# best LSV lifepo4 battery vendor



## jatgm1 (Nov 16, 2014)

hello, im posting on here today because my efforts on another site's forum have been fruitless. im am trying to find out where i can purchase the most reliable battery pack for a LSV. i am most likely going to use it in a GEM or a ClubCar villager, so a choice between 48 a 72 volts is preferable and it will have to be at least 100 amphours. if you have a suggestion please post it here, i would like to find the most reputable seller to purchase batteries of this sort from. thank you.


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## Sunking (Aug 10, 2009)

There are lots of supplies, just Google EV Batteries. 

There are many manufacture and distributors. The least expensive are CALB cells. You can find them many places. One of the least expensive suppliers are Electric Car Parts Company. They also carry several of the other manufactures. 

Myself I used GBS cells because of their modular design, 4-point terminals, and integrated covers to prevent accidental short circuits. However they are one of the more pricier manufactures. I got mine from EAS

I know golf carts and manufactures pretty good. IMHO the best LSV is the EZ-GO 2Five. I would take them over Club Car or Gem any day of the week. EZ-GO is the most popular for good reasons. Parts and Accessories are plentiful from many manufactures cheap. In addition to that EZ-GO is easily modified. With just a controller program change and you got a 30 mph LSV. Put a high speed gear in and you got 36 to 38 mph. 

But I have to ask why would you buy a new cart and immediately replace the factory $880 set of batteries with a $2000 lithium? If it were me I would just buy a stripped golf cart for $800 and put in a AC motor, controller, and batteries like I am doing. When done will be a 40 mph cart and around 25 mile range. 



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Here is another set of a friend of mine.


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## lestef (Jul 31, 2014)

Which BMS model are you using ?


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## jatgm1 (Nov 16, 2014)

lifepo4 chemistry, and as per the bms, i would like that to be included. a pre-made system is optimal. please direct me to a manufacturer that makes lifepo4 packs for golf carts. and where can i get a e-z go 2 5? also my plan is to drive it until the stock batteries die, purchase lithium cells of at least 100ah, and then when i can verrify they work properly go about finding an ac motor. and from what i understand "plum quick" sells and extremely high performance dc motor for the clubcar villager. also can someone explain to me which bms and type of batteries are the most long lasting? also i do not want to run any two cells paralell to eachother due to the fact they may potentially become out of balance. a bms with a seperate measurement for each cell is optimal.


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## major (Apr 4, 2008)

jatgm1 said:


> ...also i do not want to run any two cells paralell to eachother due to the fact they may potentially become out of balance.


How do 2 cells connected in parallel become out of balance with each other  The parallel connection forces the terminal voltage on the 2 cells to always be exactly equal, which is the definition of balanced.


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## jatgm1 (Nov 16, 2014)

i was under the assumption that due to the fact i could no longer check each cell seperately it would be harder to ensure both cells were equal. and how would i throw this into a club car?
http://www.electricautosports.com/node/248
could i fill the cavities that normally hold lead acid's with these, and then wire them together with the bms? or is it possible to have multiple bms units, one for each set of cells in a cavity and then just wire them together in serial and connect it to the motor controller? or would this kit fit in a spot that originally held only one lead acid battery? so i could half the space and have the same power? half the weight?
http://www.electricautosports.com/node/423
could i use two of these wired in serial? i like things being easily replaced, like if it stopped working, i could identify which set of cells stop working, then go further to find out which cell in spicific is not functioning properly and replace it? also do these kits have, like screw holes, so i dont have to solder them all together? it would be easier to replace that way. also i always wind up getting burned when i solder so i like to keep that to a minimum, or eliminate it if at all possible. can someone direct me to a video showing how to wire the cells to a bms? also, do these kits come with a high quality bms unit? im not good at spotting these things. im not sure what to look for. i would really rather have a drop in replacement to be honest.


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## jatgm1 (Nov 16, 2014)

also, i noticed that each of the cells in the above picture shows a small chip on it. is that some sort of bms that acts independent from the other cells to maintain proper cell balance? how does that work exactly?


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## jatgm1 (Nov 16, 2014)

also, would this be the same size or smaller than a normal lead acid battery?
https://www.electricautosports.com/node/330
meaning could i use four of these in a club car, or six in a gem? also would the high amphours damage the conrtoller somehow?


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## Sunking (Aug 10, 2009)

jatgm1 said:


> also, i noticed that each of the cells in the above picture shows a small chip on it. is that some sort of bms that acts independent from the other cells to maintain proper cell balance? how does that work exactly?


Look closely, each cell is in parallel, then in series with another pair and so on for 48 volts. The circuit board is a top end balance module. It came with the batteries. It does not keep the two cells in parallel equal, but rather the pair of cells in balance with the others. It came with my batteries and I do not use BMS because I do not run up to 100% SOC. 

There is some truth that you do not want to use parallel batteries as no two cells have the exact same Ri. That means the cell with the lowest Ri does most of the work. However there are two approaches with parallel batteries. 

Traditionally you would build one string say 48 volts or 100 AH, then another string in parallel. That is problematic and should be avoided. Not only will one string have lower Ri, but cabling and connections compound the problem of resistance. It significantly shortens cycle life of all batteries. It weakens the stronger string down to the weaker string.

However you can as the picture. Two cells in parallel, then in series with two more cells in parallel minimizes the differences.


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## jatgm1 (Nov 16, 2014)

that makes sense, thank you. also, does anyone have any input on which battery set of which i posted would be the best for/would work for my application?


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## Sunking (Aug 10, 2009)

jatgm1 said:


> lifepo4 chemistry, and as per the bms, i would like that to be included. a pre-made system is optimal. please direct me to a manufacturer that makes lifepo4 packs for golf carts.


Same exact place you buy batteries for EV's. Try Electric Motor Sports. Elite Power Solutions. Google is your friend





jatgm1 said:


> where can i get a e-z go 2 5?


Exact same place you get Club Car and GEM. From the dealers. Difference is there are a lot more EZ-GO Dealers than any other cart manufacture. Example in Dallas area there are 22 EZ-Go Dealers, 3 Club Car dealers, and 1 Gem. Google is your friend to find them. Just go to the EZ-GO web site, enter your zip code, and they will tell you where are the dealers are located.


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## jatgm1 (Nov 16, 2014)

i understand i can just google it, and i did that to get a battery for my e-bike. guess what? it stopped working. what i meant was, what battery vendors have you had good experiences with and please explain the experiences if possible.


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## jatgm1 (Nov 16, 2014)

also, have you an opinion on this? https://www.electricautosports.com/node/531
the 48v version


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## major (Apr 4, 2008)

Sunking said:


> Look closely, each cell is in parallel, then in series with another pair and so on for 48 volts. The circuit board is a top end balance module. It came with the batteries. It does not keep the two cells in parallel equal, but rather the pair of cells in balance with the others. It came with my batteries and I do not use BMS because I do not run up to 100% SOC.


I don't understand how you can say you don't use a BMS when you just described the BMS which came with the batteries and is installed in your pack. You call it a top end balance module but it is a BMS. Even if you try to short charge your pack, unless you disconnect the circuit boards, they will monitor cell (pair) voltage and take corrective action if needed. So that is a BMS. 



Sunking said:


> .... as no two cells have the exact same Ri. That means the cell with the lowest Ri does most of the work. However there are two approaches with parallel batteries.


I don't get it. The 2 cells in parallel have the terminal voltage forced to be equal by definition of parallel connection. Work is energy. "Do most of the work" means deliver most of the energy. But the amount of energy relates closely to the SOC which relates closely to the terminal voltage which is equal for the 2 cells, so how can the work, or energy, or SOC, or voltage be different between the 2 cells?

With 2 parallel cells of different Ri, there will be some transient unequal current sharing, I give you that. But I contend that the situation is self equalizing in the very short term. It has to be due to the parallel connection and equal cell voltage. If a lower resistance cell hogs current and therefore assumes a lower SOC than its parallel buddy, that parallel buddy will simply charge his lower Ri partner back to an equal SOC. This could be viewed as circulating currents and an inefficiency of parallel connections. But the ultimate work done by each cell will remain equal.

Just about every EV produced has parallel cells don't they? From the Tesla to my lowly Think. It is a manageable situation. You say no 2 cells have the same Ri. While that may be true in the philosophical sense, in an environment of quality mass production, consistent Ri cell to cell is achievable. Any deviation large enough to cause a problem needs to be weeded out before pack assembly and discarded.


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## Sunking (Aug 10, 2009)

major said:


> I don't understand how you can say you don't use a BMS when you just described the BMS which came with the batteries and is installed in your pack.


The balance boards cannot do anything if they are not interconnected and told to do anything by a controller. Like I said they came with the batteries. I did not opt for the controller and interconnect buss cable. For $200 they can be yours plus shipping. 



major said:


> I don't get it. The 2 cells in parallel have the terminal voltage forced to be equal by definition of parallel connection.


Major I agree in theory it should work. But after 35 tears in battery plants mostly Telecom and Off-Grid Solar the end result is shorter life cycle span, and inability to find faulty cells in a timely manner. One cell starts to open and you will never know it, until the mating cell fails from taking on to much charge and discharge current. If one cells shorts, it destroys its mate by fully discharging the cell.

I understand Tesla and others parallel cells, but that does not mean it is the best practice. Tesla went a completely odd route initially with the Roadster using basically laptop batteries. To try to work around all the headaches, Tesla had to come up with a rather elaborate BMS and Thermal management system. I don't know of any of the original Tesla Roadsters owners who are happy with their batteries. Not many happy Leaf owners either. Leaf has a 60 AH battery that uses 3-20 AH cells in parallel. That makes no sense to me and asking for trouble. 

With the availability of large format lithium cells today of up to 200 AH. There is no real reason to have to use parallel configurations to achieve the required AH rating. Doing so just makes it more expensive, more failure points, and more complicated then it needs to be. 

Parallel configurations are fine for emergency power applications like a UPS or Telephone office applications and is required as I have designed and built 48 volt DC plants with up to 25,000 AH. You have to use parallel batteries because there is no such thing as a 2-volt 25,000 AH battery. It would weigh in around 3000 pounds per cell. Largest you can get is 4000 AH and it weighs in around 700 to 800 pounds. 

But when it comes to cycle service like an EV or Solar System, parallel should and can be avoided. Why did I do it. Because it was cheap and I am aware of the problem and know what to monitor. Plus I intend to reconfigure to 96 volts so I am ready to go. 

There are two ways to do parallel. Stationary and Renewable Energy do it the Conventional manner, and EV use an Alternate method pictured below. Done that way if a cell opens or shorts you are screwed and may not even notice it.


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## major (Apr 4, 2008)

Sunking said:


> There are two ways to do parallel. Stationary and Renewable Energy do it the Conventional manner, and EV use an Alternate method pictured below. Done that way if a cell opens or shorts you are screwed and may not even notice it.


Either way, a proper BMS installation would alert you to the problem. FWIW, my Think uses a combination of the 2 approaches, parallel pairs at the cell level and then parallel packs at the system voltage. Works well 

I'm not going into a BMS rant here, but nobody sells a rechargeable Li battery powered product without a BMS be it an EV, power tool, flashlight, cell phone or computer. Why is that?


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## Jayls5 (Apr 1, 2012)

major said:


> Either way, a proper BMS installation would alert you to the problem. FWIW, my Think uses a combination of the 2 approaches, parallel pairs at the cell level and then parallel packs at the system voltage. Works well
> 
> I'm not going into a BMS rant here, but nobody sells a rechargeable Li battery powered product without a BMS be it an EV, power tool, flashlight, cell phone or computer. Why is that?


Because companies have a vested interest in ensuring proper charge and discharge conditions of their battery. This increases the practical life of the cell for an uneducated consumer as well as reduces liability in the event of failure.


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## Karter2 (Nov 17, 2011)

Sunking said:


> ..... Leaf has a 60 AH battery that uses 3-20 AH cells in parallel. That makes no sense to me and asking for trouble.


??? Not quite..
The leaf has "modules" of 4, 33Ahr cells . configured 2S, 2P giving each module 66Ahr and 7.4 volts nominal with a center tap to enable cell level monitoring.


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## Sunking (Aug 10, 2009)

major said:


> I'm not going into a BMS rant here, but nobody sells a rechargeable Li battery powered product without a BMS be it an EV, power tool, flashlight, cell phone or computer. *Why is that?*


Two reasons as I have stated before:

1. To have the ability to take each cell to 100% SOC a BMS must be used. Unlike Lead Acid and some other battery chemistries a lithium cell stops passing current when fully charged. Thus when the first cell reaches 100%, charge current stops and cells below 100% stop charging. What us Off-Grid Solar designers discovered is we can use lithium without the added expense of a BMS and desire to extend battery cycle life by operating between 20 to 80% SOC. We can just about double the cycle life from 500 to 1000 cycles with that simple change in operation. It also alows us to use off the shelf charge controllers made for lead acid batteries.

2. Simple Marketing of the Up-Sale, and to CYA on battery system warranty. Example a Drill or any gizmo that comes as a system. It takes a BMS to get the battery up to 100% SOC, and there is no access to the batteries to manually balance on occasion when needed. 

You don't need a BMS in a golf cart. Leaving it out allows you to use a standard golf cart charger, and we don't need 100% SOC for maximum range. 3 trips around the golf course is plenty, and going to 4 trips (100% SOC) shortens battery lifeAccessing the batteries in a golf cart is simple as lifting the seat up on hinges. 

I am certainly not saying you should not use a BMS, I am just saying it is not needed and an unnecessary expense that can be avoided if you understand what is going on and do periodic checks. 

Personally I can afford a BMS. I can also afford not to use one. Simple Economics from the User POV, not the manufacture. I work on both sides of the table.


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## major (Apr 4, 2008)

Sunking said:


> What us Off-Grid Solar designers discovered is we can use lithium without the added expense of a BMS and desire to extend battery cycle life by operating between 20 to 80% SOC. We can just about double the cycle life from 500 to 1000 cycles with that simple change in operation. It also alows us to use off the shelf charge controllers made for lead acid batteries.


So what I read here is that you use only 60% of the charge meaning that you have purchased and installed nearly double the capacity of battery that you really needed. Then you are happy about 1000 cycles when a properly sized and managed Lithium battery can be validated to 3000 cycles. Sorry, I just don't get it. Appears to me that you go to great lengths and suffer economically just in the quest to avoid the BMS 

I have some small vehicle and non vehicle Lithium battery installations around here running without a BMS. But I personally monitor those frequently, especially when charging. I would never sell one or let one out of my control for use. Yeah, like you say, when everything works well you don't need a BMS. But when something stops working well, which is inevitable, you're going to have a problem and that could be very serious, even lethal. That's what's bugs me about folks who advocate rechargeable Lithium battery installations without BMS


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## azdeltawye (Dec 30, 2008)

major said:


> … Yeah, like you say, when everything works well you don't need a BMS. But when something stops working well, which is inevitable, you're going to have a problem and that could be very serious, even lethal. That's what's bugs me about folks who advocate rechargeable Lithium battery installations without BMS


 
Very well said Major!


 Drives me crazy when all these anti-BMS folks think EV Lithium battery systems are infallible…


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## Sunking (Aug 10, 2009)

major said:


> So what I read here is that you use only 60% of the charge meaning that you have purchased and installed nearly double the capacity of battery that you really needed.


No not at all. A 200 AH pack has 160 AH maximum usable. I just use 120 to 140 AH instead of 160AH. Like I said 3 trips around the golf course or 3 days is more than enough, vs 4 going to 100% SOC. 




major said:


> Then you are happy about 1000 cycles when a properly sized and managed Lithium battery can be validated to 3000 cycles. Sorry, I just don't get it. Appears to me that you go to great lengths and suffer economically just in the quest to avoid the BMS


That defies every thing written and known about Lithium batteries. Operating between 20 to 80% SCO doubles the cycle life of operating 20 to 100% SOC you advocate. Important for an EV maybe to get maximum range, but not required or needed for a GOLF CART. That seems to be the part you are stuck on. OK?



major said:


> *I have some small vehicle and non vehicle Lithium battery installations around here running without a BMS. But I personally monitor those frequently, especially when charging. I would never sell one or let one out of my control for use. *Yeah, like you say, when everything works well you don't need a BMS. But when something stops working well, which is inevitable, you're going to have a problem and that could be very serious, even lethal. That's what's bugs me about folks who advocate rechargeable Lithium battery installations without BMS


There you go. You are setting on the Manufacture side of the table to CYA and Up Sale the product to increase profits. I sit on both sides of the table, know what I am doing, so I am confident in my abilities. I have no intention of letting my cart go to someone else. 

On the commercial side of things I can tell you exactly what the Manufacture Reps to do for LFP packs. They do exactly what I am doing with one exception. They use a Cell Balance Board across each cell like this one. It is not a BMS by definition as it has no SMARTS or Communications. It just simply turns on when the battery voltage reaches 3.55 volts and a .5 amp shunt load on the battery. If you note that is what I am using. When I notice one board actually turns on, then I know my batteries are getting out of balance. That is when I use a .5 amp trickle charge with just a flip of the switch on my charger until they all turn on. Bingo I am balanced until the next time it happens. 

LFP packs are very stable and safe with very little chance of thermal runaway which only happens when you try to push them to 100% SOC or excessively long high discharge rates. I have 200 AH cells with continuous discharge rate of 3C on a 650 amp controller. My batteries will never see 3C discharge rates, and rarely ever see 100% SOC. Safety and long life are built into the design.

I let my controller monitor pack voltage and temp. When it gets low after 2 or 3 days of use, I just charge with a modified standard cheap golf cart charger to charge up to 80 to 90%. Modified to CV at 90% (current limit set to 25 amps or about C/10), and a switch to limit current to .5 amps in those rare times I need to Balance. Easy Peasy, safe, and economical.

What is not to like?


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## Sunking (Aug 10, 2009)

azdeltawye said:


> Very well said Major!
> 
> 
> Drives me crazy when all these anti-BMS folks think EV Lithium battery systems are infallible…


I am not anti-BMS by any stretch of the imagination. I designed my cart to be safe by design and not requiring BMS. If you want to push the limits of maximum charge/discharge rates, distance, and do not mind sacrificing cycle life you will need a BMS. Golf Carts, PTV, LSV, and Off-Grid Solar systems do not need to push the limits and are much safer and longer life by design since they do not push the limits you ask of EV's. That is the part you have not worked on and unfamiliar with being on the Manufacture side of the table.


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## major (Apr 4, 2008)

Sunking said:


> by operating between 20 to 80% SOC.


80% to 20% = 60%. Close to one half. Operation limited to that means you have nearly double (actually 67% more) the capacity in the installation that you actually use. Since the Lithium cell capacity is undoubtedly the most costly aspect of the battery installation, isn't that a great deal of asset sitting there unused?

And Lithium pack validation for automotive routinely goes to 3000 full cycles with 90% capacity at the end. And these batteries are starting to find installations in GES. 

Hey, you can run your new Lithium batteries in your golf cart any way you want. I'm sure you will manage them well. 


Sunking said:


> They use a Cell Balance Board across each cell like this one. It is not a BMS by definition as it has no SMARTS or Communications. It just simply turns on when the battery voltage reaches 3.55 volts and a .5 amp shunt load on the battery.


And you can call a rose a turd, but that cell balancer is a BMS.


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## bwjunkie (Jul 31, 2013)

Sunking said:


> They do exactly what I am doing with one exception. They use a Cell Balance Board across each cell like this one. It is not a BMS by definition as it has no SMARTS or Communications.


I'd call that a BMS, but I don't think there is a definition, it is vague nomenclature, and a wiki would only point out examples of jobs common to the world of BMS-ish products.

That *sweet *balance board seems to offer a large chunk of what many users would want out of a BMS. For me anyway, over-discharge is a mater of looking at lowest voltage readings while driving, but over-charge is a problem that happens while I'm sleeping, and why I think a huge value in BMS is to bleed cells.

-josh


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## Sunking (Aug 10, 2009)

major said:


> 80% to 20% = 60%. Close to one half. Operation limited to that means you have nearly double (actually 67% more) the capacity in the installation that you actually use. Since the Lithium cell capacity is undoubtedly the most costly aspect of the battery installation, isn't that a great deal of asset sitting there unused?


You must be using Rusky Math 

A 100 AH cell used your way (20 to 100% SOC) has at best 80 AH usable. My way (20 to 80/90% SOC) has 60 to 70 AH usable, I don't need that extra 10 to 20%. If I wanted 80 AH usable I would use a 115 to 120 AH cell.



major said:


> And Lithium pack validation for automotive routinely goes to 3000 full cycles with 90% capacity at the end. And these batteries are starting to find installations in GES.


Show me one real world EV that has gotten 3000 cycles. Not accelerated test in a controlled lab, a real EV of 10 years or more use. Batteries have a shelf life even if you do not use them and keep them charged up. You can't do it, not even Tesla has been around that long, and no early model Tesla have the same battery that came from the factory that still has 90% capacity. You can find hundreds of them for sale needing a new battery. No Leaf has done it either, and they had to change battery design because the first model years already died. 

What I will say is if a lithium could last 3000 cycles operated 20 to 100% SOC, will almost double that if operated 20 to 80% SOC. I have real world experience doing just that with CALB LFP cells used in Off-Grid Solar. About 2 years or 500 cycles operated at 20 to 100% SOC, and about 4 years operated 20 to 80% SOC. Common knowledge lithium last longer if not pushed to 100% SOC and charged slower at C/10 rates.



major said:


> Hey, you can run your new Lithium batteries in your golf cart any way you want. I'm sure you will manage them well.


Thanks for at least acknowledging that. 



major said:


> And you can call a rose a turd, but that cell balancer is a BMS.


Depends on how you define a BMS. My Cell Balance are dumb devices. In my case it is just insurance so that I do not push the 100% SOC and tells me something is wrong when one comes on. But if you want to call it BMS is OK with me. For me to go what I would call a BMS would be another $1000 with a charger to work with it. I do that with my Model airplanes, but still only charge to 80 to 90% so my LiPo's last longer. 

Now if they could make cost competitive LiPo's for EV's that would be exciting. with up to 5C charge rates and 50C continuous discharge rates. You coul dwin some drag races and set land speed records. Just think 10 minute recharge fill ups and 400 mile range. Might put EV's in the main stream huh? 

Like I said we have different design philosophy. Being in the EV manufacture mindset you have to push the limits to extreme and require a BMS to keep that bomb from blowing up. Example 10C discharge rates. I do not push the limits staying well below all thermal limits of charging, discharging, and maximum range. My 200 AH pack will never see more than 3C continuous discharge rate. No max burst rates of 10C will ever happen, or be charged faster than C/10. I don't have to worry about over heating or going to far. If I do hit low voltage cut-off I walk a mile or less home and get my truck to drag it home. That ain't going to happen if I can help it.


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## dcb (Dec 5, 2009)

bwjunkie said:


> I'd call that a BMS, but I don't think there is a definition,


I would too, certainly close enough to not be a point of argument. It isn't full featured, but it helps prevent overcharge.


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## Sunking (Aug 10, 2009)

bwjunkie said:


> That *sweet *balance board seems to offer a large chunk of what many users would want out of a BMS. For me anyway, over-discharge is a mater of looking at lowest voltage readings while driving, but over-charge is a problem that happens while I'm sleeping, and why I think a huge value in BMS is to bleed cells.


Myself personally If I were to have what I call a BMS is not to bleed a cell as that counts as a discharge cycle I do not want to loose. I would bring the lower cells up. Just call me crazy and backwards.


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## bwjunkie (Jul 31, 2013)

Sunking said:


> Myself personally If I were to have what I call a BMS is not to bleed a cell as that counts as a discharge cycle I do not want to loose. I would bring the lower cells up. Just call me crazy and backwards.


If we are bleeding .1 AH then is that a cycle? Still I agree, adding would be awesome, seems a more delicate process though. Like getting an ice tray to have all water levels exactly full without spilling a drop in the process, *delicate*!

josh


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## major (Apr 4, 2008)

Sunking said:


> You must be using Rusky Math


If you use a good battery and buy a kWh of capacity, you should expect to be able to a kWh of energy from it each cycle for its rated life. What's Russian about that?

I don't yet have those 3000 cycles on my Think EV but I'm working on it. I don't discharge 100% every cycle. Only have once. But I charge to 100% every night and have my full 24 kWh available in the morning for my day use. I'll use as much as I need, or want and don't have to short cycle to baby the battery. I've got maybe 600 charge cycles on mine. I read where one owner pushes the range limit each way to work and home and charges at work and might put him around 1500 cycles of fairly high DoD. Last report I saw from him was without complaint 

These are not LiFePO4 so off topic. But there are some LiFePO4 batteries on the automotive market which have gone through the same validation as the EnerDel in my Think. The large format LiFePO4 block cells you have may just be a lower quality cell you have to baby like that. I wonder really. There should be some users with 1000's of cycles on sets in there conversions by now. I don't hear of those dropping dead.


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## Sunking (Aug 10, 2009)

major said:


> I don't yet have those 3000 cycles on my Think EV but I'm working on it. I don't discharge 100% every cycle. Only have once. *But I charge to 100% every night* and have my full 24 kWh available in the morning for my day use.


Correct me if I am wrong OK? You can't take a lithium below 20% or risk damaging the cell right? If that is correct you cannot use 100%, only 80% at most. 

Well If you are talking about using Lead Acid I would agree with that practice as FLA and SLA start self destruct modes with anything less than 100% SOC. It is one of the weaknesses of lead acid as they cannot be operated at PSOC (Partial State Of Charge), thus require recharging immediately after every day of use. It is a huge problem with Lead Acid and many other battery types. 

But that is not the case with Lithium as they work best with PSOC applications. A cycle is a cycle like a year in ones life. If your application does not require recharging after every use, then I suggest you don't because you just put one unnecessary cycle on the battery that need not be. I can play 3 rounds of golf and have 30% left in the tank. If I charged like you do would require, 5 or 6 charge cycles in a week rather than 2. That would cut my cycle life over 50% if I did that. Now I just got to figure out how to do that with taking years off this old hide of mine. 


Major I am not arguing with you or trying to bust your chops. I have a lot of respect for you and have learned quite a bit from you. All I am saying there is another way you are not familiar with. When I started this project I started to do it your way. It would have cost me another $1000, and would not last as long. My way is as safe if not safer than your way as I do not have to push the limits. All I have to do is put $1000 back in my pocket and give up 1 trip around the course which is a moot point. 

I am not Anti BMS. All I am saying is there is another way and might fit some applications. That is what this site is about right?


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## major (Apr 4, 2008)

Sunking said:


> Correct me if I am wrong OK? You can't take a lithium below 20% or risk damaging the cell right?


You can fully discharge Lithium to the manufacturer's specified minimum voltage (usually called LVC) which corresponds to a 0% SOC. For the EnerDel cells that figure is 2.5V/c. 100% SOC is 4.2V/c. So when I do a capacity test, I charge to 4.2V/c and discharge to 2.5V/c and count the Ah. This gives me the capacity (in Ah) for the 100% discharge.

The cycle life for such product is defined for a full discharge each cycle and that is how they are rated in the automotive market. The accepted benchmark is 3000 cycles without capacity loss greater than 10%. 

Here is a manufacturer's specification for a automotive grade LiFePO4 cell. Notice the cycle life chart on the second page. It clearly states "100% Depth or Discharge (DOD)".

http://liionbms.com/pdf/a123/AMP20M1HD-A.pdf


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## major (Apr 4, 2008)

Sunking said:


> A cycle is a cycle like a year in ones life. If your application does not require recharging after every use, then I suggest you don't because you just put one unnecessary cycle on the battery that need not be. I can play 3 rounds of golf and have 30% left in the tank. If I charged like you do would require, 5 or 6 charge cycles in a week rather than 2. That would cut my cycle life over 50% if I did that.


That reasoning is incorrect. Short cycling Lithium does not count the same as a 100% DOD cycle towards cycle life. You are not using up your allotted life cycles by charging after a 20 or 30% discharge. In fact, you are likely lengthening overall life. Those two 70% discharges may be more damaging than five or six 20/25% discharges and recharges.

I don't get carried away with this. I recharge may car fully pretty much every chance I get primarily to "fill the tank" in case I might want to drive 75 miles, which happens, but is infrequent. Most days are 30 to 50 miles. However on my yard tractor, I may just charge it once a month. The usage on that is a few times a week with maybe 5% DOD per use. If I anticipate a extensive job for the tractor, I'll charge it in advance. In both vehicles, I expect the battery to outlive the chassis


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## Sunking (Aug 10, 2009)

major said:


> Here is a manufacturer's specification for a automotive grade LiFePO4 cell. Notice the cycle life chart on the second page. It clearly states "100% Depth or Discharge (DOD)".
> 
> http://www.diyelectriccar.com/forums/attachment.php?attachmentid=17106&d=1379716686


Click your link and see where it takes you, then fix it please as I would like to see what you are talking about.

THX


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## Sunking (Aug 10, 2009)

major said:


> Fixed, I think


My bad Major. It downloaded a file I did not catch. THX


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## Sunking (Aug 10, 2009)

OK I think we are splitting hairs here. A lithium battery with built in LVC still has 20 % left in it you cannot access. In reality what they claim to be 100 AH is really 120 AH. In other words they just under rate the capacity which is fine by me. 

The product you are showing is marketed for commercial EV manufactures right? I sticking to DIY applications using cheap Chi-Com cells like CALB and GBS that does not have a built in LVC. Thus must be cut off once you reach 20% SOC. We have to build in that protection. I woul dlove to afford A123 Prismatic cells like champagne on a beer budget. But I get your point.


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## major (Apr 4, 2008)

Sunking said:


> OK I think we are splitting hairs here. A lithium battery with built in LVC still has 20 % left in it you cannot access. In reality what they claim to be 100 AH is really 120 AH. In other words they just under rate the capacity which is fine by me.


No, that is not the case. At the LVC, the discharge curve has gone over the knee, or cliff, and there is very little energy left in that cell, just a few percent, like 2 to 4% in most cases, certainly not 20%. Usually on a 3C (20 minute) discharge test, if I don't catch the LVC in time, it is just a matter of seconds before the cell tanks to zero volts. Here a graph I had handy showing the knee. For this battery I probably used 3.3V/c for LVC.


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## major (Apr 4, 2008)

Sunking said:


> ... A lithium battery with built in LVC still has 20 % left in it you cannot access....


You speak of LVC as if it were a physical device or switch built into the cell. This is not the case with any cells that I know about. The LVC is a value which you assign to you particular application, control or test. Usually there is a manufacturers' specification or recommendation. For your GBS cells I think it is 2.5 or 2.7V/c. 

On the curve below, if one were to use 2.7V/c as the LVC for the 3C test, the capacity indicated would be about 102Ah. You can extrapolate and see that taking it all the way to zero V/c would result in only an additional couple of Ah or percent capacity. There is no 20% past the LVC.

With flat nature of the discharge curve for LiFePO4 it is very difficult (probably impossible) to choose a LVC which would keep a 20% reserve of energy or charge. You would likely resort to Coulomb counting or simply relying on the odometer.










http://www.elitepowersolutions.com/docs/Charging Discharging Curves.pdf


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