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

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I didn't really mean the Leaf is sluggish, it feels much peppier to me than my Prius (even though it appears from my testing to have the same 0-30 and 0-60 times..). But with respect to other EVs it's not that sporty. And with an extra 300-600lbs of secondary battery I imagine it might have a tougher time.
 
Sure, that's fine. I'd argue, though, that it's much easier to just increase the EM61 to its rated 130kW instead of adding another motor, with its associated weight. Then, if you really want to get into Model 3 dual-motor territory, that's when you need to add the second motor.

It's a fairly easy mod to increase power on the Leaf to 130kW, you just do exactly what the Nismo people did: increase the current limit and run coolant continuously instead of just on the thermostat. It won't sustain that power for more than a couple minutes, so don't mistake this for a track car, but it's decent.
 
jkenny23 said:
And with an extra 300-600lbs of secondary battery...
Of course we are talking about adding 300 to 600lbs to a 3,300lb car. If it's only 300lbs then you're adding less than 10%. The GVWR of a Leaf is around 4,400lbs meaning you have about 1,100lbs of carrying capacity. If you add 600lbs you're only taking up about half the weight it can carry. You could add that much and still drive around with a 300lb friend in your Leaf.

Of course it will affect acceleration. 700lbs of batteries would affect the acceleration by 20% in my case (700lb battery = 20% of 3,500lbs or 3,300lb car + 200lb driver). So with 700lbs of batteries it will take about 1.2 times the distance to accelerate to the same speeds under full throttle.

That 20% is also going to increase rolling resistance by about that much too. But at highway speeds the main factor (more than half) is air drag, not rolling resistance. So a 700lb battery is going to decrease miles per kWh by less than 10%, unless you drive mostly at slow speeds where rolling resistance is more than half the total drag.
 
Well... I have some experience lugging around 700lbs in the Leaf. Not recommended.

For some context: I have my double extender battery in the back and was additionally lugging around another complete battery module for uh... 'research purposes'. All of the weight of the extenders and the additional loose battery was on the rear wheels, and that led to the rear view mirror being still technically legal, but only barely pointed above the horizon. Also, speed bumps in residential areas become a real bump stop hazard.

The stock rear suspension is already underdamped and fairly stiff, so you'll have to get some fairly uncommon types of springs and dampers to fix such issues. I'm also not sure if the torsion bar would like having to deal with the sway forces.

On the other hand, lugging around 350lbs of batteries as my primary extender works just fine. The car feels pretty much the same. I'd say somewhere in between, say at 500lbs, there's a maximum comfortable extender battery size.

As for range impact, I'm fairly certain I'm not getting the full range benefit of my extender because of the additional drag. I might start playing really dangerous and up the rear tires to 47psi. I'm not sure if anyone has tried that or has investigated the effects of that.
 
mux said:
On the other hand, lugging around 350lbs of batteries as my primary extender works just fine. The car feels pretty much the same. I'd say somewhere in between, say at 500lbs, there's a maximum comfortable extender battery size.

As for range impact, I'm fairly certain I'm not getting the full range benefit of my extender because of the additional drag. I might start playing really dangerous and up the rear tires to 47psi. I'm not sure if anyone has tried that or has investigated the effects of that.

Assuming money is no object, the best 18650 on the market is the LG MJ1 at 3500mAH. A 56-cell pack (14s4p) pack I built with the plastic cell holders, bus bars, and connectors and such weighs in at just over 6 lbs, so with 500 lbs you could build a 55 kWH pack (56 * 12.95WH = 0.725 kWH per 6.072 lbs). Not including any thermal management or monitoring etc., but that's a whole lotta capacity to work with. Building packs with automotive modules with lower energy density will be less weight efficient of course.
 
Yep, that is pretty much my end game. I'm not willing to spend that much money (close to $15k) on cells alone, but if I can find a way to get those or similar cells for cheap or get them sponsored, that is exactly what's going to happen to my Leaf. It's clearly technically feasible.
 
mux said:
Well... I have some experience lugging around 700lbs in the Leaf. Not recommended.
It would depend on where the batteries are located. I've driven around with 4 other passengers, 5 total, and our luggage, close to 1,000lbs of weight. I didn't notice any ill effects. But yes, If I put 5 people in the trunk that would make for a hazardous condition. If you added 700lbs of batteries you'd need to add most of it it behind the front seats in the rear seating area.
 
While installing my hitch, I noticed there is a ton of room between the rear wheels:

C11396_2013~Nissan~Leaf_3_1000.jpg


So, an aftermarket pack that was built to fit in that space would be ideal. Obviously, with the added weight, the frame members would have to be beefed up, but the volume of space there is probably close to 10 cu. ft.
 
Out of interest, I looked for the LEAF battery module specs online and found this:

http://www.electricvehiclewiki.com/Battery_specs

I'm guessing that 30 modules could comfortably fit in that space, which would add 13 kWh of additional charge - not too shabby! Apparently, the 48 modules in the stock pack weigh a little over 300 lbs, so adding 30 more modules would add roughly 200 lbs. So, an after market pack that was custom built to fit that space would likely be less than 300 lbs.

The cheapest used module price I can find is $100 US though, so it would likely be $4000+ US for an aftermarket add-on pack.

At that price, it makes way more sense to buy a replacement pack from Nissan. If an aftermarket add-on pack was available for $2500, then that would be compelling for me.
 
alozzy said:
Out of interest, I looked for the LEAF battery module specs online and found this:

http://www.electricvehiclewiki.com/Battery_specs

I'm guessing that 30 modules could comfortably fit in that space, which would add 13 kWh of additional charge - not too shabby! Apparently, the 48 modules in the stock pack weigh a little over 300 lbs, so adding 30 more modules would add roughly 200 lbs. So, an after market pack that was custom built to fit that space would likely be less than 300 lbs.

The cheapest used module price I can find is $100 US though, so it would likely be $4000+ US for an aftermarket add-on pack.

At that price, it makes way more sense to buy a replacement pack from Nissan. If an aftermarket add-on pack was available for $2500, then that would be compelling for me.

Only 30 modules = wrong voltage.
Would make a Dc-dc mandatory
 
Makes sense.

I don't claim to have the knowledge or expertise to actually design and build an add-on pack :)

I was merely speculating on what could physically fit in that space and whether it would be economically viable to sell an add-on pack using reconditioned LEAF modules. The only way I see a company developing an add-on pack solution for older LEAFs is if they can source the reconditioned modules for cheap (ie $50 - $75 per module). If not, it seems really unlikely that a third party "range extender" product will ever come to market.
 
That is exactly the space where I'm building my permanent extender pack. However, on the '11 Leaf, the space is a bit more irregular, so I have to design around that.

Also, as I'm currently finding out, getting the BMS to cooperate is a bit of a hassle. Not that it doesn't work, just that I'm already 50km into LBW right now and expect there is still at least 60-70km in the pack, meaning I have more than 100km (60mi) of range 'underneath' the GOM's 'hey your battery is empty'-state. That is a bit disconcerting to drive around with.

So just from a convenience point of view, using Leaf modules is the easiest way to add capacity. I'm trying to add NCA cells to an LMO pack, that's just asking for complications as it turns out.
 
Big update time, and for now the last extender update until I start working on either the main traction battery or an 'invisible' extender.

https://youtu.be/ZSqGBPBxfUE

For those who don't like watching video with slightly buzzy audio in the middle (sorry about that): It works! I drove 170km/110mi on a single charge, and the car accepted approx. 35kWh from the mains (~32kWh usable). This puts it closer to the capacity of a 40kWh Leaf than a 30kWh, so I'm honestly really happy with that result. This makes the car 10x more usable and at least for us a lot cheaper to drive. Fast chargers are up to €0.69/kWh here, about as expensive as a gas car! It really helps to be able to skip those on long trips and use destination chargers.

The batteries I used are about €1750 ($2200).

There are two snags in this story. First off: the new batteries are NCA chemistry, which means they are still pretty much 'full' when the GoM tells you you're empty. So you're driving on LBW and VLBW for the last 60mi. On the plus side: it really feels like the battery will just not empty, it's nice to know you can easily just go another 10mi if you need to. Fixing this will require spoofing the BMS, which is a relatively complex job I don't have the time for yet. Maybe in May or June.

Second: my 12V battery depletes when charging. I mean, we all know this is an issue, but it's exacerbated quite badly if charging takes 12 hours. I guess I'll have to add a battery maintainer that automatically recharges the 12V accessory battery while charging. Maybe I can hack into the DC/DC converter and enable it during charging? Not sure yet how to attack this problem.

TL;DR: success!
 
mux said:
There are two snags in this story. First off: the new batteries are NCA chemistry, which means they are still pretty much 'full' when the GoM tells you you're empty. So you're driving on LBW and VLBW for the last 60mi. On the plus side: it really feels like the battery will just not empty, it's nice to know you can easily just go another 10mi if you need to. Fixing this will require spoofing the BMS, which is a relatively complex job I don't have the time for yet. Maybe in May or June.

Haven't seen the video yet but sounds like great progress. For the BMS, you should get in contact with WolfTronix over on DIY Electric Car forums, he's already done the hard work of reverse engineering and replacing the microcontroller on the Leaf BMS. You just have to convince him to release the code or sell it to you (which I haven't been able to yet ;) ).

Also seems bonkers to me that the 12V DC-DC is off during charging.. how about if the car is "on" while charging? I've done this several times, and I know the car can be locked while "on", I had to leave it on while parked/locked for several hours to recover my 12V battery after it drained fully during a vacation.
 
jkenny23 said:
For the BMS, you should get in contact with WolfTronix over on DIY Electric Car forums, he's already done the hard work of reverse engineering and replacing the microcontroller on the Leaf BMS. You just have to convince him to release the code or sell it to you (which I haven't been able to yet ;) ).

Haven't been following that effort closely. So are you saying Wolftronix has fully reverse engineered the all functions of the microcontroller
used in the Leaf BMS ECU to be able to replace it with another microcontroller with his code, and then install the new microcontoller in the
original Leaf BMS ECU? Or maybe he plans to design his own replacement BMS ECU?
 
lorenfb said:
jkenny23 said:
For the BMS, you should get in contact with WolfTronix over on DIY Electric Car forums, he's already done the hard work of reverse engineering and replacing the microcontroller on the Leaf BMS. You just have to convince him to release the code or sell it to you (which I haven't been able to yet ;) ).

Haven't been following that effort closely. So are you saying Wolftronix has fully reverse engineered the all functions of the microcontroller
used in the Leaf BMS ECU to be able to replace it with another microcontroller with his code, and then install the new microcontoller in the
original Leaf BMS ECU? Or maybe he plans to design his own replacement BMS ECU?

Yes, forgot to include the link in my last reply: http://www.wolftronix.com/E10_LithiumUpgrade/index.html

He designed a PCB/microcontroller which fit in place of the original microcontroller in the BMS ECU. His microcontroller replicated all the functions/CAN messages of the original (at least as requested by Leaf Spy, I'm not sure whether there are other messages that the Leaf requests in real use), and he made some assumptions about how Hx etc. were reported. I don't think anyone's actually tried it in a real Leaf though.
 
jkenny23 said:
lorenfb said:
jkenny23 said:
For the BMS, you should get in contact with WolfTronix over on DIY Electric Car forums, he's already done the hard work of reverse engineering and replacing the microcontroller on the Leaf BMS. You just have to convince him to release the code or sell it to you (which I haven't been able to yet ;) ).

Haven't been following that effort closely. So are you saying Wolftronix has fully reverse engineered the all functions of the microcontroller
used in the Leaf BMS ECU to be able to replace it with another microcontroller with his code, and then install the new microcontoller in the
original Leaf BMS ECU? Or maybe he plans to design his own replacement BMS ECU?

Yes, forgot to include the link in my last reply: http://www.wolftronix.com/E10_LithiumUpgrade/index.html

He designed a PCB/microcontroller which fit in place of the original microcontroller in the BMS ECU. His microcontroller replicated all the functions/CAN messages of the original (at least as requested by Leaf Spy, I'm not sure whether there are other messages that the Leaf requests in real use), and he made some assumptions about how Hx etc. were reported. I don't think anyone's actually tried it in a real Leaf though.

Thanks. Looks very interesting.
 
I think my approach would not be that involved, especially considering there may be important not-yet-documented messages that have to be transmitted over the bus to/from the pack that are easily missed and could leave the car stranded if it goes wrong.

It's probably safer to just make a transparent CAN repeater that intercepts and re-transmits each message either way, EXCEPT for the GID information, which it will retransmit to include the extender pack information. That, in turn, will be generated by a separate BMS on the extender. That way I should be able to get a much better estimate of range computed by the GoM.
 
mux said:
I think my approach would not be that involved, especially considering there may be important not-yet-documented messages that have to be transmitted over the bus to/from the pack that are easily missed and could leave the car stranded if it goes wrong.

It's probably safer to just make a transparent CAN repeater that intercepts and re-transmits each message either way, EXCEPT for the GID information, which it will retransmit to include the extender pack information. That, in turn, will be generated by a separate BMS on the extender. That way I should be able to get a much better estimate of range computed by the GoM.

A re-design of the BMS ECU controlling just the battery functions would be somewhat of a straight-forward effort, but interfacing a re-designed
ECU to other Leaf ECUs via its two CANs is a much more involved and critical an effort.
 
mux said:
There are two snags in this story. First off: the new batteries are NCA chemistry, which means they are still pretty much 'full' when the GoM tells you you're empty. So you're driving on LBW and VLBW for the last 60mi. On the plus side: it really feels like the battery will just not empty, it's nice to know you can easily just go another 10mi if you need to. Fixing this will require spoofing the BMS, which is a relatively complex job I don't have the time for yet. Maybe in May or June.

Second: my 12V battery depletes when charging. I mean, we all know this is an issue, but it's exacerbated quite badly if charging takes 12 hours. I guess I'll have to add a battery maintainer that automatically recharges the 12V accessory battery while charging. Maybe I can hack into the DC/DC converter and enable it during charging? Not sure yet how to attack this problem.

TL;DR: success!

One more question I forgot, have you tried DC fast charging with the nearly double capacity Leaf yet? I recall seeing an earlier experiment when you used a much smaller extender pack, but at that scale it was just along for the ride and wouldn't have made much difference for the total capacity. I'm curious whether the Leaf will give an error when it requests ~50kW from the charger and only sees about half that going into its own battery. Would love to see a LeafSpy charging graph too, whether it allows full charge rate for longer duration since the voltage is rising slower than normal; this is really critical to making the Leaf a true long range car.
 
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