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Lithium vs Lead; the Great Cost Debate.

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

Tags lead, lithium, thundersky, trojan

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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, I’ll 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. I’ll be using Australian prices since I’ve already researched them, but the comparison is probably close in other countries too.



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 Peukert’s 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 Peukert’s 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 didn’t say how many cycles it would take on the website but let’s guess around 650 to 80%. That means we’ll 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 didn’t look very hard for the cheapest batteries and I am only guessing the cycle life of the Trojans but even if it’s not precisely accurate it does show that the myth that Lead is clearly cheaper than lithium is not well founded. Lithium’s greater efficiency and cycle life makes up for its higher initial cost. I didn’t 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 lithium’s would be maintenance free. It’s 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 that’s 13.9c/km for the cheapest ICE using fuel at $1.25/L. Clearly then EV have a price advantage over ICE’s 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 it’s just not true anymore.

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Posted in Product Reviews, Editorials

Views 4687 Comments 154

Comments

1. Quote: Originally Posted by ngrimm Does anyone have a 10 year or even a 5 year old laptop with original batteries that hold a charge anything like they did when they were new? Or how about a rechargeable drill? Just curious since I have always seen a huge drop off after just a couple years. Norm Lithium cobalt doesn't have the longevity as lifepo4. It's a big concern with the Tesla, for instance, because the lithium cobalt battery pack is such a large chunk of the cost of it.

   Posted 05-26-2008 at 01:24 AM by saab96

2. Quote: 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 Peukert’s 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 didn’t say how many cycles it would take on the website but let’s guess around 650 to 80%. That means we’ll 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. 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 it’s just not true anymore. Hi Matt, Question: Can you really discharge the Trojans to 80% DOD and still get 650 cycles? Comment: If you are going to assume the Lithium's will last 3x lead you need to be sure to purchase batteries that you are sure will last that long. This means either a reliable warranty (best) or exhaustive testing from a reliable source or an excellent track record in EV's. Otherwise you are basically purchasing a very expensive lottery ticket. There is no way in the world I would either spend $10k for a pack of Thundersky Lithiums or recommend anyone else do that either. For your comparison to hold up you need to find a reputable source with those lithium specs and prices. Best Wishes, Mitch

   Posted 05-26-2008 at 02:47 AM by MitchJi

3. My comparison wasn't to prove it once for all or definitively or anything, I just wanted to show that the overall price is similar long term even if the up front costs are different. People keep saying things like Lead is cheap but lithium is still ridiculously expensive which I think is a little deceptive if you think of the long term. I'm not sure about the cycle life of the trojans (or the thundersky's to be honest) I just estimated based on what I've seen.

   Posted 05-26-2008 at 02:53 AM by mattW

4. There was a previous commentator who said that MattW's calculations were wrong becuase there was a difference between Aussie battery prices and US prices. I checked - Matt specificed T605 whreas the commentator has I think made a mistake and thought they were T105. In fact the T605 battery is US249 from http://www.evwholesalers.com/about-us.html - who are pretty cheap - so we can see that MattW's calcualtions hold up very well. In fact I think Matt has understated the commercial advantage of lithiums given the very rapidly rising lead prices. The real issue is finding a reliable commercially available combination of batteries and battery management system. I intend to write to the BMS that Matt mentioned and see what they say, the web site is not overly specific but looked promising. Matt - how did you work out the price on the BMS? And you said you had a mate who you trusted- can you be more explicit? By the way, that is a great article you wrote.

   Posted 05-26-2008 at 03:00 AM by Weka

5. 	The batteries and BMS were recommended to me by ian from www.zeva.com.au, you may have seen his battery testing. He is using them on his Mx5 conversion. I worked out the price as $350 plus 38 slave modules (120V) at 24.20 each ($919.60) so around $1270 total
   	Posted 05-26-2008 at 03:17 AM by mattW

6. Quote: Originally Posted by Weka There was a previous commentator That would be me. Quote: who said that MattW's calculations were wrong becuase there was a difference between Aussie battery prices and US prices. I checked - Matt specificed T605 whreas the commentator has I think made a mistake and thought they were T105. In fact the T605 battery is US249 from http://www.evwholesalers.com/about-us.html - who are pretty cheap - so we can see that MattW's calcualtions hold up very well. I didn't make a a mistake in choosing the T-105. It's a battery with a similar configuration as the T-605. I also pointed out a site that had a much better price, nearly half. Here's another: http://www.bohannonbattery.com/html/golf.html The T-605s are $92. The T-105s are $119. Matt has gone out of his way to find the cheapest $/Ah he could for lithium. However he, and you, also seem to go out of your way to pick the most expensive price you can find for lead acid. I pointed out, and will continue to point out, that lead acid batteries can be had for 1/3 to 1/2 of the price that you are quoting. And as long as they are available at those prices, that even with replacement, they represent good value and lower capitalization costs than lithium. Quote: In fact I think Matt has understated the commercial advantage of lithiums given the very rapidly rising lead prices. The real issue is finding a reliable commercially available combination of batteries and battery management system. I intend to write to the BMS that Matt mentioned and see what they say, the web site is not overly specific but looked promising. Matt - how did you work out the price on the BMS? And you said you had a mate who you trusted- can you be more explicit? By the way, that is a great article you wrote. I know that it seems that I'm just flat out against lithium. I'm not. I'm just being realistic in understanding that a lot of new people who flow into the electric car industry, such as myself, are specifically here because gas prices are ridiculous and are continually rising. Therefore they are here to get value for the dollars that they spend. Lithium does not yet represent a superior value to lead acid. Right now if you compare the prices of the cheapest lithium, with suspect availability as has been pointed out in this thread, to widespread and cheaply available lead acid, the value just cannot yet be justified. I can go today, on US Memorial Day, and plunk down $1925 USD and get a 144V@225Ah pack that will last 2 years with proper care and deliver nearly 15kWh of usable energy on a daily basis. Even at 400 Wh/mile that's 36 mile range. When I can do the same with lithium, even at 3 times the price, then it may be worth taking a look. But I can't do it today. Can you? ga2500ev

   Posted 05-26-2008 at 05:44 AM by ga2500ev

7. 	Quote: Originally Posted by saab96 Do the math again. That's a 10khw pack of 20ah cells. You'd need 5 of these to get good EV range which would be about double what you can find elsewhere with 100ah bricks. Actually he did say 10 packs making a 48V@200Ah=9600kWh pack. ga2500ev
   	Posted 05-26-2008 at 06:12 AM by ga2500ev

8. Well I've looked at like 6 suppliers here in Oz and I can't find any Trojan's cheaper than that $225 mark. Are they made in the US? That would explain the price difference between here and there. If you can get them for $92 then go for it. I have only seen 2 suppliers of thundersky cells in Australia and I actually used the more expensive price of $2.50 per Ah when my other supplier can do it for $2.40 normally or even as low as $1.83 for bulk orders. As I said in the blog, it would be different for different countries.

   Posted 05-26-2008 at 07:14 AM by mattW

9. Quote: Originally Posted by mattW Well I've looked at like 6 suppliers here in Oz and I can't find any Trojan's cheaper than that $225 mark. Are they made in the US? Yup. There's a Trojan manufacturing or distribution facility within 5 miles of my home. I'm actually thinking about dropping in one day and seeing if they have any deals. Quote: That would explain the price difference between here and there. If you can get them for $92 then go for it. I have only seen 2 suppliers of thundersky cells in Australia and I actually used the more expensive price of $2.50 per Ah when my other supplier can do it for $2.40 normally or even as low as $1.83 for bulk orders. As I said in the blog, it would be different for different countries. Understood. ga2500ev

   Posted 05-26-2008 at 07:18 AM by ga2500ev

10. Quote: Originally Posted by mattW My comparison wasn't to prove it once for all or definitively or anything, I just wanted to show that the overall price is similar long term even if the up front costs are different. People keep saying things like Lead is cheap but lithium is still ridiculously expensive which I think is a little deceptive if you think of the long term. I'm not sure about the cycle life of the trojans (or the thundersky's to be honest) I just estimated based on what I've seen. Hi Matt, http://www.evworld.com/news.cfm?newsid=18037 Quote: Source: Mother Jones [Apr 18, 2008] SYNOPSIS: Long-time EV experimenter Lee Hart finds the search for the perfect battery is fraught with obstacles Hart points to one of the latter—made in China, it's known as the Thunder Sky—and declares, "That would be a wonderful battery if it met the specs claimed by the manufacturer, and some of them do. But that tested out at about half the specs. You put this in a [gas-powered] truck, it would be hard to notice. But if you have a stack of underperforming batteries in an electric car, it makes a difference." <snip> A connoisseur of batteries and a debunker of the so-called breakthroughs that come around like clockwork every couple of years, Hart makes it his business to parse hype from performance. Whenever he hears about a new battery, the 58-year-old self-employed electrical engineer (he did lab work at Eastman Kodak and Honeywell) writes the company and asks for a prototype to be sent to his home in Sartell, Minnesota. "I'm a cheapskate, and sometimes they'll send me a free one," he jokes. So far, he still prefers lead-acid batteries. Using a life-extending charging system he designed himself, he's converting his third electric car to handle 14 of them; a buoyant pride creeps into his voice as he notes that most of the batteries are 8 to 10 years old. "Just like you don't feed an old dog puppy chow," he says, an old dog himself with the white tufts on the sides of his balding head combed up to resemble Mercury's wings, "you treat old batteries differently." Hi Matt, Spending $13k on lithium cells some of which test out at about half their spec's isn't a good investment. Until you find a source for reliable lithium batteries with the price and specifications you mention IMO you have not proven that costs are currently similar, although you have shown that long term costs are closer than they seem at first glance. On the other hand compared to Lead, using Lee Hart's Maintenance methods, Lithium might be even more expensive in comparison. Best Wishes, Mitch

    Posted 05-26-2008 at 12:32 PM by MitchJi

11. Hi Matt, I think weak cells are likely to cause problems with cheaper Li-Ion Packs. Maybe you can get around this if you do your own testing and replace any weak cells. The following is from a company that sells much smaller (ebike) packs so there would be a higher failure rate with larger packs: http://www.ebikes.ca/batteries.shtml Quote: Capacity Matching Reputed companies that build the battery packs will use cells that have been individually selected to have identical capacity. Then all cells in the pack will go flat together and there is little risk of cell reversal. We have found that almost all companies claim that cells in each pack are matched within 2 to 3 %, but our own testing has shown that a significant percentage (sometimes over half) of packs have at least one cell that is will outside of this specification. http://www.ebikes.ca/store/#Batteries Quote: Testing and Guarantee We cycle discharge test every single battery pack several times before selling it to guarantee that it delivers the full rated capacity and that there are no premature cell reversals. With your battery there is an ID number and if you request we can send you the actual discharge test results. Our experience has shown that upwards of 20-30% of the batteries in any shipment will have at least once cell that does not deliver to the specified capacity and could cause problems down the road. With some manufacturers this can be as high as 50% of the packs, so keep this in mind when purchasing from suppliers that don't do independent testing. Best Wishes, Mitch

    Posted 05-27-2008 at 02:33 PM by MitchJi

12. 	matt... you forgot tax!
    	Posted 05-27-2008 at 04:08 PM by fire92658

13. Lol, for a simple comparison on paper I didn't think I'd be under so much scrutiny! Mitch the battery specs that are half what is advertised is the current rating. They only put out 3-5C not 10C as advertised. I have already designed my ReCYCLE project around the tested parameters i.e. 300A peak from my 60Ah pack. But thanks for the research. If anyone wants to disagree with my conclusions then go ahead and do a comparison with the batteries you are considering. I just did it for the batteries I was considering, and as they were both from vendors inside Australia they already included the tax.

    Posted 05-27-2008 at 09:18 PM by mattW

14. 	Matt, I know this may sound elementary but.. what is 3C ? is that the discharge rate? thanks
    	Posted 05-28-2008 at 10:42 AM by fire92658

15. 	I've never heard it explicitly explained but it is basically 3x Capacity or a discharge rate in amps of three times the capacity in Ah. SO for a 60Ah pack, 3C means a 180A discharge. A 100Ah pack gives 300A at 3C.
    	Posted 05-28-2008 at 11:11 AM by mattW

16. I think shelf life needs to be addressed more than anything. It is already known that the power per weight is far better than lead. What is the real shelf life? It would not matter one bit if my batteries could be charged and discharged thousands of times if the shelf life is only a few years. And from what I have heard it is around 3 years. So if that is true then lithium is out the door before it even starts. For small products it is more likely that they will be tossed out or replaced with a better item before the battery life is gone. But with an EV needing to last 10 plus years or more then the battery shelf life as well as use life needs to meet the demand. I only hear of what kind of power they have and the shelf life is avoided in conversation. Why? Well I guess time will tell and only time will tell if it will meet the needs of the EV crowd. Pete : )

    Posted 05-28-2008 at 03:13 PM by gottdi

17. ga2500ev et al You are quite right with respect to the price of the Trojan batteries - there is certainly a quite incredible price difference in the United States with respect to advertised prices - in my sweep I found 8 stores all with different prices ranging from over $200 to $150 to as you say $92. I would note that postage and packing on 450 odd kilos would add quite a bit ... but the point is well made. I guess the key item is that I perceive lithiums as the future and would not want to invest in lead batteries as I think it is now "throw-away technology". A bit like investing in CP/M (for those who remember such things) when MS-DOS first came out. The issue is that they are on the bleeding edge and as usual the pioneers get arrows in them ... sometimes through them. It would be good to get references from people using it, the link supplied by MattW is quite interesting in this respect.

    Posted 05-29-2008 at 01:23 AM by Weka

18. 	Well the MX5 should be finished in early june so I will pass on any performance reports I get.
    	Posted 05-29-2008 at 02:00 AM by mattW

19. Just to coninue posting items that are off-topic (why break a habit) here's my draft budget for an electric conversion using the lithium battery price point and BMS figure you supply. Although I notice that according to the Aussie Thundersky site they are about to drop their prices 15%. Any comments? Units are Australian dollars Budget for electric car Mazda 5,000 Motor 2,300 Controller 1000 BMS 1300 Batteries 10450 Adapter plate 1000 Engine mounting1000 Other 1500 Total 23,550

    Posted 05-29-2008 at 05:54 AM by Weka

20. I'm thinking of going with thunderskys. In my quest for knowledge about the LiFePO4 I came across a tech.yahoo group that is quite active and swapping testing info and such. The group started when a couple group deals (for the lithium cobalt cells) in the UK and US went through and the US shipment had a bunch of bad cells (which we all hear about and fear is the norm). Aside from this one bad shipment I have had a difficult time finding anyone giving bad reviews (which are different than bad rumors) about the LiFePO4 cells. Buying in bulk (>100,000Ah) gets the price down to $1/Ah so IF the shelf life and reliability is good then they could prove to be very good. Performance wise any vehicle will run better with 300lbs of batteries vs 1500lbs. My quest continues...

    Posted 06-05-2008 at 07:36 AM by kkjensen

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