> This is not achievable since the efficiency will need to be over 100%.
> 
> Max input power: 34V x 7A = 238W
> Max output power: 48V x 5A = 240W

Although the sun is shining a lot more of the time than the cart will be
in use (probably)

I'm no expert with SMPS so can't help with an actual circuit for your
numbers but many of the ICs I looked at (MC34063, LM25xx and
others) for a project had app notes for external switching elements
(bipolars and FETs) for high-current outputs. A basic circuit for the
LM2576 can deliver 3A without additional parts, so it's not a huge
leap to 5A

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