Last year we introduced you to our newest project car, called simply "Project Boxster Clubsport". In that first installment we found the right car, we purchased it for a song, and it was sitting politely in our garage waiting for its first modifications. So far, the Boxster has been happy to simply rack up the miles and keep things rocking along. It's an excellent Porsche, and we aim to make it just a little bit more excellent with each improvement.
Part 7 - Our Porsche is looking a little better, sure, but the main goal of this project is to get some weight out of the car and make it more of a "clubsport". The biggest weight loss I've found so far has been in the battery. Let's start there!
Investigating Lithium Ferrous lightweight batteries.
I have known for years that batteries are heavy, and batteries in Porsches especially heavy. Just for the heck of it, one day i thought I'd throw the battery, which was in the car when I bought it, on a scale. It turned out to be heavy. Very heavy, in fact.
Okay, so we've got a very heavy lead-acid style battery that is sitting very high on the cowl in the front of my Boxster. This is a problem. A lighter battery would not only decrease overall weight, but it would also remove some high-mounted weight to help lower the center of gravity. This can only be a good thing.
So how light can we get a battery that will still crank a car? I've heard of a number of people, especially in race cars and small bore sports cars using various traditional lawnmower batteries to get their batteries down to about 9 pounds. While impressive, I was aiming for something a little better. I started looking at motorcycle batteries, where the technology has started to transfer into lightweight high-power lithium ferrous batteries. I'd even seen a few people installing Lithium Poly batteries from a few RC plane applications, and even electric wheel chairs. So that was considered, as well.
Why Lithium Ferrous over Lithium Poly?
The first thing to consider is safety. Light weight is nice, but if a battery has potential to cause a fire, or explode, that doesn't sound like a good trade for me. Lithium Poly (known as LiPo) has a history of causing small scale explosions and fires in the RC community. Those batteries are often charged and stored in buckets of sand in order to minimize the danger of a house fire. This kind of battery has come a long way, apparently, from when they were introduced, and the danger is much lower now than it was in the past. Even still, that's not something I'm willing to risk.
Lithium Ferrous (known as LiFePO4) is slightly heavier, but is a much more stable chemistry. This type of battery charges more evenly across the cells, can stand up to heat and pressure, and can even still operate after having been shot with a bullet. Many of those things would greatly increase the ease with which a LiPo battery will explode, but the LiFePO4 batteries are diligently tested for safety. I'll sacrifice a pound or two in exchange for the ability to run my car hot without being scared of burning down my apartment complex.
There are a few other brands out there making these batteries, including Shorai. In general, these fitments are for performance motorcycles and ATVs, where weight really matters. Deltran launched this series of Lithium Ferrous batteries just over a year ago, and they are by far the least expensive options on the market. Even though I couldn't find much information about the battery, I decided to order one anyway just to be the guinea pig. The battery was available on Amazon.com for a song, so I bit the bullet and ordered it up. Being that I would likely be using the battery only in the summer, I opted for the smallest one they make, sacrificing cold crank amperage in exchange for weight savings. This one only weighed 2 pounds, thus saving a full 38 pounds from the front of my car. I got for just over one hundred dollars.
I was pretty happy with the outcome, as the Porsche is now a good bit lighter on the front. It's not exactly easy to tell the difference when 38 pounds is gone from the front of the car, especially when the car is almost 3000 pounds, but it certainly made a difference, and compounded with all of our other weight saving applications, should add up.
So what did I need to do to install this?
Really not that much, honestly. The battery, being a universal fit motorcycle battery, didn't have traditional car battery posts. I ended up purchasing a set of regular lead battery posts, drilling a hole down through the center of them, and using a nut and bolt to hold the post terminal to the motorcycle terminal.
After figuring out the posts, I needed to find a way to keep the battery in place while driving briskly. Obviously this battery wouldn't fit down in the standard battery tray of the Boxster, so I had to get creative. Rather than building a heavy cage for the battery that would negate some of the weight savings, I purchased a set of military grade 3M velcro strips and used that to affix the battery to the bottom of the tray. Being that it's lightweight, there's no amount of lateral G-force that can get that battery to move at all. It was a pretty slick solution, if you ask me. [You might consider strapping it down from the top as well for an added safety margin]
What are the downsides of a battery this small?
Well, a battery like this has very little reserve. If you leave your Porsche to sit for too long, say 3 or 4 days, there is a chance that the battery will not have enough charge to start the car. Also, if you leave your headlights on, or an interior light, or are digging around in the trunk for too long (say 40 minutes or so), then you'll have a flat battery. Lastly due to its limited cold cranking power, it's not great for cold mornings, or cold evenings, or winter for that matter. I can daily drive on this battery, and if you have a garage spot and a trickle charger, it's not too bad, really. Sacrifices need to be made, but it's not really awful.
Why would you make this move?
Well, if I'm honest, I would probably recommend, if you're going to do this, that you buy a bigger version of this battery, perhaps even the biggest one they offer, that weighs 3.75 pounds. They sell almost a dozen different sizes and amperages of this battery style, and there is probably a bigger one that is better suited to car use. It's not a bad battery to have, especially if you're only going to use it in the summer, or you're using it in a race car to save weight. There are a lot of scenarios where this battery absolutely rules, but there are instances where you really wouldn't want it. A Cayenne, for instance, would be a terrible application for this battery. It would be great for pretty much any back-road sportsman, or autocross/road race specific Porsche (or non-Porsche, I suppose).
Lightweight Battery Swap Costs
- $120 (Amazon.com)
- $6 (Amazon.com)
Military Grade 3M Velcro - $7 (Home Depot)
Total - $133
Lightweight Battery Swap Weight Loss Total - 38 pounds