I’ve been shopping around for an emergency jump starter to carry around in the car. I’ve found jump packs that are roughly a little larger than a cell phone, and produce 1000 amps or more. What is keeping them from being a main car battery?
In: Engineering
Because lead acid is good at dumping a whole bunch of current really quickly. It’s power density is very low and it hates to be discharged fully… But when it comes to hitting a starter motor with a massive surge of juice to get a stiff engine block moving, a lead acid battery is a pretty cheap way to do it.
What I’ve just described is essential what’s known as the “power” of a battery. It’s not a metric that’s often discussed, usually people are very wrapped up in energy density or cycle life, but for some applications it’s less important how much energy a battery can hold overall, and more important how quickly it can discharge that stored power.
Anyway, you could easily hold the volume of power a typical lead acid battery has in a much smaller space using a lithium battery, but that’s not really what you care about when it comes to starting your car. You care about getting a large amount of current to your starter for a few seconds at an affordable price. For all it’s faults, your standard car battery is just fine for this. Yes, you could spend way more to get a smaller battery under your hood… but why would you?
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