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Lithium vs Lead; the Great Cost Debate.

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Posted 02-03-2009 at 01:21 PM by mattW

I've decided to try and work out the cost comparisons for a Lithium pack vs a Lead pack for a set range and a set number of years. Is Lead Acid actually cheaper or does is just seem that way up front? This article aims to find that out. The method is to get 10kWh of usable energy, Iíll try to get that with Lead and with Lithium and see what we find is cheaper in the long run. Assuming an efficiency of 250Wh per mile (a compact car) we should get a range of 40 miles (65km) with either pack. Iíll be using Australian prices since Iíve already researched them, but the comparison is probably close in other countries too.

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The first step is to source a lithium pack with 10kWh of usable energy. The Lithium batteries I have chosen get 2000 cycles to 80% DoD and I estimate that at the 1 hr rate they will deliver 95% of their rated energy due to the Peukertís effect. So to give our total energy we multiply our usable energy by 1.35 meaning we need 13.5kWh to get out 40 mile range with lithium batteries. If we assume a 120V conversion this means we need 112.5Ah. The cheapest Lithium batteries I have seen in Australia are Thundersky LiFePo4 LFP prismatic cells $2.50 per 3.2V per Ah. So our 13.5kW pack would take 38 3.2V cells at ~110Ah and would cost $10450 at normal prices (no group discount), without shipping or BMS.
For a Lead Acid pack we also need to keep the batteries at less than 80% DoD and at the 1hr rate we can only expect to get 55% of the rated energy of the pack back due to the Peukertís effect. That means we need to multiply the usable energy by 2.25 to get our total energy, in this case its 22.5kWh. Trojan T605 batteries could make up a 22.5kWh pack with 18 batteries (108V, 210Ah) at $225 each or $4050, it didnít say how many cycles it would take on the website but letís guess around 650 to 80%. That means weíll need to replace our lead Acid pack around three times for every lithium pack we buy, meaning our total cost for the lead packs goes up by a factor of 3 to $12150 over 2000 cycles.
Now I must admit that I didnít look very hard for the cheapest batteries and I am only guessing the cycle life of the Trojans but even if itís not precisely accurate it does show that the myth that Lead is clearly cheaper than lithium is not well founded. Lithiumís greater efficiency and cycle life makes up for its higher initial cost. I didnít know what the results would be like before I started. The10kWh number was chosen just to make it easy to calculate, it has little influence on the result one way or the other. I thought the results would be close but not this close. Please note that the Lithium pack would require a BMS, which would cost $1270 but that still means you are going to pay around $12k whether you go with Lithium or Lead. It would also be worth mentioning that you would be paying for more electricity over that time with Lead; 36MWh costing $3600 compared to 21.6MWh $2160 @ $0.10 per kWh and recharging 80% of capacity. You would also need to water the batteries if you went with the Trojans, while the lithiumís would be maintenance free. Itís also worth mentioning that there are apparently disputed copyright issues with the thundersky cells and their previous record with customer support apparently not good, but this was just a cost comparison and the number look pretty convincing.
The total cost per km for the 2000 cycles is $15 750/ 130 000km = 12.1c per Km (19.7c/mile) for Lead Acid and $13888/ 130 000km = 10.7c per km (17.4c/mile) for the LiFePO4. These would obviously increase slightly when factoring in tire and brake wear. Just for comparison a the cost per km of a bunch of small ICE cars are listed here the cheapest being 41.44c/km but only 33.5% of that cost was for fuel and servicing (the rest being common cost for EVs as well) so thatís 13.9c/km for the cheapest ICE using fuel at $1.25/L. Clearly then EV have a price advantage over ICEís especially now that normal unleaded is averaging $1.48/L.
In summary, while Lead Acid may be cheaper up front new lithium packs are more cost effective in the long run as well as being lighter, smaller and maintenance free. Obviously battery choices are highly dependant on individual conversions and budgets but it should not be assumed that Lead is the budget option, since itís just not true anymore.
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  1. Old Comment
    JRP3's Avatar
    Quote:
    Performance wise any vehicle will run better with 300lbs of batteries vs 1500lbs.
    Unless those 300lbs of batteries don't work You might want to check out this thread, discussion about a group purchase of PHET lithiums:
    http://www.diyelectriccar.com/forums...ase-14074.html
    Posted 06-05-2008 at 07:03 AM by JRP3 JRP3 is offline
  2. Old Comment
    Quote:
    Originally Posted by DIY Electric Car Blogs View Post

    I've decided to try and work out the cost comparisons for a Lithium pack vs a Lead pack for a set range and a set number of years. Is Lead Acid actually cheaper or does is just seem that way up front? This article aims to find that out. The method is to get 10kWh of usable energy, Iíll try to get that with Lead and with Lithium and see what we find is cheaper in the long run. Assuming an efficiency of 250Wh per mile (a compact car) we should get a range of 40 miles (65km) with either pack. Iíll be using Australian prices since Iíve already researched them, but the comparison is probably close in other countries too.
    Hi,

    Check this out (scroll way down):
    http://www.diyelectriccar.com/forums...ery-14296.html
    Quote:
    The thing about kokam that is scaring me off right now is that nasty >800
    charge cycles to 80% capacity...

    Thundersky lists >2000 cycles for the same discharge level. I know you cannever be sure about specs, but that's a big difference.

    In case you care: I've been head-to-head comparing Kokam'1 100Ah cell with Thundersky's 90Ah cell.

    Kokam's 100Ah cell lists peak discharge current at 800A = 8C, wheras the
    thundersky lists 10C. Also TS lists 3C charge, while Kokam lists 2C.

    Kokam has a slight edge in weight at 2.7Kg vs. 3Kg. I also really worry
    about the integrity of Kokam's main tabs. That's just me, but I really like
    the idea of positive locking threads for connections. Making a pack out of
    Kokam's cells looks like it could be a bit of design/fabrication effort too,
    so the weight might be a wash anyway.

    BIGGEST ISSUE (for me): compare Kokam's $1.60/Wh retail, to thundersky's sweetspot cell - the 3.6V90Ah, which is much closer to $.50/Wh. The Kokam cell is going to have to be a lot better than the datasheet, and the thundersky a lot worse to make the economics work out for me. Even if theyhave a 5-10% DOA rate, TS look damn good to me.
    Jon
    --------------------
    Yes but it's Thundersky. They have a reputation for being less than
    honest with their specs.

    Since they don't come with any warranty, what are you going to do if it
    turns out they are only good for <400 cycles ?

    Kokam, on the other hand, has a reputation for being striaght shooters and honest about their product.

    Thundersky's specs are meaningless since they don't guarantee them and
    wouldn't honor the guarantee if they did.

    I'd go with the Kokams

    Unknown
    --------------------
    That is true, but at about a third the cost - it would still be a better bet
    to buy two sets of TS cells that radically underperform than one set of
    Kokam.

    Anyway all this is going to be very dependant on the quality of the BMS
    monitoring each cell and the use scenario.
    Jon
    --------------------

    A while back a group of EVDL members arranged a group buy from TS. TS had a bunch of batteries that didn't pass their crappy QC so they decided to offload them on the Stupid Americans. They KNEW they were bad cells and they sold them anyway.

    These days folks that are smart go to the factory in China and test the
    batteries before buying them. They end up rejecting many of them that
    pass Thundersky's QC.

    If TS is willing to sell known defective batteries to us, what do you
    think they are going to do with ones that pass their "QC" but aren't
    purchased by the above buyers?

    Even folks who buy LOTs of batteries from TS, have had batteries that
    looked good initially but failed within the first year. Internal
    corrosion caused by poor quality control during assembly.

    Thundersky NEVER replaces defective cells regardless of who buys them or why they failed. Well, I've heard rumors that they might honor their warranty for Chinese customers, but never for foreign customers.

    If you're comfortable taking that kind of crap shoot with that much money,
    knock yourself out.

    Unknown
    --------------------
    Jon Wagner wrote:
    > That is true, but at about a third the cost - it would still be a better bet
    > to buy two sets of TS cells that radically underperform than one set of
    > Kokam.

    You can buy 5 sets of thundersky batteries and get another 5 for free.
    It's not going to help you - if one set is 100% crap, and you get 5
    sets, you still get 100% crap. Just 5 times bigger pile of it.

    Of course, people is people. Makes no difference if it's crap as long as
    it's cheap. Good luck.

    > Anyway all this is going to be very dependant on the quality of the BMS
    > monitoring each cell and the use scenario.

    A BMS is not meant to fix bad cells in a battery. It is to balance
    natural deviations of *good* cells from target one as no two cells
    are alike.BMS will take care of balancing 98Ah cell and 101Ah one,
    but not 90Ah and 30Ah which in a month may turn into
    60Ah and 0Ah That's what Thunder-sky might supply to you.
    But it's sure cheap, so never mind that it's a waste of money.
    Again, good luck!

    Recent crop of cells is different design than the crap I know about.
    TS's business culture, care of customer and mentality is not different,
    I don't think they can be trusted. You sort out the cells, throw away
    70% of it and put 30 of more-less alike ones in a car, and those
    go out of balance in a month, some die from unknown cause, some
    develop high internal resistance, some - terminal corrosion, some
    bulged cases, forcing you to scrap whole thing. But, who cares,
    they are cheap to buy, right?

    So for the last time, sincere good luck. You've been warned.

    Victor
    '91 ACRX - something differnt
    --------------------
    Dan Maker wrote:
    > Victor,
    >
    > I've been reading your CRX conversion and you mention that you are
    > using TS LiOn batteries, from this post I'm guessing that didn't go
    > well and you've replaced the battery pack. If this is the case it
    > would be helpful for noobs that stumble on your site to know this.
    >
    > Thanks, and thanks for your informative websites.
    >
    > Dan

    Yes, perhaps you're right. The sight though is about conversion,
    technical info what I did and how. It is not consumer complaint
    site. However, I should mention my experience for others to know.

    Again, as I mention, it may or may not represent what TS produces
    today; some people report better outcome. Yet, I feel that the
    company and info they produce cannot be trusted.

    I'll mention my facts on the site without passing on judgments.
    Everyone will have to make their own conclusions.

    Victor
    '91 ACRX - something different
    Hi,

    Comparing Lead from a reputable company whose batteries have a good track record with Lithium Batteries made by a company with an extremely bad reputation and whose batteries have an extremely bad reputation is not a valid comparison. Taking it a step further and stating that even though their Lithium's are more expensive they will be cheaper in the long run because they will last longer doesn't make any sense at all.

    I thought about not posting this but I am concerned that:
    1. Matt is going to spend a bunch of money for junk cells.
    2. Someone else is going to stumble across this thread and spend a lot of money for junk cells.

    I think either the thread should be deleted or the above comments on TS should be moved up to the second post on the thread.

    BTW this is Victors site and he is using Kokam on his latest conversion:
    http://www.metricmind.com/

    Best Wishes,

    Mitch
    Posted 06-06-2008 at 11:51 PM by MitchJi MitchJi is offline
  3. Old Comment
    mattW's Avatar
    There have been serious issues with Thundersky in the past, and a lot of the EVDL guys have been burned by them and are completely against them which is understandable. A lot of it I think had to do with Chinese vs western Quality control expectations, something I think thundersky has learnt their lesson from. I haven't heard any negative reports about the latest model of thundersky batteries. Rob from EV power has done 10,000km on them without any problems. Ian from Zeva is using them in his MX5 even after his extensive testing of lithium batteries. Trev from Foundry and Fiberglass has no problems with his new batteries. I will be monitoring those conversions up until I buy my own batteries but I think the newer batteries are trustworthy, and have not heard of a single report of bad cells of the LFP batteries.
    Posted 06-07-2008 at 12:38 AM by mattW mattW is offline
  4. Old Comment
    david85's Avatar
    Actually I'm with Matt on this one. I feel most of the bad wrap that comes up against TS is rooted in the original 2003 purchace. Their newer batteries tend to get th esame feedback by default. But of those that are actually using TS batteries right now I am having a very hard time finding some one that will talk badly about them. I wonder if the mythbusters had any problems with them.
    Posted 06-07-2008 at 10:06 AM by david85 david85 is offline
  5. Old Comment
    Quote:
    Originally Posted by mattW View Post
    Rob from EV power has done 10,000km on them without any problems. Ian from Zeva is using them in his MX5 even after his extensive testing of lithium batteries. Trev from Foundry and Fiberglass has no problems with his new batteries. I will be monitoring those conversions up until I buy my own batteries but I think the newer batteries are trustworthy, and have not heard of a single report of bad cells of the LFP batteries.
    Thanks for posting this info...I've been looking for a while for POSITIVE info about the newer cells since I understand it was the older cobalt ones that had probs. I'm starting to lean towards the C-LiFePO4 cells from PHET...apparently they have the patent on the process that give A123 their oomph and A123 pays them a premium, hence the higher price. If TS cells prove to be more consistent and reliable then the better price is the icing on the cake.
    Posted 06-07-2008 at 11:44 AM by kkjensen kkjensen is offline
  6. Old Comment
    With this BMS, has anyone asked metric mind or the australian supplier whether they would sell at least the cell-level BMS circuits as kit sets? Assembling and testing of all those must take some time and really push up the delivery times.
    Posted 06-09-2008 at 04:37 PM by linz linz is offline
  7. Old Comment
    david85's Avatar
    I know of at least one example of a conversion of TS batteries where the builder sourced a separate BMS through metric mind. No idea what the price was though.
    Posted 06-09-2008 at 04:51 PM by david85 david85 is offline
  8. Old Comment
    Matt

    Can you clarify exactly what Thundersky battery you considered in your hyothetical battery pack? Was it the following battery or one of the bigger and heavier ones?

    LFP40AHA 3.2V 40AH 120A 2000 190x116x46 1.5k

    Also, what is the relationship between the BMS and the number of cells? In other words, do you need to reduce the number of BMS modules if the number of cells are reduced?
    Posted 06-11-2008 at 01:09 AM by Weka Weka is offline
  9. Old Comment
    mattW's Avatar
    I'm going with the 3.2V 60Ah cells, they weigh 2.2kg each so my total pack weight weill be around 53kg. Considering the engine weighed 66kg that is pretty good . You need one slave module per cell so the higher the voltage the higher the cost, but its not too bad.
    Posted 06-11-2008 at 01:18 AM by mattW mattW is offline
  10. Old Comment
    Manntis's Avatar
    I used 90aH TS cells for greater range. They're still reasonably small - my traction pack weighs approx. 294kg (647lbs).
    Posted 06-11-2008 at 02:32 AM by Manntis Manntis is offline
  11. Old Comment
    mattW's Avatar
    I didn't know you used TS manntis? What sort of current are you getting out of them? I am hoping I can squeeze 5c every once in a while but it looks like 3c is the norm.
    Posted 06-11-2008 at 02:36 AM by mattW mattW is offline
  12. Old Comment
    Manntis

    Are you referring to 90Ah Thunderskys at 3kg each - that would indicate that you have 98 batteries nearly 30k/w of energy stored which would be the most powerful vehicle I know of?
    Posted 06-12-2008 at 01:11 AM by Weka Weka is offline
  13. Old Comment
    Manntis's Avatar
    28.2 kWh, actually
    Posted 06-12-2008 at 02:24 AM by Manntis Manntis is offline
  14. Old Comment
    helloworld's Avatar
    What?

    and you guys end the thread there?
    I just read this entire thread from start to finish, and it felt like I reached the crescendo plot of a novel, grinding away at the great cost debate of lithium vs lead, and then......... nothing.

    OK, so Manntis has the biggest pack at 28.2kWh using lithium from thundersky

    do they work well?
    are the rumours of thundersky gear unfounded?
    what was the cost for 28.2kWh of lithium using the 90Ah units???
    where do you put 98 batteries?


    and where did the lead advocates go?
    does anyone have a comparable 28.2kWh setup using lead?
    and what does their setup weigh in at?
    what was the cost?


    I think there are a good number of brilliant people participating on this forum which is what makes it such a great place to read the threads.

    but now I feel blueballed after reading six pages of excellent dialogue on what I would consider the greatest bottleneck of every EV conversion.
    it was a wonderful back and forth discussing the pros and cons of each, incredibly useful links and reference information, took me about 4 hours to read everything associated to this thread; with no conclusion?

    and then.........
    Posted 06-17-2008 at 11:48 PM by helloworld helloworld is offline
  15. Old Comment
    mattW's Avatar
    Well where I live it is cheaper or at least just as cheap to go with lithium in the long run, assuming they hold true to their 2000 cycle life. That's not taking into account the added benefits of their smaller size and weight. It may be different for you where you live, so I suggest you do your own research, just make sure you size your pack with the usable energy not the total energy rating of the pack. You can use a much smaller lithium pack due to peukert's effect as I outlined in the blog.

    Sorry there isn't a more conclusive answer but I guess its just 'It depends', I'm glad you liked the thread though
    Posted 06-18-2008 at 12:59 AM by mattW mattW is offline
  16. Old Comment
    Manntis's Avatar
    Quote:
    Originally Posted by helloworld View Post
    OK, so Manntis has the biggest pack at 28.2kWh using lithium from thundersky

    do they work well?
    are the rumours of thundersky gear unfounded?
    what was the cost for 28.2kWh of lithium using the 90Ah units???
    where do you put 98 batteries?
    I don't know if I've the largest pack; I only know my pack size. Keep in mind I'm also using a 312V motor.

    each 90aH LiIon battery is considerably smaller than its lead acid counterpart, so packaging them wasn't that bad. Ideally batteries should be in the same location for common humidity, etc. but in a small car like mine that's just not practical.

    The main pack is where the storage bins behind the seats used to be, keeping the mass low and centered fore-aft as much as possible. The balance of the batteries are in 'saddle bag' boxes around the motor up front (an RX-7's engine bay is surprisingly large given the tiny size of engine), still keeping it between the axles as much as possible.

    Even in a stock RX-7 there's almost 2 feet of dead space between the bumper and rad; with the rad gone there's a lot of space left up front but I wasn't about to a) put heavy mass forward of the front axle nor b) put very expensive parts in the crumple zone where it could get, well, crumpled in the event of a head on collision.
    Posted 06-18-2008 at 02:42 AM by Manntis Manntis is offline
  17. Old Comment
    helloworld's Avatar
    OK

    so here is what I can glean from the knowledge contributed to this thread.
    there are many factors involved in the battery selection process, granted, everyone will agree to that. Leaving cost aside for a moment, trying to ascertain what is better, lithium or lead for an EV.

    I am focusing on Watts/KG as a simple measure of comparison.

    Manntis uses the 90AH lithium cells at 3.2V each, and 3KG per unit
    3.2V X 90AH = 288AH X 98U = 28224WH of storage
    98U X 3KG = 287.76KG
    28224WH / 287.76KG = 95.92W/KG
    (3.2V*90AH)/3KG=95.92W/KG

    There was repeated mention of the T605 as a solid contender for the Lead camp, so using that as an example:
    6V X 210AH = 1260AH X 24 = 30240WH of storage
    24U X 22.08KG (50lbs) = 529.8KG
    30240WH / 529.8KG = 57.08W/KG
    (6V*210AH)/22.08KG=57.08W/KG

    Now using that calculation as a base, it would be my opinion that if you are doing a small EV with a small target range on a tight budget, the lead battery is definitely the right choice.

    there is also the issue of discharging that mattW brought up, most of the larger motors require a larger draw of amps, and if the lithium do not reach 10C as advertised and are truly limited to 3C to 5C as stated earlier in this thread then that would be another strike against lithium.

    But if you are doing anything with larger vehicles and larger ranges, the lead acid batteries just dont scale as nicely as the smaller and more energy dense lithium packs. And there were too many excellent arguments on supply/availability/costs/management systems etc... to quote.

    I have a 3/4 ton GMC I am converting with a standard payload rating of 1698KG(3847lbs)
    for roughly $100 per T-605 comparable (Canada), I can fill my truck for 5K to achieve 60.48kWh of battery.

    my vote goes to lead unless someone can find an error in my logic????
    Posted 06-18-2008 at 12:46 PM by helloworld helloworld is offline
  18. Old Comment
    Are you going with 300 v or 150 ish done with s/p combo? 50 or so batteries at about 80lb ea? (you said 5k at $100 each) I am very new to this but that's a lot of weight. Is the extra weight worth the volts/ah?
    Curious
    Posted 06-18-2008 at 12:58 PM by kcblkeeley kcblkeeley is offline
  19. Old Comment
    mattW's Avatar
    Well as I worked out in the blog, Peukert's effect and DoD play a big role in the usable energy of the packs. If you go to 80% DoD with Lead Acid (and a lot of EVers prefer to stay above 50%) and assuming you get 55% of the 20hr rate at the 1hr or so you will actually use the battery at you only get 44% usable energy for Lead Acid Batteries whereas Lithium would give you 76%. Rehashing your numbers that means that:

    Manntis uses the 90AH lithium cells at 3.2V each, and 3KG per unit
    3.2V X 90AH = 288AH X 98U = 28224WH of storage x 0.76 = 21450 usable Wh
    98U X 3KG = 287.76KG
    28224WH / 287.76KG = 95.92W/KG = 74.54 usable Wh/kg
    (3.2V*90AH)/3KG=95.92W/KG

    There was repeated mention of the T605 as a solid contender for the Lead camp, so using that as an example:
    6V X 210AH = 1260AH X 24 = 30240WH of storage x 0.44 = 13306 usable Wh
    24U X 22.08KG (50lbs) = 529.8KG
    30240WH / 529.8KG = 57.08W/KG = 25.11usable Wh/kg
    (6V*210AH)/22.08KG=57.08W/KG

    So for a given weight you can have three times the energy with Lithium, or for the same sized pack your lithiums should weight 1/3 the weight.

    On the discharge note, most controllers are only 500A which only requires a 100Ah battery pack which would be a pretty small range for most EVs so I don't think that's an issue, if you want higher discharges there are more expensive lithiums that can do bursts of up to 40C.

    The only real advantage Lead Acid has is upfront cost, which is a big advantage I'll admit, but I don't think its worth the maintenance, weight, size and inefficiency of Lead, especially when the high cycle #'s of lithium make the lifetime cost comparatively similar (at least within the ballpark).
    Posted 06-18-2008 at 02:35 PM by mattW mattW is offline
  20. Old Comment
    helloworld's Avatar
    My bad, forgot the Peukert variable.

    When you put it that way, the lead does not look very appealing at all.
    Posted 06-18-2008 at 03:24 PM by helloworld helloworld is offline
 
 
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