Re: Help Please: 12V battery and 24V panel
There are a number of voltages that are relevant.
A "12 volt panel" might have a maximum voltage of ~25 volts (Voc) (open circuit voltage) and a voltage around 17-18 (vmp) You need a voltage significantly above battery voltage to be able to charge a battery,, hence the 17-18 Vmp (Voltage @ maximum power)
So in fact I have never heard of a 18 volt panel (though they may exist), are probably looking at the 2 voltage numbers of the same panel.
A 24 volt panel will have numbers ~ double those above.
PS Welcome to the site,,, there are some very smart folks here. The real common sense is here,,, and perhaps home power magazine. Folks here have reinvented the wheel here so that others don't have to over and over again.
Please note, being a moderator does not add any weight to my opinions 300 watts Siemens/BP panels,plus a Sun 90,, making ~400. ~30 amps into Rogue MPT-3024, 450 ah of Trojan T-105, Morningstar ts300 inverter, a Tri-Metric meter.a collection of antique generators, plus 2 Honda eu-1000i's (also a BS2512 IX controller) and assorted other stuff!