I was writing a reply yesterday but didn't finish it- I was going to say, for the first iteration of the product you could consider using classic lead-acid ins

I was writing a reply yesterday but didn't finish it- I was going to say, for the first iteration of the product you could consider using classic lead-acid instead of LiPo. It's cheap, so it would help keep you price-competitive. It's absolutely proven as an automotive battery chemistry. The difference vs. a classic battery would be, your smart circuitry to shut off the battery, and the cap stage would allow for a tiny battery even on big engines. Your LiPo model already sacrifices capacity, and the only other reason for a big battery is CCA, which the caps solve. Thus you could put an itty-bitty 10Ah lead-acid in an F-550. Bigger & heavier than a 10Ah LiPo? Sure, but still way smaller and lighter than modern F-550 batteries. You could then move to LiPo for later versions as you get the truly novel parts of the product dialed in and costs starts to come down.