In order to charge a 14.4V lithium-ion battery from a 12v source, they must have a DC-DC boost converter in this thing - which must have some sort of current rating.
No, "12V" is just a vague nominal term.
And each of the many lithium-type chemistries has its own voltage-per-cell profile, none of which come out to 14.4V.
But say it's LiFePO4 aka LFP @3.2Vpc nominal, usually around 13.2V per 4s pack. Mfg spec might allow 14.4V charging, but optimal for longevity is 13.8-13.9V.
And even if the vendor says "max charging current 20A" or something, if you can get direct access to the internal batt, bypassing any protective BMS or converter circuitry, you can usually safely recharge from flat to empty in one hour, long as you know what you're doing.
But the vendor will scream no you can't because this is litigious Amerika.
> As it claims to accept 12-30V, I would assume it has a charge controller built in, but what is the current rating? Kind of a key specification to know if you are planning on buying a solar panel to charge this thing
As I said, they obfuscate this stuff for marketing purposes. Obviously they want you to buy that specific solar panel.
The target market for these units is noobies with way too much money.
Avoid.
