Evo Lightweight Battery

Finally got around to installing a lightweight battery for the Evo. Reached out to the good folks at Shorai to pick up one of their amazing lightweight batteries & chargers:


There is a wide range of small battery options available for the Evo – what’s impressive about the Shorai is it’s weight – a scant five pounds (!) while providing 540CCA – more than enough to start an Evo. That is roughly 10lbs lighter than it’s “usual” competitor – the Odyssey PC680. The PC680 only provides 170CCA, and it’s capacity is smaller than the Shorai as well. This is due to better technology in the Shorai – I believe it is Lithium Iron.

Now that I’ve owned both I can happily say the Shorai is much more impressive. Anecdotally, I know someone who daily drives his Evo 8 with the Shorai, as well as autocrosses the car frequently, with zero issues. The alternator that comes on the Evo 8/9 is well suited to small batteries, and the Shorai is no exception here. I should note here that in general, any small battery/non OEM spec batttery is not advised for these cars. That said:

A fairly straightforward swap – I removed the battery I was using, an Optima Yellowtop:

I purchased the Yellowtop because I went for long periods of time without driving the car. When it came down to it though, I drove the car so infrequently that I ended up always having the car on a trickle charger anyway. I figured if I’m always on a trickle charger, may well be time to lose the weight of a full sized battery and go with a lightweight one. The position of the battery is also a great spot to lose weight off the car. Weights below:

vs the Shorai:

Battery for battery, this is a 33lb difference on the top front of the car, directly in front of the driver. This should tip the Evo’s weight under 3,200lbs, right around 3,170 – pretty darn good for an MR.

This will give or take slightly with the hardware used. I used the “Z” shaped brackets to raise where I mounted the battery posts – XS Power 580 short brass post adapters – originally, I tried without these, but it could not fit the Evo’s battery adapters:

With that, I used some cheap battery tie hooks to keep the battery in place, along with some of the padding that the battery came with stuck to the stock battery tray. I purchased an STM battery tie plate, as it was one of the only tie down plates skinny enough to leave me room with the battery. It was still a bit of a squeeze to get everything to fit, mainly due to the brake master cylinder brace I am using. I also had to move the negative terminal ground from it’s original place to where the ECU case is bolted down, right by it.

Very, very happy with the fit!

I took the car for a quick spin after the install. The car started right up, with zero issues or abnormalities. The car runs perfectly with this battery. As mentioned, I know someone who dailies & races with this battery with zero issue as well. As long as you understand small batteries, I absolutely recommend this battery, as well as it’s charger.

The charger fits in to the flap in front of the battery and charges the Shorai. As it was explained to me, this is a much better method of charging this battery – other chargers, and trickle chargers, work like water filling an ice tray – with excess charge spilling over to the other cells. The Shorai charger charges the battery in a balanced method. Given how frequently my car is going to be sitting, I felt it was appropriate to use this over a standard trickle.

A big thanks to Shorai & I look forward to future product developments!


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