Dear,

 

I bought a second hand Twike 3 (nr 511).

I want to replace the battery packs with a local battery pack service center.

 

See attached images of my current setup: Twike3_CurrentSetup.png and  BatteryPack.png

 

The current cell is a Sony US18650VT:  https://secondlifestorage.com/t-Sony-US18650VT-Cell-Specifications

 

I know its dangerous 350 V DC!

I'm electronics engineer and wear protective gloves working on the battery pack.

 

I want to replace them with another cell, somebody got experience with this?

Rework setup should look like:  WantedSetup.png

 

• Does anyone know how to reset the BMS?
  
• Can I change it to another cell with a higher nominal voltage cell?
  
• Should I not connect one string of batteries to one BMS ? In stead of setting them in a parallel setup.
  

Thanks in advance

 

Jan

Dear Jan,

 

historically the TWIKE battery (NiCd at that time) was configured as two or three blocks, each block 3-3.6Ah equivalent of cells packaged with its own BMS. There were two cable connections to the main TWIKE control PCB (AK-Print) located on the back of the vehicle: One for the high-voltage power lines and one for the RS485 data bus. The BMS communicates with the inverter located in the back of the driver seat and even bootloads the firmware from the inverter's EPROM. To my knowledge only the german TWIKE manufacturer has access to the source code. The EPROM is so fully packed with code that changes are virtually impossible.

 

Given that legacy unfortunately it is very difficult to implement changes in the way inverter and BMS work together. Therefore, LiMn, LiPo, or LiFe battery concepts for TWIKE generally work in two possible ways:

 

1) Use the old BMS controllers and connect them to a new cell configuration. A minimum of two controllers are required, otherwise the inverter won't go into drive mode. Probably because equilibration currents between drifting Li cell packs cannot be handled by the old-style BMS boards, the packs are balanced, hardwired in parallel, and then connected to the two BMS as seen in your vehicle.

 

2) The BMS is substituted by a new controller, which also needs to take over the communication with the inverter. This is the way it was implemented in the dreifels-controller (http://www.dreifels.ch/page.asp?DH=40) and in several homebrew solutions (e.g.hb9xcg/energex project) that reverse-engineered the communication protocol. The controller is then emulating two or three of the old-style battery packs.

 

Both solutions have their advantages and disadvantages. The two-old-style-BMS solution is very cheap to implement, because you already have everything in place. You are, however, limited by the parametrization as it is programmed in the inverter right now. The dreifels solution is very flexible, has a broad range to parametrize the handling of the battery pack, but costs quite few bucks extra. I was driving my TW448 (R.I.P.) and TW415 with the first solution with NiCd for several years and and around 100k kilometers before I migrated to the dreifels controller and LiFePo4 cells. My TW713 has been equipped with the dreifels controller right away - this was necessary because of warranty reasons for the initial rental-battery pack in this vehicle.

 

BTW: Where do you live? In the Zurich area I could offer a chat & coffee ;-)

 

 

BR,

Florian + TW415 + TW713

Thank a lot, I live in Belgium so unfortunately not close to Zurich. Anyway thanks for the invitation

My Twike is around 18 years old and got a new battery pack at Twike in 2008.

My odometer reads 94 000km. So I don't want to spend more than 5000 euro for new battery pack.

Also I prefer to do it myself, a drive to Twike or Dreifel is pretty far.

 

So the options so far:

 

* Order from Twike: Around 3700 euro for a 9Ah battery

* Rework my battery packs locally: 3000 euro for around 20Ah. Here is the question if I need to change some settings of my BMS settings.

* Order a driefel BMS system and battery pack. Price unknow.

* Create my own from the energex project.

 

Anyone experience with the energex project ? Is it still alive ?

Anyone experience with simple change the cell's of the battery packs ?

 

Thanks in advance,

 

Jan

Hi Jean,

 

the fastest & cheapest way indeed is to just replace the packs and keep the hardware configuration as-is. Maybe some other members of the forum could comment on how an increase in battery capacity to 20Ah is being parameterized in the newer versions of the TWIKE firmware so that the range calculation is correct. I am running the very old 5.31R from 2002, and with the dreifels controller the capacity/range values in the Inverter do not matter anyway.

 

 

BR,

Florian + TW415 + TW713

Thanks,

 

Dreifel does not support Twikes outside Switzerland.

So I go for the cheapest option and rework the packs here.

Somebody already experience with a battery rework ?

How does the controller react on a revision.

 

I'm investigation which cells I would use, for example:

Samsung INR18650-29E 2900mAh E7 - 8.25A

Sony / Murata Konion US18650V3 2250mAh - 10A

Hi Jan,

 

english is no problem, my netherlands is much worse  

 

I still use my old NiCd batteries 2x5Ah with about 5,5Ah capacity.

 

There is a option to enter a service menu in the twike computer, you have to press Prog + Shift + Enter at the same time. I think you need a code to save settings here, never tried yet.

I would also like to learn a bit about that mode, probably anybody else has some experience with this.

You can adjust Ah, cut off voltages, loading voltages and lots of other stuff in this menu.

 

Celltypes is also a very interesting question

The last ones I was investigating we're AMP20M1HD-A LiFePo4

There is a project of a twiker who built a battery from 15Ah Headway Cells (https://twike.weebly.com/projekt-lifepo4-batterien.html)

He e.g. set loading voltage to 386 V (112s LiFePo4)

 

Energex seems also like a very cool project.

Probably the only system which deserves the name bms and can communicate with the Twike computer? At least I know no bms like that, even the dreifels controller has no single cell monitoring as far as I know. Do you have no need for the old battery prints with the mediator and supervisors? 

 

Only found this schematics

 

Regards

Philipp

All,

 

I successfully reworked my battery packs. Removed all the battery packs, remove the old cell and replace by new ones. 

Now I just have to adjust the voltage setting to charge and discharge my batteries.

 

First I wanted to use a samsung cell but they are to big to fit in the pack so I ended up with a panasonic cell:

 

Panasonic NCR18650PF 2900mAh - 10A

 

If anyone needs help with its battery pack, do not hesitate to contact me.

 

Regards,

 

Jan

Am 29.10.2018 um 17:07 schrieb JeanJean:

 

Hello JeanJan,

who designed your pack configuration?

Looking at those images, it dont think this is a recommended configuration considering Liion packs.

It is not recommended to connect several 400V packs in parallel due to the different resistance of the strings which will reduce overall performance and might increase the risk of a cell damage. Unless you make really sure that all cells have the similar capacity and internal resistance... but this is then still a compromise...

Instead of this, there should only be 1 string with 400 V (This is also how Tesla is doing it).

 

Here is a good read about it.

https://www.orionbms.com/manuals/pdf/parallel_strings.pdf

bearbeitet 31. Dezember 20205 Jr. von michael w

 

Hi,

This setup was there when I bought my Twike second hand. I think its a setup from Twike itself.
What I have done:
 

• Replace all cells in every battery pack, I have done this with a local company who revised battery packs for bikes.
• Charged every pack to same level
• Mount it in the twike and done, all still working fine now.

than its recommended to check very pack every year or 2 year if they are still at the same level.
If you want more info let me know.

Regards,

Jan

Hello Jan,

thank you for your response. I think if you connect multiple 400 V strings like this, you need to make really sure that the capacity of each string is matching very well. Do you know the reason why they have multiple 400 V strings in parallel instead of a single 400 V string?

Do you know what type of BMS is used?

Are those 400V strings directly connected or is there a fuse in between? Are there any current sensors and relays in between those 400v strings?

What is the maximum charge/discharge current going through a single cell?

Do the single cell have fuses? Here an example:

 

Thank you,

Michael

 

bearbeitet 1. Januar 20215 Jr. von michael w

 

Do you know the reason why they have multiple 400 V strings in parallel instead of a single 400 V string?
Yes, you need multiple strings to get enough power (amps) for acceleration

Do you know what type of BMS is used?
Its not a real BMS, its the twike "BMS" with themp sensors, in every pack there is a temp sensor.

Are those 400V strings directly connected or is there a fuse in between? Are there any current sensors and relays in between those 400v strings?
For safety reasons you can add a relay between the packs, so you can decouple the whole string and divide it in safe voltages.
In every battery pack there are 2 fuses I think, but if you like you can use fuse wires.
Its a good idea to add some relays inbetween for safety reasons but that you need also a battery pack to power the relays.
You can also add a voltage/current meter for each 352V string, to keep an eye on the balance between the cells.

 

Note: you can configure the limits for discharge en charge. I think default you do not drain the batteries below 20% of capacity en charge unitl 80% capacity.
So in real live you only use 60% of the total capacity, this will extend your battery lifetime.
If you need a long trip, you can adjust this limits a bit.

 

Regards,

Jan

bearbeitet 1. Januar 20215 Jr. von JeanJean

Am 1.1.2021 um 15:04 schrieb JeanJean:

Do you know the reason why they have multiple 400 V strings in parallel instead of a single 400 V string?
Yes, you need multiple strings to get enough power (amps) for acceleration

Hello Jan,

maybe I explained myself wrong, you can have the same current if you only have 1 string instead of 3 strings, simply by adding more batteries in parallel (e.g. instead of 14S4P, 14S12P will allow 3 times more current).

On the picture, I saw 3 strings with 352,8 V each, consisting of 7 packs with 14S4P. Instead of this, 1 string with 352,8 V, consisting of 7 packs with 14S12P could be used.

Imagine if 1 pack or cell has low resistance in your 3 string system, the other strings will pump current in the damaged string.

I attached a picture to explain myself better.

I also dont understand why those 3 strings have only 2 BMS. How are those BMS connected?

Best,

Michael

bearbeitet 3. Januar 20215 Jr. von michael w

 

Yes, that will work aswell but don't know if you can puzzle the battery packs like you discribed in a way that they will fit in the housing.
 

 

 

bearbeitet 3. Januar 20215 Jr. von JeanJean

Am 3.1.2021 um 11:01 schrieb michael w:

I also dont understand why those 3 strings have only 2 BMS. How are those BMS connected?

Hi Michael,

late answer 'cause I just stumbled upon this thread by chance; maybe it still helps.

The reason is simply legacy. The TWIKE inverter SW expects a minimum of two BMS (aka Batterieprints) to be connected to work, ideally there are three of them enabling higher charge & discharge currents. However, since you need special SW to re-program a BMS print to act as #3 and since there are not too many #3 programmed BMS in the wild, DIY Twiker are predominantly using the two BMS configuration. And FineMobile does so for cost reasons, obviously.

Best regards,
Florian + TW415 + TW713