Extra Battery, How to Integrate with 24kWh Traction Battery?

[mux]

You'll either sit before the current sensor and cause the BMS to throw balancing/end of charge errors as well as not properly accounting for capacity (because the LBC is limited to 24kWh nominal capacity internally - and you can't flash the 30kWh firmware without re-pairing, and the pairing key does not work across battery types), or you'll sit after the current sensor and get current mismatch errors as well as not being able to account for the extra capacity at all.

Plus, your secondary battery pack will need its own BMS that works together with the car.

I built a company around all of this, it took me a year to get basic functionality to work consistently. Given the expertise or lack thereof you've displayed so far, I'd also highly recommend either not going through with this project or committing much more time to figuring out all of this yourself and learning from it in little steps.

[EVDRIVER]

You'll either sit before the current sensor and cause the BMS to throw balancing/end of charge errors as well as not properly accounting for capacity (because the LBC is limited to 24kWh nominal capacity internally - and you can't flash the 30kWh firmware without re-pairing, and the pairing key does not work across battery types), or you'll sit after the current sensor and get current mismatch errors as well as not being able to account for the extra capacity at all.

Plus, your secondary battery pack will need its own BMS that works together with the car.

I built a company around all of this, it took me a year to get basic functionality to work consistently. Given the expertise or lack thereof you've displayed so far, I'd also highly recommend either not going through with this project or committing much more time to figuring out all of this yourself and learning from it in little steps.

Excellent advice.

[Irling]

You'll either sit before the current sensor and cause the BMS to throw balancing/end of charge errors as well as not properly accounting for capacity (because the LBC is limited to 24kWh nominal capacity internally - and you can't flash the 30kWh firmware without re-pairing, and the pairing key does not work across battery types), or you'll sit after the current sensor and get current mismatch errors as well as not being able to account for the extra capacity at all.

Plus, your secondary battery pack will need its own BMS that works together with the car.

I built a company around all of this, it took me a year to get basic functionality to work consistently. Given the expertise or lack thereof you've displayed so far, I'd also highly recommend either not going through with this project or committing much more time to figuring out all of this yourself and learning from it in little steps.

Thank you very much for your response. Yesterday I used an additional current sensor, which I installed on the last element of the battery (positive wire). For the experiment, I will make three wires, one common, and the other two will be connected before the current sensor and after the sensor. Thus, I was able to choose a better option for me. Firmware from 30 kW is already used in some cars in our city, it works well, the mileage forecast has increased, however, if the main and additional batteries have an energy reserve of more than 30 kilowatt hours, then problems may occur. 3 bms 32S can be used to balance the extra battery https://item.taobao.com/item.htm?spm=a3 ... 6044502892 but yesterday I used the second LBS module from the Leaf, connected in BMS only mode. This works well to display the voltage level of each element, however there is no balancing and protection function. If your technical solution allows you to use an additional module for balancing, and can also issue a control signal to interrupt the power circuit - this will be a breakthrough Sorry for my bad english

[Irling]

Not really, still trying to get a bunch of pre-mass production boards out to my friends and co-devvers in the community. Things are going slower than I'd like.

Hi Mux, how are you? Is your device available for order?
I plugged in a second battery, however the turtle appears after 24 kilowatts of energy has been consumed

[map40home]

Hi Mux. Any chance we can buy yet (US customers)? Just the boards and the instructions. I would be willing to sign you off any liability (If I didn't die when I had my V8 town car running for 2 years with my home made hydrogen cell, 400V are not going to kill me).
Me personally, I am not interested in all the bells and whistles. Just how to design and connect the extender pack and the CAN. I can live with the GOM being a little off, or some alarms in the dash. I am not interested in selling it, just using it. I love standing by the big lifted trucks here in Florida that look at you like a roach and leave them behind crying because they can't take off as fast as my leaf. The problem is that if I do that twice, the goes half my battery...
I'm sure we can get some batteries here that can work for the extender concept (we had no e-golfs here until this year).

[jkenny23]

Hi Mux. Any chance we can buy yet (US customers)? Just the boards and the instructions. I would be willing to sign you off any liability (If I didn't die when I had my V8 town car running for 2 years with my home made hydrogen cell, 400V are not going to kill me).
Me personally, I am not interested in all the bells and whistles. Just how to design and connect the extender pack and the CAN. I can live with the GOM being a little off, or some alarms in the dash. I am not interested in selling it, just using it. I love standing by the big lifted trucks here in Florida that look at you like a roach and leave them behind crying because they can't take off as fast as my leaf. The problem is that if I do that twice, the goes half my battery...
I'm sure we can get some batteries here that can work for the extender concept (we had no e-golfs here until this year).

Seconded, been waiting eagerly for the electronics. I'm sure Mux will finish it just as quick without us pestering him though

I'd be happy to help with battery selection/testing for the community, I've already had some experience with this (see my testing several pages back, probably easier just to search my posts), if you want to stay in the safe operating envelope of the car's charging/discharging rates, you'll need some pretty high drain cells, which is why I went with the PHEV cells, it's a lower energy density, but can accept much higher charge and discharge because it's only a 9.8kWH nominal pack that needs to put out (or accept from regen) 20-30kW to/from the motor.

[Irling]

Maybe the Mux solution doesn’t work too well, because the whole problem is hidden in the LBC Module. For AZEO, this module has a maximum capacity of 285 Gids., We can correct any readings on the dashboard, however if the battery has a capacity of more than 285 gids, there will still be a turtle. Correct me if I am wrong

[mux]

My solution only works for batteries that have a separate BMS and are switched in parallel to the main battery on the HV bus. It is HIGHLY discouraged for a multitude of reasons to either replace the main cells with a different chemistry or to parallel them inside the main battery. Different battery = different BMS.

My boards are ordered in bulk, they should arrive *somewhere* this month, after which I'll be happy to sell them to anyone.

[Irling]

My solution only works for batteries that have a separate BMS and are switched in parallel to the main battery on the HV bus. It is HIGHLY discouraged for a multitude of reasons to either replace the main cells with a different chemistry or to parallel them inside the main battery. Different battery = different BMS.

My boards are ordered in bulk, they should arrive *somewhere* this month, after which I'll be happy to sell them to anyone.

if the second battery does not have bms, and one bms is used for two batteries, this will not work correctly?
what happens when bms 24kwh aseo counts 285 Gids?

[mux]

You run into multiple issues.

If parallelling each cell individually, the BMS will likely have too little balancing current available in the long term. The BMS in the Leaf uses table look-up for determining SOH, internal resistance, allowable charge and discharge rate, etc., which is chemistry-specific and really even cell-specific. Parallelling cells together with potentially different chemistries will make this useless and will possibly cause the battery to determine the wrong SOH, SOC and allowable current at different times.

Parallelling the entire pack together means one pack will not have cell-level balancing and monitoring. This will cause fire and death. You can't have a BMS-less pack.

If the Leaf's BMS were designed a little bit better, the first approach could actually work fine, but it's got the 285 GID maximum as well as monotonic degradation memory (meaning a battery can never get 'better', only 'worse' according to the BMS), which makes it hard to properly gauge capacity and SOC witht he existing BMS. This can't really be solved with a CAN MITM workaround.