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Discussion Starter #1
Hi all,
I've heard that there's a few guys on here that have converted their cars to run on leaf batteries and I can't seem to find the threads. I was hoping that someone has gone thru the trouble to documenting from start to finish a lead acid to Leaf battery conversion for us simple minded DIY'ers who want to do it, but aren't sure how to. I bought a geo metro (Lead acid powered) and the pack crapped out only after two months. I really don't know much about conversions but am eager to learn. Can anyone provide a link? BTW- I've already read the "Leaf battery pack as a doner" thread among a few others, but seem to go around in circles when searching for the threads that spell out how to do it.

Thanks,

Bflo
 

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Hi Bflo

What voltage was your lead acid pack? and what motor and controller are installed?. Essentially the job involves removing your lead acid batteries taking appropriate care while working with high voltage. and installing your leaf pack probably connecting it into 3 parallel 120 volt strings and connecting your positive high voltage cable where the lead acid positive cable was and likewise for the negative. You should be able to leave fuses, contactors, motor, and controller untouched if you are keeping the voltage the same or similar. Your charger will probably need to be reconfigured and changes may need to be made with your instrumentation/ battery management. You need to consider the physical dimensions of the pack and how it will be mounted, whether it will fit where the lead acid batteries were and what sort of engineering (cutting, welding, fabricating boxes) may be required to make it fit. I personally have enjoyed the creativity and problem solving required in designing my own electric vehicle and feel it is a wonderful project to get involved in.

All the best
David
 

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This should be straightforward. David covers most of it in his posting. You need to know the voltage of the original lead acid system so we can match it and what the current limits are set to in the motor/controller to ensure that the batteries are not pushed too hard. And the termination voltage of the charger. Those are the electrical questions. The physical mounting of the new pack is the other side of the coin. This is usually not a problem because Lithium batteries take up so much less space and weigh so much less for the same capacity. But the leaf pack could be too tall or have its terminals in a bad place so it will require some checking. I am guessing that Davids suggestion for reorganizing the leaf pack into a 16S 3P arrangement of modules is a good one. This requires 48 modules and would give you a nominal 118.4 volt pack at 180 ah (21.3 kwh). As David mentions you will probably have to adjust or replace your charger but with a careful selection you might be able to use the existing charger. It depends on the termination voltage of the charger. For example if the charger is configured for twelve 12 volt lead acid cells the termination voltage will be between 160.8 and 172.8 but this is called a 144 volt system because twelve cells of 12 volts nominal is 144 volts. To use that charger without modification means you need to match the cutoff voltage. The cutoff voltage for the Leaf type cells is 4.2 volts per cell or 8.4 volts per module. It is ok and probably even good for the Leaf type cells to be slightly undercharged. If the charger cuts off at the low end (160.8 volts) then you would want 20 modules in series so that the charger voltage never exceeds the 168 volt max charge voltage of the pack. If the charger takes it up to 172.8 then you would need 21 leaf cells in series.

I am sort of remembering yours was not this high of a voltage, probably 96 volts nominal. That makes the peak charge voltage somewhere between 107.2 and 115.2 volts. In that case a 16 cell in series leaf pack pack voltage of 134.4 is quite a bit too high. The pack would never get charged. A 14 cell in series pack of Leaf cells would be slightly undercharged using a 96 volt lead acid charging system that charges to 115.2 volts. If the charger only takes it up to 107.2 then a 13 cell in series pack would be the correct size.

In all cases I suspect that a 3 parallel arrangement is probably what you would want to do. 2 cells in parallel might not like the peak amp draw of your relatively low voltage system.
 

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Discussion Starter #4 (Edited)
This thread can hopefully can lay out the groundwork for someone in the future attempting to do the same as I am, so if I overdo it with the questions- my apologies.

What voltage was your lead acid pack? and what motor and controller are installed?.
It's a 96V system, the motor is a D&D 72-144 VDC 18hp Single Shaft, and the controller is a Kelly 09501 24V-96V Nominal Voltage Range, 18v-120V Max Operating Range. My charger is a Kelly HWC4B 96V/12A charger which unfortunately doesn't have a variable voltage.

If I am able to snatch up a leaf battery at a junkyard, I'm guessing that I should be able to also use the charger from the donor Leaf car.

taking appropriate care while working with high voltage
From what I learned from Aviation Mech. school, it's not the volts you have to worry about, but the amperage- which is why a (high voltage) coil on an ICE engine will wake you up but not kill you...I want to check the brushes on the motor but have put that off until I know I'm not going to get zapped by a capacitor somewhere in the system that I'll have to inevitably discharge beforehand I'm guessing even though the pack is disconnected from the system.

changes may need to be made with your instrumentation/ battery management
I don't believe this car has any sort of BMS on it. I know that Rickary from EVTV thinks that you can run the Leaf batteries without a BMS, but others on here have mentioned that no BMS would probably will lead to overheating and a possible fire situation.

I just went to the Maker's Faire here in San Mateo and was talking with a guy with a Miata that had a BMS that didn't like his controller (I think that was the dueling component). Apparently the type of controller confused the BMS into thinking the batteries were in a different charged state than they were in, leading to headaches and wasted money into the $1000's. I'm hoping to avoid that obviously. I'm guessing taking the BMS out of the Leaf would be too much of a headache as it may be so integrated into the rest of the car.
 

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Are you able to find any Leaf batteries? I got lucky to get mine, unless you can find a crashed one where the batteries are still in good condition...I'm not aware of the battery plant selling to DIYers. That would be cool if they did though.

You might want to check out my Entire Wiring Diagram thread. I drew that up using the 16 cells in series, 3 parallel layout.

I'm not sure about the BMS that comes with it... I don't have the monitor or anyway to see what it is doing, nor do I know how to power it up. I have started looking into the BMS cable connections to see if I can get the voltage of each cell somehow. It is looking good, but for some reason they used a 30-pin connector when they needed 32-pins...:rolleyes:

You will want to go with 12 cells in series, 3 rows in parallel though to keep everything at 96V. And I've heard to only charge each cell to 4.05V-4.1V times 2 (8.1V-8.2V). This will help prevent any overcharging problems.
 

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Discussion Starter #6
I got lucky to get mine, unless you can find a crashed one where the batteries are still in good condition.
I live in nearby a bunch of junkyards so I'm hoping to get lucky too. I've heard about them showing up on occasion and I can wait. I really need to do the research first to see if it's worth my time as they sound more apt to fires than LiPo4's.

Thanks for the heads up on your Entire Wiring Diagram thread.

You will want to go with 12 cells in series, 3 rows in parallel though to keep everything at 96V. And I've heard to only charge each cell to 4.05V-4.1V times 2 (8.1V-8.2V). This will help prevent any overcharging problems.
This is going to sound like a stupid question, but do you mean if it's a 96V system, then you're saying I should make sure I don't let them charge more than 98.4V (4.1V x 24cells)?

According to DougIngraham
I am sort of remembering yours was not this high of a voltage, probably 96 volts nominal. That makes the peak charge voltage somewhere between 107.2 and 115.2 volts.
it looks like my charger won't work for that set up as it would have to be 13 cells. I'm getting a little confused at this point...
 

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Hi Nobrush

Are you aware of this placehttp://hybridautocenter.com/HAC4/in...&cid=14&name=nissan-leaf-batteries&Itemid=605

I think caps is right in that splitting the pack into 4 modules at about 90 volts nominal is the way to go. if you go for three modules of 120 volts it will likely overwhelm your controller but if you purchase individual cells like in the link above you have a bit more latitude. Batteries are listed at a nominal voltage in case of lead acid it is twelve volts but actually can be anywhere from 13.6 Volts(fully charged) to 11.6Volts(fully discharged) this is why Doug lists the cutoff voltage for the charger as 107.2 to 115.2 volts. similarly the leaf cells are 7.6 Volts nominal which is 8.4 fully charged and 6 volts fully discharged. As far as using the leaf charger goes that would be tricky as I understand it the leaf operates at 360 volts nominally and is a charger, inverter, ac controller, and DC converter all in one all with software to be decoded to make it usable. You may still be able to use your charger if its voltage cutoff is not lower than what you require for your leaf cells as a charger will only put electricity in at the voltage that the pack is at. For example your leaf cells are discharged to 80 volts and you want them charged no higher than 100 volts and your charger normally switches off at 110 volts. You could plug your charger in and charge your pack and have it monitored externally by a programmable voltmeter such as the JLD404 which drives a relay and shuts your charger off at 100 volts.
My personal opinion around lithium batteries catching fire is that the risks are overstated and are caused by overcharging and trickle charging something you will avoid doing along with over discharging and while I feel that complicated battery management systems are unnecessary and if poorly implemented destroy batteries by introducing parasitic loads that unbalance the pack it is important to know the state of charge of your pack and operate it within safe parameters.

I hope this makes things clearer and not more complicated
 

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Discussion Starter #9
Thanks for the heads up. I'll be interested in seeing how it goes with your car. Are you using the Leaf charger as well?
 

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Thanks for the heads up. I'll be interested in seeing how it goes with your car. Are you using the Leaf charger as well?
As will I, I am not using a BMS nor do I plan to. I try to always charge them to 100% but there have been times I have had to un-plug before the charger light turns green. I have never discharged the pack below 50 volts.

I'm using an Elcon PFC 2500 from EVolve Electrics.
 

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Discussion Starter #11 (Edited)
I am hoping to not have a BMS as well, but I did want to monitor the temperature of the modules as from what I read they sound like they can overheat and cause a fire. I'm hoping to do that relatively inexpensively but that will take some more research. I'm not sure if I can just monitor all of them and only have the hottest one register to make the temp. sensing system simpler, and then figure it out somehow(maybe by testing voltage when it's charging or it a depleted state?)

Did you top or bottom balance your pack?
 

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Discussion Starter #12
As will I, I am not using a BMS nor do I plan to.
I am hoping to not have a BMS as well, but I did want to monitor the temperature of the modules as from what I read they sound like they can overheat and cause a fire. I'm hoping to do that relatively inexpensively but that will take some more research.

I try to always charge them to 100% but there have been times I have had to un-plug before the charger light turns green.
Was the reason you had to unplug the charger because the pack was getting too hot?


Did you top or bottom balance your pack?
 

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Discussion Starter #13
Are you aware of this placehttp://hybridautocenter.com/HAC4/ind...ies&Itemid=605
I am aware Davidmillin of this place but I'm hoping to get a deal on used ones from a junk yard. Thanks though.

As will I, I am not using a BMS nor do I plan to.
I am hoping to not have a BMS as well, but I did want to monitor the temperature of the modules as from what I read they sound like they can overheat and cause a fire. I'm hoping to do that relatively inexpensively but that will take some more research.

I try to always charge them to 100% but there have been times I have had to un-plug before the charger light turns green.
Was the reason you had to unplug the charger because the pack was getting too hot?


Did you top or bottom balance your pack?
 

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I am hoping to not have a BMS as well, but I did want to monitor the temperature of the modules as from what I read they sound like they can overheat and cause a fire. I'm hoping to do that relatively inexpensively but that will take some more research.
From what I have seen so far (1200 miles) these batteries DO NOT get hot during discharge or recharge, they barely even get warm to the touch. I can see in a higher voltage - higher amperage situation it might be a concern. I was initially worried about heat and fire also but after much research I had to consider the fact that Nissan is circulating hundred of thousands of these modules with very low numbers of "thermal events" on record. I am living proof that you are more likely to catch fire in a gasoline powered automobile.

Was the reason you had to unplug the charger because the pack was getting too hot?
Definitely not, I unplugged because I needed to be somewhere and could no longer wait to finish the charge.


Did you top or bottom balance your pack?
I guess I top balance - if I understand the meaning of the term correctly. I charge completely and then check the voltage of each cell individually with a Fluke digital multimeter. I am not sure what I would do if I had to remedy an out of balance cell.
 

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Its been a while since I posted on this forum. After 4 years using lead-acid, I am now converting to lithium, probably with salvaged Leaf batteries so this discussion is really helpful (note another discussion in this forum with good information on this subject is here: http://www.diyelectriccar.com/forums/showthread.php/place-selling-nissan-leaf-batteries-92122.html). I thought I would share my plans in case it's of interest, and would welcome any comments. I am trying to do this as economically as possible, keeping as much of my existing stuff as possible.

My old system was eight 12V Trojans, and my plan is to use 13 Leaf modules in series, with either 2 (120 Ahr) or 3 (180 Ahr) banks in parallel. This should replicate the voltage of my existing pack, so nothing else has to change. While even 2 banks should be improved performance over my current batteries, and thus meet my driving needs, seems adding an extra bank should also extend the life of the pack, so I am leaning that way.

My old charger is an Elcon 1500. I would have that reprogrammed for a 620v algorithm. Apparently that algorithm allows fine tuning the end point voltage in 1 volt increments by the selection button that is active when the unit boots up (or at least thats what I infer from the seller). I don't plan to have a BMS. Rather, do a bottom balance, and tune the peak charging voltage (as detailed in many other posts).

This is my car:
http://www.diyelectriccar.com/garage/cars/171

If I go with 3 banks (39 modules) , the car will still be 320 pound lighter, and at least twice the kW/hrs. Even with lead, the car managed quite well and was fun to drive. I am anxious to see what this will give.

Don
 

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What kind of set up did you order as they don't have a choice for 7.6V (8V nominal), charging curve, etc?
They have to configure it for you, no matter what battery type or voltage you choose. I sent them the charge and discharge curve that came with the leaf batteries and they matched it as closely as they could with one of their available curves.
 

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From what I learned from Aviation Mech. school, it's not the volts you have to worry about, but the amperage
I hate it when people say this. It is technically true, but entirely misleading and incredibly dangerous.

Yes, it is amps that will kill you. But consider Ohm's law: V=IR. This states that for any given resistance, voltage and current are proportional. Now, the resistance of your body will change based on whether you are wet or sweaty, whether you are conducting a path to ground through shoes, etc. But whatever it is it is, so the amount of current flowing through your poor carcass will be directly based on how high the voltage is.

The ONLY situations where high voltages are safe are 1. When the power source is current limited at a level below the danger zone. In this case, the supply will actually drop the voltage to whatever it takes to supply that current. 2. The power source is a capacitance so small that the high voltage cannot maintain a high current for a significant amount of time (Van De Graffe generator, dragging your shoes on the carpet, etc). In this case, the voltage also drops rapidly to a low level.

Neither of these cases are true with a traction battery. If the voltage is high enough, and you use your body as a current path, they'll give you as much current as you can handle, and much much more.

So by all means, please DO be careful working with the high voltage. 120 volts might not kill you, but it easily could if your body resistance is low at the time.

For that matter, be careful even at the lower voltages. Lithium batteries hold a lot of energy, and they love to give it up fast. You can easily burn yourself badly if, say, your ring were to short across a single 3.6V cell.
 

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Discussion Starter #19
I sent them the charge and discharge curve that came with the leaf batteries....
Thanks for the heads up.

I will most likely be buying them from a junkyard. Do you happen to have that info or a scan of the paperwork you recieved with the batteries?
 

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thanks for the heads up.

I will most likely be buying them from a junkyard. Do you happen to have that info or a scan of the paperwork you recieved with the batteries?
this is information published on hybrid auto center's website, I purchased from them and will buy more as soon as funds are available;)

discharge new leaf 20a L.jpg

charge new leaf 20a L.jpg
 
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