Choosing a lithium battery

I have decided to try the Antigravity lithium battery for my 348 (YTX12-24 | Antigravity Batteries). Compared to other lithium batteries, the antigravity performs very well.
I should be receiving it next week. Meanwhile, I will remove the bullet connector between the battery and the starter.
I will document the installation and testing....

 

I posted about this topic in another thread but got my head bitten off for even suggesting it .... ;(

Here's a re-post of the info.

Its the very latest Lithium LiFEPO4 battery built using A123 cells to accomplish a 40Ah rating. It weights approximately 5kg's.

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Latest A123 cells (20Ah batteries x 2 cells)
Weight approximately: 5 kg
Protection board: instantly 80A continuous
output current: 60A
Battery pack size: 28x18x6.5cm
Full voltage: 14.5v
Operating voltage: 12v
Under-voltage protection: 10v
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Not bad for (US) $349 including delivery...

Note: Lithium will require a lithuim battery charger, not your usual battery tender to ensure long life...

Ebay item no: 130919453273

Edit: Added A123 link about cell tech...

Prismatic Cell | Pouch Cell Battery 20Ah | A123 Prismatic Cells
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Is this just a single cell with a connector cable and maybe a fuse? A LiIo battery needs a battery management system (short BMS), or you will ruin it sooner or later - but most importantly, you have a considerable fire hazard. If you have seen one of the big cells burning, you will not want to take any risk there. There's a reason why the big boys have hundreds of engineers working on BMS for their automotive battery systems.

 

No, from what I read it has a small micro-controller and software which controls everything including voltage drop and charging as well as voltage protection.

I totally understand, done a lot of research on this myself.

 

Agree those cables don't look like they could possibly carry the kind of current required to turn over the starter motor of a require car.

 

All is fine then (except for the cables )! Looked like a raw cell to me at first sight...

 

I have seen several posts where people build their own A123 car battery. The technology is very cool!
Myself I debated for a long time if I should spend three times the cost of a lead-acid battery in order to go light weight lithium. I kept on going back to the same augment, and that is; the best way to improve performance is to add lightness (remove weight)!

 

I know I get on everyones nerves and realize that most or all of you know anyway, but again my word of caution: Do not tinker with raw cells, do not try to build a BMS on your own. For being able to manage the battery you need to know its behaviour under all conditions. Getting to know that behaviour requires serious measurement and conditioning equipment and is nothing anyone can do at home. DIY jobs will lead to what is called 'thermal events' in the industry

 

Don't forget that cable resistance is linear with cross-sectional area and length. A 3 inch 14-gauge cable will handle about the same current as a 3 foot 4-gauge cable.

 

power is measured in watts... starter motors need a lot of grunt to spin an engine...
a starter is not voltage sensative and cares little about voltage... all it cares about is watts ( power ) which is made up of amperes and volts... as volts drop the appitite will go up for amperes to get the watts it needs to start an engine... cable size is all about the amperes that can be carried, a cable will heat up as it's capacity to carry amperes is exceeded...same applies to motor windings... a weak or small battery will go out af spec quickly ... the voltage drops, which means the amperes increase in an effort to deliver the required watts... causing heat and eventaul breakdown of cable covers and windings
which is why the start motors heat up quickly in seconds of operation and can be burned up if not allowed to cool

weight saving for competition is good for performance, but is hard on the electonics, which are used very little... for daily driving one needs to be cautious when using small capacity / light weight batteries...short of being on the track for an event, saving weight is more about stroking the ego and bragging than winning the race between stoplights...

 

Just to add a little oddity

We been running a small odyssey motorcycle battery in the shop toyota 4 cyl with a solar 1.5 watt charger. Been on the money for over 7 years now without an issue. Looks strange when you open the hood and the battery looks like a D cell. Weighs no more then 7-8 pounds total.
Did it because the OEM battery died and its all I had in the shop not in use, was not a intentional weight saving deal
Still need to put that bike together

 

It does lighten the helm. You can feel this by removing the spare tire and tools. The problem in the rear of the boxer is not necessarily total weight, it is a Mid but that the weight sits high, lightening the front doen not affect this.

Possibly lightening the front may add to understeer, but I already run PS2 tires and have more negative camber that that is not the issue.

BTW running 275 section PS2 tires and tyheir stiffer sidewall does leave the rear so much better planted that the hight center of gravity is now mor one of letting the car settle from transitions than worrying about snal oversteer. The stiff sidewall and better grip of a mder tire diminshes a lot of handling vices allowing you to exploit the handling better. To this end a lighter more responsive helm adds to the joy.

 

Try the Shorai, proper battery connection 5lbs and 37 AH.

 

So for this to work correctly you have to have a special charging system or else it catches fire?

What about while you're driving the car? Does the alternator need to be modified?

 

However, the ignition system IS sensitive to the voltage level that the starter has dropped the battery to.

 

You can cgarege a shorai with a regular charger so no need to modify the alt. The Shorai is designed for the Honda gold wing which is a 1800 6 cyl engine in a bike with all thypes of chochkies. For alotus this battery is easy street.

 

From what I understand on the Shorai the voltage does not significantly drop like a regualr battery as the wattage is used up.

From te discussion it seems the major drawback is that the battery lacks the wattage reserve of a regular battery so if you were at a stoplight, ac on stero on full it could conceivably overwhelm the alternator assuming the charge is low.

An alarm and other bits is going to kill it pretty quick. On the other hand its a real easy and simple plug in connection to the maintainer/charger. This means that when weekend fun is over its really easy to just plug the car in to maintainbattery in top top operating condition.

Even if you had abigger lithium batttery plugging it in is still a good idea, run a litium below 30% and its toast. So if youa re going to plug in your car or battery week to week the smaller reserve seems like no further handicap.

How imortant is it to save 50lbs on a relatively heavy ferrari?

On a Lotus you can lose 30lbs easy on the exaust plus another 30 on the battery, bith from the heavy part of the car, then various other bits can easily take you down another 20lbs.

My lotus with hardtop in place lightweight battery, harness nar and some suspension and brake bits, otherwise stock scaled at 1920lbs with 1/2 a tank of gas. So anything that is going to loose another 20-30 lbs is significant.

On the boxer losing the stock exhaust probably took 40-50 lbs out, maybe more. Removing the spare and tools must be another 50-70 lbs. I lost another 10 or so from the flywheel.
Wheels and modern tires, cant say what the loss is maybe 20lbs. so lets say 120-130lbs total, without doing much.

Next I am going to an aluminum rad(my old one has sprung a leak again) which will be 50lbs lighter and have better cooling for further power changes. So if I can loose another 50 or so of battery weight the toatal loss will be somewhere around 200-220lbs. That is the weight of a really heavy passenger. 70% of the weight loss comes from points ahead of the front wheels or behind the rear wheels, plus unsprung weight. These things cumulatively start to have a big effect, and we are not talking changing any bodywork.

On a 3300- 3400lb car every 10 lbs must be worth 1 hp, plus benefits in braking and and handling.

Maybe 2 Shorai in paralell is the answer for a boxer, but that then is $700 in batteries. Fortunatly the boxer has close to zero current draw when parked, so no need for battery maintainers, but one short in the system(ask me how I know) and you are out $700.

Of course take the weight savings, add these to the killer 512M motor I bought last month, some upgraded shocks and springs with great pads and you have a truly killer classic, easily put back to stock and as fast or faster than a modern, certaily wayt too much go for the street, plus totaly engaing and charismatic..

If you loose 50llbs from a348 its equiv to how much power gain, plus handling and braking. Weight loss is the singes best way and easiest way to improve performance. Plus its a fun way to fiddle.

 

I agree, the best performance modification is to make the car as light as possible.
I have received my Antigravity battery yesterday and fabricated the new battery brackets last night. I hope to install everything in the car tonight and go for a test drive. I will be providing a writeup this weekend with some pictures….

 

yes, with explanation, when you say "correctly"

there is more to a battery than the voltage marked on the side, mismatched charging system and battery can lead to issues... especially with Li batteries than can cost in the $1,000-$2,000 or more... in the short term, any battery marked as "12v" will work, the news reports have shown the worst case of battery issues with fires... in most cases the issues are spending a lot for a battery, that is not used as intended, while delivering less than expected performance... it's only money :=)

 

So if I leave it without a specific for that type of battery trickle type charging system then left just disconnected from the car it will discharge and eventually fail?

 

IU know the discharge rate is significantkly lower thana lead acid, something like 4% per year, so irrelevant. Of course cars draw so if not disconnected then you need some type of trickle system. The Shorai can use any charger expept the type that sends bursts of power to de sulfate a lead caid, this is not good for a ltihium.

 

yes, as long as there are accessories that need to be powered up ( door locks, memories etc) power will be consumed until gone... you can use a std wet cell charger to keep you out of trouble... but long term there are differences in requirements which may prevent a full charge and get full potential out of the battery... ultimately they all will work without any changes...it is about getting value from a high tech battery... used ineffectively high tech batteries are a waste of resources...

 

The battery management system (ie, an electronic circuit with a controller) should be integrated in the battery. If not, run fast.

Every battery will do that, LiIo less than lead acid, for example.