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Discussion Starter #1

Hello everybody.
I am long time reader of this and similar EV forums, and owner of first gen Leaf.
I would like to introduce my project to all of you and need to hear your opinion on it.
Last 6 months I was working on this project.
To build additional battery for Nissan Leaf 24 and 30 kwh, to extend range of vehicle on one charge.

1. Characteristics:
- Li-ion battery with energy capacity 8.8kwh. ( Usable capacity 7 kwh )
- weight of all together 55 kg.
- size 1000 x 600 x 100 mm

2. Construction:
Battery will be installed at bottom of boot , and fixed to boot floor. As results floor boot will be
raised by 100mm.

3. Permanent mods to vehicle:
Few hols to boot floor for battery fixing and air valves.

Performance:
In my Leaf, current state of battery capacity 75% , according to LeasSpy. At test runs, additional battery will add 30 – 40 miles of range.
At motorway ( A2) with constant speed 60 Mph I easy made 100 miles., and some charge still left in battery, probably for another 5-10 miles.


Additional battery will be charging together with main battery, while you using slow, fast, and rapid charger , it will charge main and additional battery.

Price for complete set £4000 .

At this stage it is all in prototyping, and not ready for demo, but I would like
to know if any one will be interested to install/buy this additional battery, and
what questions and concerns future users/buyers will have.


Andrew
 

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Concerns? Certainly, safety and insurance. Hacking into the existing systems and adding weight at the back of the car won't help reliability or handling.
Surely it's easier and better to buy a Gen 2 car?
If I was to modify the Leaf it would be to put 18650 cells in the original battery box, with liquid cooling. I reckon maybe 60kWh could be feasible.
 

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Discussion Starter #3

Hi SCanfer,

Thank you for replay.

Regarding safety.

  1. Battery, power electronics and cables build inside steel airtight box. Witch completely inculate battery from saloon space. In case of fire inside battery, pressure release valves will open, and direct hot air and gases under car. It will allow occupant enough time to left vehicle.
  2. Battery have Battery Management System, which monitors temp, voltage, current of battery , and will disconnect it if any of parameters go outside normal range.

Weight. 55 Kg at boot doesn't affect driving at all.


Insurance. At this stage I dont have answer, how match It will affect price for insurance of vehicle. I hope some or readers can recommend way to insure this mod to car.


To buy new car - yes it is good option. But not for everyone, and not in this context.
 

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It doesn't sound any worse, in principal, than people who installed LPG tanks to their ICE cars.
More bulk in the boot area etc.
I wouldn't be interested though, I'm an owner who is comfortably covered by the existing range.
 

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Discussion Starter #6
Battery build from ground on 18650 cells.
Packs from Audi or Prius can be used as well, but they are not available in big quantities, so do not want to tight myself to one component or supplier.
 

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Where do you make the connection to the HV bus? Inside the battery box (so the leaf thinks current going into and out of the auxiliary pack is going in and out of the main pack?) or outside?(so the leaf has no idea the extra pack is there).

What does the range meter show?

How are you controlling the contactors for the auxiliary pack?(this has been tried and abandoned by a YouTube poster after it disabled his car)

What cell chemistry have you used? Are you sure it can cope with 50kw charging without any cooling? And 80kw discharging?
 

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Discussion Starter #8 (Edited)

Additional battery connected in parallel to main battery before current sensor. So Leaf will think that his battery just bigger and last longer.


Range meter. So far I done just couple of test runs, so BMS need to learn new capacity. GOM during driving will drop remaining mileage slower then normal, and will stop at 5 miles. At this mark I can drive for about 20 miles, and then it will start reducing again.


Yes I saw that YouTube videos. I build separate controller witch control additional battery relay, and watching thermal sensors, difference in batteries voltage, data stream from BMS. And according to this activating add. battery relay.


I have not made any practical tests with Rapid charging yet, so no information on this one, But I did test with Leafs onboard charger, - all ok. Battery not getting hot or even warm.
 

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I found another video of someone doing something similar:

His pack has the same problem as yours, the auxiliary pack and leaf pack are different voltages at same SOC, so when the leaf pack is nearly empty the auxiliary pack is still more than half charged. The leaf doesn’t know this so the onboard instrumentation is pretty useless (which is why it will blink “5 miles” for 20+ miles). While that’s ok for a hobbyist, I can’t hand the car over to my partner with two small children in the back and expect her to do mental arithmetic and monitor pack voltages to estimate to remaining range :(
 
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