Is there a 12v volt source in the frunk?

[cvollers]

DC to DC converters produce an AC ripple that can be dampened by a battery.
Also, the DC converter would have to be on all the time which means it would increase the standby loss. Meaning your battery would drain faster just sitting there.
Having a buffer battery let's you store power so you can turn off everything so standby loses are much lower.
On the side of safety, if the converter died while on the road you would instantly loose all the 12v systems where with a battery you would have some warning.
Could you make a converter system work? Probably, but like you said, it would be more expensive and complex.

Super helpful explanation…thanks!

 

[Paul Rodgers]

Hey ditch the 12v lead for an LiFe, same size, same weight, same current capacity, 4x the watt-hours, and right now only about 4x the cost, needs a different charge-controller tho.

By time Slate ship it'll only be 2x the cost

 

[GreatLakes]

Hey ditch the 12v lead for an LiFe, same size, same weight, same current capacity, 4x the watt-hours, and right now only about 4x the cost, needs a different charge-controller tho.

By time Slate ship it'll only be 2x the cost

Might be a little more complicated than that. The LiFe car batteries I've seen have required heaters for cold weather. (usually built-in to the sides of the battery) They need to warm up before the battery can be charged, and possibly before the battery can be used. So maybe you are waiting ten minutes before your car is ready?

For old-style vehicles with alternators, the charging voltage needs to be changed. And the BMS needs to know not to disconnect the LiFe battery without accounting for the alternator blowing out if the load just disappears. Those issues could probably be dealt with in an EV.

 

[sodamo]

Might be a little more complicated than that. The LiFe car batteries I've seen have required heaters for cold weather. (usually built-in to the sides of the battery) They need to warm up before the battery can be charged, and possibly before the battery can be used. So maybe you are waiting ten minutes before your car is ready?

For old-style vehicles with alternators, the charging voltage needs to be changed. And the BMS needs to know not to disconnect the LiFe battery without accounting for the alternator blowing out if the load just disappears. Those issues could probably be dealt with in an EV.

And no need to add any cost or complication unless benefit it overwhelmingly positive and compelling.