Battery Vehicle Society

The BMS used by ECC was a proprietory one built for them. The software enabling the accessto the recorded cell data was never made available and is under various copyright constraints.
As users of the vehicles would you find a version that allowed you to download the recorded data and clear the records be of use?

As an owner would you be willing to pay something for this?

I am considering getting a version produced by the original designer, with ECCs permission, but not funded by them.

I have recently found how important downloading and clearing the data is. I have a vehicle in for work that hasnt had a download in about two years, and it was full up about a year ago. The result is that none of its recent problems have been recorded, so making a definitive diagnosis very dificult.

If there is any interest in this I will progress it further.

Grumpy-b

Sorry if this is going a bit too high level but have you considered just taking the BMS out?

In my experience they are just not needed for LiFePO4. especially small packs.

Sorry if I'm missing something fundamental with the evie.

Cheers,

Mike

The BMS / no BMS debate is a long and interesting one. For instance, CALB will only consider warranty claims if you have data, ie outputs from a Battery Monitoring System.

If a BMS can prevent a cell going high through charging, or low through excessive discharge, then I can see the point.
In the EVIE, the BMS is complex, it controls the charger and how it produces the charge, as well as when it cuts off the charger. SO you cant just unplug it as the charger then needs modification to do any thing on its own. They were modified especially for ECC. They can be unmodified, but at a cost.
Many users of evies are seeing the BMS cut down performance to stop cells going too low, its a pain if your driving, but does prevent the pack from further damage. The berlingos did this as a simple voltage cutback, it certainly prevents more serious cell failure.
The Evie BMS also actively tries to balance the pack at all times, this can lead to the pack being depleted if left uncharged for a while, as it will take it right down to 0v. Hence ECC saying to keep it plugged in when not in use.
If however something goes wrong with the balancing circuit, one or more cells can be unbalanced if the bleed circuit fails, others get bled but they dont. Result is the pack is even more unblanced than before.

There are a number of Thundersky cells that are not performing well, probably about 10% of them exhibit some form of reduction in capacity. Even consecutive cells, in the same batch vary hugely.
I personally prefer to install cells once they have been initially charged and exercised a bit, then bottom balanced. I also have a 25 set of CALB 180s in my smart, fully bottom balanced, but one of these is exhibiting a slightly high voltage during charge.

The problem is that EVIEs were not designed for enthusiasts who can wield a volt meter and understand the data from a BMS, they were designed for people who wanted a plug in electric car that they could get in and drive. In general thats what a lot have but a few do have problems.

The BMS / no BMS debate will continue, but I think if the manufacturers of the cells require it for monitoring purposes, then one has little choice. Its then a question if its just monitoring or if its used to manage the cells as well.

Grumpy-b

This is the basis on which the BMS controls the charge process.
I got this from the designer.

1. Overcharge cut off when a battery is greater than 4.35V
2. Charger switched off if total voltage > 129V
3. Charger switched back on when stack is < 124.8V
4. Constant voltage phase for the charger is controlled as follows;
Lowest cell < 2V try to pull back the charger to lower current mode (by changing the digital pot on the BMS)
Lowest cell > 3.3V highest cell < 3.5V (pull back charger to lower voltage)
Lowest cell > 3.37V highest cell < 3.7V (pull back charger to mid range voltage)
If the highest cell is < 4V with no low cells (max charge voltage allowed)
Otherwise if we have reached the end stage with all cells above 4V (lucky you!) then ramp back the voltage on specific time/voltage relationship.

A useful insight.

Grumpy-b

Hi Grumpy-b, do you know if this is the same for the BMS on the cars with the 25 cell pack as that looks like details for the 32 cell version? I have been told that the BMS for the 32 cell version differs to that on the 25 cell version. Would be interesting to know.

Hi,

As i know the battery charge end state is to high, and might be the reason why cells die because tundersky changed spec for the TS-LFP160AHA lifepo4 cells:

http://translate.google.com/translate?s ... batteri%2F (http://techmind.dk/citroen-c1-evie-elbi ... 4-batteri/)

I am not sure if i can make a hack of some kind to stop the charger, but still let the cell balancing unit run until al cells are 3,65 Volt, also i have looked around to find a new BMS for the car

Hi
I have turned the Zivan controllers back to controlling the charge themselves. I remove the ECC connection replace the missing component and replace the logic EPROM. The charger can then be set to whatever charge volt
age ( within its range) you wish, and once having hit the end of the CC cycle shuts down after two hours of CV. I now charge to about 93 to 96v and that seems fine, and does not force the cells into very high voltages and frankly does not make a lot of difference to the overall stored power. Going from 3.8 v to 4.1v or higher takes but a few minutes (some cells will go from 3.4 to over 4 in about ten minutes, these are not the best of condition but stillservicable), but those few minutes can see other cells go way above 4.1V .So charging to 93v is my favourite, it also triggers the Curtis to go to full (100%) . I can supply the parts and instructions to convert the Zivan.

Grumpy-b

Hi sounds like a posible fix also i trust the zivan charger algoritme more than the BMS. So as i understand This the zivan stop at 93 volt and bms continue to balance cell after this? Do You have any idee about how many miles this lower charge will affect the max distance for the car?

After this fix, the BMS still kontrol the battery lower voltage cutoff, any easy hack for this?

Thanks

I know that the BMS does send commands to the controller to cut back the power when it sees any cell drop below a certain voltage. If this is continuous then it will stop the car completely by telling the controller to shutdown.

I would imagine that you could perhaps program the controller to ignore these commands? I know you can program the controller to not go in to slow speed mode when the BMS gets to 25%.

Matt

If the zivan charger is changed to stand alone, a buzzer could be connected to the cutoff pin from the BMS, or af flashing led.

Would be great to remove the 25 % Low speed function, ør change it to 10 % if possible?