# Lithium over Lead? It's really not that clear.



## Ziggythewiz (May 16, 2010)

It feeds into ROI, but cycle life should be in the list for pros of lithium. 

Also, I'm not sure where you get that lithium costs 5-6x lead. Everything I've seen is lithium around 3x the cost of cheaper lead options, and only double or less that of the higher end lead options.

More anecdotal evidence for you: When my lead began to die it was one at a time. I wasn't going to throw away the old and replace with new, especially since they were under warranty, full then prorated. It took about 8 months to transition from one pack to the next, which saved over $700 vs dumping one pack and switching for the next, but is cost countless hours in circuit reconfigs to keep things running over that window.


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## dladd (Jun 1, 2011)

meanderingthemaze said:


> So, by now, I think many of you know I've been perusing the boards for awhile now. I've heard a lot of fanatics on either side of the argument. But to me, after crunching real numbers, and unfortunately only having access to a lot of anecdotal case studies, the case is not clear. It's quite grey actually when it comes to the most important aspect of the DIYer's decision making process: ROI.


I would question your premise. I do not think ROI is the most important aspect of the DIYer's decision making process. I'm not sure it was even in my top 5! Hell, from an ROI standpoint, I'd be ahead driving around in a 15 year old 30mpg Saturn than spending 15k to convert it to battery power...

and fwiw, I have not heard from these lead acid 'fanatics' at all. In fact, it seems fairly universal. Even those who have lead would prefer lithium. No one with lithium wishes they had stuck with lead. Well, maybe I shouldn't say 'no one', I'm sure there's someone out there that will say that.  Certainly the upfront cost is high, and prohibitive for some. BUT, if you can swing it, Lithium is clearly better. In the short, and in the long run.

lithium is most likely better on ROI, but as you say, how can that be guaranteed since lithiums haven't really been used for more than a few years yet? It does seem clear though, an EV in daily use of any decent range will ruin it's lead pack in 2 years. I've read about that happening time and time again. Some may claim 5 years on lead, but that's going to be occasional use, short trips, and intensive babysitting of the batteries. 

I'm not sure where you are seeing a 5-6x increased cost for Lithium, i think it's more like 3-4x at most. Making the crossover more like 6-8 years. Initial data shows that lithium cells will probably last that long, but it's no guarantee. However, in the mean time you'll have better range, better performance, less weight, and higher efficiency. Plus, you won't have the hassle of swapping out battery packs every 2 years.


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## meanderingthemaze (Jan 25, 2010)

dladd said:


> I would question your premise. I do not think ROI is the most important aspect of the DIYer's decision making process. I'm not sure it was even in my top 5! Hell, from an ROI standpoint, I'd be ahead driving around in a 15 year old 30mpg Saturn than spending 15k to convert it to battery power...
> 
> and fwiw, I have not heard from these lead acid 'fanatics' at all. In fact, it seems fairly universal. Even those who have lead would prefer lithium. No one with lithium wishes they had stuck with lead. Well, maybe I shouldn't say 'no one', I'm sure there's someone out there that will say that.  Certainly the upfront cost is high, and prohibitive for some. BUT, if you can swing it, Lithium is clearly better. In the short, and in the long run.
> 
> ...


You are right to question my premise as I am using anecdotal evidence from what I've seen on the boards. Most people seem to be most concerned about finances, even though there is a subset of people, like racing enthusiasts or wealthier individuals who can afford to play with their money more. Even if this thread is only for those that are concerned with ROI, then I think it's worthwhile to lay out the cards on the table for analysis. 

I've updated the above Lithium pros list to include less labor, since you bring up a good point about the work involved in switching packs. 

As to the 5-6x cost, check out the spreadsheet I've linked to to see the figures. I'm comparing kWh. However, I should be comparing effective kWh, so maybe it is closer to 4x. I'll double check that now.


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## subcooledheatpump (Mar 5, 2012)

This goes along with the BMS thing, but what about safety issues? Lithium, as I understand because of it's high energy density, can be quite explosive if the cells overheat or are exposed to overvoltage/overcurrent. Lead batteries are much more tolerant to overvoltages. No BMS to worry about for charging, but also for those (like myself) with regenerative braking, it means you won't have to stress when the voltage climbs up during regenerative braking. Just my thoughts


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## Ziggythewiz (May 16, 2010)

Lead I pay about $310 per useful kwh, lithium would be around $558. 

Part of the expense with lithium is that if you're going to spend that much anyway, why not spend some more and get 50 miles instead of 30. I could get the range I need out of 60 AH cells, but I'd rather save up and get 100s.


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## PTCruisin (Nov 19, 2009)

Here is another "data point" regarding ROI:

I spent $5600 for a 12kWh LiFePO4 pack nearly two years ago. I drive an average of 20 miles/day, 7days/week, 50 weeks/year. Annual driving = 7000 miles.

The cost to charge the pack after the 20 mile commute is approx 50 cents - based on 8kWh from the wall plug @ 6.5 cents/kWh.

When the vehicle was ICE-powered, I would use 1 gallon of gas for the same commute @ $3.75/gallon on average.

Annual fuel costs = $1300
Annual electricity costs = $175
Annual savings = $1125

$5600/$1125 = 5 years to pay off batteries with cost savings.

So ROI is at 5 years. Since I use about 50 to 60 % of the capacity, I expect to get around 10 years of service out of the pack.

I know this is not comparing Li to Pb but I expect you would have to replace the Pb after 2 or 3 years anyway.


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## somanywelps (Jan 25, 2012)

PTCruisin said:


> $5600/$1125 = 5 years to pay off batteries with cost savings.


And then you have very low (no?) maintenance and HOV access and not having to stop at gas stations.


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## meanderingthemaze (Jan 25, 2010)

Ziggythewiz said:


> Lead I pay about $310 per useful kwh, lithium would be around $558.
> 
> Part of the expense with lithium is that if you're going to spend that much anyway, why not spend some more and get 50 miles instead of 30. I could get the range I need out of 60 AH cells, but I'd rather save up and get 100s.


So, this is an area I'd like clarified with calculations. I think it's very difficult to gauge useful kWh in a pack given the number of variables involved. However, is there a rule of thumb for adjusting the advertised AH rating given by manufacturer to the effective useable kWh that you'll see in your conversion? If so, please share. I'm curious to see how you are calculating that. Someone else in another thread suggested at 1C discharge that Lead would decrease to 65% of the advertised 20 hour rate. 

Also, your cost sounds ridiculously expensive for Lead. Are you using AGMs? I think we should talk about wet batteries as they are the most widely used and the best cost advantage. I'm not sure how AGMs would be used. 

If you check the above calculator link, it shows that a 6V 232AH lead battery costs $90. That's 90/6*232 = ~$65/kWh. However, if we say they're 65% efficient, that raises the number to ~$100/kWh. If Lithium is @ $558/kWh, you can see how I'm getting the 5-6x difference. 

You could argue that you need less Lithium than you would Lead because the vehicle is lighter, but by how much? Factor that in and again, I don't see how it could be better than 4x difference. 

In my opinion, the difference between Lead and Lithium costs need to be closer to a 1:3 to make it feel like a good investment, or better yet, 1:2...IMO.


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## evnz (Jul 24, 2010)

ROI mean what?


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## MN Driver (Sep 29, 2009)

Only a couple states offer free HOV lane access for electric cars. In Minnesota there is no HOV sticker, you pay 25 or 50 cents(or more if that lane starts getting congested to a speed lower than 50mph) to access the lane if you aren't carpooling on the highways that charge the express lane toll for that lane if you aren't a carpooling vehicle, motorcycle, or bus. I've never been on those highways where it is busy enough to even think about buying the electronic unit though. IMHO, I've never really understood the point, it ends up becoming a political issue for people to attack hybrid and electric cars.

There are ROI points that don't include the batteries too though, the other components can be used in a different car. The battery could be too, if someone decided to swap cars, as long as everything is compatible.

I think its clear to go with lithium, it's about the only real way to get a higher performance system that is lightweight, much easier to fit with more cargo room, longer life, they don't need to be watered like a plant to prevent them from dying, you can go higher voltage without having the excess weight without the extra capacity like lead, peukert requires you to buy more capacity to cover for it, same with adding extra capacity(and weight) to cover the range you lose when the lead-acid pack starts to dig itself a hole, lower efficiency charging and discharging. These are a few of the extra costs that aren't as apparent when going with lead.


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## meanderingthemaze (Jan 25, 2010)

evnz said:


> ROI mean what?


http://lmgtfy.com/?q=roi


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## MN Driver (Sep 29, 2009)

evnz said:


> ROI mean what?


Return on investment. This thread is discussing the cost difference, over time, of using lithium instead of lead. It doesn't make money so it's not technically an investment, but the gains that we can get in reduced operating costs by using an electric drivetrain go together with the costs of buying and using the battery packs, there are some value calculations to it and that is what we are discussing.


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## Ziggythewiz (May 16, 2010)

65% is close, I was going with .6, but then you also times by 50% for DOD, so your actual multiplier is something like .25 - .35 Compare that to .7 for lithium and it does seem pretty clear.

GC8s from sams for around $100 are 135 AH (20 hr) so using .3 as a multiplier gives ~$310 / kWh. Obviously 6v batts are cheaper/kWh but there's no way I'm putting that much weight in my bug.

It's already 1:3, with 5x the life


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## DIYguy (Sep 18, 2008)

Its really not about ROI in my little brain. One thing I agree with JR about is;
Lead = science project
Lithium = viable car.

Sorry to all u pb users. I started there also. No shame in that. Once u have done both, there just is no comparison to make. Forget the ROI. One choice "works".

Also, just for the record. . regarding complexity I assume u r talking floodies because AGM's actually require a BMS, where lithium doesn't necessarily need one depending on some choices and abilities. 

All the best.


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## CrunchTime (Feb 13, 2009)

dladd said:


> I do not think ROI is the most important aspect of the DIYer's decision making process.


I agree. My decision came down to this: according to my calculator, with Lead I could have a 40km, 1 passenger vehicle; with Lithium I will have a >100km, 3 passenger vehicle (in NZ we cannot go over the manufacturer's weight limit (GVWR), and have to allow 80kg for each passenger)

In fact the Li cost distracted me from the real point: without LiFePO4 I wasn't going to be happy with the car, so there would have been less than no point in doing the conversion.

Personally, the ROI is not a factor - the conversion is for "fun" and to be a bit different, not because it's green, or cheap, or cool. (Well maybe a bit because it's cool ) (It is cool, right?)


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## Frank (Dec 6, 2008)

I didn't look at the numbers in your link but if they say a 6V 232AH PbA battery is $90 I suspect it's a little out-of-date. At least to get a quality battery. Last year around here, a single T125 was $175. Pallet pricing would be cheaper but not by that much.

A significant factor is weight and terrain: my pickup has a 120 volt system (i.e. 20 6V batteries) that weighs 1320# (batteries only.) An equivalent amount of useable energy would be contained in about 300# of lithium. A weight savings of 1000# is very significant! My truck goes well enough on the flat but is a pig when climbing hills. A real pig.

With lithium you're not relegated to pickup trucks. With PbA you need the load-carrying capacity and pickups were the traditional conversion candidate. Anything will work with lithium. Prismatic cells really are a game changer.


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## rtcaldwell (Apr 4, 2012)

I can understand how ROI may not factor in to many different applications, but it does factor in for me. I am still in my infancy of building a conversion and will be using a 1962 Ford Fairlane (an old american classic) which could carry both Li or Pb. 

ROI is a major factor for me and I appreciate 
meanderingthemaze brining up this as a post. If good information gets generated, possibly even creating a sticky. I would love to see a sheet worked out that was 'fairly' accurate when it comes to ROI. Possibly where one could even put in current figures/cost in their area.

Question, how much does recycle/core charge fit into this ROI idea? after 2-3 years when you return your lead batteries, don't you usually get some money back? or is that only if you purchase MORE batteries?

From what I have discovered, I am most likely going to go with Lithium because I have a few extra $$$ I can spend in an upfront investment, but a calculator like something that is being suggested would help people make informed decisions if they decided that Return on Investment was important to them.


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## evnz (Jul 24, 2010)

CrunchTime said:


> I agree. My decision came down to this: according to my calculator, with Lead I could have a 40km, 1 passenger vehicle; with Lithium I will have a >100km, 3 passenger vehicle (in NZ we cannot go over the manufacturer's weight limit (GVWR), and have to allow 80kg for each passenger)
> 
> In fact the Li cost distracted me from the real point: without LiFePO4 I wasn't going to be happy with the car, so there would have been less than no point in doing the conversion.
> 
> Personally, the ROI is not a factor - the conversion is for "fun" and to be a bit different, not because it's green, or cheap, or cool. (Well maybe a bit because it's cool ) (It is cool, right?)


The ROI is not a reason to build an ev, you and i need to change the way people think of ev's.
I am regularly asked why i am doing it i tell them if people put a V8 in a mini why not put a electric motor in a j1 bedford
I am doing it with lead for the first set then lithium after that.
I have a 15 km round trip to work and back


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## Ziggythewiz (May 16, 2010)

evnz said:


> The ROI is not a reason to build an ev


Maybe not for you, it certainly is for me. It all depends on your alternatives. If you would otherwise spend $15K to purchase a vehicle, your conversion instantly pays for itself, along with saving $1-3K / year on gas. 

If you don't get any additional utility from the car, I would expect the ROI to be around 8-10 years whether using lithium or lead. Maybe in a good economy that would be a bad investment, but right now can you tell me anything else (other than raw materials) that would have fared as well over the last 8 years?

More than anything though, I consider it a matter of national security and energy independence. We wouldn't have to keep 2 carrier groups in the middle east if oil weren't the lifeblood of our country.


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## DIYguy (Sep 18, 2008)

A discussion on ROI usually assumes all other factors are reasonably equal. Regarding pb vs LI, it's just not the case. This is why most of the people who bring this up don't have the experience with each to draw from. 

It's not the same car. Not even close. Forget the $ for a moment and just look at the viability and performance. With Li, it drives like a car/truck, not an overloaded boat. . . and if it doesn't feel like an overloaded boat. . it means u have enough energy to get you not-far-enough to make it worthwhile. Of course "worthwhile" is the operative word and it has a different meaning to each person. 

If its all you can manage, by all means, go for it. That said, u will go lithium after . . . and if u did it first, u would be money ahead.


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## palmer_md (Jul 22, 2011)

DIYguy said:


> If its all you can manage, by all means, go for it. That said, u will go lithium after . . . and if u did it first, u would be money ahead.


Yes, just as other have said. If you build a car with lead and then later upgrade to lithium the ROI is about the first 30 seconds of joyful driving. You'll be amazed at the difference and wonder why you did not just use lithium first.

edit: see if you can find a response from someone who has built both and still thinks the lead acid was the way to go in order to save money.


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## FarFromStock (Mar 16, 2009)

DIYguy said:


> A discussion on ROI usually assumes all other factors are reasonably equal. Regarding pb vs LI, it's just not the case. This is why most of the people who bring this up don't have the experience with each to draw from.
> 
> It's not the same car. Not even close. Forget the $ for a moment and just look at the *viability and performance*. With Li, it drives like a car/truck, not an overloaded boat. . . and if it doesn't feel like an overloaded boat. . it means u have enough energy to get you not-far-enough to make it worthwhile. Of course "worthwhile" is the operative word and it has a different meaning to each person.
> 
> If its all you can manage, by all means, go for it. That said, u will go lithium after . . . and if u did it first, u would be money ahead.





palmer_md said:


> Yes, just as other have said. If you build a car with lead and then later upgrade to lithium the ROI is about the first 30 seconds of *joyful driving*. You'll be amazed at the difference and wonder why you did not just use lithium first.
> 
> edit: see if you can find a response from someone who has built both and still thinks the lead acid was the way to go in order to save money.


 
I am so on-board with you guys about this! My conversion was done a few years ago when Li was not a cost effective option. I have gotten to the point where I don't even enjoy driving my car with the AGM's because it doesn't even get me a round trip from home-work-home anymore! I used to be able to get a couple hours of opportunity charging but that went away. I have now resorted to taking my Honda EU2000 generator to work and running it for about 2-3 hours just to comfortably make it home.

I am sooooo looking forward to getting rid of the AGM's and get back to being excited about driving my EV rather than worrying if it's going to get me there and back.


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## meanderingthemaze (Jan 25, 2010)

ROI is certainly a significant selling point for EVs, so to discount it as not important is to disregard people's concerns. They may not be your concerns, but they are real to a lot of people.

I appreciate everyone's sentiments about why Lead sucks and Lithium rules. But, that wasn't the purpose of this thread. It was to provide fact based analysis of the financial aspects of running lead vs lithium. It is my contention that in doing so we will answer many of the newbie questions of what they should be doing AND WHY!!! The why is the most important factor when you're trying to understand something that is new to you.

I appreciate Ziggy's response with numbers of how he calculated his figures. Useful kWh is an important thing to be able to guesstimate.

If Lead sucks, and is not worth using for real people living real lives, then prove it. Please! People who don't have the money for Lithium either need a reality check like "maybe it's not time for me to try this conversion thing" or empowerment like "ok, i may be fighting an uphill battle with Lead, but it still is worth doing until prices come down" etc etc.


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## DIYguy (Sep 18, 2008)

meanderingthemaze said:


> ROI is certainly a significant selling point for EVs, so to discount it as not important is to disregard people's concerns. They may not be your concerns, but they are real to a lot of people.


No one said ROI is not a significant point for EV's. What ppl are saying is that pb vs Li in a DIY conversion makes ROI a less significant, perhaps mute point.
ROI related to EV's (OEM) is the main reason they do not sell any.



meanderingthemaze said:


> I appreciate everyone's sentiments about why Lead sucks and Lithium rules. But, that wasn't the purpose of this thread. It was to provide fact based analysis of the financial aspects of running lead vs lithium. It is my contention that in doing so we will answer many of the newbie questions of what they should be doing AND WHY!!! The why is the most important factor when you're trying to understand something that is new to you.


With all due respect, this issue has come up a thousand times and if you had taken the time to research it, you wouldn't be asking. The folks who have replied did so out of courtesy and because they have some experience to share that you do not. 

Calculations are straight fwd. crunch away.........


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## meanderingthemaze (Jan 25, 2010)

DIYguy said:


> No one said ROI is not a significant point for EV's. What ppl are saying is that pb vs Li in a DIY conversion makes ROI a less significant, perhaps mute point.
> ROI related to EV's (OEM) is the main reason they do not sell any.


Well, actually a few people did. But that's really beside the point. 



> With all due respect, this issue has come up a thousand times and if you had taken the time to research it, you wouldn't be asking. The folks who have replied did so out of courtesy and because they have some experience to share that you do not.
> 
> Calculations are straight fwd. crunch away.........


Forums are voluntary and if people want to respond they will and if they don't they won't. If calculations are straightforward, then why do so many people continue to ask? If you have done those calculations, why not copy and paste them here for us to discuss or learn from? 

The reason I started this thread is because of the lack of calculation-based assessment. Sure it's been discussed to death, but most of the discussion is not really useful. I have done quite a bit of research and have been unable to find real world information that substantiates the claims people commonly make of Lithium. If it's so clear, then show it to the forum! 

What my calculations show is that Lead is about 5x cheaper than Lithium per useful kWh. If Lead suits your needs and lasts 3 years, that's 15 years of lead for 1 lithium pack, which is only guaranteed for at most 10 years from OEMs, who tend to be very conservative.


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## mora (Nov 11, 2009)

Here is some simple math.

Single 100Ah Calb lithium cell costs 145$ (3.2V/100AH). If you can only use 80% of capacity (safety margin & long life) that makes ~566$ per kWh.

Trojan T105 lead block costs 132$ (225Ah/6V). If you can use 50% of its capacity in EV use that makes ~195$ per kWh.

Trojan promises 300-500 cycles for these batteries. Calbs should last 1500 cycles if only 80% of available capacity is used. Even after that Calbs should have at least 80% usable capacity for unknown amount of cycles. But let's say you need to replace pack after 1500 cycles.

Best case scenario: Trojans last 500 cycles. You will go through three sets of Trojans when only one set of Calbs reach 1500 cycles. Lead got triple price at 585$ / kWh.

Conclusion: omg, lead is almost as cheap as lithium. Which one will you choose?

While lithium keeps going strong cycle after another lead keeps dropping performance as their cycle life gets closer to the end. Range has probably dropped to half of what it was when lead pack was new. Lithium will still give you the same range at 1500th cycle. Even if lithium and lead were equal in usable kWh lead would still get lower range. Weight matters.


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## DIYguy (Sep 18, 2008)

meanderingthemaze said:


> If calculations are straightforward, then why do so many people continue to ask?


Good question. My guess is that they want to somehow convince themselves that it is the right decision.


meanderingthemaze said:


> The reason I started this thread is because of the lack of calculation-based assessment. Sure it's been discussed to death, but most of the discussion is not really useful. I have done quite a bit of research and have been unable to find real world information that substantiates the claims people commonly make of Lithium.


I beg to differ. I have been on here for several years and I've seen it discussed in detail many times. . . right down to charge efficiencies. The open question was always "well, how long does lithium really last?" All indications are that the specs are conservative.
Additionally, check the Wiki. It has all you need to calculate. No phd required.



meanderingthemaze said:


> What my calculations show is that Lead is about 5x cheaper than Lithium per useful kWh. If Lead suits your needs and lasts 3 years, that's 15 years of lead for 1 lithium pack, which is only guaranteed for at most 10 years from OEMs, who tend to be very conservative.


Perhaps you should show your calculations and we can help you to fine tune them.

The point I was trying to make from my first post. . . is that ROI is commonly used when performance of product is reasonably comparable. This just isn't the case. So, you can compare cost . . but it needs to be put in perspective and I think that is what ppl are trying to help with.

A push mower and riding mower both have a ROI. . .if you value not riding, you can compare them. 
If you want to push your car around, Lithium is lighter.


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## meanderingthemaze (Jan 25, 2010)

Thanks mora. But I thought lead could be discharged more than 50%. There doesn't seem to be consensus on that. Also, you give the best case scenario for Lead. But, what is the worst case scenario for Lithium?

diyguy:


> I beg to differ. I have been on here for several years and I've seen it discussed in detail many times. . . right down to charge efficiencies. The open question was always "well, how long does lithium really last?" All indications are that the specs are conservative.
> Additionally, check the Wiki. It has all you need to calculate. No phd required.


Well, I must have missed those discussions because I've been here awhile too. Linking to posts would be more useful here. The Wiki has some information, but its kind of a mess too. Plus some of the info doesn't cite its source. 



> Perhaps you should show your calculations and we can help you to fine tune them.


It would help if you read the thread before responding because I did post calculations. The greyest area seems to be nailing down useable kWh for both Lead and Lithium. You can't seem to trust the advertised specs for your range calculations for example. It's not that there isn't information out there about this, but it's all over the map. It's easy to make a claim, but rarely do I see people qualify those claims or justify them with figures or calcs. 

This is why a lot of people get confused about this issue. There is a lot of opinion being floated around. We still don't know in real life how long the Lithiums will truly last. But you hear people making the claims as though they are indeed trying to convince themselves that it's true and justify their decisions. Others will admit they are putting their faith in Lithium. 

If the phrase ROI is getting things confused then let's not use it. We're talking about overall cost in your real life project that will suit your needs.


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## EVfun (Mar 14, 2010)

Lead is only good for about 1/2 of the 20 hour capacity mostly due to Peukert's capacity issues. The other half of the capacity isn't lost, you just can't get it out at rates useful to drive an EV. Even Optimas are noted to only have about 30 amp hours available in EV service (the group 34 Optima is a 55 amp hour battery at the 20 hour rate.) 

If someone is trying to build for range lead presents another disadvantage. You will have to do significant suspension upgrades to handle the weight. These modifications add to the conversion cost and time. If you build for a similar range in Lithium the suspension can often be left unchanged except for an alignment after completion. 

The performance of golf cart battery powered EVs is truly weak. A golf cart battery weighs about 60 lb. and can put out about 500 amps at 5.2 volts. That means the battery can make about 3.5 horsepower, which will be about 2.9 horsepower from a typical EV motor. If the EV pack 1/3 of its weight in batteries then you have about 2.9 horsepower for every 180 lb. of vehicle weight. You're pushing 62 lb. of vehicle for every horsepower! That is comparable to the performance of a 36 HP (pre 1961) VW Beetle. The 0-60 time will be longer than the 1/4 mile time, most people find that kind of vehicle performance inadequate.


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## DIYguy (Sep 18, 2008)

meanderingthemaze said:


> diyguy:
> 
> Well, I must have missed those discussions because I've been here awhile too. Linking to posts would be more useful here. The Wiki has some information, but its kind of a mess too. Plus some of the info doesn't cite its source.


I did an advanced search in the Battery section for "Cost", in titles only and got 250 hits. (it's capped at 250) There are thousands. . Including cost per mile, charge efficiency, cycle life discussions, plenty of conjecture, but lots of data from ppl also.

As for the Wiki.......... it doesn't seem too messy to me.... 

*Step 3: Make allowances for your battery type.
*Electric conversions use deep-cycle batteries which have some important characteristics that affect how they can be used in EVs. *The two major factors are the Depth of Discharge (DoD) limitations and the Peukert effect*:

EV batteries do not like being emptied down all the way and so emptying them completely will drastically shorten their life (the number of times you can use them). In order to counter this most EV conversions arrange things so that their battery pack never goes below 20% full. This is usually known as 80% DoD, or depth of discharge. So for our battery pack we need to make sure that when we have traveled our full range we still have 20% of our energy still in the batteries. *To make sure this happens we take the the Ah rating we worked out in part 2 and multiply it by 1.25*. This will mean when we have traveled our required distance we still have 20% left in the batteries. So for our previous example we worked out the Amp-hours to be 83.3Ah so we multiply by 1.25 to give us about 104Ah.

The Peukert effect sounds fancy but it simply means that *the faster you use up the energy in the battery the less you will get out in the end*. Battery Amp-hour ratings are usually given for a pretty slow discharge over 20 hours. However most EV conversion will use up their power much faster than that, usually in about 1 hour. Because the faster you use the energy the less you get altogether most EVs using Lead Acid batteries will only be able to use about 55% of the energy of the 20hr rate and we need to again compensate for this in our total pack size, by multiplying by 1.8. So our the amp-hour value in our example of 104Ah becomes 187Ah. When sizing the battery pack we need to make sure that the batteries we choose have an Amp-hour rating of 187 or better to achieve our range of 40 miles.

Lithium based batteries perform much better under high strain loads so you should be able to use 95% of the 20C energy rating. This means for a lithium pack you only need to multiply by about 1.05 to compensate, so a smaller pack is needed compared to a Lead Acid pack.

_The third step in Sizing a battery pack is compensating for the characteristics of the batteries we choose, for Lead acid batteries this can be achieved by multiplying our Amp-hour rate from step 2 by 2.25, For Lithium batteries __this can be achieved by multiplying our Amp-hour rate from step 2 by 1.32._
[/QUOTE]


Look, lead has been around for over a hundred years and you cannot even nail down HOW LONG IT LASTS! You will get everything from 100 cycles to 1000 cycles. . . and they are probably all true! You really think you will get a difinitive answer on the life expectancy of Lithium?

It has been documented that researches are predisposed to getting the results they anticipate from a study because they inadvertently do things to influence the outcome. . . with out even knowing it sometimes. Sure, u can say it's all baloney. . . or u can say it's all true. If your heart is set on something, by all means, go ahead and do it.
I've had two lead packs and one lithium in my first build. What have you had? How did it work?
While your at it, you can factor in the extra cost of boiling those floodies. . . and the watering system. . . and the difference in rolling resistance from the weight. . or not being able to run to the market when u get home from work or or or or...... 
The main reason I sometimes jump into the battery discussion (and it's gonna be less. . I can tell . . lol) is that I agree with JR on another point also. . . that Lead Acid builds actually do more to harm the adoption of EV's than they do to help it. These builds, in most cases, exemplify all those common beliefs about EV's. Make a car that will exemplify the best traits that an EV can have. . . or don't do one. Just one man's opinion. . . but I'm allowed . . . my wife said I could ...


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## Ziggythewiz (May 16, 2010)

meanderingthemaze said:


> Thanks mora. But I thought lead could be discharged more than 50%. There doesn't seem to be consensus on that. Also, you give the best case scenario for Lead. But, what is the worst case scenario for Lithium?


He was being far too generous for the lead. You can only use 50%, but because of peukert you only get around 60% of that. 

Also, why would you compare best case for lead with worst case for lithium? Best case for lithium would be lasting for decades. That's part of the reason we run numbers, but are still doubtful of some of the projected results. 

For example, some of my calcs would give a lithium pack at 80% DOD a longer lifespan (16 years) than at 70% DOD (12 years) because I could charge every other day, using 3 cycles/week instead of every day at 6 cycles/week.

There is simply not enough data to answer all our questions, and that's not going to change any time soon. I'm not aware of anyone with the resources to do a good test besides a manufacturer. A good test would involve about a dozen cells, from a dozen different batches (so 100-150/test) run in a dozen different use cases. Since the manufacturers never publish the results of more than a couple of their tests, the only data we will ever have is anecdotal from us, and it will take 8-20 years to collect that through actual use.

Theoretically I could size a pack so I could charge every 2 days while using at 70% DOD, and it would last around 24 years (and then I could switch to charging every day and get another 12 years?). However, at some point the shelf life matters as much as the cycle life and I don't think they could possibly last that long.


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## GizmoEV (Nov 28, 2009)

I got only 5000 miles out of the set of T-875s that came in my Gizmo. If I add the miles which were on the odometer when I got it the total would be 7500 miles. A pack of six T-875s looks to cost around $900 right now. I put 2500 miles/year with the lead acid pack so this would mean I could get 3 years use before the range went below useful for me. In January of 2010 I installed a LiFePO4 pack of 40 TS-LFP100AHA cells in a 2p20s configuration. I wasn't sure of what I needed due to the need for ballast and keeping the C rate down so I went over board on pack size. I spend $5000 on the pack and another $800 for a BMS (which I'm not using at the moment, btw). Now that I have had this pack for the past 29 months I'm quite sure I could have done fine with a pack half this size which means the cost would have been $2500 + $800 or $3300. Basically three times the cost of a lead acid pack which I took out.

Using just these numbers would mean I would need to have this pack last 9 years to break even on costs. What the numbers don't show you is that now I drive my rig over twice as much as I did with a lead acid pack. This means that over 2500 miles/year is not being put on my gas rigs. This would most likely be at ~25mpg but lets use 32mpg of my Corolla. That equates to ~$300/year in fuel savings alone. This makes the equivalent cost of driving my Gizmo with a T-875 pack to be $600/year ($300 for the amortized battery cost and $300/year in extra fuel costs for my car). $3300/($600/year)=5.5 year cost break even point. For the LiFePO4 pack I did install it would be $5800/($600/year)=9.7 year break even point. And this is using numbers which don't favor using lithium. Right now I would have to drive my 15mpg truck since my Corolla is not available so my break even point would be even sooner. The extra fuel costs for my truck would be $650/year so the cost of driving my Gizmo with a T-875 pack would be $300+$650=$950/year. This makes my break even point at $3300/($950/year)=3.5 year break even or $5800/($950/year)=6.1 year break even point.

All of this ignores the vastly improved drive-ability and significantly reduced maintenance of battery watering and cleaning terminals. Add to this the fact that my range with half the LiFePO4 pack I put in would be 35 miles and this could diminish to 20 miles before it would give me the useful range of the T-875 pack before it died. With my 200Ah pack my useful range is 70 miles driving any way I want except only up hill. 70 miles is not the farthest it could go on a charge at a constant optimum speed. This is a real put it in the bank drive any way you want range. It could drop to 20 miles or less than 30% of its original range before the pack would be unusable for me.

So what do you think. Was it worth my investment? It was to me, that is for sure.

As for calculating true energy available: Using my CycleAnalyst I take the Wh used and divide by the Ah used on a 40-60 mile run where the average current draw is around 130A or 0.65C and I generally get 64V (3.2vpc) to 62V (3.1vpc) when the pack is below 10°C. This is why using 3.2vpc is a realistic nominal voltage for energy calculations with LiFePO4 cells. The peukerts is so low that I don't notice any difference in heavy or light discharges so if a battery is rated at 100Ah that is what you will get, worst case 95Ah assuming you aren't abusing the cell.

The T-875 has a 170Ah rating at the 20 hour rate. The 5 hour rating is only 145Ah. Tests have shown that a 50% DOD gives the most miles for the life of a lead acid pack. If you are trying to minimize pack life this is the value you should use but understand that you can't use the 20 hour rate. A 1 hour rate would be more like it. The 1 hour rate for a LiFePO4 cell is very close to its 2 hour rate which is very close to its 5 hour rate. For my calculations for using LiFePO4 I take the Ah rate at face value and use 80% for extremes or 70% for conservative values. With lead acid I use 50% of the 20 hour rate as equivalent to 80% DOD.

With LiFePO4 you can always buddy pair a second cell with an initial pack for more range. It won't matter that the old cell and new cell have slightly different capacities. They will work as a single cell once paralleled as long as neither cell is damaged and both are the same chemistry. That is not something I would even consider doing with a lead acid pack.


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## piotrsko (Dec 9, 2007)

you also need to amortize the charger cost and whether or not you bms. I won't even talk about wiring them together. there is a huge series of threads about drilling, materials used and <corrosion>.

My charger cost $40 to make, no bms. Betcha yours cost more.

How well can you abuse the LIpo batteries? Can you drastically over charge, draw them down to below 2 voltsthen expect them to work? Cell reversal? Can you go down to Joebobs house of batteries in your town and just buy a new one? Do they even have a warranty? Have you tried to return a defective cell? Do you need to speak a different language or learn another culture to buy Pb's?

Yeah it is 100 year old technology, and it kinda sucks, but my vehicle is rolling under its own power.

Finally: Many of the lipo fanatics used PB chemistry once.


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## Frank (Dec 6, 2008)

Another factor not yet mentioned is that PbA conversions typically have to (or at least, should) be in pickup trucks so as to not exceed GVW. Lithium lets you choose the vehicle you want. My small Toyota has 1320# of T125's (not quite a "ton" but pretty damm heavy nonetheless.) An equivalent amount of energy could be contained in maybe 400# of LiFePO4's (not LiPo's) which are a pretty safe cell. Taking 900# out of my truck would make it infinitely more useable. Sure, it does okay on the flat but is a pig going up hills. I'd be surprised if any PbA conversion does well on hills. When the batteries get totally pooched (they're getting weak now, in the 6th year of usage) I'll transplant the EV stuff in another chassis with prismatic LiFePO4's. BTW, I'm convinced the only reason the batteries have lasted as long as they have is that I'm paranoid about not abusing them.

My latest m-cycle conversion uses 72V of 100AH T-Sky's. It's a bit more battery than I need but the bike is pretty fun. I use CellLog's to monitor, no BMS and the cells stay very close together. There's no need for chargers to be more complex than PbA chargers and voltage stays more stable than it would with any PbA pack. When your PbA pack wears out, have a serious look at prismatic LiFePO4's, you won't regret it.


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## mora (Nov 11, 2009)

meanderingthemaze said:


> what is the worst case scenario for Lithium?


Few cycles and ready for replacement (overcharge few times or even once). Over discharge isn't that bad unless you run down to 0V resting voltage. Your car stops moving way before that happens though. Opposite for lead. Drain a lead battery too empty once and it is nothing but downhill from that point. Care must be taken to ensure good cycle life no matter chemistry. Maybe some old flooded NiCds are exception though.


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## GizmoEV (Nov 28, 2009)

piotrsko said:


> you also need to amortize the charger cost and whether or not you bms. I won't even talk about wiring them together. there is a huge series of threads about drilling, materials used and <corrosion>.


No matter what chemistry you have to get a charger. Why would you need to amortize the charger cost? It is a capital expense like buying the car in the first place. Do you amortize the seats, doors, windows, etc?

What are you talking about with the drilling, materials used etc part?


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## piotrsko (Dec 9, 2007)

my charger cost 40 USD. Not a big expense. I havent seen many lipo chargers for that price. What happens during an over charge? Can you say bang?? Not an issue with lead. So I am saying that the cost of the charger and BMS system (if you use one) is an integral part of LIPO useage and sort of irrelevant with lead.

My battery connections including the ones to the controller, all made from 2-0 cable cost about 100 usd, and took about an hour to make. Haven't seen the equivalent for LIPO. Then there can be the too long screw issue, corrosion, materials disimiliarity, swelling, strapping, boxing, whatever.


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## TomA (Mar 26, 2009)

What about corrosion and chassis leaks to ground so common with floodies?

I haven't seen or heard of a single LiFePO4 pack that has needed ventilation, emitted acid vapor, has caused corrosion on the terminals, battery racks or battery boxes, or been the source of a chassis ground leak other than by contact of the HV wiring to the chassis. Long term, that's worth something to me.

Still, this is all minutiae. The simple fact is that the conversion I want to do (Daewoo Matiz) isn't possible with lead batteries. Can't do it. Hard stop. Oh, sure, it could be done at 72V with a 20 mile range and terrible performance, but that isn't the conversion I want to do. Its only possible to do a 130V HPEVS powered car, and have about a 16kWh pack and 50+ mile range, with lithium-based cells. 

So the question "Lithium over Lead?" is only "really not that clear" if the performance envelope of the conversion you want to do (like with a small pickup) is feasible with lead. The smaller the glider, the harder it is to make lead work. For a 4 seat glider under 1700lbs stock, its practically impossible.


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## GizmoEV (Nov 28, 2009)

piotrsko said:


> my charger cost 40 USD. Not a big expense. I havent seen many lipo chargers for that price. What happens during an over charge? Can you say bang?? Not an issue with lead. So I am saying that the cost of the charger and BMS system (if you use one) is an integral part of LIPO useage and sort of irrelevant with lead.


So did you not see that I included the BMS in my analysis? When done properly there is not going to be an overcharge issue. Furthermore, with lead there is thermal runaway with too much overcharge. In addition, with every full charge of a flooded lead acid and flooded NiCd packs there is corrosive acid vapors to deal with and highly combustible H2. Have you seen the bulging pickup bed and lids blown off battery boxes? I have. That is just one why you should have a temperature compensated charger for lead. Also, LiFePO4 have different characteristics than LiPo.



> My battery connections including the ones to the controller, all made from 2-0 cable cost about 100 usd, and took about an hour to make. Haven't seen the equivalent for LIPO. Then there can be the too long screw issue, corrosion, materials disimiliarity, swelling, strapping, boxing, whatever.


Again, LiPo is not the only chemistry out there. I have had my LiFePO4 pack in place for well over 2 years and over 12k miles and haven't had any pack connection issues or battery failures like I did with lead acid.

What again is the problem with LiFePO4?


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## DIYguy (Sep 18, 2008)

There is no need to try and justify your decision. It's yours and you are allowed to do what you like. There are considerations attached to every decision. Even within the lead family of batteries, the sealed ones need a bms even more than Li. I started with lead, and I'm not ashamed of going that way. I did however, not invest a lot and the purpose was to prove everything out. It's a bit of an evolution but for those who have moved on to Lithium, there are some experiences worth sharing.



piotrsko said:


> My charger cost $40 to make,


I would like to point out something about the chargers though. For those of you who are using lead, it actually is to your advantage to buy a good charger with some well developed algorithms. Lead charging profiles are much more complicated than lithium charge curves. Lithium is dead simple. CC then switch to CV and allow taper of current. Good lead chargers have 3 or 4 stages and many include pulsation techniques to improve life and usefulness of lead. Floodies are certainly more tolerant however the venting and boiling causes some nasty issues.


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## rmay635703 (Oct 23, 2008)

Ziggythewiz said:


> 65% is close, I was going with .6, but then you also times by 50% for DOD, so your actual multiplier is something like .25 - .35 Compare that to .7 for lithium and it does seem pretty clear.
> 
> GC8s from sams for around $100 are 135 AH (20 hr) so using .3 as a multiplier gives ~$310 / kWh. Obviously 6v batts are cheaper/kWh but there's no way I'm putting that much weight in my bug.
> 
> It's already 1:3, with 5x the life


Depends on what lead batteries you compare to, overcharging the crap out of a 48v 250ahr pack of Greensaver Lead silicone batteries I am still at roughly 95% summer time range over 7000 miles, that includes 10 100% DOD's 50 80% Dod's and lots of little ones (less than 50%).

Now that its warmer my father is racking up miles on his Miles ZX40 again.

The gel batteries do not seem to be affected by overdischarge the way some floodies are, I would estimate the lifespan on this gel pack is going to be in the 5-10 year area assuming it doesn't castrophically fail all of a sudden.

I guess from what I am told 7000 miles off a 48v lead pack is considered good, maybe there are some better lead solutions out there?


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