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Discussion Starter · #1 ·
Hi. My 2014 smart fortwo EV car is giving a lot of problems trying to charge the main battery.
But seems that both batteries get uncharged . There is something sucking the power on both batteries don't retain the power after charge. And if charges it is only half ways once I put the ignition key in batteries get uncharged. Is this cause by the dc to dc inverter ???
 

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What is the age of your12v battery? If it is the original, I'd get it out of there yesterday.

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
 

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To add to @sokoloff's comments: if the 12V battery (similar to a "normal car's battery") is weak, the car will attempt to periodically turn on the DC-DC convertor to "top up" the 12V battery.

If that battery voltage drops quickly, even with top-up, those top-ups will happen more frequently, draining the main EV battery more quickly (and in software versions prior to Oct 2014, seems to be able to kill the EV battery entirely).
 

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MY08 cabrio MY09 cabrio Brabus MY15 ED
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Welcome to SCoA. If you are not the original owner and have no maintenance history you could be on a VERY slippery slope.

The 12V is the heart & soul of ED as it awakens all (battery management) systems in order to launch ED.

As mentioned, a weak 12V can ultimately cause “irreversible” damage to the HV leaving you with a powerless sled.

Start with the 12V age/replacement and please let us know if that solves the problem?
 

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Discussion Starter · #5 ·
What is the age of your12v battery? If it is the original, I'd get it out of there yesterday.

Len
2014 EV Coupe 21,500 miles
2014 EV Cabriolet 22,500 miles
2015 EV Coupe 20,000 miles
The battery is 2 years old by interstate
 

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Next time you visit the dealer, I'd ask them to ensure that the battery software version is at least week 18 of year 2014 on your car. If the software is older than that, your car is susceptible to drawing the main battery too low trying to keep up the 12V battery.

You can also probably troubleshoot this (in terms of figuring out if the DC-DC convertor is turning on too often by watching the HV contactor cycle counts from a scan tool. The contactor starts out with a rated life of 300,000 cycles, with the car using one cycle for every time you turn it on to use it and one cycle for every time the car turns itself on to charge the 12V battery. If the car is consuming cycles that you aren't aware of, it's probably the issue. (Or said differently, if it's NOT consuming any cycles other than you driving it, it's probably NOT the DC-DC convertor that is at the heart of your problem.)
 

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MY08 cabrio MY09 cabrio Brabus MY15 ED
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The battery is 2 years old by interstate
BUT, even a 2 year old battery can fail.

Without testing, you can’t get beyond your current issue.

A “good” 12V should fall within the range of 12.4 - 12.8V.
 

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Discussion Starter · #9 ·
Next time you visit the dealer, I'd ask them to ensure that the battery software version is at least week 18 of year 2014 on your car. If the software is older than that, your car is susceptible to drawing the main battery too low trying to keep up the 12V battery.

You can also probably troubleshoot this (in terms of figuring out if the DC-DC convertor is turning on too often by watching the HV contactor cycle counts from a scan tool. The contactor starts out with a rated life of 300,000 cycles, with the car using one cycle for every time you turn it on to use it and one cycle for every time the car turns itself on to charge the 12V battery. If the car is consuming cycles that you aren't aware of, it's probably the issue. (Or said differently, if it's NOT consuming any cycles other than you driving it, it's probably NOT the DC-DC convertor that is at the heart of your problem.)
I also read an article that if you have multiple cell chargers connected to your cigarette lighter it might throw off the system of the car. So far the mechanic told me that I need a battery charger and a system module. I appreciate your response. Jl
 

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The 12V accessory port / cigarette lighter is turned off when the car is turned off, so that's not likely to be implicated in anything in terms of retaining charge while parked and turned off.

It could theoretically be that the car isn't being well charged during operation if there's too much draw on the 12V system, but that seems not very likely as the chargers are probably pulling < 5 Amps at 14V during operation (70 Watts). "When you hear hoofbeats, look for horses not zebras."

I wouldn't go throwing any expensive parts at the car without more diagnosis. (A 12V battery I'd be willing to look the other way if you wanted to throw that part at the car, because it's cheap and known wear item, but anything beyond that, I'd want some evidence to suggest that part is specifically bad because otherwise you can end up in a frustratingly long [and expensive] series of part-shotgunning and never have a clear smoking gun to know that you nailed it.)
 

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I also read an article that if you have multiple cell chargers connected to your cigarette lighter it might throw off the system of the car. So far the mechanic told me that I need a battery charger and a system module. I appreciate your response. Jl
Can you get a clarification what the battery charger and "syatem module" is? My understanding is that the dc-dc converter (which is what charges the battery) is integral with the AC power inverter/motor controller module - and is presumably a very expensive part.
 

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So far the mechanic told me that I need a battery charger and a system module.
Rather vague diagnosis, did he provide a cost estimate?

Did The Dealer install the Interstate battery? Is this a M-B dealer/mechanic?
 
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