Project Suzuki Cappuccino Autocross Lineup

Project Cappuccino: DIY Lithium Battery Installation

One of the easiest, simplest upgrades an owner of any sportscar can make is to upgrade the battery from a fat, heavy lead acid battery, to a light and compact lithium battery.  For owners looking to shed every ounce, a lithium battery is the ultimate in lightweight and powerful technology.  

Companies are now offering bolt in kits for popular platforms.  MotoIQ’s own Project RX-7 Restomod, Project EVO IX, and Project GT3 RS all use off the shelf kits to easily install a lightweight lithium battery.  No such kit exists for the Cappuccino.  This would require us to design and fabricate our own, just like the owner of a certain Hayabusa powered Miata.  We have seen lots of DIY battery installations and it’s amazing some of these cars haven’t burned to the ground!  Zip ties, bailing wire, duct tape, and bungee cords are not acceptable battery straps.  Self tapping screws are not acceptable for battery terminals.  Insufficient mounting can lead to electrical fires when the battery breaks loose and shorts to the chassis.  Poor connections will lead to electrical issues, poor running, and dead batteries.  Properly sizing and installing a lightweight battery isn’t hard if you do a bit of planning.

Suzuki Cappuccino OEM Battery
We started our search for a battery by measuring what the Cappuccino came with. Our car had a Panasonic 40B19R, an OEM replacement battery for the Cappuccino. This battery has 270 CCA and 28Ah of capacity. We decided to pick a battery that has similar specs. Undersizing a battery will kill it quickly and leave you stranded at inopportune times. It is secured with a stamped steel strap secured by an M6 bolt on the firewall and a J-hook that attaches to the battery tray.
Suzuki Cappuccino Battery Location
Now we need to figure out where the new battery is going. For our Cappuccino, the best option is the factory location. Logistics wise, this means we don’t need to make new battery cables and we only need to fabricate a basic tie down strap. Performance wise, there is little benefit to moving the battery out of the engine bay. The firewall mounting location (red box) is already between the axles keeping polar moment of inertia low. There may be a small performance benefit to moving the battery into the passenger compartment: not only would the weight be even more centrally located but it could be lower as well. The downside is we would either lose some passenger space (already at a premium) or be forced to use a much smaller battery to fit under the passenger seat. This would also require longer battery cables and this would start to add weight back to the car. For a primarily street driven car, the extra fabrication, cost, and effort just aren’t worth the miniscule performance benefits.
Cappuccino Battery Tray Location
Next, we need to figure out how to mount the battery to the car. Ideally we would bolt the battery straight to the body, but Suzuki runs a brake line under the battery tray so using the stock tray is the quickest and easiest solution. Knowing we will use the stock tray determines the maximum footprint of the battery.
Shorai LFX21L6-BS12 Battery Vs OEM Battery
With electrical requirements and maximum size determined, we settled on a Shorai LFX21L6-BS12 battery for the Cappuccino. This battery is around a third the size of the OEM battery while producing more cold cranking amps (315 vs 270) though slightly less capacity (21 Ah vs 28Ah). Matching or exceeding the capacity would require moving to a much larger Shorai battery. This battery is meant to replace the battery in a Harley XR1200, so this should be plenty of power for our 660cc engine. We went with Shorai as their lithium lead construction is less volatile than a lithium-ion battery. These batteries are also around half the price of a lithium-ion battery. The disadvantage is a slight weight penalty, due to lower power density, compared to a full lithium-ion battery.
Related Topics
6 comments

  1. Nice! I’ve had a Shorai in my CBR600rr for like a decade. OEM batteries died after 2-3 years each. The Shorai, even a decade old, cranks up super strong even after sitting for two months. I’ve never had to put a tender on it like I did the factory batteries and those still died after a couple years.

    Reply

  2. Was the vice mounted metal bender you used fabricated or purchased? If purchased, may I ask where you got it? Thank you. Nice work on the Cappo. It’s probably my favorite build series on here.

    Reply

    1. They’re called manual rod (or flat) benders. The one in the article specifically is a Huth manual rod bender. They run about $100.

      Reply

    2. What Augustus said below is accurate. It’s a handy tool for bending rod or small flat stock.

      And thank you for the kind words, I love this little car and it’s currently getting some winter updates to the interior and cooling system.

      Reply

Leave a Reply

Your email address will not be published. Required fields are marked *