[Elecraft] Car-Starter battery packs

[Charlie T, K3ICH]

I'm seeing a lot of good deals on these Lithium battery, emergency "car
starter" packs.

They're typically rates from 12000 to 24000 mA-hr, or, as we're inclined to
call them 18 to 24 Amp-Hr.
Prices vary from about $40 up over $80.

They come in a nice durable case with a charger and output cables.

At first glance, they'd seem ideal for a field pack for portable radio
operation.
They certainly can't be limited in their current capability, considering
what it takes to start even a small car's engine.
But then, their ratings may be extremely optimistic.

Anybody gat any thoughts on these?

73, Charlie k3ICH