# What kind of batteries are used in the Tesla Roadster?



## kosstheory (May 26, 2008)

I know that they are lithium Ion batteries, what I don't know, is what specific type. They look like ordinary 1.5 V lithium ion batteries, but they're obviously not, right?


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## 3dplane (Feb 27, 2008)

Hi!
I believe they are 18650 (18mm Dia.x65mm long) and they are 3.6V each.6800+ of them (don't know the exact number)in some kind of series-paralell configuration. Barna


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## kosstheory (May 26, 2008)

Do you know what the system voltage is? 144v? Or do you know where I can find these details out? I only asking, because I've very seriously considering a similar approach, using many small batteries instead of a dozen large batteries.

Thanks


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## wakinyantanka (Apr 8, 2008)

kosstheory said:


> Do you know what the system voltage is? 144v? Or do you know where I can find these details out? I only asking, because I've very seriously considering a similar approach, using many small batteries instead of a dozen large batteries.
> 
> Thanks


Well over 300v for the whole thing. The batteries they are using require liquid cooling and an advanced bms system. I believe the total weight on that monstrosity is 900 lbs.
No thanks, I'd rather not see my car go up in flames due to thermal run-away!
LIFEPO4's baby, the only way to fly!!!


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## kosstheory (May 26, 2008)

wakinyantanka said:


> Well over 300v for the whole thing. The batteries they are using require liquid cooling and an advanced bms system. I believe the total weight on that monstrosity is 900 lbs.
> No thanks, I'd rather not see my car go up in flames due to thermal run-away!
> LIFEPO4's baby, the only way to fly!!!


I thought the liquid cooling system was installed to increase the life of the batteries, not to prevent thermal run-away.

Anyway, which of these do yout hink I should go with and why?

http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=1225


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## Madmac (Mar 14, 2008)

The Tesla pack is a nominal 375 volts. The pack rating is 53KWt Hrs with a total weight of 450Kg. The water cooling system both heats and cools the batteries to keep them at their most efficient.

A total of 6831 batteries are used. The weight for an individual battery is between 44 and 46gms depending on rating and manufacturer. Taking 6831 * 46 is 314Kg the remainder of the weight being BMS and the packing / case. There is no other battery at the moment that can give that energy density at an acceptable cost.

The 18650 size battery is made in large volume, around several billion a year on automated production lines. The cost has remained fairly static over the last two years so it is unlikely that we will see a dramatic price drop.

The better quality cells are fitted with a PTC fuse and a pressure disconnect and packaged in a steel tube. In the Tesla it works out to be about 69 cells in parallel, they seem to use the 2.4Ah so total rating is 165Ahr. Max discharge is not recommend at over 2C so max current 330Amps.

If electric cars were the norm and a manufacturer suggested introducing a petrol driven vehicle wakinyantanka would probably against driving that as petrol is explosive.

Madmac


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## wakinyantanka (Apr 8, 2008)

"If electric cars were the norm and a manufacturer suggested introducing a petrol driven vehicle wakinyantanka would probably against driving that as petrol is explosive."

Madmac

First: I'm not against driving a Tesla. If you have that kind of money go by one! 
Second: Ever had a laptop melt down and catch on fire? Not pretty, and thats the same type of battery they are using. 
Third:Tesla had one hell of a time getting that thing to clear FHSA regulations. (probably lined someones pocket) Don't know what regulations are elsewhere but here those batteries are considered hazardous cargo and must be transported in limited quantities, in special trailers. Why you ask?! THERMAL MELT DOWN!!!!!!!!!!!!! In the event of an accident.
Fourth: Have a little class dude... Don't go picking fights and making statements like the one above while not knowing the person your quoting at all. If you disagree fine, state your reasons and leave it at that. Don't get personal it degrades the forum.


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## Madmac (Mar 14, 2008)

Hi wakinyantanka

As with all products there are manufacturers producing at all price points. The lower cost units reduce material costs by leaving out PTC and pressure trip as well as using very thin cases.

When you consider the vast numbers used every year the number of incidents is very low. They have been in production for around 15 years. These days they are made on fully automated production lines. Most of the 'meltdown' issues are caused by the plastic case of the battery pack not the cell rupturing. I could find no issues with systems that encase the cells in metal battery packs.

As the cells evolve the reasons for issues are slowly being understood. Sony has solved the metal particle problem in their cells.

Many people dismiss the cells without looking at the reliability data which has changed over time. In an EV a number of items have the potential to produce an incendiary result yet the LiOn cell is the only one mentioned. A poor connection on any battery system can cause high local heating.

To get the best value for money a balanced judgment of issues is needed and that needs to be reviewed as time passes. I had a quick Google for battery issues in the last 6 months and found one. Going back several years and the number is a lot higher.

Thermal meltdown of existing vehicles is a common occurrence, from figures for the UK that would seem to be 3 a day (1000 per year). The point I was making is the petrol is a very inflammable and explosive material yet we all accept the risk, you included I would guess.

Madmac


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## Madmac (Mar 14, 2008)

By thermal meltdown I mean catch file rather than end up as a pool of molten metal!!
Vehicle fires are a lot more common than most people imagine. In the London area last year the total number of fires was 4723 of which 66% were deliberately started. The figure for the whole of the UK and just cars was taken from an insurance company data for last year.

details of London fires can be found at www.london-fire.gov.uk/lfepa/reports/2008/P-PMC35.rtf


Interesting to note 11% of primary vehicle fires were put down to the battery.

Madmac


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## wakinyantanka (Apr 8, 2008)

Madmac said:


> Hi wakinyantanka
> 
> As with all products there are manufacturers producing at all price points. The lower cost units reduce material costs by leaving out PTC and pressure trip as well as using very thin cases.
> 
> ...


Yes, I have spent the last 27 years of my life making a living, racing and being a master technician on i.c.e. vehicles. Liquid gasoline will not burn, as you know, it has to be vaporized. So there is some safety to it. You are correct many things can cause excessive heat in a battery system. I just worry that in the event the vehicle gets hit and the batteries get smashed they would go thermal to easy. Also, when designing my ev, I decided that the weight of the cooling system and the extra components needed to manage all that was prohibitive. Others may think that the price of the lions off set the risk, they are far better than lead acid that much is certain. I feel the cell style lifepo4 is a better way. Yes they are more expensive upfront, but with easier management and no chance of run-away I felt it was better for my application. I saved weight, and it was easier to design a location for them, that makes the vehicle less complicated to build and own.
Tesla has no doubt advanced ev technology with their design and kudos to them. They have enlightened and excited the general public with their sexy little roadster. I wish I had half of their r&d budget to get my design finished, I'd be right there beside them soaking up some of that glory.
My design seats four and is much lighter than the roadster they have built.
I can also get more than my golf clubs in the trunk.
Who knows with some luck and a little more hard work maybe I can have a show down at the track with them.


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## Madmac (Mar 14, 2008)

Most of the companies making lifepo4 batteries are doing so in low volume and by hand. That means there will be a good percentage difference between each cell. This makes needing a BMS more important. With 18650 cells a number of users including the later Tzero used no balancing or equalization without problems.

Compare that with lifepo4 feedback at the moment with cells failing. There are a number of failure modes and some of them can result in fire. Remember most of the films used in construction are flammable plastic. The cases are also plastic. 

The cells that seem to be preferred by the various auto companies are cylindrical which is easy to automate manufacture. They also seem to be going for large stud electrodes to prevent heating issues during high current discharge.

I'm sure in the future lifepo4's will be the much safer choice, at the moment I think it is marketing hype.

Madmac


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## wakinyantanka (Apr 8, 2008)

Madmac said:


> Most of the companies making lifepo4 batteries are doing so in low volume and by hand. That means there will be a good percentage difference between each cell. This makes needing a BMS more important. With 18650 cells a number of users including the later Tzero used no balancing or equalization without problems.
> 
> Compare that with lifepo4 feedback at the moment with cells failing. There are a number of failure modes and some of them can result in fire. Remember most of the films used in construction are flammable plastic. The cases are also plastic.
> 
> ...


Yes, the lifepo4s I'm waiting for the quote on are manufactured in a factory by automation and have the large stud electrodes for high current application. The company also has a very high success rate with their prismatic modules, but those still can not handle a high burst. Something like 12c or 15c max, the cell style can really put it out, somewhere between 55-60c.
So thats the route I'm taking.


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## Wirecutter (Jul 26, 2007)

kosstheory said:


> Do you know what the system voltage is? 144v? Or do you know where I can find these details out? I only asking, because I've very seriously considering a similar approach, using many small batteries instead of a dozen large batteries.
> 
> Thanks


I found the skinny on the Tesla's battery somewhere online - maybe wikipeadia (sp?).

The battery pack is made of 11 "sheets" wired in series. Each "sheet" is composed of 9 "bricks" wired in series. Each "brick" is composed of 69 of the famous 18650 lithium ion cell (18mm dia by 65.0 mm long) wired in parallel. Nominal pack voltage is 375v, capacity is stated as 53kWh, and peak output is 200kW. Of course, there's also all kinds of battery management going on. Total energy carried onboard the Tesla has been compared to carrying about 8 liters of gas/petrol.

Correct me if I'm wrong, but isn't the major failure mode (of lithium ion cells) from overcharging? There's a video floating around on YouTube showing the effect of deliberately overcharging a large lithium cell. It's a pretty spectacular fire. What doesn't convey in the vid is all the poisonous discharge from the battery.

Oh, and I saw a "melted down" ICE just yesterday on the way home from work. (Dodge minivan that burned a few hours earlier, resulting in a rust-and-grey colored heap and a horrendous traffic jam.) By comparison, (knock on wood), I've _never in my life_ personally witnessed any kind of battery fire. (I've seen video.) The worst I've witnessed is a battery heating up or venting, then being rendered useless. I've seen several vehicle (fuel) fires.

We all take risks all the time - some we know of and some we don't. IMHO, gasolene is potentially a lot more dangerous than batteries simply by virtue of the fact that it represents a lot more energy. Whenever you release lots of energy, there's danger. It's a question of whether you'll be poisoned, electrocuted, or simply carbonized. 

-Mark


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## SuperChuck_A11 (May 29, 2008)

Wirecutter said:


> By comparison, (knock on wood), I've _never in my life_ personally witnessed any kind of battery fire.
> -Mark


First 2 cars I ever bought were battery fire victims. one 61 Impala SS conv. for $75 and 1 72 Chevelle Heavy Chevy for $711. both had more damage due to the extinquiser than the fire.

Had 2 batteries blow up on the road, one in a 56 Ford Truck with the original harness, (well original when we left home hahah), wiring short under the hood, draw on the wires blew battery, I watched the insulation melting go from under the hood to under floor board then we ran a lil. hahah. 
The guy that owned the truck was wacking the fire with his tee shirt trying to get it put out, every time on the down stroke he'd sayyy OWWWW. I asked why he was yelling, as I'm watching the fire progress and he says "I keep getting shocked !!!' then I put 2 and 2 together on the insulation and we hauled it. as the battery was directly under the floorboard. ...Good times...

And one in My 69 Gs Conv. 
On the GS I had stopped for gas in Dallas and when I got back in and turned the key, BOOM, then some smoke. I ran in the store got thier extinquiser and some baking soda, opened the hood and had a party. 
Then being in Dallas and not wanting to leave my car overnight or have it towed, I took a cab to the local Chiefs 24 hour auto parts and got a battery and waaa laa on the road.

On the GS, it was a pure Battery explosion, no short. 
I guess when you have a 6000 amp stereo and a 11.5 to 1 big block, it puts ALOT of cranking draw on the battery, hahahh 

In My limited experience,
Those cars burning to the ground just cause of a battery blowing, must be dirty as heck with oil, the acid by itself doesn't seem to cause a fire, the heat from the short, before the battery lets go, must be igniting dirty underhood oil. 
Lots of smoke from the insuation, but no real fire. 
Once you blow the top off the battery, and the acid gets blown out, it doesn't make power anymore so the heat goes down.
I bet since the new style batteries since they are not wrapped in plastic, with it's low melt point, and they can't release the acid, the heat just goes up and up.

Seen 2 gas fires from rubber hose on the carb.
If you manage to set the belts on fire, they burn quite nicely, and the water hoses will too.
You may have guessed I like old cars......

Dallas and Ft Worth metro area has 5.7 million ppl almost the same as London, I can't even find car fire statistics for it cause all the quiereis are about UK. 
they did have 20 in Dallas itself in one month.......
But 6,000 cars a year, in one town ?? WOW.
Man that is so spectacular I'll say it backwards. WOW.

note to self: don't park car in London.


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## Madmac (Mar 14, 2008)

From Manntis's post 10 in thread

http://www.diyelectriccar.com/forums/showthread.php/gm-volt-back-vengence-2010-14637.html

there is a vehicle fire every 90 seconds on average in the US. I'm sure he will post his source if you need to look further.

Madmac


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## megajoules (Jun 1, 2008)

Here is a pdf from Tesla with the technical details on the battery system:

http://www.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

They employ several active (microprocessor controlled) and passive safety features; from individual cells, to modules, to system. The document is worth a read for anyone who doesn't believe Tesla has taken the safety and reliability of this system very seriously.


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## Manntis (May 22, 2008)

Madmac said:


> From Manntis's post 10 in thread
> 
> http://www.diyelectriccar.com/forums/showthread.php/gm-volt-back-vengence-2010-14637.html
> 
> ...


That figure includes vehicle fires only responded to by US fire departments.

Overview of 2001 U.S. Fire Experience
Michael J. Karter, jr.
NFPA, Fire Analysis and Research, Quincy, Mass.
page 2, bottom. 
Published by NFPA Journal



SuperChuck_A11 said:


> In My limited experience,
> Those cars burning to the ground just cause of a battery blowing, must be dirty as heck with oil, the acid by itself doesn't seem to cause a fire, the heat from the short, before the battery lets go, must be igniting dirty underhood oil.


Have you ever seen batteries arc? even 24V can create an impressive zap just before the batteries blow. That can ignite carpeting (and its backing), insulation, interior fabrics, adhesives, etc.


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## SuperChuck_A11 (May 29, 2008)

never seen it myself, but yea the arc must be lighting something, the acid doesn't seem to light stuff off, and the insulation seems to quit when the battery is done suppling heat. 

Every 90 seconds?? 
So that is 7,008 for each state. London itself is at 6,000 for the year by itself.
Dang.


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## Thalass (Dec 28, 2007)

If you recall that Mythbusters episode, where they tried to replicate the old movie scene where the hero shoots at a puddle of fuel left by the badguy's retreating car. The fuel ignites and blows up the car... or so the movie would have you believe. 


Petrol was the easiest to ignite, compared to jet fuel and diesel, though it didn't burn quite as quickly as the movies say. 

This is the argument my coworkers use to justify running their diesel engines on JetA1, and I might do the same on my hybridised EV one day... It's not about it being free or anything...


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## xrotaryguy (Jul 26, 2007)

From what I have read, Tesla has gone to great lengths to keep the car's batteries from doing anything dangerous. Even in the event of a collision, protecting a car's vital "organs" isn't really that difficult. Take an ICE car's engine. Engineers design the car so that the engine will turn sideways or go under the car in the event of a collision. Doing something similar with an electric car's battery pack should not be terribly difficult.


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## Manntis (May 22, 2008)

xrotaryguy said:


> From what I have read, Tesla has gone to great lengths to keep the car's batteries from doing anything dangerous. Even in the event of a collision, protecting a car's vital "organs" isn't really that difficult. Take an ICE car's engine. Engineers design the car so that the engine will turn sideways or go under the car in the event of a collision. Doing something similar with an electric car's battery pack should not be terribly difficult.


The Tesla pack is centred in the vehicle. If the car gets hit hard enough to crush the pack, odds are the occupants are already human salsa.


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## xrotaryguy (Jul 26, 2007)

The engine in an MR2 is also in the middle of the car. If the car gets hit hard enough that the engine compartment decreases in volume, the engine goes under the car. This is very likely the same type of folding act that the Tesla performs. At least I HOPE that's the case.


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## Manntis (May 22, 2008)

xrotaryguy said:


> The engine in an MR2 is also in the middle of the car. If the car gets hit hard enough that the engine compartment decreases in volume, the engine goes under the car. This is very likely the same type of folding act that the Tesla performs. At least I HOPE that's the case.


That's function of the firewall shape and the engine shape and position (canted). As the pack is a rectangular block, such "submarining" is unlikely - though the firewall does have a slanted face, so it's possible. It depends on the design of the subframe supporting the pack, I suppose.


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## unclematt (May 11, 2008)

Manntis said:


> The Tesla pack is centred in the vehicle. If the car gets hit hard enough to crush the pack, odds are the occupants are already human salsa.


"human salsa" ?

Thats classic


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## kosstheory (May 26, 2008)

So, to get the topic back on track, not that I don't appreciate a good diversion as much as the next guy, why do you suppose the choice was made to use these smaller cells in the Tesla? The batery back is huge, so it probably wasn't for space consideration. The car was obviously designed with all of it's components in mind. Whereas most of us are or will be working around the limitations of our factory designs. So, is there some reason why they would want to use 6,831 small batteries instead of 25+ large ones?

I'm only asking, because I'm in the component search phase of my own conversion project, a cherry 1967 Ford Mustang, and I want to make a point with it...I want to get the most bang possible out of it, because I want people to question whether or not they should go electric too. So, it's my desire to make the conversion process as desireable as possible to everyone that I have the opportunity to talk to about it.

The conversion process needs to be inexpensive within reason, effecient, and simple.

Now, I realize that each person's perception of what is or is not inexpensive is dependant on a great many things. However, I also believe that most would be willing to make an investment if they could see the return, and with fuel costs rising with no end in sight, I don't think this is a difficult case to make.

My 'day car' is a For Focus, which supposedly gets 33 mpg, and if I didn't have my Aprilia Atlantic 500 scooter I'd likely spend about $60.00/week keeping that focus moving. That works out to about $3,600.00/year in fuel costs alone, and doesn't include the other piggy bank smashing maintenance. Next year that figure is going to be much higher. In fact, if current trends continue, It's going to be about 20-25% higher, as crazy as that sounds. I can only imagine the horrors that are already befalling people with a fuel effecieny that is in the low 20's.

This should be an easy sell. Most people keep their vehicles for about 3 years anyway, and in that time any conversion expense could easily be eaten up...

We all just have to work toward making it as feasible as possible. It's like I told one of my friends...I'm not trying to get rich, I just want to change the world.

So, why 6,831 instead of 25 12v batteries?


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## Manntis (May 22, 2008)

kosstheory said:


> why do you suppose the choice was made to use these smaller cells in the Tesla? [snip] why 6,831 instead of 25 12v batteries?


a) more surface area for better cooling of the battery during charging and heavy load discharging, and

b) they were the best cells available for the application _at the early phase of design in which the pack cells were selected._ Had they gone back and changed the batteries later in the vehicle's design, there would have been a 'cascade effect' of hundreds if not thousands of design changes, all of which cost money.

When John DeLorean changed his mind about certain crease lines in the body of his infamous sportscar between the second prototype and the fresher design that went to production, the engineers and accountants were about ready to strangle him. Seemingly small changes - fractions of an inch, really - in the exterior skin meant redesigning the VARI underbody molds, lock mechanisms, wiring harnesses, window guides, etc.

Changing the Tesla cells would have meant re-engineering the pack, it's envelope (and therefore the aluminum chassis), the controller programming, charger programming, hardware placement, weight distribution, etc. ad nauseum.


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## Madmac (Mar 14, 2008)

The highest ratio of cost to power density. The 18650 cells are made in huge volume each year on completely automated lines for high consistency. 

They still give the lightest pack for a given power density including all the overhead.

It is still practical to build a 18650 based pack but does require more effort. It does mean designing your own BMS as there is not a product out there that is tailored to these cells.


I remember reading in one of the Tesla blogs that the battery pack is designed to support other battery technologies when they are power density and cost effective.

Madmac


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## kosstheory (May 26, 2008)

Madmac said:


> The highest ratio of cost to power density. The 18650 cells are made in huge volume each year on completely automated lines for high consistency.
> 
> They still give the lightest pack for a given power density including all the overhead.
> 
> ...


From what I've found the highest amp hour rating on these batteries is 2.6.

Further calculations show that It's likely that I would need 2000+ 18650 batteries to have a useful battery system. Considering that each battery costs about $10 USD, this is simply out of my price range.

Madmac, do you know of a place where these batteries can be obtained for a lower price?


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## Madmac (Mar 14, 2008)

There are places out there that will do small quantities of cells. I suggest you go for 2.4AHr ones as these are quite a bit cheaper and used in greater volume.

An example is
http://ledsee.com/index.php?page=sh...n=com_virtuemart&Itemid=27&vmcchk=1&Itemid=27
which is run by a Dutch guy in China (so I am told). I bought the cells for developing a BMS and charging circuit prototypes from this company. Not a full voltage pack. The design I am working on will need 4900 cells (350 volt 120AHr) and I will get these thru an industrial supplier.

Make sure you buy one of the major Japanese ,Taiwanese or Korean manufacturers.

To get the best price you need to buy thru industrial distributors in the far east and they will not deal with individuals. 

Madmac


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## aeroscott (Jan 5, 2008)

Madmac , Im using the same cells from a 10 volt laptop battery . I was hoping to use what I think is a bms on each battery . can you tell me about your bms . thanks john


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## Madmac (Mar 14, 2008)

There is one issue with using the BMS from portable PC packs. If you are putting packs in series to raise the voltage to a usable level, over 300V if for an AC system, then the cut off circuit will have a problem. As the cells are discharged they are monitored for excess current and also low voltage. If either of these occur the electronic switch is opened to protect the pack.

The switches, usually MOSFET transistors have a low voltage rating, so when they interrupt a high voltage pack that high voltage is across the device and it will fail.

To build a large pack the BMS needs to be configured to deal with the high voltage, high current cut off. It is difficult to do this with semiconductors without expense or losses. A better way is to combine the BMS with disabling the relay or contactor as a final cut off. Before that it should cut the max current that the motor control can draw, as well as give the driver a warning.

Finding exact details of how to get the max life out of Li-ion is difficult. One site that does have a good bit of information is

http://www.batteryuniversity.com/index.htm

The prototype I have developed is waiting on a decision about charging. The original idea was to have a separate charger (switch mode power supply modified) for each block of 7 parallel strings. 

I had intended to buy an inverter to go with the Siemens / Ford / Ranger motor I have. All attempts to buy just the inverter failed as they seem to want to only sell motor plus inverter. Because of this I have been working on extending the Circuit Cellar design. Part of this is using the same components as a single high voltage charger.

I did look at the AC Propulsion patent and did consider trying to implement this but decided it was a great deal of work. Using the Circuit Cellar / Microchip design cuts out a lot of development.

The BMS is a circuit board that monitors 7 series of parallel strings of batteries, they can be any chemistry. Each string can be as many batteries as needed. Using Li-ion 18650 cells the design I am aiming at will be 50 x 2.4 AHr giving 120AHr and the pack voltage is 7 x 3.6 or 25.2 Volts. To give an idea on power density this block will be 80 x 272 x 490mm and weigh approx 17Kg including BMS and water cooling for a rating of 3KWHr.

Each string voltage is monitored and checked for being in spec. During charging a bypass can be switched in to prevent over charge. I have also included an experimental flying capacitor system to transfer charge between cells to equalise them during discharge. 
As many sets of 7 string blocks can be wired in series as needed, each BMS is linked together to allow the master to control and monitor all voltages and temperatures. The master will also check max current and keep track of state of charge as well as shutting off the whole battery if a problem is detected.

Madmac


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## aeroscott (Jan 5, 2008)

thanks madmac , your system sounds good . I just got some stand alone chargers for my 10 year old Nec li-ion batteries . they have dropped to 4 volts or lower . So the next step is to see what . put one in the charger and it only went to 10.49 volts the next went to 12.09 volts . I'm slow charging the next one on a power supply , very slow . 1/10 C to 2 volts per cell ( 6v. for the pack ) or something .


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## kosstheory (May 26, 2008)

Madmac, about how much do you suspect this setup will cost when it's all finished, BMS, and batteries?


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## MrCrabs (Mar 7, 2008)

What if the BMS sends a shutdown message to the controller, that then coasts/ramps to a stop?
You don't want to use your contactors unless if is an emergency, I like your idea of the warning light as well. It would say "hey pull over, your out of electrons"


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