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I'm thinking of creating a battery pack out of LiFePo4 cells for Nissan LEAF. I figured this is almost impossible from zero content I've found online regarding DIY batteries for LEAF.

  • Has anyone tried this before?
  • I'm thinking of modifying the Leaf BMS to accomodate LFP cells along with a seperate BMS to actually monitor the LFP cells.
  • Another approach I was thinking is to create a secondary battery pack and a DC-DC converter with CC to tap into the HV battery output of the main battery and feed it from the secondary battery (Range extender method)

Has anyone tried/have an idea about this? I'm flying blind.
 

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Discussion Starter · #2 ·
P.s I've thought about doing this cause there is no Nissan support in my country and there are thousands of LEAFs in here that gets thrown out or converted to petrol everyday.
 

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Your main problem would be that the energy density of LiFePO4 cells is poor compared with stock Leaf cells.
To make it to 360V you'd need 113 cells, each of which takes up only slightly less volume than the original Leaf cells (of which there were only 48).
You could definitely operate the motor on less than that but 300V is still 92 cells.

So you'd effectively need at least twice the physical space of the original Leaf pack to convert the car to LiFePO4.

Your range extender idea would suffer from the same problem since you'd need to still reach 360V. Either way you'd need to find some other type of batteries with better energy density.
 

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To make it to 360V you'd need 113 cells, each of which takes up only slightly less volume than the original Leaf cells (of which there were only 48).
The original-style Leaf actually has 192 cells in a 96S2P configuration. "Leaf cells" in the above refers to Leaf modules, which are 2S2P, so there are 48 of them.

Leaf modules are about 303 mm x 223 mm x 35mm, for a volume of 2.4 L and 3.8 kg, or 113 L and 182 kg. The lowest-capacity Leaf battery was 24 kWh, or 500 Wh/module.
To hit 24 kWh in 113 LiFePO4 prismatic cells, each would need a capacity of 212 Wh, or 67 Ah per cell @ 3.2 V. A CALB CA60 cell is close at 115 mm x 244 mm x 41 mm (for 1.2 L) and 2.0 kg... that's 130 L and 226 kg in total, for 21.7 kWh

So the LiFePO4 cell mass and volume is greater than the Leaf module mass and volume, even to match the lowest-capacity Leaf battery... but it might work in the Leaf battery case volume and might be acceptable in capacity. A problem might be that the CALC LiFePO4 cells are only rated for 2C discharge, which be only about half of the original Leaf's rated motor power. A bigger problem would be that these cells are probably more expensive than a good used Leaf battery.
 

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Apologies, I mistakenly used the word cells instead of modules. I was using a rough size calculation based on the volume of a particular LiFePO4 100ah "cell", assuming you wouldn't want to replace a degraded pack with one that had a lower capacity than the OEM one. The cell I had selected, the CA100Fl - also has a 3C discharge rate (according to EVTV anyhow), making it workable for the Leaf.

However, as you pointed out, cost is also a large factor.
 

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I'm thinking of creating a battery pack out of LiFePo4 cells for Nissan LEAF. I figured this is almost impossible from zero content I've found online regarding DIY batteries for LEAF.

  • Has anyone tried this before?
  • I'm thinking of modifying the Leaf BMS to accomodate LFP cells along with a seperate BMS to actually monitor the LFP cells.
  • Another approach I was thinking is to create a secondary battery pack and a DC-DC converter with CC to tap into the HV battery output of the main battery and feed it from the secondary battery (Range extender method)

Has anyone tried/have an idea about this? I'm flying blind.
Guy on YouTube put extra battery pack in parallel with the original battery then found out after x? Kw wouldn’t work even if extra battery pack was still good there are workarounds i heard
 

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Guy on YouTube put extra battery pack in parallel with the original battery then found out after x? Kw wouldn’t work even if extra battery pack was still good there are workarounds i heard
What about voltages with Lifepo4 and the stock BMS, would the BMS not overcharge most DIY lifepo4's?
 

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What about voltages with Lifepo4 and the stock BMS, would the BMS not overcharge most DIY lifepo4's?
Yes, the Leaf's cell voltages would be too high for any LiFePO4 cell. The proposal was to "modify" the Leaf BMS - it's not clear how the threshold voltages would be changed in the BMS.
 

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So, while the density might not be as good, isn't the longevity better on the Lifepo4's? I'd be happy with 150 miles of range for $6,000 if that was true.

I know I've read that people have "hacked" some of the code on the leaf, but that is for sure not up my alley.
 

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So, while the density might not be as good, isn't the longevity better on the Lifepo4's? I'd be happy with 150 miles of range for $6,000 if that was true.

I know I've read that people have "hacked" some of the code on the leaf, but that is for sure not up my alley.
Hobbiest
LIFEPO4 is at best no different in reliablity than the leafs OEM

Far worse in bad situations
 
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