When new, initial charge is 8-9 hours. Thereafter 1 1/2 hours.
With a charger specifically designed to charge this battery.
I have learned that when i get new batteries for my hobby cars you want to fully charge the battery to the recommended hrs, you want to charge the battery fully because it will improve how long your battery will last on one charge and how long the battery's life will be.
How long does it take for an 18v battery to charge
I assume you mean how long to charge the battery. You should never let the alternator charge a dead battery if possible. The alternator is designed to keep the battery charged but not to charge a dead battery. You put a strain on the alternator and it can cause a diode to burn out. Drive home and then put a battery charger on the battery to fully charge it.
2 hours
Indefinitely.
Depends on the condition of the battery. Most will hold a charge for at least 6 months if they are not connected to anything.
As long as both batteries are the same voltage, you can jump start with the battery. If you want to charge the battery then use a battery charger.
How long should I leave a battery on charge
A long low charge is best for the battery. A fast high charge can lead to battery damage/explosion. Purchase a small battery charger and follow directions.
it takes about 18 hours to charge.(1.2x(Mah of battery)/300
The firs time the FitBit is charged it can take up to 4 hours to charge the battery completely.