# mix lead and lithiun battery pack



## aredxwrestler (Oct 10, 2011)

Is it possible to make a pack with lead to get the ah and add lithium batteries to get the volts? I want to go with lithium but they cost so much more than the lead. I was going to go 144v 220ah. Could I do half pack lead half lithium?


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## Ziggythewiz (May 16, 2010)

No. amps don't add in series. volts don't add in parallel. you don't get something for nothing.

Half lead half lithium will not work well because the charge profiles are too different.


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## rwaudio (May 22, 2008)

aredxwrestler said:


> Is it possible to make a pack with lead to get the ah and add lithium batteries to get the volts? I want to go with lithium but they cost so much more than the lead. I was going to go 144v 220ah. Could I do half pack lead half lithium?


The short answer is yes, the better answer is no, it's simply not practical and the complexity you would add by trying to keep two different battery strings happy during charging and discharging would eliminate any benefit you actually saw.

If you share more of your goals on range/performance/vehicle there are a lot of people here who could help you understand what type of battery you would need for your application.

you won't get much in the way of Ah from lead since you shouldn't discharge much below 50% and the peukert effect will further reduce what you actually get out of a battery. A lithium cell can be discharged to 80% or even 100% with minimal peukert effect.


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## EVfun (Mar 14, 2010)

aredxwrestler said:


> Is it possible to make a pack with lead to get the ah and add lithium batteries to get the volts? I want to go with lithium but they cost so much more than the lead. I was going to go 144v 220ah. Could I do half pack lead half lithium?


It would be impractical. The problem with lead is having enough for a decent range. They are very heavy and large for a given capacity. A Lithium range extender on a lead pack would be more practical, but doesn't make sense anymore. It used to be hard to get LiFePO4 cells that could put out more than 1C continuous so awkward things like hybrid packs where tried. Now there are Lithium offerings that can easily supply more peak current than lead acid.


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## MN Driver (Sep 29, 2009)

There is a guy at my local EAA who made a lithium range extended pack by using high Ah LiFePO4 cells and a 30 amp 48v(nominal in) to 132v nom. out DC-DC converter and charges the two pack separately. It takes a whole bunch of electrically wasteful equipment that was kludged to the two packs to make it all work and the money spent on the setup was nearly 2 grand and if he drives a long enough distance he still has to park and wait for the 160Ah pack to drain into what is now a 50Ah lead acid pack. FWIW with the setup he is still managed to milk 25k miles out of a lead acid pack on a 40 mile round trip and is still going with his Metro. Lots of luck, almost nobody else shares it. The two packs are in series but charged on their own. For the price of the lead-acid, lithium, tons of wiring, weight, and hassle, he could have bought about 13.5kwh of lithium to begin with and saved a ton of trouble and have provided more range than he uses today, not to mention less weight and more space. The only thing that makes it worth it to him is that he already had a decently performing lead-acid to start with before he decided to do this. I disagree with his thoughts where he thinks he will replace his lead-acid batteries with used ones to keep his EV running down the road when his 25k 'lead-acid odometer' climbs to where those cells need to be replaced. FWIW the 30 amps of reduced load has decreased the Peukert Effect.

...seriously though, those of us who are using LiFePO4 or are planning to use it were shaking our heads at this guy because of how complicated this setup is. Not to mention I wouldn't want to have anything made by the Enginer folks in the back of my car, a DIY EV is enough of a rolling prototype as it is to be putting their prototype equipment that they clearly haven't figured out yet.

Putting separate similar lead-acid and LiFePO4 strings in parallel by contactor while driving and disconnected while charging would work better, be cheaper, reduce the lead-acid peukert, reduce some weight versus a pure lead-acid car and make the lead-acid last longer due to lower amp draws on the lead-acid but you are still stuck with a heavy pig of a car that is going to be another low voltage 144v car(lead-acid is too big and smaller Ah batteries are volumetrically large in terms of what you get out of them versus running a lower voltage system) that has lackluster performance if you ever need to hit the highway and want to actually pass someone easily if you need to, like you would expect from a car. You just need to put the right number of LiFePO4 cells in to properly match the load characteristics between the two types of batteries, you'll want the LiFePO4 to take the brunt of the acceleration load and the lead-acid to be drawing off their power as you drive along.


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## DIYguy (Sep 18, 2008)

aredxwrestler said:


> Is it possible to make a pack with lead to get the ah and add lithium batteries to get the volts? I want to go with lithium but they cost so much more than the lead. I was going to go 144v 220ah. Could I do half pack lead half lithium?


You don't want to do this. . at least not the way you have described it. That said, LiFePo and lead acid actually can coexist rather well. The trick is to build two packs with the same final voltage. The amp hours will add, minus the peukerts effect on lead. The lower IR of the lithium can actually help your lead live longer. This may not be the idea you have, but you could build a lead pack with smaller batteries and then pick the size (capacity) of LiFePo you can afford and build the same final voltage pack as the lead. Of course you need to manage them appropriately with respect to charging.


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## aredxwrestler (Oct 10, 2011)

I have an 87 spider that I want to convert. I have 27 mile commute one way to work and wanted to round trip it. 20 miles is 65 and the other 7 is 55. I was planning on using a 11inch motor that I am getting at a good price and the the paul and sabrina controller. What would a liothium pack cost for that? I was using numbners of 1.25 per ah and I was getting around 7k not including bms


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## DIYguy (Sep 18, 2008)

aredxwrestler said:


> I have an 87 spider that I want to convert. I have 27 mile commute one way to work and wanted to round trip it. 20 miles is 65 and the other 7 is 55. I was planning on using a 11inch motor that I am getting at a good price and the the paul and sabrina controller. What would a liothium pack cost for that? I was using numbners of 1.25 per ah and I was getting around 7k not including bms


What kind of Spider?


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## Ziggythewiz (May 16, 2010)

DIYguy said:


> What kind of Spider?


A daddy long legs won't need much current, but goes pretty slow as well. A wolf on the other hand, eats amps like crazy, along with anything else in it's path.


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## cruisin (Jun 3, 2009)

aredxwrestler said:


> I have an 87 spider that I want to convert. I have 27 mile commute one way to work and wanted to round trip it. 20 miles is 65 and the other 7 is 55. I was planning on using a 11inch motor that I am getting at a good price and the the paul and sabrina controller. What would a liothium pack cost for that? I was using numbners of 1.25 per ah and I was getting around 7k not including bms


Most everyone uses the CALB 180ah cells, but that could cost a lot of money if going to 144v or higher. You may want to consider the 100ah which I sell for $1.25ah. The BMS runs agout $14 a cell and the straps/bolts about $3 a cell. That should provide more than enough for the range you are looking for.


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## aredxwrestler (Oct 10, 2011)

Even at that price it still seems expensive. But they are much lighter weight than lead so it does add even more power. I saw a group buy offer for 1.10 per ah for sinoply. How does sinoply compaer to the thundersky that you have?


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## cruisin (Jun 3, 2009)

aredxwrestler said:


> Even at that price it still seems expensive. But they are much lighter weight than lead so it does add even more power. I saw a group buy offer for 1.10 per ah for sinoply. How does sinoply compaer to the thundersky that you have?


I would doubt very much that the Sinoply cells would come to the US after all the fee's for $1.10 per ah. How would you handle a bad cell? Who is going to pay to return to china? You cannot send them by air. The CALB is available to you trhrough me at $1.25 per ah in the US. The advantage of CALB over the other cells is that the average ah on the 180 CALB cells is around 208 ah. Can the others say that.


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## aredxwrestler (Oct 10, 2011)

Are all of the cells under rated? If I can cut some cost then I will be very happy. Do I need to get an individual bms or can I get one unit that connects one to them all?


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## cruisin (Jun 3, 2009)

aredxwrestler said:


> Are all of the cells under rated? If I can cut some cost then I will be very happy. Do I need to get an individual bms or can I get one unit that connects one to them all?


The BMS I sell cost about $14 per cell and $35 for the main board. i have installed a lot of these and they work very well in protecting your investment with no worrys.


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## Zak650 (Sep 20, 2008)

I've heard stories of adding capacitors to a lead acid pack making the pack last much longer. I don't have any direct knowledge of this myself but paralleling a lipo4 pack would have much the same effect but should add more range than the capacitors would.


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## Ziggythewiz (May 16, 2010)

The problem with paralleling a lifepo4 pack with lead is that you must charge them separately, or somehow keep the lithium from going too high during the gas phase, which can easily be 1.5x nomimal voltage.


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## aredxwrestler (Oct 10, 2011)

cruisin said:


> The BMS I sell cost about $14 per cell and $35 for the main board. i have installed a lot of these and they work very well in protecting your investment with no worrys.


Can you post a picture of what it looks like? Each battery has a bms then they plug into a main board? I am buying 40 batteries so that's. Another 520$ for bms


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## cruisin (Jun 3, 2009)

aredxwrestler said:


> Can you post a picture of what it looks like? Each battery has a bms then they plug into a main board? I am buying 40 batteries so that's. Another 520$ for bms


here is a picture of the cell board and head board


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## aredxwrestler (Oct 10, 2011)

How do the cell boards connect to the head board?


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## cruisin (Jun 3, 2009)

aredxwrestler said:


> How do the cell boards connect to the head board?


One 18ga from cel to cel ending at head board.


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