the Harbor Freight one you have?


With three batteries to keep tabs on, it probably makes sense to have one at my finger tips rather than drive to one of the McParts stores with the footwell taken apart.

Len
Yep, has worked well for me and friends over the years. Good investment.
 

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Most “chain” auto parts stores will do a load test.

Because the smart battery is in the vehicle rather than under the hood (in our contagion world) they may request that you remove it and/or loan you the tool?
Is the 453 EQ's 12v battery still inside in the passenger side footwell?
Or is it up front under the service hood like the gas models?
 

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453 - 12V is no longer under the floor but up front under the bonnet for both ICE & ED.
 

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Len, scientifically you noted the original voltage reading was 12.5 V, and after 15 months of plain sitting if read 12.53 V. So 12.5 can mean anything between 12.53 V and 12.54999.....

That sounds like a healthy battery to me. But no one wants to be responsible for a bricked HV battery so just as you did changed it out "just in case". I wouldn't personally hesitate to use it in case one of your current ones dies.

In residence for emergency use next to the front door. Luckily my wife hasn't sent me an eviction notice (yet). Every once in a while I'll disconnect the (-) and reconnect to restart the charging process....


Sent from my moto g(7) power using Tapatalk
 

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Discussion Starter · #11 ·
Thinking about doing a load test on a 12v battery in an EV. How important or necessary is a load test, since I don't think the 12v battery in the Smart EV's have that big power demand like an ICE does when starting. As soon as you turn the key ON, the HV battery begins charging the 12v battery. Just curious.

Len
 

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I don’t personally like load tests, because they drain the battery in the process. I do prefer the capacitance test that some testers use. It is supposed to be very accurate though admittedly not perfectly accurate…
 

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I think the 1 minute-ish load tests are fine and, in some sense, the gold standard of lead-acid battery health quick-check. I don't like full-drain capacity tests (such as are mandated on some light aircraft) as those do put actual wear on the battery from the test itself. A 30-90 second load test with a modest current isn't something that I'd get worried about.
 
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