OEM lithium battery
09-26-2012, 07:45 PM
#31
Racer
Here's one put together using four A123 Systems 20Ah lithium (LiFePO4) prismatic battery packs. These are latest in lithium battery technology, and the same batteries used in the Fisker EV cars and originally developed for the Chevy Volt. The four 3.6v packs in series make a 14.4v battery with a 20Ah capacity. These are a true 20Ah capacity, not a 'Pb equivalent' rating used by others such as Shorai/Braille/Ballistic etc. which using their formula of actual capacity *3 would make this rated a 60Ah Pb-eq. These batteries are also known and tested to deliver a high 30C discharge rate for 10 seconds, or 600+ amps (20Ah * 30), more than required for a GT3 starter.
Total cost about $200. Enclosed in an old Porsche battery case, total weight comes to 6.5 lbs, half the weight of the Porsche lithium battery with a bit more capacity.
Total cost about $200. Enclosed in an old Porsche battery case, total weight comes to 6.5 lbs, half the weight of the Porsche lithium battery with a bit more capacity.
09-26-2012, 09:20 PM
#32
Here's one put together using four A123 Systems 20Ah lithium (LiFePO4) prismatic battery packs. These are latest in lithium battery technology, and the same batteries used in the Fisker EV cars and originally developed for the Chevy Volt. The four 3.6v packs in series make a 14.4v battery with a 20Ah capacity. These are a true 20Ah capacity, not a 'Pb equivalent' rating used by others such as Shorai/Braille/Ballistic etc. which using their formula of actual capacity *3 would make this rated a 60Ah Pb-eq. These batteries are also known and tested to deliver a high 30C discharge rate for 10 seconds, or 600+ amps (20Ah * 30), more than required for a GT3 starter.
Total cost about $200. Enclosed in an old Porsche battery case, total weight comes to 6.5 lbs, half the weight of the Porsche lithium battery with a bit more capacity.
Total cost about $200. Enclosed in an old Porsche battery case, total weight comes to 6.5 lbs, half the weight of the Porsche lithium battery with a bit more capacity.
What's the wiring to carry the amps from the cells? (I'm not seeing anything with enough gauge?
I imagine about 1 or 2 lbs of the setup is the old plastic box.
09-26-2012, 09:25 PM
#33
I am hoping that this information is used just for clarification and to educate the fellow car enthusiasts, racers, etc. regarding lithium batteries. These are the facts based on my experience with lithium batteries and as a car builder and race driver. This may only be relevant to those who have a lithium battery, are looking to upgrade to lithium or want to know if their lithium battery is bad or not. Lithium batteries are just like street or track tires.....you can buy cheap ones or you can spend money getting ones that will deliver superior performance.....you get what you pay for. It's all just a choice and I am not trying to persuade anyone to buy something they don't need. At the very least, more quality information is always good when making an educated decision on what will meet our needs.
Here is how you can check to see if a lithium battery has been damaged or if it is still good. First, lithium charges at a higher voltage, so an AGM charger will charge at a lower voltage, thus not charge a lithium battery to full capacity. A charge voltage of 14.4 volts is ideal. If you charge the lithium battery to full capacity and let the battery sit overnight, the voltage should not drop below 13.5 volts or it has a bad cell(s).
Also of note, AGM batteries will self-discharge at 3-5% a month, not including parasitic draw. Lithium will self discharge at 1% or less, so they can sit on a shelf for 6 months and have almost no loss, where as an AGM battery can be down 20-30%, getting it real close to a voltage that won't start the car.
The key is having capacity! Putting a small lithium battery designed for a motorcycle is just asking for loss in life cycle and/or premature failure due to parasitic draw, lack of capacity, etc. This is also the case with small AGM batteries.
Just like anything, not all lithium batteries are created equal (build quality, cell chemistry, etc), you ultimately get what you pay for. If you are putting a lithium battery into a nice, high end car like a Porsche, I personally would feel better going with a DOT approved product. From my knowledge, the Porsche Lithium and Braille Lithium batteries are the only automotive batteries with DOT certification.
Here is a quick comparison, just for those interested in an apples to apples comparison of a few 12v Automotive Lithium (SLI) batteries:
Porsche OE Lithium battery: $3000
Braille I48CE is half the price, has double the cranking amps and 50% more capacity than the OE unit. This is a direct comparison, the Braille is a few pounds lighter, DOT approved and has a 3 year warranty (even if raced or tracked).
Braille I48CS is $500 less than OE, has 4.5 times the cranking power, 3 times the capacity of the OE model, DOT approved and 3 year warranty.
The Flying Lizard Porsche team runs the Braille I48CS in both of their ALMS GT cars. Other factory ALMS GT teams that run Braille lithium include Corvette, Ferrari, Lotus and Viper, along with most of the prototypes. They are also used exclusively in the DTM (German Touring Car) series in every Audi, BMW & Mercedes. There is a reason that all of them run Braille Lithium.
Besides weight savings, those teams have reported quicker starting, improved engine management & data logging performance and less HP draw from the alternator due to efficient charging (5 times faster than AGM).
Lastly, when it comes to capacity, I have seen a Porsche 911 (997) with equipped with the Braille I48CS sit for 6 months without a charger and still start the car. This is another benefit for those who don't drive their cars regularly, still want a light battery that has more capacity than the OE battery and has a life construction of 7-10 years. This is why many Porsche dealerships are Braille distributors, as they want to offer their customers a way to shave significant weight off the car, offer better performance and do it as cost effectively as possible, without compromise. Just my 42 cents.
Here is how you can check to see if a lithium battery has been damaged or if it is still good. First, lithium charges at a higher voltage, so an AGM charger will charge at a lower voltage, thus not charge a lithium battery to full capacity. A charge voltage of 14.4 volts is ideal. If you charge the lithium battery to full capacity and let the battery sit overnight, the voltage should not drop below 13.5 volts or it has a bad cell(s).
Also of note, AGM batteries will self-discharge at 3-5% a month, not including parasitic draw. Lithium will self discharge at 1% or less, so they can sit on a shelf for 6 months and have almost no loss, where as an AGM battery can be down 20-30%, getting it real close to a voltage that won't start the car.
The key is having capacity! Putting a small lithium battery designed for a motorcycle is just asking for loss in life cycle and/or premature failure due to parasitic draw, lack of capacity, etc. This is also the case with small AGM batteries.
Just like anything, not all lithium batteries are created equal (build quality, cell chemistry, etc), you ultimately get what you pay for. If you are putting a lithium battery into a nice, high end car like a Porsche, I personally would feel better going with a DOT approved product. From my knowledge, the Porsche Lithium and Braille Lithium batteries are the only automotive batteries with DOT certification.
Here is a quick comparison, just for those interested in an apples to apples comparison of a few 12v Automotive Lithium (SLI) batteries:
Porsche OE Lithium battery: $3000
Braille I48CE is half the price, has double the cranking amps and 50% more capacity than the OE unit. This is a direct comparison, the Braille is a few pounds lighter, DOT approved and has a 3 year warranty (even if raced or tracked).
Braille I48CS is $500 less than OE, has 4.5 times the cranking power, 3 times the capacity of the OE model, DOT approved and 3 year warranty.
The Flying Lizard Porsche team runs the Braille I48CS in both of their ALMS GT cars. Other factory ALMS GT teams that run Braille lithium include Corvette, Ferrari, Lotus and Viper, along with most of the prototypes. They are also used exclusively in the DTM (German Touring Car) series in every Audi, BMW & Mercedes. There is a reason that all of them run Braille Lithium.
Besides weight savings, those teams have reported quicker starting, improved engine management & data logging performance and less HP draw from the alternator due to efficient charging (5 times faster than AGM).
Lastly, when it comes to capacity, I have seen a Porsche 911 (997) with equipped with the Braille I48CS sit for 6 months without a charger and still start the car. This is another benefit for those who don't drive their cars regularly, still want a light battery that has more capacity than the OE battery and has a life construction of 7-10 years. This is why many Porsche dealerships are Braille distributors, as they want to offer their customers a way to shave significant weight off the car, offer better performance and do it as cost effectively as possible, without compromise. Just my 42 cents.
(I have no affiliation with either, other than as a customer.)
While I agree that over-stressing a small battery (I use a jet ski battery for $200 that's lighter than the factory Li-Ion I have in the RS 3.8) but at their price and convenience, well, it's been at least three years and still, so long as it stays on the simple Porsche cigarette lighter adapter tender (it's a rarely driven car) the battery has no problem (even when used to crank the engine without spark to build oil pressure before cold starting.)
What charger/tender do you recommend?
Also, do any of these teams run a wide-open-throttle disconnect on the alternator?
09-27-2012, 09:07 AM
#37
Race Car
I was about to pull the trigger on the Shorai 36 A/HR battery when I read this. It's down to $275 on Amazon, 540cca, 4.96lbs I thought it was a pretty good compromise for the price. I do realize it doesn't have the fancy electronics that the voltphreaks and other more expensive batteries do but worth a shot for the price if you ask me.
I have a good friend who could very likely build a setup like Steve's for me if I had a little more info. I see those battery packs online but listed for sale only in big quantities. Steve, can you give us a little more info please?
Andy
I have a good friend who could very likely build a setup like Steve's for me if I had a little more info. I see those battery packs online but listed for sale only in big quantities. Steve, can you give us a little more info please?
Andy
09-27-2012, 02:32 PM
#38
Racer
Thanks guys. More info on the cells:
http://www.a123systems.com/prismatic-cell-amp20.htm
spec sheet:
http://ecomodder.com/imgs/a123_syste...data_sheet.pdf
These were never intended for sale to the retail market as they were originally focused on supplying the automotive OEMs. However, you can find the cells from any number of sources, including Ebay if you use the keywords 'A123' and 'prismatic' or '20ah'. The cells can be found both new and 'used'. Used cells show up with the tabs partially cut off the top because many suspect they came from new to little used battery packs that were recalled earlier this year from the new Fisker Karma EV cars due to a potential flaw in how some of the battery pack assemblies (not the cells) were welded together in their Michigan factory, and a lot of these packs somehow ended up through recyclers/resellers in China. The cells above were purchased new from a U.S. Ebay seller here:
http://www.ebay.com/itm/A123-AMP20M1HD-A-20Ah-Prismatic-Cells-/330795404721
If you wanted even more battery capacity, you would configure eight packs in what is a 4S2P configuration; two 3.6v 20Ah cells in (p)arallel creating a 3.6v 40Ah pair and connected (s)eries with another three pairs, making a 14.4v 40Ah battery, equal to a 40-50 lb lead battery. Each cell weighs 496 gms, so each pack of four adds about 4.5 lbs. However 20Ah is more than sufficient for a track toy and race car. That's a capacity similar to a 20-25 lb lead battery. In comparison, the Porsche lithium battery is rated at 18Ah and weights 12 lbs. Ah is the rating the total electrical capacity of a battery. In other words, a 20Ah battery would supply 20 amps continuous (about 275 watts) for one hour before being completely discharged, or at a 1 amp load(13-14 watts) take 20 hours to completely discharge .
As I noted before, only in the car market do lithium battery makers over exaggerate the true capacity of their batteries by 3x. For example, the Shorai ‘36Ah’ unit actually is actually only 12Ah if you read their FAQs. The clue to determining if a battery maker is overexaggerating its capacity is to compare their Ah rating to weight ratio. With current lithium technology, the max possible density is about 4.5Ah/lb when you weight just the cells, and when you include the weight of the case and battery posts, comes to less than 3.5Ah/lb.
However when choosing a brand of lithium cell, capacity is not the only factor to go by. A high C discharge rate is very important to deliver a high surge of current necessary to turn over the starter of a high compression motor. High C discharge cells are much more expensive and there are only a few companies that have the engineering to produce such cells. With most lithium cells you would be lucky to produce a 10C discharge rate, which with a 12Ah pack, would be 12*10 is about 120 amps max, barely enough to turn over a small 4 cylinder motor. A123 Systems cells with their >30C discharge rate, are the standard and what virtually everyone in the RC and EV world tries to use. Their chemistry was developed and patented by MIT scientists and proprietary to them. Five years ago, the RC guys discovered their power in their cylindrical 26650 2.3Ah cells but the only way they could get them were to cannibalize DeWalt power packs. A123 26650 cells are what’s used in the Ballistic and Antigravity packs, but with their newest prismatic cells, there’s no need to use the old cylindrical cells. It would take about 9 of the 26650 2.3 Ah cylindrical cells to equal the capacity of one 20Ah prismatic cell, or 36 total cells to create a 20Ah battery pack for use on a car. The high number of cells increases the odds for pack failure with every increase in the number of cells. With the prismatic packs, you only need 4 cells to create sufficient capacity for an automotive battery.
The connection kit in the pics is made and sold by a guy named Agnius in Northern Europe:
http://endless-sphere.com/forums/vie...af9f8af3382a52
The above thread links to another forum dedicated to a whole subculture of electric vehicle and battery technology, if you want to explore the topics. You will need the 4S kit, which means 4 cells in (S)eries configuration. 3.6v/cell * 4 = 14.4 volts. You don't need the above kit to join the packs but it makes for a tidy setup. People have come up all kinds of connecting methods, such as folding the tabs over tightly and using a piece of side slitted 1/4" copper tubing crimped over them with an Anderson crimper, to spot welding. Soldering is next to impossible because while one of the tabs is made of copper, the other is aluminum.
All lithium batteries require proper management, so for that you can use any number of chargers popular in the RC market. You want one that manages LiFePO4 batteries, which is the type of lithium chemistry used by A123 Systems, and incidentally is the the chemistry type used in the Porsche battery, Shorai, Antigravity, Ballistic, Voltphreaks, etc. The one I use is a SkyRC IMAX B6 charger, which properly charges and balances each lithium cell. If you get one of these, it is important to get a genuine SkyRC version with the verification hologram on back, not one of the many fake Chinese clones you'll find such as on Ebay:
http://www.skyrc.com/index.php?route...0&product_id=9
Most RC chargers require a separate power supply. The charger above requires an 11-18v 5A power supply. You may have an old laptop or XBox power supply that will do the job. Be careful of cheap low quality overrated $10 Ebay Chinese specials that would only last a few days/months.
You will also need a 4s cable with the correct 5 pin JST plug for connection to the balancing port of the charger:
http://www.ebay.com/itm/2x-5pin-JST-...item3cc9d07a63
The battery's current passes through to the heavy copper tabs you see on the battery pack, onto the 4 gauge cables connected to the battery posts you see on the case top. The cable's lugs are soldered onto the lead battery posts of a Porsche battery top with a M8 screw added just in case. Some electrical solder, flux, and a propane torch with a small flame provided sufficient heat to properly solder the copper lug to bottom side of the lead post so the screw wasn’t really necessary if done right.
The gutted Porsche battery case weights about 1.75 lbs and was quite a bit of work to gut, but was the perfect LxW dimension to contain the packs, not to mention is totally stealth. Yellow fuel cell foam is used to take up the remaining space in the case and support the pack as its lightweight and breathable to keep the pack cool if necessary. An easier option is to use a polycarbonate NEMA case and add your own posts:
example posts:
http://www.ebay.com/itm/1-Pair-Gold-...item45fd9a7886
http://www.ebay.com/itm/XS-Power-586...314581&vxp=mtr
It is important to never overcharge a lithium battery (>3.6v/cell) or you will destroy the battery because the excess current will go into boiling the electrolyte and possibly cause a fire, which makes the case for a proper balance charger such as above which will monitor the voltage of each cell and keep them all to equal voltage and capacity. For example, if one of the cells discharged to 50% capacity, while the other three were at 100%, you could never charge all the cells evenly with just a basic battery tender, the pack’s capacity will continue to stay imbalanced in that respect or could get worse, and there’s the possibility the other three could get overcharged while the low one never gets fully charged. The small JST wires coming from the battery pack connects a balance charger to do all this. The main power cables from the charger feed the current to the battery pack, while the JST wires read and bleed off excess current from the higher voltage cells if necessary to keep the balance. As a car starter battery, once balanced, the pack should stay balanced on its own for a long time, unlike an EV vehicle which may take these packs through thousands of complete charge and discharge cycles. Plugging in the balance charger to the battery pack once a month should be sufficient to keep them all in balance. Likewise it is also important to never let a lithium cell drop below 10% capacity (<2.8v/cell) or it is likely to be permanently damaged and not recover. Also never allow a workshop hook up their 150 amp rapid charger to a lithium battery or you could be asking for an explosion if overcharged. For best life on any Lithium battery it's best to keep the charge to between 85-30% of capacity and I wouldn't be surprised to see these last for 7- 10 years. If you cannot keep the above discipline, then stick with a lead acid/AGM battery such as a Deka or Westco.
http://www.a123systems.com/prismatic-cell-amp20.htm
spec sheet:
http://ecomodder.com/imgs/a123_syste...data_sheet.pdf
These were never intended for sale to the retail market as they were originally focused on supplying the automotive OEMs. However, you can find the cells from any number of sources, including Ebay if you use the keywords 'A123' and 'prismatic' or '20ah'. The cells can be found both new and 'used'. Used cells show up with the tabs partially cut off the top because many suspect they came from new to little used battery packs that were recalled earlier this year from the new Fisker Karma EV cars due to a potential flaw in how some of the battery pack assemblies (not the cells) were welded together in their Michigan factory, and a lot of these packs somehow ended up through recyclers/resellers in China. The cells above were purchased new from a U.S. Ebay seller here:
http://www.ebay.com/itm/A123-AMP20M1HD-A-20Ah-Prismatic-Cells-/330795404721
If you wanted even more battery capacity, you would configure eight packs in what is a 4S2P configuration; two 3.6v 20Ah cells in (p)arallel creating a 3.6v 40Ah pair and connected (s)eries with another three pairs, making a 14.4v 40Ah battery, equal to a 40-50 lb lead battery. Each cell weighs 496 gms, so each pack of four adds about 4.5 lbs. However 20Ah is more than sufficient for a track toy and race car. That's a capacity similar to a 20-25 lb lead battery. In comparison, the Porsche lithium battery is rated at 18Ah and weights 12 lbs. Ah is the rating the total electrical capacity of a battery. In other words, a 20Ah battery would supply 20 amps continuous (about 275 watts) for one hour before being completely discharged, or at a 1 amp load(13-14 watts) take 20 hours to completely discharge .
As I noted before, only in the car market do lithium battery makers over exaggerate the true capacity of their batteries by 3x. For example, the Shorai ‘36Ah’ unit actually is actually only 12Ah if you read their FAQs. The clue to determining if a battery maker is overexaggerating its capacity is to compare their Ah rating to weight ratio. With current lithium technology, the max possible density is about 4.5Ah/lb when you weight just the cells, and when you include the weight of the case and battery posts, comes to less than 3.5Ah/lb.
However when choosing a brand of lithium cell, capacity is not the only factor to go by. A high C discharge rate is very important to deliver a high surge of current necessary to turn over the starter of a high compression motor. High C discharge cells are much more expensive and there are only a few companies that have the engineering to produce such cells. With most lithium cells you would be lucky to produce a 10C discharge rate, which with a 12Ah pack, would be 12*10 is about 120 amps max, barely enough to turn over a small 4 cylinder motor. A123 Systems cells with their >30C discharge rate, are the standard and what virtually everyone in the RC and EV world tries to use. Their chemistry was developed and patented by MIT scientists and proprietary to them. Five years ago, the RC guys discovered their power in their cylindrical 26650 2.3Ah cells but the only way they could get them were to cannibalize DeWalt power packs. A123 26650 cells are what’s used in the Ballistic and Antigravity packs, but with their newest prismatic cells, there’s no need to use the old cylindrical cells. It would take about 9 of the 26650 2.3 Ah cylindrical cells to equal the capacity of one 20Ah prismatic cell, or 36 total cells to create a 20Ah battery pack for use on a car. The high number of cells increases the odds for pack failure with every increase in the number of cells. With the prismatic packs, you only need 4 cells to create sufficient capacity for an automotive battery.
The connection kit in the pics is made and sold by a guy named Agnius in Northern Europe:
http://endless-sphere.com/forums/vie...af9f8af3382a52
The above thread links to another forum dedicated to a whole subculture of electric vehicle and battery technology, if you want to explore the topics. You will need the 4S kit, which means 4 cells in (S)eries configuration. 3.6v/cell * 4 = 14.4 volts. You don't need the above kit to join the packs but it makes for a tidy setup. People have come up all kinds of connecting methods, such as folding the tabs over tightly and using a piece of side slitted 1/4" copper tubing crimped over them with an Anderson crimper, to spot welding. Soldering is next to impossible because while one of the tabs is made of copper, the other is aluminum.
All lithium batteries require proper management, so for that you can use any number of chargers popular in the RC market. You want one that manages LiFePO4 batteries, which is the type of lithium chemistry used by A123 Systems, and incidentally is the the chemistry type used in the Porsche battery, Shorai, Antigravity, Ballistic, Voltphreaks, etc. The one I use is a SkyRC IMAX B6 charger, which properly charges and balances each lithium cell. If you get one of these, it is important to get a genuine SkyRC version with the verification hologram on back, not one of the many fake Chinese clones you'll find such as on Ebay:
http://www.skyrc.com/index.php?route...0&product_id=9
Most RC chargers require a separate power supply. The charger above requires an 11-18v 5A power supply. You may have an old laptop or XBox power supply that will do the job. Be careful of cheap low quality overrated $10 Ebay Chinese specials that would only last a few days/months.
You will also need a 4s cable with the correct 5 pin JST plug for connection to the balancing port of the charger:
http://www.ebay.com/itm/2x-5pin-JST-...item3cc9d07a63
The battery's current passes through to the heavy copper tabs you see on the battery pack, onto the 4 gauge cables connected to the battery posts you see on the case top. The cable's lugs are soldered onto the lead battery posts of a Porsche battery top with a M8 screw added just in case. Some electrical solder, flux, and a propane torch with a small flame provided sufficient heat to properly solder the copper lug to bottom side of the lead post so the screw wasn’t really necessary if done right.
The gutted Porsche battery case weights about 1.75 lbs and was quite a bit of work to gut, but was the perfect LxW dimension to contain the packs, not to mention is totally stealth. Yellow fuel cell foam is used to take up the remaining space in the case and support the pack as its lightweight and breathable to keep the pack cool if necessary. An easier option is to use a polycarbonate NEMA case and add your own posts:
example posts:
http://www.ebay.com/itm/1-Pair-Gold-...item45fd9a7886
http://www.ebay.com/itm/XS-Power-586...314581&vxp=mtr
It is important to never overcharge a lithium battery (>3.6v/cell) or you will destroy the battery because the excess current will go into boiling the electrolyte and possibly cause a fire, which makes the case for a proper balance charger such as above which will monitor the voltage of each cell and keep them all to equal voltage and capacity. For example, if one of the cells discharged to 50% capacity, while the other three were at 100%, you could never charge all the cells evenly with just a basic battery tender, the pack’s capacity will continue to stay imbalanced in that respect or could get worse, and there’s the possibility the other three could get overcharged while the low one never gets fully charged. The small JST wires coming from the battery pack connects a balance charger to do all this. The main power cables from the charger feed the current to the battery pack, while the JST wires read and bleed off excess current from the higher voltage cells if necessary to keep the balance. As a car starter battery, once balanced, the pack should stay balanced on its own for a long time, unlike an EV vehicle which may take these packs through thousands of complete charge and discharge cycles. Plugging in the balance charger to the battery pack once a month should be sufficient to keep them all in balance. Likewise it is also important to never let a lithium cell drop below 10% capacity (<2.8v/cell) or it is likely to be permanently damaged and not recover. Also never allow a workshop hook up their 150 amp rapid charger to a lithium battery or you could be asking for an explosion if overcharged. For best life on any Lithium battery it's best to keep the charge to between 85-30% of capacity and I wouldn't be surprised to see these last for 7- 10 years. If you cannot keep the above discipline, then stick with a lead acid/AGM battery such as a Deka or Westco.
