200 mile range Leaf anyone?

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Rory166
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200 mile range Leaf anyone?

Postby Rory166 » Sat Jun 14, 2014 11:04 pm

Just thinking through what would be required to double the battery capacity on the leaf. I imagine a false floor in the boot could accommodate quite a few cells. But how to connect them? Ideally you would just add more cells to each voltage level but it may be more feasible to leave the existing pack as standard and add a second pack complete with bms. Unfortunately that leaves nowhere to connect the data output.

Rory
Electric Seicento conversion, Leaf

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Rory166
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Re: 200 mile range Leaf anyone?

Postby Rory166 » Thu Jul 03, 2014 10:22 pm

Apologies for bumping my own thread.

I had the privilege of discussing this with Peter yesterday. It seems that merely adding battery capacity would be unlikely to work because the Leaf probably assesses the state of charge by counting used power and might simply refuse to use the extra capacity. The only thing is that the Leaf somehow monitors the battery as it looses capacity so maybe it can somehow evaluate the increased capacity as well. If I add an extra battery in the boot, with its own bms and contactor to prevent it from over or under charge of cells, the cell data will not be accessible to the network.

I have not tried putting 160 Kg in the boot but it certainly made my BMW 3 series sink low when I collected the battery. The usual rubber spring assisters sold for caravaning may help.

I will need some battery connectors to make a T piece to connect the extra battery so I will try the wanted section.

It would be nice if one could simply declare the new battery capacity to the canbus network.

Rory
Electric Seicento conversion, Leaf

flaninacupboard
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Re: 200 mile range Leaf anyone?

Postby flaninacupboard » Fri Jul 04, 2014 4:09 pm

There's a few options:

Connect individual cells in parallel to the existing individual cells/modules. You need to rebuild the entire pack, and then hope the Leaf can register the added capacity. It is certainly capable of determining capacity values between 67ah and lower, I haven't seen anyone try and find what the top of it's calculatable capacity is.

Connect a complete parallel pack, with contactor BMS and monitoring etc, outside of the current sensors of the existing pack. When drawing 200amps from the two pack in parallel 100amps come from the stock pack, and 100 amps from your auxiliary pack, and the car only reads 100 amps. It thinks you are getting amazing wh/m readings and the guessometer works correctly to take account of this.

Connect a complete parallel pack, with contactor BMS and monitoring etc, inside the current sensors of the existing pack. Drawing 200 amps still takes 100 amps from the stock pack and 100 amps from the auxiliary pack but the car thinks it's taking 200 amps just from the stock pack. If the capacity rating will go above 67 on it's own this should work ok.

Please try it and let us know what happens :mrgreen:

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Rory166
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Re: 200 mile range Leaf anyone?

Postby Rory166 » Fri Jul 04, 2014 7:50 pm

The method that I am intending to try is having a second pack with contactor and BMS, no data linkup. The only parts I am needing are a pair of battery connectors to make a T-piece. And a contactor.

In my view the packs will not share load current equally, particularly as I will be using different battery technology. However the pack voltages will need to equalise so current will flow between packs to enable this to happen. The main pack may see regen at odd times.

Rory
Electric Seicento conversion, Leaf

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skooler
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Re: 200 mile range Leaf anyone?

Postby skooler » Sun Jul 06, 2014 6:30 am

Posts by Mike Schooling
Director and tech lead at indra.co.uk

Mazda RX8, Soliton Jr, 24KWH Sinopoly LiFePO4, Kostov 11alpha
http://www.diyelectriccar.com/forums/sh ... 61556.html

Beemer
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Re: 200 mile range Leaf anyone?

Postby Beemer » Wed Jul 16, 2014 6:14 pm

Just a thought and far outside from actually fitting them.
If one uses LiFePo4's in a Leaf there is the issue of differing voltages during discharge.

No bullet points?
1) Assume all are the same at full charge. i.e. Charge stops when the first Leaf cells hit 4.1V each. So the LIFEPo4's hit 3.5V each.
2) When driving, the Leafs cells will discharge voltage almost according to the SOC.
3) The fitted pack will want to stay around 3.3V
4) This will discharge the fitted pack first! You don't want them discharged!

5) So some method of live disconnect needs to be implemented which will mess up your clocks and the 'puter.

Using a "half pack" from another Leaf might be workable.

Personally, I'll wait until one can spoof the CANBUS and go Tesla all inside the battery box.

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Rory166
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Re: 200 mile range Leaf anyone?

Postby Rory166 » Fri Jul 18, 2014 9:12 pm

Beemer

For the benefit of those like me who are not quite up to speed, would you be kind enough to expand your info.

SOC % Leaf V LifePo4 V

100 4.1 3.5

50

2

I am not sure which you are calling the fitted pack?

A half pack of Leaf cells would have half voltage unless the cans are opened I think.

Rory
Last edited by Rory166 on Sat Jul 19, 2014 12:49 pm, edited 1 time in total.
Electric Seicento conversion, Leaf

Beemer
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Re: 200 mile range Leaf anyone?

Postby Beemer » Fri Jul 18, 2014 9:42 pm

Oh! My bad, you are right there Rory. Leafs (etc.) have them doubled up inside the cans.

The discharge voltage rates across differing cell chemistries need to be visualized. Match a pair of discharge graphs of same capacity and you will see why. :)

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skooler
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Re: 200 mile range Leaf anyone?

Postby skooler » Sat Jul 19, 2014 7:27 am

Beemer wrote:Oh! My bad, you are right there Rory. Leafs (etc.) have them doubled up inside the cans.

The discharge voltage rates across differing cell chemistries need to be visualized. Match a pair of discharge graphs of same capacity and you will see why. :)


It's not the discharge curves that matter - Its the resistance inside the cells themselves.

As long as the 100% usable SOC voltages and the 0% usable SOC voltages are the same then there will be no issue.

the LiFePO4 pack actually reaches '0%' earlier, our plan was to simply disconnect it with a contactor until the next recharge.
Posts by Mike Schooling
Director and tech lead at indra.co.uk

Mazda RX8, Soliton Jr, 24KWH Sinopoly LiFePO4, Kostov 11alpha
http://www.diyelectriccar.com/forums/sh ... 61556.html

Beemer
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Re: 200 mile range Leaf anyone?

Postby Beemer » Sat Jul 19, 2014 7:44 am

Lifepo4 is a lower voltage so more required. The operating voltage range is much more narrow. The leaf voltage range per cell has a %age difference. The only fears are top and bottom of charge. Nothing should go too high or too low.

If one speaks of differing "internal voltages", thats a minefield with temperatures, different chemistries and heat properties and so on.

Whatever is used must be able to slip in and oout
out. Erm, on a dc motor controller?

Expect the GOM to go to pot.


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