# Simplest battery option for 1st build--LiFePo4 or FLA?



## ewdysar (Jun 15, 2010)

I believe that the increased performance, lower weight, smaller volume, etc. available from LiFePO4 batteries are worth the increased price over FLA or AGM.

I would suggest prismatic LiFePO4 batteries like Thundersky's with shunting modules like MiniBMS or EV Works. Add a charger that has been programmed for your battery configuration, including the BMS modules and your Lithium pack will be fairly well protected. On my batteries, I am wiring the single wire NO/NC control loop from the EV Works modules to shut down my Elcon charger in case of an over-voltage condition in a single cell. I currently don't have any automated under-voltage protection.

Eric


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## PTCruisin (Nov 19, 2009)

I'm near completion on my first build and I have to agree with Eric, go with the LiFePo4s. I started down the same path as you, first considering 12x12V AGMs but eventually bought the Lithium batteries because of the better ROI and performance. That process started in January and I will finally get the batteries delivered to the shop tomorrow! But that's another story.

Ralph


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## pgt400 (Jul 12, 2008)

PTCruisin said:


> I'm near completion on my first build and I have to agree with Eric, go with the LiFePo4s. I started down the same path as you, first considering 12x12V AGMs but eventually bought the Lithium batteries because of the better ROI and performance. That process started in January and I will finally get the batteries delivered to the shop tomorrow! But that's another story.
> 
> Ralph


Batts from EVC or another source?


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## vpoppv (Jul 27, 2009)

If you have the money, go for Lithium. I sure would if I could afford it. Can't make a LiFePO4 72v pack for $42 though......


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## ewdysar (Jun 15, 2010)

vpoppv said:


> If you have the money, go for Lithium. I sure would if I could afford it. Can't make a LiFePO4 72v pack for $42 though......


Does this mean that you can make a usable 72V pack for $42? 

Although at $35 for a 20 pack of Lithium AA batteries, you could get 72V for less than $90. Unfortunately, the range would be a little restricted.  Even cheaper, at $5 per Ultralife Lithium 9V, 72V is only $40...

Eric


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## vpoppv (Jul 27, 2009)

ewdysar said:


> Does this mean that you can make a usable 72V pack for $42?
> Eric


 Yes.

See my build thread:

http://www.diyelectriccar.com/forums/showthread.php?t=34523&highlight=metro

My biggest advantage is my modest requirements. But I do very much want to get into the world of lithium. Given that I only need a range of 1.7 miles, I think a pack of 20 lithium cells of only 5 Ah might do it without going over 50% DOD. Something like this:

http://www.powerscaner.com/product_1.php?id=109

Just thinking out loud really, because there is no way I'm spending that kind of money when the $42 pack gets the job done, even if it takes a lot of work.


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## dtbaker (Jan 5, 2008)

PTCruisin said:


> ...go with the LiFePo4s. ...better ROI and performance. That process started in January and I will finally get the batteries delivered to the shop tomorrow! But that's another story.


agreed on both counts.... current pricing makes cost/mile of the Li lower than FLA if the cycle life holds true. 

possible complications are the cost of a BMS; but I am among the few who will at least start without a BMS. I am building in a loom so I can monitor balance, but NOT installing a BMS.

second issue is actually GETTING the batteries.... and not getting burned by a 'bad vendor' like EVC. I'd suggest paying a little more, pay by credit card/paypal, and get air freight to avoid the ocean shipping/customs delay unless you order from somebody who has stock and can ship via ground freight right away.


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## ewdysar (Jun 15, 2010)

dtbaker said:


> agreed on both counts.... current pricing makes cost/mile of the Li lower than FLA if the cycle life holds true.
> 
> possible complications are the cost of a BMS; but I am among the few who will at least start without a BMS. I am building in a loom so I can monitor balance, but NOT installing a BMS.
> 
> second issue is actually GETTING the batteries.... and not getting burned by a 'bad vendor' like EVC. I'd suggest paying a little more, pay by credit card/paypal, and get air freight to avoid the ocean shipping/customs delay unless you order from somebody who has stock and can ship via ground freight right away.


While I don't have a master control unit, I am running stand alone BMS modules on each TS cell. This allows for shunting which helps keep the pack in balance and has the simple, single wire control circuit to shut off the charger if any single cell exceeds the high voltage limit (4.2V for TS cells). I'm lucky because my battery pack is only 16 cells (48V nominal) and the modules cost between $10 (MiniBMS) and $13 (EV Works) per cell. I do think that the cell modules are worth buying, at about 5% the cost of my 160Ah cells, they seem like good insurance.

Apparently, I lucked out when I received my cells from EVC in February after paying for them in November. There are other vendors that I consider more reputable (Evolve Electric in Colorado), that are close to EVC's price point for TS batteries ordered from China, their in-stock inventory carries a surcharge for the convenience. Since I already have my batteries, I haven't ordered more, but Evolve got my custom progammed charger and instrumentation into my hands in less than a week. If I buy more LiFePO4 cells, they're at the top of my list.

Eric


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## JRP3 (Mar 7, 2008)

ewdysar said:


> I am running stand alone BMS modules on each TS cell. This allows for shunting which helps keep the pack in balance


To be accurate, it keeps the pack "balanced" at the top, and unbalanced at the bottom. I'm happily running without a BMS with a bottom balanced pack. It does take a little work at first to get them all balanced and to get the charging setup properly. A BMS with HVC would be nice but I don't see a benefit in shunting.


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## ewdysar (Jun 15, 2010)

JRP3 said:


> To be accurate, it keeps the pack "balanced" at the top, and unbalanced at the bottom. I'm happily running without a BMS with a bottom balanced pack. It does take a little work at first to get them all balanced and to get the charging setup properly. A BMS with HVC would be nice but I don't see a benefit in shunting.


How do you bottom balance your pack? The top balancing gets the cells within a .05V range at rest every cycle. With the stand-alone modules, it takes no operator intervention.

Eric


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## dtbaker (Jan 5, 2008)

JRP3 said:


> ...I don't see a benefit in shunting.


I have noticed enough reports of batteries killed by failed shunting that I decided to start with manual periodic monitoring and balancing. Probably go with top balancing, rely on the charger to follow its charge curve, and keep close watch not to over-discharge at the bottom end since I *should* be well within expected capacity with 50%-60% dod most of the time.

My plan is to check cells once in a while near the end of charge cycle, and apply individual loads or charge to balance as closely as possible so that charger curves don't overcharge any individual cell.


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## ewdysar (Jun 15, 2010)

dtbaker said:


> I have noticed enough reports of batteries killed by failed shunting that I decided to start with manual periodic monitoring and balancing. Probably go with top balancing, rely on the charger to follow its charge curve, and keep close watch not to over-discharge at the bottom end since I *should* be well within expected capacity with 50%-60% dod most of the time...


My Elcon charger is set to run constant current to 3.60V per cell and taper down to C/100 by 3.8V per cell (algorithm #513, IIRC). This should leave enough headroom below the limit of 4.25V, the modules set to 4.2V have never (in the few cycles that I've run) triggered a fault/shut down the charger, even during their initial balancing. But I already own them, no sense in taking them off...

I'm not running any automated low-voltage protection either.

Eric


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## pgt400 (Jul 12, 2008)

JRP3 said:


> To be accurate, it keeps the pack "balanced" at the top, and unbalanced at the bottom. I'm happily running without a BMS with a bottom balanced pack. It does take a little work at first to get them all balanced and to get the charging setup properly. A BMS with HVC would be nice but I don't see a benefit in shunting.


How do you bottom balance? Take each cell down to say 2.5v then charge till first one hits say 3.7??


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## ewdysar (Jun 15, 2010)

pgt400 said:


> How do you bottom balance? Take each cell down to say 2.5v then charge till first one hits say 3.7??


That sounds right, but I was more interested in how to do that from a practical perspective. How does one manage to bottom balance on a regular basis without a BMS?


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## JRP3 (Mar 7, 2008)

That's the thing, you don't need to regularly bottom balance, you only do it once in a while. This is how I did it the first time with my SE/CALB cells, I took my pack down to around 3.10V per cell by driving, should have actually taken it further to make it easier. Then I used a 12 volt headlight on 4 cells at a time to pull them as close to 3.00 as I felt comfortable with. I've learned you really can go lower as they spring back up a bit when the load is removed. Then I took a resistor circuit on each cell set to cut off at 3.00 volts exactly, though you could do the same with some other load manually. Basically you can pick any voltage around 3.00 or lower as your target. Probably the lower you go the more accurate, to a point. If you pull some lower than the rest you can give then a little shot to bring them up a bit, I used a 6V charger, only for a few seconds at a time, to bring up the low ones.
After a few months of driving I checked them again after a long drive, they were all within 0.10 volts. They were still being broken in and I had a celllog8 on 7 of the cells for a while so this added to the slight imbalance. This time I rebalanced with a better meter and let the cells rest more after adding or subtracting charge, and took them all to between 2.994 and 2.998 volts. Now when charging they all come up to full even closer than before, and I set my charger to stop when the first cell gets between 3.45 and 3.50V. I plan to run like this for the rest of the year and then bottom check them again and see where they are. So far I see no massive imbalance happening, even after one low discharge to 1.77V per cell, (under load), average. Now pack voltage has real meaning on the low end, and if I deeply discharge my pack I know I won't have a single low cell being driven to zero and damaged.


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## dimitri (May 16, 2008)

vpoppv said:


> Given that I only need a range of 1.7 miles, I think a pack of 20 lithium cells of only 5 Ah might do it without going over 50% DOD.


Such small pack might have enough energy for 1.7 mile range, but it likely lacks power to do it. Assuming 3C-5C capable cells, or even 10C, you'd only get 15-50 Amps of current at 64V, which is 3.2kW. Can your car accelerate at 3.2kW? I seriously doubt it.

When planning the battery pack you must look at energy for range and power for speed and acceleration, together.

If your range requirement is low, then high C rate cells are much better fit, but you still need to do the math. For example Headway 10AH cells, which cost around $20 each and rated 5C ( although I saw 10C mentioned, not sure who to believe ). You still need a few in parallel to get decent acceleration currents, then bunch of those parallel packs in series, depending on how much voltage you need.

Do the math before buying your cells....


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## PTCruisin (Nov 19, 2009)

pgt400 said:


> Batts from EVC or another source?


Lithium Storage. The batteries arrived yesterday in less than three weeks from order date. I was burned by EVC but managed to get a charge back on my CC.


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## pgt400 (Jul 12, 2008)

PTCruisin said:


> Lithium Storage. The batteries arrived yesterday in less than three weeks from order date. I was burned by EVC but managed to get a charge back on my CC.


Yeah me too...have not purchased new cells yet. There's strong evidence that the cells that LS now has came from EVC. So you more then likely got the cells you originally ordered.


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## PTCruisin (Nov 19, 2009)

pgt400 said:


> Yeah me too...have not purchased new cells yet. There's strong evidence that the cells that LS now has came from EVC. So you more then likely got the cells you originally ordered.


Strong evidence? All I've heard are accusations and speculation. I asked Mike Collier at Lithium Storage point-blank if the TS cells were from EVC or if they were subject to the litigation that EVC is involved in. He assured me that they were not. Good enough for me.

I send out request for quotes to all the "known" battery vendors and specified that I would only buy from existing stock. Lithium Storage responded with the best quote and included pictures of the batteries in their warehouse.


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## pgt400 (Jul 12, 2008)

PTCruisin said:


> Good enough for me.


Like you said, good enough for you.


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## MN Driver (Sep 29, 2009)

vpoppv said:


> Yes.
> 
> See my build thread:
> 
> ...


The cells you would need come in a package of 8 cells in series at 5.8Ah that can provide 145 amps continuous and 203 amps in a 10 second burst. The series of 8 cells costs $97 plus shipping from Hong Kong. Fully charged 2 of those in series would provide 67.2 volts and you would consider them discharged at about 59.2 volts since they don't sag much. This might be light on power so if you have the ability to run at a peak fully charged voltage of 100.8 volts you could have 3 in series for more total available energy. Putting another set in parallel would allow for 406 amps. You would need to have enough available amperage or a good way of preventing ever going over the maximum amperage or you'll destroy the pack. ...but then again 406 amps would have the pack dead in 1 minutes and 42 seconds too. ...over $600 shipped though but it would be cheaper than LiFePO4 for the range though, there are other ways to swing it too for cheaper cost but this makes it a bit simpler and easier to manage with less packs to play with. 1kwh or so would have enough available power for about 3 miles while still maintaining a decent cycle life and keeping them safe. A few hobby chargers and power supplies designed for 8 cell packs would run roughly $200. It's a bit spendy but easier and much lighter IMO, but you have to be absolutely sure you aren't going to run out of range and destroy the pack too.


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## pgt400 (Jul 12, 2008)

PTCruisin said:


> Strong evidence? All I've heard are accusations and speculation. I asked Mike Collier at Lithium Storage point-blank if the TS cells were from EVC or if they were subject to the litigation that EVC is involved in. He assured me that they were not.


 
Maybe you've heard...during a sworn deposition this week it came out that LS in fact bought their TS cells from Morrison. So looks like you got your original batteries after all.


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## PTCruisin (Nov 19, 2009)

pgt400 said:


> Maybe you've heard...during a sworn deposition this week it came out that LS in fact bought their TS cells from Morrison. So looks like you got your original batteries after all.


I guess I wanted to not believe the accusations and to take the word of Mike Collier. Evidently, you have to be a liar to sell LiFePO4 at a reasonable price. 

If I did receive the original batteries that I ordered from EVC, then I figure I finally got what I paid for 6 months ago.


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## pgt400 (Jul 12, 2008)

PTCruisin said:


> I guess I wanted to not believe the accusations and to take the word of Mike Collier. Evidently, you have to be a liar to sell LiFePO4 at a reasonable price.
> 
> If I did receive the original batteries that I ordered from EVC, then I figure I finally got what I paid for 6 months ago.


I hear you, I would have done the same. How is your build coming along?


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## PTCruisin (Nov 19, 2009)

pgt400 said:


> I hear you, I would have done the same. How is your build coming along?


Slowly but surely. I hesitated to build battery boxes until I actually had batteries and I am glad I did. A friend of my Dad is going to make custom boxes from sheet metal. I'll have two boxes: one under the middle seat and one where the gas tank was located. A total of 38 cells with 20 in the rear box, and 18 in the middle box. I wish now that I had purchased 40 cells instead of 38. I'm finishing up the wiring diagrams and am about ready to cut and terminate the 2/0 cable.


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