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Discussion Starter #42 (Edited)
So, as a data point, you pushed it to 0 range left and then some more, and the safety feature never kicked in. How far past the 0 point did you go?

I must say that you are pretty gutsy to do have done that, unless you were just driving in a near circle close to home!
I had done it before in the RAV so I assumed there was some margin. It was the day I drove the Smart home from the dealer and my wife was following me in the other car. I also had a portable GPS so I knew the miles to home. I just don't have a clear recollection but I remember being frustrated because the remaining miles went off the screen at 10 miles to go and the display read "charge immediately" or something like that. I didn't know enough about the display to get the remaining miles back on the display.
 

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As I noted earlier, I don't think the SOC is dropping more than 20% total from the actual battery. If it did, we'd have to be getting a lot better than 3.5 miles/kWh to get the ranges promised. At best we have 10% on either side, probably more like 5% on the top and 10% on the bottom with a minor over-drive capability built in.

A lot of this is also making assumptions about marketing understanding anything about batteries. They may very well have gotten the specs on the battery/motor, did some simple math, and started promoting it with those numbers. I'm far more inclined to believe flat numbers on capacity than I am to believe soft numbers, like calculated mileage or average m/kWh. Anyone can read a sticker and report how large a pack is. Turning that into useful info like drivable distance is guess work at best.
 

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There must be some sort of standard they use as guide for rated energy output. As stated before, the total energy output is based on rate of discharge as well as other variables. A battery is not like a bucket of water, based on the variables you can't always put the same amount in or get the same amount out. I would assume they are basing their values on continuous steady state driving at 60km/hr (i.e. city use) at somewhere between 20 and 30 celsius ambient temperatures. This is also assuming they are basing their capacity on the amount of energy that can be discharged as opposed to the amount charged - battery capacities are typically measured on how much you get out of them that's why I make that assumption.
 

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I posed a question to the MB customer portal a couple of weeks ago regarding whether they would recommend not fully charging if a full charge is not required to meet your daily driving needs (i.e. if you only need to use about 50% of the SOC as an example, would it be better to stop charging at 80% and operate on a daily basis between 30-80% SOC, or if it would be better to fully charge and operate between 50-100% SOC).

They responded that it doesn't hurt to not fully charge, but they would recommend fully charging so that the maximum range is available for use..... Would seem to indicate more concern about deep discharging than there is about over charging. I assume this would be because the BMS can more easily control what happens at the top of the charge than it can control what happens at the bottom of the pack, when a driver, for whatever reason, ends up at the bottom of the pack.

Whereas, we drivers might ignore the warnings and flashing alerts that occur, starting at 20% SOC, it much easier for the BMS to simple stop charging when the pack is charge to the safe level that it is programmed for, be it 80%, 95%, 98% or whatever is safe enough from their perspective to prevent dangerous fires and deliver the cycle lifetime that makes the lease not break the bank from their perspective.

I've followed up with a question regarding whether we should occasionally do a deep discharge into the 5-10% or lower range so that the BMS can keep it's set points calibrated in order to give reasonable predictions of range and SOC%. Will advise if and how they respond.
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Has anyone been able to get into smarttekinfo.com? I'd like to have some shop manuals that might take away some of the guess work regarding how things work (or should work) and I'm willing to spend $19 if I can download some of them.

I've tried several times over the last week, but keep getting a "technical difficulties, try later" message. I've tried with Safari and Firefox on a Mac and with IE8 on WinXP.
 

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Discussion Starter #47 (Edited)
I posed a question to the MB customer portal a couple of weeks ago regarding whether they would recommend not fully charging if a full charge is not required to meet your daily driving needs (i.e. if you only need to use about 50% of the SOC as an example, would it be better to stop charging at 80% and operate on a daily basis between 30-80% SOC, or if it would be better to fully charge and operate between 50-100% SOC).

They responded that it doesn't hurt to not fully charge, but they would recommend fully charging so that the maximum range is available for use..... Would seem to indicate more concern about deep discharging than there is about over charging. I assume this would be because the BMS can more easily control what happens at the top of the charge than it can control what happens at the bottom of the pack, when a driver, for whatever reason, ends up at the bottom of the pack.

Whereas, we drivers might ignore the warnings and flashing alerts that occur, starting at 20% SOC, it much easier for the BMS to simple stop charging when the pack is charge to the safe level that it is programmed for, be it 80%, 95%, 98% or whatever is safe enough from their perspective to prevent dangerous fires and deliver the cycle lifetime that makes the lease not break the bank from their perspective.

I've followed up with a question regarding whether we should occasionally do a deep discharge into the 5-10% or lower range so that the BMS can keep it's set points calibrated in order to give reasonable predictions of range and SOC%. Will advise if and how they respond.
I would not put a lot of emphasis on what Smart customer service says about LiIon batteries unless they demonstrate some real knowledge of the chemistry. EDIT Their answer sounds like they are placating you.

I also doubt that the BMS has any calibration regarding range. What the BMS does is manage the charge levels of the cells when charging and presumably when discharging.

As discussed in other threads, and presumably the best assumption, is that there is some rolling average of recent drives. That rolling average of kWhrs/mi multiplied times the kWhrs left in the batteries is what goes into the displayed range meter. The SoC meter presumably uses Amphrs in (charging) and Amphrs out (driving) for its gauge with some non linear skewing as noted by others. The SOC meter may get that information from the BMS.

I don't mean to split hairs here and as far as I know there may be a cpu in there that performs Battery Management, range and SOC functions. In less complicated vehicles, I have seen these things done by separate devices. In the case of the RAV4EV and the Tesla not much is known because Tesla has chosen to keep that information proprietary, to protect their technological lead. Since MB does NOT have a technological lead there is no reason they would not disclose what these systems do. I hope that at some point the information is disclosed in a transparent manner.
 

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Sorry to necropost, but last night I took my 2016 Fortwo ED down to 0%. I actually had to stop at my ex-wife's house, which was 3 miles away from my house and plug into her 110volt outlet and get me back up to 2% to get home.

Now I'm wondering if I could have made it that extra 3 miles without stopping?

Here are screenshots from my OVMS app connected to my OVMS module, while at 0%. The first is the graphical display of my battery health, and the second is me querying the module metrics related to the battery.

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Isn't the OVMS-App showing the rSoC instead of the SoC? In this case you wouldn't been able to drive 3 miles without recharging at first.
 

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I'm not sure. The developers of the Smart module form OVMS changed some things in the last few months.

Still wondering if there was that 10-20% overhead that would have allowed me to "limp" home at slower speeds. Next time, I may try to drive around the my block several times to see what happens.
 

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I've discussed the topic lately with the developer. Right now it's like that:
SoC is shown as SoC
SoH is shown as rSoC*

So actually the SoC is the SoC, in this case you would have been able to get home with the smart without charging, when driving very slow. It would have been a close one. You've still got about 3% when the SoC is at 0%. There isn't that much headroom. Normally the battery is being used between rSoC 3% and 97%.

* After asking him why it's doing that and telling him, why that's wrong and how he's going to get the actual rSoC he's going to fix that in a upcoming update.
 

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Since this thread has been bumped from the way-back past, here are the key things we would now like to know about the Smart 451 ED battery:

1.a. There are many reported cases of Smarts that have been left in storage for a few months and when attempting to put the car back into use, the 12V battery is dead, and once the 12V battery is recharged, the HV pack has somehow been discharged completely flat with a P18051c code. What is causing this? Is it a bug or a misbegotten safety feature?

1.b. Intrepid DIYers have successfully removed and opened the HV battery pack, and recharged the 93 cells from completely flat - but they are still left with a P18051c code that immobilizes the car. In N. America, it is not possible to just take the car to a MB dealer - becasue the dealer will refuse to just reset this code, but rather will only replace the HV battery - effectively resulting in a total loss of the car if it is out of warranty. Is there any way we can work around this? (yes, I know about this shady shop in Russia that you can send the BMS module in for reprogramming - but there need to be an easier or cheaper way.)

2. There is a 2016 service campaign No. 2016060002 which is a software update to the BMS. Is this update a fix to the above problem, or was it something else? Is it possible to find cases of the above problem occurring to cars that have had this update done?

I know, it may be easier to answer the questions regarding the origin and fate of the universe before we get these question answered...
 

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2. There is a 2016 service campaign No. 2016060002 which is a software update to the BMS. Is this update a fix to the above problem, or was it something else? Is it possible to find cases of the above problem occurring to cars that have had this update done?
I've got the update. Never tried if it fixes 1.b, but nether found anything else that changed after that.
 
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