As long as you don't plan on pulling hundreds of amps, the best way to get 12 volts out of a lithium-ion battery made with 18650 cells is to use a 7S configuration and a buck converter.
How to convert 60V to 12V?
You're better off with a buck converter that will take the 60V and convert it down to 12V. I am using an MPPT (connected to solar array) for charging purposes and the battery has a BMS system attached to it. I needed the 12V for controlling relays and ither small instruments.
At 2500 Watts, the 12 Volt inverter would need over 200 Amps from the 12 volt converter. At 2500 Watts, the 12 Volt inverter would need over 200 Amps from the 12 volt converter. That would need some very fat cable. .When you're dead, you don't know it, the pain is only felt by others. The same thing happens when you're stupid.
Can You charge a 24 volt battery with a 12 volt charger?
These exposed connections (also called 'Bridges') you can very effectively charge a 24 or 48 volt battery with 6 volt or 12 volt chargers simply by connecting to the appropriate number of cells. This is a fairly common battery used in race cars, it is 16 volts at the end terminals.
DC seeks it's OWN current source. *IF* you need 12 volts from ANY battery in a 24, 36 or 48 volt Series string, you simply attach your positive & negative cables to a single 12 volt battery and draw 12 volts from it.
Is there a 12 volt tap?
While the entire battery gets an 18 volt charge, there is a 12 volt 'Tap' for sensitive electronics. Some racing ignition systems and electronic fuel injection systems won't tolerate 16 volts, so a 12 volt Tap is provided for that sensitive equipment. Just throwing this out there for the guys that don't know about this...
When connected (negative) at the 12 volt terminal, and (positive) at the 16 volt terminal, it's a closed DC circuit, and with a 4 volt charger you would only reach the last two cells in the battery. It's a Gel Cell, lead/acid, so just charging the battery as a 16 volt battery charges all cells.