Nissan Leaf Modules Li Conversion - Questions

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Kocho
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Nissan Leaf Modules Li Conversion - Questions

Hi,

The 19 cell conversion post here got me curious to learn more. Looks like a very simple, drop-in conversion. Almost too god to be true, mainly because there is no BMS. Can someone care to educate me about why such a battery would work in the long term (i.e., why would it not get out of balance and cry some individual cells)? I understand it relies on a version of the Laird's software, but that is applied to the entire pack and there is no control on individual cells. So what's stopping that conversion from going out of balance over time?

Also, would combining the Leaf modules with the idea of parallel NiMh cells for top balancing work? I don't see why not, if it works with the Panasonic cells.

Looks like there is a source in the US that sells new Nissan leaf modules for a bit over $100 each. That would be a roughly $2,000 conversion. Or a set of modules may become available from scrapped Leafs eventually. I am tempted at this price, as it would give the Vectrix a really useful range for me.

Thanks!

MEroller
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Re: Nissan Leaf Modules Li Conversion - Questions

That is a truly intriguing question: why would a series pack of Li-something cells that was originally fully blanced go off balance from normal usage (no extreme discharging or overcharging)?
1. Such cells (at least dendrite-free healthy ones) have no physical principle that would warrant self-discharge
2. They are connected in series: exactly the same current flows through EVERY single cell in the pack, during charging and discharging

So there is no real physical reason why they should become unbalanced...

Only at the extreme ends of cell capacity does imbalance occur due to different useful individual cell capacities.

My rides:
2017 Zero S ZF6.5 11kW, erider Thunder 5kW

antiscab
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Re: Nissan Leaf Modules Li Conversion - Questions

Only at the extreme ends of cell capacity does imbalance occur due to different useful individual cell capacities.

Bingo - use an Ah counter and never over discharge

The other issue is the original ESD charger's have a fault which means they occasionally don't stop charging

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
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LithiumVectrix
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Kocho,
The battery packs that are used in the Nissan Leaf are a good choice to use in a Li-Ion conversion of a Vectrix scooter. These NMC modules fit into the battery compartment. There has been some concern about premature aging with these battery packs in environments with high average yearly temperatures. It depends on where you live.
http://www.electricvehiclewiki.com/File:Battery_Aging_Model_Graph.png
The correct voltage for Vectrix is 35 cells in series with the Leaf modules having 2 in series and 2 cells in parallel each battery module. The correct number of Leaf modules is 17 and a half. Bit hard to do but possible. 18 modules could be used but the regenerative braking won't work for the first 6 Km. 19 modules is not recommended. The leaf cells can be kept in balance using NiMH batteries as my 90 Amp/Hr design or using a balance board. If you don't fit a method of balancing the cells will go out of balance. This is well known by anyone who builds battery packs with Li-Ion batteries fitted to Electric Vehicles. You could balance them manually as part of your maintenance with balancing required more often when the batteries age. The Lairds Li-Ion software will protect the pack from damage due to run flat or over voltage as long as the correct number of batteries are fitted in series to the scooter and the battery has balancing system fitted. A cycle analyst is not recommended as this will detract from the scooters looks and its resale value.

Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

Interesting discussion about whether or not they will go unbalanced ;) From reading online, looks like experience suggests that in practice they will go unbalanced in a Vectrix application. But by not much and rather gradually if staying within good margins on both charge and discharge. So, a BMS will not be necessary on a good pack, provided the cells are balance-charged from time to time. If a cell goes bad though, I won't know until it's too late, but checking the voltages on each cell manually every once in a while will help identify potential trouble.

I think I would be OK with bottom-balancing manually via a resistor once every few months. I can just have leads permanently connected out of the battery via some sort of plug where I can measure individual cell voltage and attach a resistor to discharge to the same voltage manually (or with some sort of cheap RC-style automatic charger/maintainer). And, if I ever get the time, might build an Ardino-based or similar BMS.

Here is an interesting thread: http://ecomodder.com/forum/showthread.php/lithium-battery-bms-questions-28703.html

I might pull the trigger and get 18 cells. I use a household timer for charging the Vectrix, so even if the ESD charger gets stuck "ON" it should not be an issue (unless it gets stuck during the CP phase and thus overcharges before the time is up). Any idea how that bug happens? At which point does the charger get stuck (CP, CC, EC)?

Also, what is the Laird's modification to the Li software? What are the voltages and times? I'm guessing the main mod is the number of Ah that the charger will pump, correct (the Leaf is 60ah vs. probably less than 30Ah on my pack now)? Is there an option to use the original firmware and just change the capacity limit via ScooterDiag software? I really like the 68mph limit on the motor controller firmware...

antiscab
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Re: Nissan Leaf Modules Li Conversion - Questions

Also, what is the Laird's modification to the Li software? What are the voltages and times? I'm guessing the main mod is the number of Ah that the charger will pump, correct (the Leaf is 60ah vs. probably less than 30Ah on my pack now)? Is there an option to use the original firmware and just change the capacity limit via ScooterDiag software? I really like the 68mph limit on the motor controller firmware...

The mod is more or less whatever you want

If you are happy to use a cycle analyst, the MC firmware doesn't have to match the charger firmware
just means the original fuel gauge doesn't work (not that it ever did)

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2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
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Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

If you are happy to use a cycle analyst, the MC firmware doesn't have to match the charger firmware
just means the original fuel gauge doesn't work (not that it ever did)

I did not trust the fuel gauge, so have been going according to the voltage readout. My concern is that there may be some interaction b/w the controller and charger software that would mess up something else. If you are sure there isn't anything else going on other than the gauge, I will put back the latest motor controller firmware to gain my extra 5mph (and lose some acceleration, apparently).

Why would I need a cycle analyst? Can't I go by voltage only when riding to know when the batts are going low, so when they go down to 120V (NiMh or 18x Leaf cells)?

Archi13
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Re: Nissan Leaf Modules Li Conversion - Questions

Hello Kocho,
You just need that the voltage stay between 152 volts in charging mode and 120 volts in use, see my other post:
http://visforvoltage.org/forum/13757-new-project#comment-72364

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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Kocho,
The original Vectrix charger firmware charges with an Amp/Hr count upto a maximum of 30 Amp/Hr. It is designed for NiMH and can’t charger a Li-Ion battery correctly. It also won’t charge a battery larger than 30 amp/Hr. This is the maximum available setting in Scooter diagnostic. The Laird’s Li-Ion firmware changes this to the correct profile for charging Li-Ion battery which is constant current constant voltage. Specifications are constant current of 10 amps, constant voltage of 148 volts. This firmware is not dependant on the size of battery and the same firmware can be used for any conversion tested upto 90 Amp/Hr.
The other point I will make is that all the instrumentation works correctly including the bar battery gauge on right cluster. Over charge and run flat protection also works.

Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

Archi13, that is very encouraging that after nearly 10000km your cells are balanced without a BMS.

I'm going to check the Vectrix liquidation auction next month - if a newer scooter comes up at a low cost, I might buy it instead of fixing my current one. A Li+ Vectrix would serve my needs quite well.

If they sell too expensively for me, I will need to decide weather to upgrade my old one to Li vs. try to replace individual cells on the NiMh (with almost 11,000 miles on my bike already, I'm not sure if I want to spend much money on it - it feels like it could use new shocks in the front and who knows what will break next...)

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Re: Nissan Leaf Modules Li Conversion - Questions

Batteries Slide 15.jpg
Hi Guys, I want to show you a slide from a presentation I gave on Li-Ion battery last week. I want you to look at the discharge curves and the mathematical explanation given on the right. If a LiFePO4 battery pack has individual battery voltages + or – 0.01v from each other than the battery is out of balance by 20%. This is a small voltage difference per cell and requires a 4 digit multimeter to be able to read. So the point I am making is that people tell me that there batteries are staying in balance but they are not measuring it accurately enough. In this example we have an imbalance of 20% which can cause cell damage unless a cycle analyst is fitted and only 70% of the battery capacity is used. Li-Ion batteries will drift in balance by varying amounts depending on quality of manufacturing so be careful. Electronic balancing is one of the functions of a BMS system. These systems are complicated and expensive so I understand that people don’t want to buy them. Manual balancing has been used by some and does work.
References : http://www.diyelectriccar.com/forums/showthread.php/j1939-and-communication-structure-83861p2.html

Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

The red chart supports your logic, but I see other charts that have much steeper discharge curves. Like this one for the LEAF batteries:

http://www.absoluteefficiency.com/images/EIG_LiMn_discharge.jpg

In the flattest section in the middle of the chart, the voltage drop from about 80% full to about 20% full is 0.4V, which is a lot more than in your example with the red line. Every 10% drop in charge voltage is approximately 0.07V. One should be able to detect that with any decent volt meter. If all cells are almost perfectly matched for capacity, there should be little disbalance for a long period of time, as long as one stays within the flatter areas of the curve, between 20-80% roughly.

That makes the assumption of excellent matching of the cells AND that they age the same over time. Both are very strong assumptions, hence my hesitation to believe the pack will remain reasonably balanced for long without a BMS. But one should be able to detect disbalances on the LEAF cells easily.

Also, given that somewhat steep discharge curve, the BMS needs to be accurate to only about 0.05 Volts to do a pretty good job of detecting disbalance even in the flat areas of the curve. Your chart for the LiFePo is a lot more demanding in its flat section.

However, does a disbalance in the flat section matter much in practice? The cells there have plenty of capacity left. As long as one can detect the much bigger voltage change at the ends of the curve, one would be able to detect a disbalance. Even a low-accuracy BMS will detect disbalances in the left and right ends of the curve, where the voltage change is much faster for a given capacity change.

So is there a real problem in practice? If I can read individual cell voltages down to 0.1V accuracy, even on your red line example, I will be able to identify if a cell nears its last 10% capacity and do something about it. Those are the "bad" consequence dosbalances, where one cell is low and the rest are high. Disbalances in the center of the curve don't seem to matter much (where some cells may be 70% full and others only 30% full are not harmful as no cell reversals will happen).

Is my logic right?

LithiumVectrix
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Kochi,
Looking through your post I support your logic about the Leaf batteries. The reason I posted the discharge graph is because the LiFePO4 discharge curve is so flat compared to the batteries used in electric vehicles. I have had others claim that their LiFePO4 batteries have stayed in balance but they don't realise just how close the voltages of each cell have to be to make this claim. Now your Leaf cells have a different discharge curve which is the blue line on the graph. Due to wider voltage range these cells are far easier to check if in balance. They are also easier to balance manually. You can balance them on the flat part of the curve whereas LiFePO4s have to be top balanced as engineers do or as some hobbists have tried bottom balanced. I think we have discussed this topic enough and can move on to something else. I like your choice of Leaf batteries and good luck with choosing a scooter for you project.

Mik
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Re: Nissan Leaf Modules Li Conversion - Questions

The main issue with claiming that Li batteries need no BMS is that the average punter may end up measuring open voltages at any SOC and take that as representing the voltage shown in discharge curves (as shown above).

If you want to know if your battery is balanced, then you need to compare cell voltages at either extreme of the batteries SOC (probably best to do it at both ends), and the voltage needs to be measured while there is at least a small load (or charge) on the battery.

Do Lithium battery voltages pop back up when the load is removed (provided they did not get discharged beyond their safe voltage range)? If so, then measuring open voltages will fool most people most of the time (into believing that they do not need a BMS and that their batteries are balanced).

Mik (who has yet so start experimenting with his first Lithium battery and may well be wrong ...)

This information may be used entirely at your own risk.

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Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

Do Lithium battery voltages pop back up when the load is removed (provided they did not get discharged beyond their safe voltage range)? If so, then measuring open voltages will fool most people most of the time (into believing that they do not need a BMS and that their batteries are balanced).

Mik (who has yet so start experimenting with his first Lithium battery and may well be wrong ...)

If the discharge curves are any indication, the voltage should drop during use, then come back. I'm looking at a chart like this one: http://www.lipohobby.com/images/upload/Image/5000-30C.jpg which shows a drop of 0.1V per cell between 35C and 25C discharge rate. Probably 0.13 drop compared to no load. If we take that as a given, multiply it by about 40 times (what's the number of such cells in the Vectrix pack?), so that in the Vectrix the voltage drop would be as much as 4-6 volts for the battery when in use. However, the chart suggests that this drop stays relatively the same as the battery discharges, up to down of about 80% SOC (after that the drop under load seems to increase, which could be a good indication that you need to plug in!).

Don't know if my math is exactly right - did it in my head off random charts - but I think the general conclusion should be sound.

However, the chart still does not answer the question how quickly the batteries do go up in voltage (recover) once the load is removed... The below link suggests that they do, but only a little, and not immediately. So a quick voltage readout immediately after the load has been removed might still be useful.

I found this useful explanation about Li batteries in general. In mostly layman terms: http://www.rchelicopterfun.com/rc-lipo-batteries.html

hempev
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Re: Nissan Leaf Modules Li Conversion - Questions

I don't think you can directly equate LiMn2O4 chemistry with lithium-polymer or lithium-ion. This is the chart supplied by the folks who sold me mine: http://hybridautocenter.com/HAC4/index.php?option=com_content&view=article&id=72&Itemid=631 (not being used on a Vectrix).

Mik
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Re: Nissan Leaf Modules Li Conversion - Questions
Do Lithium battery voltages pop back up when the load is removed ...)

If the discharge curves are any indication, the voltage should drop during use, then come back. ...
...

I am asking about how the V / time discharge graph would continue on the right side after the load is removed. The voltage will bounce back up to some degree, and I suspect that it bounces up to a relatively larger degree if the cell was discharged lower.

I.e. if the discharge continued to 3.0V, it might bounce up to 3.5V open after the load is removed, and if the discharge was terminated at 3.2V it might bounce up to 3.6V open. After the load is removed, a cell that had been getting close to being damaged due to over-discharge would therefore look very similar to one that had been comfortably within it's design parameters before the load was discontinued. As I said, I'm speculating, because I have not tested Li cells myself and all the discharge curves I have seen (like the ones posted and linked to in this thread) stop at the point in time when the load is removed because the cut-off voltage has been reached.

When you measure open voltages to assess balance of your battery, you need to use open voltage graphs to interpret your measurements. But it looks like some people use voltage under load graphs to interpret open voltage measurement results.
The degree to which the resulting misinterpretations will be significant depends very much on SOC at measurement time and the exact type of battery, I suppose. Significant misinterpretation of level of imbalance between cells means that some cells will be destroyed due to either over-charge or over-discharge.

Mik

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antiscab
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Re: Nissan Leaf Modules Li Conversion - Questions
Do Lithium battery voltages pop back up when the load is removed ...)

If the discharge curves are any indication, the voltage should drop during use, then come back. ...
...

I am asking about how the V / time discharge graph would continue on the right side after the load is removed. The voltage will bounce back up to some degree, and I suspect that it bounces up to a relatively larger degree if the cell was discharged lower.

Jack Rickard did a test like that on a CALB SE 100Ah cell - 400A for 22 sec with 60 second recovery

full discussion here:
http://jackrickard.blogspot.com.au/2010/07/4c-lifepo4-power-tests.html

it would be interesting to do a similar test on the Leaf cells

on my Winston 60Ah cells, the cells that are close to empty have a lower no load terminal voltage than the rest.
But you basically get little warning - that's why I top balance and AH count.
If any cell can't give me at least 48Ah (60Ah cells) then it's at end of service life anyway

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion

Soyouz
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi everybody,

I was not recently on the forum and I missed this post.

I have my bike with 19 Leaf modules ridding since 2 months. The Laird has done a software that can put 60 Ah and charge it to 80% at 153V. We are discussing to improve it.

With this configuration, I ride 90 km with half trip at maximum speed, with no power derrating! The bike is 210 kg, 20 kg lighter than NiMh! A really other bike indeed !

I decided to not use a BMS. But it is my personal choice. Another VX-biker, who I delivered modules, is installing an EMUS BMS on such modules, it will be interesting to see what it looks like soon.
The reason of my choice :
- I had a bad experiment with a BMS that killed one cell on my former bike
- Leaf modules are quite safe as they have been designed with automotive safety instruction
- And I made a "manual" BMS, idea from MICHEL74, by putting a plug directly under the sit. So that I can control regularly the state of each cell. And they are stable !
bornier2.jpg
bornier3.jpg

By the way, if people are interested by Leaf modules, I have some left to convert other bikes. Tell me by PM. I live in France.

Regards

Kocho
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi,

What did you use for the "manual" BMS? Also for the connectors and any other parts that you needed.

Thanks!

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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Soyouz,
Good to see another Vectrix conversion using Leaf cells. These fit easily into the Vectrix battery box and suit the discharge current range of the Vectrix. Others have found the same as you that the batteries stay in balance and only occasionally need a manual rebalance. You can use the Laird's firmware to monitor the battery pack voltage and no cycle analyst is required. These batteries don’t suffer from voltage spiking during charging as LiFePO4 do, so no individual cell monitoring BMS is needed in this application.
Now I would like to make the same comment I have made many time before. The maximum voltage of the Vectrix motor controller is 146 volts. If you exceed this it won’t blow up but the regenerative braking won’t work. The change in charging firmware does not resolve this. With the NiMH battery and it finishs charging, the voltage falls below 146 volts when you start riding. The other problem is low voltage protection of the pack which is provided by the motor controller. With a 38s configuration the cells are discharged below 3.0 volts before the scooters low voltage protection starts. If a small imbalance in the pack occurs you will damage the lowest cell.
The correct configuration for Vectrix is 35s with a maximum charge voltage of 147 volts. A 36s configuration is also acceptable as some don’t want to open a Leaf module and use half of it. 36s is 18 Leaf battery modules.
The Laird has a version of his Li-Ion firmware which charges to 148 volts and it will charge a 60 amp/Hr battery to 99%. There are members of this forum who have been riding Vectrix with this version of the Laird's firmware for 18 months. You can remove 1 Leaf pack and ask the Laird for the correct software. Then the scooters brakes will function correctly and the firmware will protect your battery.

Jeff Spooner
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Re: Nissan Leaf Modules Li Conversion - Questions

This seems to be excellent news for those of us seriously needing new batteries. I think I'm going to take the plunge, since right now my Vectrix is useless & just taking up space. Being more mechanically than electrically inclined, I have a few concerns before making the big (battery) investment.

1. Does the LEAF conversion use the old NiMH temperature sensors (mine show some corrosion, thus not sure if useable).

2. It should be feasible to circulate air between the cells for hot weather with 18 cells, is there enough space with 19 cells installed, to circulate air between?

3. Does anybody out there repair the onboard chargers? I'm using a bank of (9) 12v solar panels in series to trickle charge the NiMH battery to keep it alive
since the charger quit charging. What I don't know is if something downstream (bad NiMH cell, sensor, etc) could be causing the charger to not charge at
all.

4. If anyone has a source for the chargers (left-overs from the auction) I would appreciate info. Thanks,

Jeff S.

rEVolution Rocks

Soyouz
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Re: Nissan Leaf Modules Li Conversion - Questions

Hello,

@Kocho :
For my manual BMS I use some 4 mm plug :
http://www.conrad.fr/ce/fr/product/731155/Douille-Banane-noire-4mm-10A-SCI, It would have be better to use safety ones, but more expansive.
I installed them on a Dibond plate. This one is fixed with 4 screws on the battery cover under the seat. Sealing is done by window seal.
I also get the plug bar that comes with these Leaf modules. All the wires were already placed, that is practical. I remove the original plug and connected all the wires to my home-made plug. And it is done!

@LithiumVectrix :
Yes, I know that 18 modules is better for regenerative break, but more modules means less current, more autonomy, and more durability for battery. So I stay like this. But 18 modules is possible, lighter also. The 2 possibilities are OK.
By the way, I know very well these modules and have all datasheet needed.

@Jeff:
1. Does the LEAF conversion use the old NiMH temperature sensors (mine show some corrosion, thus not sure if useable).
I don't use the temperature sensors on my 2 bikes (one with Calb LiFePo4, one with Leaf module), these circuits are indeed not reliable. Problem is that without these circuits, charger won't charge. This is corrected thanks to Sandy's software. Only Ok for ESD charger.
Another french guy, who I distribute leaf modules is converting his bike and has find a charger that can replace the original one for few money. As soon that it works I will ask him to post his conversion description. Good think is that without the original charger, the gauje is simply a voltmeter, that is very useful!

2. It should be feasible to circulate air between the cells for hot weather with 18 cells, is there enough space with 19 cells installed, to circulate air between?
Lithium cells don't heat up like NiMh. So you just have to remove the 2 battery fans (less weight). These cells just don't like > 45°C ambiant air when fully charged. It is never the case for me. In fact, I try to keep the heat in. Because when battery is cold it has less capacity... So I isolated the battery tray with polystirene. It is exactly the opposite than NiMh ;-)

3. Does anybody out there repair the onboard chargers? I'm using a bank of (9) 12v solar panels in series to trickle charge the NiMH battery to keep it alive
See 1. Maybe your T°C sensor don't work or one cell heats too much. That would be corrected with LI conversion. You should try the Laird software.

4. If anyone has a source for the chargers (left-overs from the auction) I would appreciate info. Thanks,
See 1. If the alternative charger works I will post the caracteristic.

regards,

Sylvain

LithiumVectrix
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Soyouz,
3 years ago I built a 38s battery pack and fitted it to a Vectrix scooter. I observed that the regenerative braking would not work for the first 15km if the pack was fully charged. This is a safety issue. Running the scooter I observed that the low voltage / run flat protection provided by the motor controller will not protect the pack if run flat. Does your BMS give run flat protection? How do you plan to address these 2 issues?
The current reduction from 38s to 36s is 3% when you include the reduced conversion efficiency at higher voltage of the buck converter in the controller. This is a small amount. I apologise for pushing my point.
If you use a 37s battery pack and The Lairds 60AHLION03.hex firmware, then all functions, instrument gauges, charge monitoring and low battery protection will work. The nominal battery pack voltage rises from 125 volts to 136 volts. Charging is to 148 volts. This will give you a fully functional scooter with no compromises. You are using a BMS so no manual balancing is required. This is good as battery balancing is maintained automatically.
Jeff,
the temperature sensors can be used or removed depending on which version of the charger firmware used. Cooling is provided by airflow from the air vents in the front and out the rear past the motor controller while riding the Vectrix. The fans are removes as no cooling is required while charging.

Jeff Spooner
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Re: Nissan Leaf Modules Li Conversion - Questions

Thanks Sylvain & LithiumVectrix for the pointers. It sounds like Lairds firmware combined with the Leaf modules can offer a bike better than factory (lighter, quieter charging, longer range, far less connections to fail, etc). However I've read about the risks with the Lairds firmware install & might hold off in the beginning(if possible). I say this after reading of some cases of Vectrix becoming bricked (doorstops) here on the forum. Anyone know the %success rate for Lairds installs (is it known why some installs don't work, is it procedural error?).

I'll remove my NiMH's, drop in 18 or 19 Leaf cells (bare - NO BMS hardware or temperature sensors etc), wire in series, hook up pos & neg main cables(with the precautions using a light bulb resistor if need to), charge at 140v @1 amp off of my solar array. With the original Vectrix factory software (I don't even have the 68mph update), will my bike "run" at this point? I understand about the onboard charger (if it still works) not being correct for Lithium, & that precautions would be need to be taken to not run cells flat.

As far as the overheating, it sounds like you're saying that the Vectrix has a better venting arrangement, which offers better cooling than the Leaf cars, thus less problems.

Sylvain: I look forward to info on an alternate charger. Thanks

Jeff S.

rEVolution Rocks

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Re: Nissan Leaf Modules Li Conversion - Questions

18 (36S) or 19 (38S) leaf modules need to be charged at ~4.05v per cell (80% full) which will be 146/154V.

I had a dead charger in mine that I replaced with 4 meanwell 36V 150W LED power supplies in series. These are cheap, waterproof and shockproof, and work really well as chargers for lithium conversions.

I took out the charger and temperature sensors and just hooked up a 43S lithium battery with absolutely no problems - just works.

One thing I havn't heard discussed, is the requirement for these Leaf modules to be compressed as they normally would be in a Leaf battery pack - this would be done with threaded rods and two solid pieces of metal on each end - I would be most comfortable with using 18 modules (36S) and using the extra space afforded to compress the modules together.

There is anecdotal evidence that they do swell at high current draw, and their capacity is affected as well when uncompressed.

I'm probably going the leaf module route myself, nothing wrong with the 40AH lithium conversion, just would like the extra range and high current charge ability that they allow (Ie. 0.5/1c charging).

MEroller
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Re: Nissan Leaf Modules Li Conversion - Questions

What is the size and weight of one Nissan Leaf cell? And the approximate capacity would be around 40Ah?

My rides:
2017 Zero S ZF6.5 11kW, erider Thunder 5kW

reikiman
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Re: Nissan Leaf Modules Li Conversion - Questions

Woah, this is interesting that Leaf modules can directly go into a Vectrix.

I want to weigh in with my observation on using a BMS on a lithium pack going on 2 yrs 10 months. In my car - http://ekarmann.com - I have a 45 cell Thundersky 100ah pack, sitting inside a box designed by my friends at Lightning Motorcycles, and using the same BMS they put on their race bikes. The BMS gives me a display showing the voltage for each cell .. as well as pack voltage, average cell voltage, etc. It's fascinating to watch this as I drive, if only I didn't have to keep my eyes on the road to stay safe ;-)

As Mik said earlier in this thread - the voltage under load is what you want to look at. The resting voltage at any given time is not indicative of much, since the resting voltage curve is so flat. I've configured the system for a 3.82 volts per cell fully charged target voltage, and once charged it quickly falls off. The resting voltage will range between 3.4 and 3.2 volts per cell (depending on depth of discharge) until it's nearly depleted.

Under load (while driving, that is) the cell voltages don't rise and fall evenly. They voltage for each cell, under load, depends on that cell's capacity. A cell with lower capacity will reach the target charging voltage more quickly - and reach the minimum discharge voltage more quickly - and read lower than pack average during discharge.

In the pack in my car, at steep discharge rates (while accelerating), the difference between high and low cell voltages can reach .3 volts or more.

In order to keep the weakest cell from going below the minimum safe voltage point, I have to monitor the BMS display and if the voltages go too low back off on the throttle.

That's for the Thundersky LiFePO4 chemistry as it was manufactured in 2010. Now that the company is known as Winston, their cells may behave a little differently. Nissan modules may behave a little differently, because they're such a different chemistry.

My conclusion after nearly 3 years using a BMS is that one MUST have a BMS on a lithium pack.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
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antiscab
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Re: Nissan Leaf Modules Li Conversion - Questions

What is the size and weight of one Nissan Leaf cell? And the approximate capacity would be around 40Ah?

A nissan leaf module is composed of 4 x 3.8v 30Ah LiMnO2 cells arranged in a 2S2P configuration for 7.6v 60Ah.
Each modules weighs 3.8kg

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah
Vectrix 60Ah Lithium Tyres Fuel Registration Insurance cycle analyst 2 x TC Charger & MC
conversion

Soyouz
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Re: Nissan Leaf Modules Li Conversion - Questions

Hello,

@LithiumVectrix :
I fully understand your point and agree, 36S is better for bike caracteristic. 38S is better for battery. I made the 2nd choice, that is mine. Both are feasible.

@Jeff :
There is a risk to freeze MC soft when uploading The Larid soft, basically, you must not cut off the sccoter during upload. Else, I never had issue.
I agree with heathyoung for voltage value. If you respect these value you can charge your battery from external charger and your bike will run normally.
Leaf battery hasn't any cooling system ;-) That's why VX can only be better, even by removing fans...
Here is a link for the charger :
http://www.green-vision.fr/catalogue/Produit/77/16/batteries-lithium-lifepo4/chargeur-lithium/chargeur-lithium-1200w.html
It is from french dealer but you can find other place, mainly from China.
I was confirmed that Voltage and current can be set by internal potentiometer, but I didn't try.

@Heathyoung :
You are right, These modules are quite compressed in Leaf.
I made it through wood blocks against the battery tray. Modules just have to be slightly pressed at beginning. They will swell several percent during life because of wear, like every Li cell. So compression will increase a bit.
You can use 2 metal plates and 4 long bolt, similar to leaf battery design. There is enough room for such assembly with 19 modules (tested).

@MERoller :
Modules weight is 3.9 kg. Dimension : 223 mm x 320 mm (with connector) x 35 mm.
They are 66Ah for 3.65V nominal. As there are 2S, it means 480 Wh per module. So ~9kWh pack for 19 modules.

@reikiman :
LiFe and Leaf (LMO/NMC) chemistry are very different. And discharge behaviour is also not the same. It is simpler to follow cell discharge by checking voltage with Leaf cell, as discharge curve is not flat.
I don't trust BMS like you do. It is great to get permanent cell value but be aware that having this information means that BMS draw permanently a few current on each cell and can unbalance your pack. BMS quality is very important.
I used a BMS on my first Li bike, and that is what killed a cell.... Then I removed it :-)

LithiumVectrix
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Re: Nissan Leaf Modules Li Conversion - Questions

Hi Reikiman,
I see that you are driving a Converted Karmann Ghia. I wanted to ask how many miles have you travelled on the Thundersky batteries? What are your experiences with the car and was it converted as by Minddrive? I am a part of the Australian chapter and we find the Karmann Ghia an easy vehicle to convert and maintain with simple Volkswagen mechanics.

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