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IssacZachary
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 11:44 am

mux wrote:I do recommend putting in more than I did for now. I have another 8.7kWh currently balancing, ready to install. That will increase the range to about 160km/100mi real-world in winter. I feel like your 10kWh figure is a bit on the low side. Take into account that the car only charges up to 4.05V/cell and down to like 3.5V, so a lot of capacity is left untouched. That 10kWh only translates into maybe 7-8kWh usable, which is 40km/25mi in hilly terrain or at high-ish highway speeds. Of course, once you have the wiring and contactors, you can essentially keep expanding every time you find a good deal on batteries.


Thanks for the tips and encouragement!

Yes, 10kWh total isn't much. The 24kWh battery of mine with 11 bars only puts out around 17kWh of actual energy. And yet I have made it 65 miles climbing 6,000ft and descending only 4,000ft with that battery capacity. It's just nerve racking to make it home with less than 10% after driving at 35mpg down a 60mph highway for two hours in fair weather. If I add even just 2kWh of actual usable energy that alone would be a big help. But like you said, this could grow and grow. Ideally I'd like to build up to close to double the actual range. But even 1.5 times the current range would make a world of difference for me.
2013 SL SOLD :cry:
1972 VW Beetle SOLD :cry:
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lorenfb
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 12:02 pm

IssacZachary wrote:The question is where the current is being measured? It sounds like the Leaf judges battery resistance measuring current from the motor controller. In that case, the more you add to the main bus in batteries the less resistance the Leaf will sense and the more regen it will have. But if it measures current from inside the battery case and before the bus then it's only measuring the Leaf's own traction battery's resistance, and wouldn't include the auxiliary traction battery's resistance in the equation.


Both LeafSpy and LeafDD read total battery charging & discharging current from the BMS ECU data. So the BMS by using the change in output
voltage divided by the change in output current, the internal resistance of the battery is determined. Both LeafDD and LeafSpy provide
a calculation of the Leaf''s battery's internal resistance. LeafSpy will indicate the accessory, e.g. fans, current draw with just the ignition
being on (not driving), so it has access to current data without using the motor controller's data.
Last edited by lorenfb on Sun Mar 11, 2018 12:08 pm, edited 1 time in total.
Leaf SL MY 9/13: 66K miles, 50 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

jkenny23
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 12:08 pm

mux wrote:I have just finished my first trip on a tiny (8.7kWh nominal) trunk extender battery. For the first time this winter, even though I had a lot of headwind and rain on the way, I've broken 100km (60mi) with the Leaf, which is a decent feat in itself. But as a reply to the above: I've also gained back all of my regen. From about 4-5 bars down, I was able to brake at more than 20kW again, which was not possible on the worn stock battery.


Excellent progress! Question, how are you (or aren't you) balancing/monitoring the second extender pack? My plan was using a second Leaf BMS with a dedicated phone and Leaf Spy to monitor it, and if WolfTronix ever sells his BMS MCU replacement use that for monitoring and cutoff control.

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IssacZachary
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 12:25 pm

lorenfb wrote:
IssacZachary wrote:The question is where the current is being measured? It sounds like the Leaf judges battery resistance measuring current from the motor controller. In that case, the more you add to the main bus in batteries the less resistance the Leaf will sense and the more regen it will have. But if it measures current from inside the battery case and before the bus then it's only measuring the Leaf's own traction battery's resistance, and wouldn't include the auxiliary traction battery's resistance in the equation.


Both LeafSpy and LeafDD read total battery charging & discharging current from the BMS ECU data. So the BMS by using the change in output
voltage divided by the change in output current, the internal resistance of the battery is determined. Both LeafDD and LeafSpy provide
a calculation of the Leaf''s battery's internal resistance. LeafSpy will indicate the accessory, e.g. fans, current draw with just the ignition
being on (not driving), so it has access to current data without using the motor controller's data.

Maybe regen current is limited to max voltage?? It only cuts back once it reaches near max voltage??

If there's a hall effect sensor reading current on the battery to calculate battery resistance I don't see how it could indicate less resistance with the addition of an external battery.
2013 SL SOLD :cry:
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lorenfb
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 12:53 pm

IssacZachary wrote:If there's a hall effect sensor reading current on the battery to calculate battery resistance I don't see how it could indicate less resistance with the addition of an external battery.


Correct.
Leaf SL MY 9/13: 66K miles, 50 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

mux
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 11, 2018 11:19 pm

jkenny23 wrote:
mux wrote:I have just finished my first trip on a tiny (8.7kWh nominal) trunk extender battery. For the first time this winter, even though I had a lot of headwind and rain on the way, I've broken 100km (60mi) with the Leaf, which is a decent feat in itself. But as a reply to the above: I've also gained back all of my regen. From about 4-5 bars down, I was able to brake at more than 20kW again, which was not possible on the worn stock battery.


Excellent progress! Question, how are you (or aren't you) balancing/monitoring the second extender pack? My plan was using a second Leaf BMS with a dedicated phone and Leaf Spy to monitor it, and if WolfTronix ever sells his BMS MCU replacement use that for monitoring and cutoff control.


The packs I'm using as my temporary extender (which I just drove with) are VW GTE batteries, which have a CAN connection that I will just... directly connect to the vehicle CAN. Then I am planning to, at some point, build a little screen on top of my dash that shows me relevant vehicle information. The pack will then also self-balance. However, I need to still do some reverse engineering to get this to work.

Another progress update: the car just finished charging for 10 fucking hours. I did the math: the car was *just* at VLBW when I plugged it in (i.e. remaining range showing dashes), which means there should be about 5-6kWh left in it. The original pack is 24kWh, but its state of health is 70%, so there's really only 16.8kWh left. The new pack is 8.7 kWh nominal, so the total nominal capacity in the car right now should be 25.5kWh. I measured the total energy going in with a wall socket energy meter, that was 21.4kWh, so if you subtract ~8% conversion losses that's 20kWh of actual charge. And yep, that's 5.5kWh below the expected capacity of the pack. The math checks out! And also: the extender pack has performed nominally, it's not degraded. Awesome!

jkenny23
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Thu Mar 15, 2018 1:50 pm

Just had another crazy idea this morning, but it would probably exceed the cost/effort threshold of saving up to buy a dual motor Model 3 or something equivalent;

What about adding another electric drive motor to the rear wheels? I'm not a mechanical guy, so this is probably way too much effort in itself, finding a suitable rear axle with differential to add to the rear of the car, but this would give some extra power on the drive (as opposed to approaching the weight limit of the Leaf's drive system and keeping the sluggish 80kW motor), and also give some extra regen to the second pack. This also frees up the second pack to be a different voltage (of course no longer in parallel) with the main pack, since it's got its own drive system. You would need a controller that would take the throttle input and maps it to appropriate values for the main motor and auxiliary motor to give the desired power output. You could modify these values as the packs discharge to maintain the 2 batteries at roughly the same level, kinda like a Hybrid maintains its battery at ~70% by changing the power from/to the electrical motor vs. the ICE.

mux
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 18, 2018 1:26 am

First of all - I'm unsure whether you can really call the EM61 sluggish. I can reliably pull the motor into ESP, even on dry, cold roads, with stock (equivalent) tires. Sure, more grippy tires would help a lot, but what really is the value of an extra motor if the car is already at city driving speeds in about as much time as it takes you to push and then let off the throttle? How often do you really need more power? Seriously?

I've driven in eco cars a lot - the Mitsu Mirage most recently, and the Suzuki Alto before. Now those are cars that need more power. Those are cars that even with 2 people inside can't climb a steep slope at highway speeds. They're consistently slower even at maximum acceleration than anyone else pulling out from a traffic light. You're a hindrance in these cars.

The Leaf? If I floor it, I see cars standing still, quickly becoming smaller in my rear view mirror. It can climb a steep grade at highway speeds, fully loaded to 4k lbs. I just did that yesterday.

I'm aware that the EM57 (2013-17 Leaf) is quite a bit less torquey, so the 'feel' of the car may have changed a bit. Also, even though my Leaf accelerates well over three times quicker from a stop than the Mirage, the sheer lack of noise gives a false impression of slowness. Still, it's got plenty of power.

All that aside: is it possible? Yes! In fact, there is plenty of room around the rear subframe to mount a rear motor. I'm pretty sure that with a lot of dedication, you can just put a Leaf drive unit flat instead of upright under the car, and it will fit just fine. Note that there is a sea of empty space behind the rear axle. All you have to find a new place for is the electric parking brake, which arguably you should just replace with a hand-operated one if you're making the car AWD. The car also has pretty good anti-dive, decent sideways stiffness and the original drive unit comes with a differential in the package, so no need to do funny stuff to it to make it work. It won't fit stock, don't get me wrong - you'll need to make a bunch of adapter brackets to fit it to the existing suspension points and hinges, not to mention grind off a whole lot of crap, but from a volume and size perspective, this is possible.

-----------------------

Another update: I've driven with the car fully loaded (max. GVW) by installing a second layer of batteries AND lugging around another battery, just sitting in the car doing nothing, and a bunch of other luggage, and a girlfriend. Also, we had very cold weather (couple degrees freezing) and a 6Bft head/sidewind. Despite all that and my 12V battery dying, I managed to drive 100km with 11km on the GoM, so a decent 7-8kWh still remaining. I'm thoroughly impressed with the range now. This car only needs some aeromods and it'll be an acceptable car!

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

Sun Mar 18, 2018 9:24 pm

The ambiguous line between sluggish and sporty is defined by each driver's opinion. Personally I feel like a road warior driving my 1972 VW air cooled Beetle with its stock 1600cc engine, tiny stock single barrel carburetor and "pea shooter" tail pipes. Anyhow, it feels much more powerful than my 1985 non-turbo 1.6L diesel that died and I am fixing. I never ever use "full throttle" in the Leaf. (I'm not sure if "full throttle" is the correct term for both electric and diesel cars since neither have throttles.)

But as far as driving a second axle is concerned there also is the pusher trailer concept. I'm actually split between either adding more L-ion cells to my Leaf or converting the diesel into a natural gas powered pusher trailer. Each has it's own pros and cons.
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LeftieBiker
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Re: Extra Battery, How to Integrate with 24kWh Traction Battery?

Sun Mar 18, 2018 9:40 pm

Back in the Eighties, one of the car magazines took a Honda Civic wagon, and added a second Civic drivetrain (automatic) in the rear, with the steering locked. It wasn't twice as fast, but it had quite a bit of Pep - and weight.
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