SAN997

About 8 months ago, I decided to upgrade the OEM Porsche lead acid starter battery to a Lithium ion battery. At first, I looked at the Porsche one available for the GT3, did the math, and realized that Porsche is charging roughly a 500% markup. This set about a quest to find a reasonably priced alternative. I looked a Braille, but their batteries are also over priced. I know this because it is no secret what standard lithium iron phosphate cells cost from the suppliers.

First, it is important to note that there are a lot of cheap Amazon/eBay lithium "power sports" batteries being sold that have no protection circuitry and, do not live up to their rated discharge/charge current and, apparently, are not actually the safer, non-explosive lithium iron phosphate LiFePO4 cells that are used for power tool and car batteries.

Fortunately, I found EarthX, which designs and manufactures batteries in Colorado, right here in the USA. Another selling point is that EarthX includes more charging/discharging protection circuitry than even Braille. It has built in cell balancing, over discharge protection and short circuit protection. Additionally, their website describes it as suitable for up to a V8 engine and 120 amp alternator.

I compared the specs carefully, and as far as I can tell, this battery is the same or better than the OEM GT3 one. My guess is that it is about 1.5x the capacity and probably has more protection circuitry than the Porsche one.

I also liked how the sales lady explained on the phone how the company was founded by an electrical engineer that just wanted to design and sell battery batteries. I get the feeling from the other companies, Braille included, that they are playing the typical battery scam game, where its all marketing with a huge markup, but inside the pretty case is an inferior product.

I've been using this battery for about 8 months without issue. It actually cranks the car faster than a lead acid battery. However, it is very important to keep it hooked up to a special lithium float charger when in the garage, since the usable capacity is about half that of a lead acid, and they don't like over discharge very much.

EarthX ETX48E LiFePO4 battery for 120 amp alternator
http://earthxbatteries.com/shop/etx48e

OptiMate Lithium Charger
http://earthxbatteries.com/shop/opti...harger-lifepo4

To mount the battery, you need to fabricate a bottom mounting plate to adapt to the OEM Porsche battery tray. I used a sheet of 3/8" PVC plastic whereby I traced a cutout for the battery and dropped it in the hole. I than drilled two large holes that allow me to bolt directly into the two OEM battery clamp mounting holes in the black battery track.

To hold the battery down, I used a very strong nylon strap cut from a ratchet assembly (used for roof rack tie downs) and bolted it to the PVC plate by tapping two holes in the plate. I used washers to secure the strap with the bolts, and carefully separated small holes in the strap, used a lighter to melt the nylon a little so it doesn't fray, and bolted it down. It holds quite securely and the whole setup is very light weight.

Additionally, you need to fabricate adapters/stand offs for attaching the OEM battery clamps to the battery. The battery comes with M6 threaded holes for + and - terminals. I used a 1.5"x1/8" aluminum plate to bring the terminals out. This accomplishes two things: (1) it gives you space to bolt in a pair of brass battery terminals. (2) it moves the terminals out. Otherwise the OEM battery cables are not long enough to reach into this tiny battery.

ADias

The battery plus the special Li-Ion maintainer makes for an $830 proposition just for those two items. Compare that to $150 for a direct lead acid replacement or $250 for a good AGM Optima redtop.

jdgamble

I can't imagine going through that much effort and cost for a battery, but props to you. Looks pretty neat. You obviously got the install right.

SAN997

Right, but the idea is to save weight that is high up in the vehicle. The dollars per pound savings for the battery is a far better payoff than any of the other ways to save weight. I won't mention the $150 I spent on titanium wheel bolts to save 1.5 pounds...

ADias

No argument there (7lb vs 50lb) and you did a great job!

Lvt19672

Nice job, when can you do mine?

SAN997

I can stamp "PORSCHE" on the top and do yours for $3500!

jhbrennan

Nice work!! Question - strap and tray look pretty secure - did you have to do anything special to determine if it's legal for club racing and time trials (SCCA-PCA-POC-NASA)?

SAN997

I don't know if is racing legal or not, but for any kind of racing use, I would upgrade to an aluminum enclosure that bolts directly to the battery tray. I think EarthX sells the enclosure part for which you could attach to an aluminum plate on the bottom.

I just made made it this way since it is light, simple and fairly strong. The battery doesn't weigh much, so it's not like you need a steel cage to hold it in.

Quadcammer

I'm assuming you are heavily tracking this vehicle to do such modifications?

fazeShift

Great info!

I always do this to my motorcycles because it saves 7-10+ lbs off a vehicle where every gram makes a difference!

Have you noticed it cracking more powerfully, too? That is always a nice side effect on bikes (starting faster / better).

Backmarker

Nice weight saving mod

You saved about 43 lbs for $900, or ~$20/lb saved. Nice work.

Compare that to a set of lightweight forged wheels, same 40lbs saved at 10lbs/corner, but $4,000 so ~$100/lb saved

Or a lightweight exhaust, saves 20 lbs for $4000, so $200/lb saved

Quadcammer

except the wheels are unsprung reciprocating weight.

yvesvidal

The improvement in performances is simply due to your wallet being lighter.... :-)

Yves

user 72902

OP you mentioned that you need to keep the battery on a charger when parked due to discharge concerns. What limitations do you have when parking on the road? How many days can you go before the battery will not start your car? Thanks