Safely trickle charge a bricked pack in/out of car - solution

[nick]

Update - after a busy week of analysis I have a PCB design in the works that is a drop in replacement for the BMB PCBs to allow a bricked pack to be safely trickle charged in car (or out of car).

The Roadster has 99 bricks in series - the design is basically 99 fully-isolated charging circuits with communication back to a PC for monitoring.

If a brick is very low the charging starts at 20mA so shorted bricks can be auto-detected (20mA max through a shorted cell). Once it has been determined the brick isn't shorted it is charged at 100mA (still very slow). Each brick is individually voltage and current controlled so no risk of cell over-voltage like you have with putting voltage across a sheet or the pack.

Use 1 - if you have removed a pack from a damaged car this system is a way to safely keep the pack charged.

Use 2 - if a pack is bricked this system will tell you the voltages of all 99 bricks in car so you know the health. If it is just a little under voltage you can likely unbrick the pack without removing it from the car. Once charged enough the car can take over normal charging duties.

Use 3 - if a pack has shorted cells this system will keep the other bricks charged so you don't lose the other bricks.

I will have boards back from fab next month.

If there is interest I will create a Kickstarter to build more of them.

 

[nick]

I should add that there is no magic here - it won't recover cells which have been damaged (for example being left in an under-voltage state for extended periods of time).

 

[nick]

After a lot of testing it is clear the battery in this car isn't recoverable. Too many years sitting.

I have a set of dummy BMB boards in fab... changed the design to just exposing access to the 9 bricks for monitoring or up to 100mA injection. Keep it simple.

I will post pictures end of month when the boards arrive.

 

[Rolf68]

Cool the know such things are possible, thanks

 

[nick]

Boards are assembled...

Dropbox - 2018-03-05 18.58.43.jpg

The boards provide access to the 9 bricks in each sheet and stick out far enough to be easily accessible and easily removable.

 

[automixcars]

hallo Nick
the photo look nice of the boards
will it be possible to get a price inc shipping to me in Denmark for maybe just one board because I have a damaged roadster on the way to me from USA in a container right now and this car have also not driven fore years and will need the battery to be tested.my plan was to just use one board at a time to test the 9 bricks and see if I need to pull the battery from the car

if you do not want to sell a board maybe you can sell me the schematic drawing of it and I can make one here in DK?
Kind regards
Michael

 

[X.l.r.8]

Had to be 9s, if it were 8 bricks you could have a cellLog 8s piggybacked and read the voltages at the same time

 

[nick]

hallo Nick
the photo look nice of the boards
will it be possible to get a price inc shipping to me in Denmark for maybe just one board because I have a damaged roadster on the way to me from USA in a container right now and this car have also not driven fore years and will need the battery to be tested.my plan was to just use one board at a time to test the 9 bricks and see if I need to pull the battery from the car

if you do not want to sell a board maybe you can sell me the schematic drawing of it and I can make one here in DK?
Kind regards
Michael

If you are good soldering the two connectors to each board I can post links for ordering the PCBs and ordering the connectors.

Give me a few days.

 

[automixcars]

If you are good soldering the two connectors to each board I can post links for ordering the PCBs and ordering the connectors.

Give me a few days.

sounds good THANKS

 

[spaceballs]

sounds good THANKS

Please monitor all 9 bricks in the sheet as you charge them. I've recovered a few ESS, 1.5 are more tricky than 2.x units. A sure sign something is wrong is when you charge up a sheet, then certain brick(s) in the sheet start to consume power and voltage drops on them.
Also remember this can be a fire hazard, so make sure the Roadster/ESS is far away from anything you care about.

 

[piwhy]

If you are good soldering the two connectors to each board I can post links for ordering the PCBs and ordering the connectors.

Give me a few days.

Hi Nick,
I'm located in Europe and I'm loooking for a solution first to check voltages of each sheet on a potentially bricked roadster. I need it pretty rapidly... Are you able to provide at least the mouser ref of the BMB connector ?
Thank you very much.

 

[bigbill]

My roadster drained it's battery while I was away. I had it plugged in, but it stopped charging for some reason. Since it was plugged in it kept running the cooling system and killed the battery pack. It refused to charge, so I looked in the service menu and saw VMin was under 2V, so I immediately pulled the service plug to prevent further drain.
I pulled a BMB and sourced the connector. It and some proto boards are arriving tonight. I am hoping I can save the pack since it went to zero miles just a few days ago.
Can anyone post the pinouts of the BMB's? I looked at the board and using the fuses I can see which pins are to bricks, but I don't know which is which. It would save me some time if someone has the pin info.

 

[X.l.r.8]

Can I get the part no’s and the pcb details so I can get some boards printed

 

[X.l.r.8]

Bigbill. You should have a look at bms wiring. In series the negative of one battery is the positive of the next cell in series.
So as the readings increase you are reading the whole pack voltage up to that series connection. So your readings 3, 23, 1, 19, 5, 20, 6, 22, 4
Are probably 1,3,4,5,6 indicating 1v, 2v, 1v, 1v,1v
Your getting some pretty random readings but probably because the pack is parallel series series so I’m not sure you can start reading the cells until they are all unplugged.

 

[bigbill]

View attachment 303749 Bigbill. You should have a look at bms wiring. In series the negative of one battery is the positive of the next cell in series.
So as the readings increase you are reading the whole pack voltage up to that series connection. So your readings 3, 23, 1, 19, 5, 20, 6, 22, 4
Are probably 1,3,4,5,6 indicating 1v, 2v, 1v, 1v,1v
Your getting some pretty random readings but probably because the pack is parallel series series so I’m not sure you can start reading the cells until they are all unplugged.

You misunderstood. Those numbers are the pin numbers on the 24 pin BMB connector, not voltages.
My post was in a different thread. How did your response get here?

 

[X.l.r.8]

I read all the threads

 

[X.l.r.8]

On the PC you can see the negative, after that write down all the voltage readings in every pin, then put the numbers sequentially and the difference between numbers will give you cell voltage. You can correlate the pin to sequential voltage making the next set quicker to read. I used to have a 9 cell reader but the new data loggers are 8 cell,but a hobby charger will read the 9 cell groups and charge them but it won’t be balanced so dangerous if one cell absorbs all the wattage and over heats, much better to work at cell level until you know the entire pack condition.

 

[nick]

If anyone want to build more of these BMB probe boards I have published the files:
nickkelsey/tesla_roadster_bmb_extender

 

[X.l.r.8]

Superstar, I'll get them off to the board printer.

 

[nick]

Update - I have 7 sheets on charge with 63 isolated per-brick chargers (9 per sheet).

63 power adapters plugged into 30 power strips

All bricks are healthy. 6 have reached the target voltage.