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post #221 of 315 (permalink) Old 06-30-2019, 08:14 PM
 
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Originally Posted by Jon Renner View Post
Yes, the only thing you have to remove or disconnect is the cooling system. All the electrical stuff can stay connected because the BMS doesn't seem to do anything if the battery is disconnected from the car (The BMS's are on top of each module, under the large black plastic cover in its center.) If you look at the picture attached, you can the BMS and see how the cells are connected in series, and where to begin counting/measuring. My battery modules were a little worse than yours when I started as the whole pack measured just a bit over 12V.

I am doing my "manual charging" with a lab power supply that can regulate both voltage and current, but only up to 10A at 35V. Because of this I did try to charge 8 cells at a time, but found that when I did that some cells took more of a charge than others, leaving a real mixture of "at rest" voltages. By charging one at a time, I can bring each cell to exactly the same voltage as it's neighbors ... and that's one of the things the BMS looks for.

And when you remove the cooling plates, if you are careful you'll be able to save the thermal blanket & reuse it. Oh, and keep metal tools off of the pack! Lots of HP there.

Right now I'm about half way through the center module, and it measures 120.5 ... which is pretty good.
Curious, what voltage are you charging them to? What current are you starting them at? Are you using the CC-CV protocol where you hold the cell voltage at the "full" voltage (4.1 to 4.2?) and let the current taper down?
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post #222 of 315 (permalink) Old 07-01-2019, 12:45 PM
 
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Looks like most of my cells range from a few mv to half a volt no real pattern seems a mixed lot.

One thing I did notice is pack voltages have come up a few volts since I disconnected the fuse and it was cooler this am they yesterday so I would think it should have dropped.

I am thinking some of the cells have gone to deep sleep others hanging on this could account for the mixed bag of reading.

Still not decided if I should hit the whole pack with the 300v power supply real low ma just to wake it up then take the reading again or go for each pack individually.

From what I have been reading if the cell is deeply discharged you do have to wake it up first.
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post #223 of 315 (permalink) Old 07-01-2019, 01:50 PM
 
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My inclination would be to go for each cell individually if at all reasonable/possible. If you're not able/willing to do that, going for strings of cells is better than trying a massive one-size fits all/is optimal-for-none approach.
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post #224 of 315 (permalink) Old 07-02-2019, 06:26 AM
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MY17 smart 453 ED cabrio w/Lemon branded title UPDATE!

After reviewing the service records of this 453 - THIS WAS NOT FAILURE OF THE HV BATTERY PACK!

Benzel-Busch service records
suggest that they found code P0852F1, PERFORMED RECALL 2019030010 BMS SOFTWARE and replaced the (dead) 12V Starter Battery 453-982-02-00.

"NO HV MALFUNCTION."

The Certificate of Title reads - "Returned to Manufacturer under Lemon Law or other procedure."
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post #225 of 315 (permalink) Old 07-02-2019, 07:38 AM
 
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I found something interesting the batteries are made by https://www.li-tec.de/en/company one very interesting item I have bolded.

ELECTROLYTE AND SEPARATOR
The transport of charge carriers between anode and cathode occur via electrolyte and separator. Additionally, the separator electronically isolates the electrodes, anode and cathode, preventing short circuits.

Electrolytes comprise of either organic, inorganic or polymeric materials with high ionic conductivity. In lithium ion batteries usually organic solvents are used, containing dissolved lithium salts and additives.

Highly porous polymer films are used as separators. Those may be supported by a surface functionalization suitable for electrodes and electrolyte.

Our development goals are high ionic conductivity plus chemical and electrochemical stability over a wide temperature and potential range.

Micro porous structure of the batteries separator
DESIGN OF COMPONENTS AND BATTERY CELLS
Key factors that determine the safety, performance and costs of battery cells include the selection of the active materials and also the structure of the components and the cell design.

Targeted optimisation of the balance between anode and cathode allows an ideal combination of high energy density and long cycle life to be achieved. Other factors affecting the energy density include the sizing of the individual electrode sheets, the format of the electrode separator composite (stacked, z-folded or wound) and the materials and design of the inactive cell components, for example the housing and the current collectors.

We are able to draw on our experience from series development and expertise in the simulation of large-format cells for automotive and industrial applications to achieve the ideal design and optimisation of the battery cells.
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post #226 of 315 (permalink) Old 07-02-2019, 05:08 PM
 
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Originally Posted by 007bond View Post
I found something interesting the batteries are made by https://www.li-tec.de/en/company one very interesting item I have bolded.

ELECTROLYTE AND SEPARATOR
The transport of charge carriers between anode and cathode occur via electrolyte and separator. Additionally, the separator electronically isolates the electrodes, anode and cathode, preventing short circuits.
There is nothing special in this description - it looks like this is just a general marketing description of lithium polymer cell or lithium-ion with polymer separators cell design which is a hybrid of the two. This type of design often takes the form of soft-sided "pouch" cells.

I assume you can't see the physical cells in the modules - only the connections at the top? They might be a pouch-cell design.
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post #227 of 315 (permalink) Old 07-02-2019, 05:38 PM
 
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Looks like most of my cells range from a few mv to half a volt no real pattern seems a mixed lot.

One thing I did notice is pack voltages have come up a few volts since I disconnected the fuse and it was cooler this am they yesterday so I would think it should have dropped.

I am thinking some of the cells have gone to deep sleep others hanging on this could account for the mixed bag of reading.

Still not decided if I should hit the whole pack with the 300v power supply real low ma just to wake it up then take the reading again or go for each pack individually.

From what I have been reading if the cell is deeply discharged you do have to wake it up first.
A cell voltage of 1/2 volt should be considered totally dead too.

As someone who has assembled and prepared lithium battery packs for home EV projects (electric MC's) I have typically charged the cells in groups (up to the capacity of the power supply) up to 90 percent full or so, at which point I switch to charging individual cell using the CC-CV method - set the power supply voltage to 4.1 volts and when 4.1 volts is reached the power supply will hold at 4.1 volts and taper the current down asymptotically toward zero. When it is down to 0.3 amps or so the cell is fully charged.

In you case, since step 1 is slow resurrection at a very low milli-amperage charge rate, then charging the whole pack is fine for this first stage. Remember that a string of anything in series must have the same current passing. through it. You can then move to individual modules at a couple amps but you will have to watch to make sure some cell voltages don't "run away" as the BMS probably discharged the cells down individually and so they are now way out of balance (or maybe not - with the voltages you are seeing, the cells have been effectively been "bottom balanced"). If some individual cells do start to go toward 4.1volts, then you have to switch to individual cell charging. If a cell voltage starts running away early in the process, the cell is likely bad.

I hope you have a lot of free time - both because it is going to take a long time and for safety's sake - you will have to camp out in your garage (hopefully separate from you house?) next to the battery pack. Have a fire extinguisher nearby.
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post #228 of 315 (permalink) Old 07-02-2019, 08:02 PM
 
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A cell voltage of 1/2 volt should be considered totally dead too.

As someone who has assembled and prepared lithium battery packs for home EV projects (electric MC's) I have typically charged the cells in groups (up to the capacity of the power supply) up to 90 percent full or so, at which point I switch to charging individual cell using the CC-CV method - set the power supply voltage to 4.1 volts and when 4.1 volts is reached the power supply will hold at 4.1 volts and taper the current down asymptotically toward zero. When it is down to 0.3 amps or so the cell is fully charged.

In you case, since step 1 is slow resurrection at a very low milli-amperage charge rate, then charging the whole pack is fine for this first stage. Remember that a string of anything in series must have the same current passing. through it. You can then move to individual modules at a couple amps but you will have to watch to make sure some cell voltages don't "run away" as the BMS probably discharged the cells down individually and so they are now way out of balance (or maybe not - with the voltages you are seeing, the cells have been effectively been "bottom balanced"). If some individual cells do start to go toward 4.1volts, then you have to switch to individual cell charging. If a cell voltage starts running away early in the process, the cell is likely bad.

I hope you have a lot of free time - both because it is going to take a long time and for safety's sake - you will have to camp out in your garage (hopefully separate from you house?) next to the battery pack. Have a fire extinguisher nearby.
Thanks yes some cells are just a few hundred mv my plan was to use https://www.circuitspecialists.com/p...er-supply.html set at first to CC connected to the whole pack starting at 20ma just to wake things up. Then assuming voltage rises slowly raise up the ma maybe up to 50ma and see how things go. If they can get to say 2.2v then increase ma slowly up to 350ma and once up to 2.8v per cell I can probably give it the full 400ma.

Then I have this https://www.circuitspecialists.com/b...csi12001x.html that I was planning to use on each pack to get them up the rest of the way.

If all goes well and all the cells are generally in spec I was thinking put back in the car, reset all codes, and see if it charges and let the BMS do what it was designed to do balance the pack.

Lucky I work from home most all days so I can keep an eye on it most all the time. I was thinking if I have to go out then I will have to stop charging as the risk is to high. I have a infrared temp tool to keep an eye on each cells temp.

Let me know your thoughts assuming the PS's show up tomorrow I plan to start so if you have some suggestions to my plan do let me know.

Thanks
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post #229 of 315 (permalink) Old 07-02-2019, 08:52 PM
 
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That power supply only puts out 400 ma? That is going to take a long time - 5.2 days theoretically from empty to full at the fastest rate. But then, at 300 volts, you can charge the whole pack at once to +/-3.2 volts in in maybe a week counting the initial 20ma charging. While that is getting done, buy a lower voltage/higher current power supply (30V/5A or so) to finish the charging of individual cells or groups of cells to 4.1 volts.

Be careful with that amount of voltage on that first power supply!
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post #230 of 315 (permalink) Old 07-03-2019, 04:20 AM
 
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I think you have a solid plan and grasp of the risks. However, I would personally not do this charging in any building attached to my house.

There's no fire extinguisher that doesn't come with wheels on it that's going to put out a lithium battery fire. Just my $0.02.
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