thanks, very helpful information, I think I should replace it with one new battery.LAXpilot, The answer is No to both. I do not have the same ball machine and the charger is not 1.5A. But I have access to a secret tool called "Google" - but don't tell anyone!
SportsTutor, the manufacturer of your ball machine, sells replacement chargers through their web site. The same chargers are available through third parties, like Do It Tennis, at the same price. They sell two chargers, the standard one for $55 which is 12 V, 0.8 A, and Fast/Smart one for $95, which is 12 V, 3 Amps. The fast one charges faster
Sports Tutor manufactures and sells practice machines for Tennis, Baseball, Softball, Volleyball, Soccer and Pickleball. Accessories and Upgrades.sportstutor.com
You have an SLA (sealed Lead Acid) battery. These batteries generally prefer charging current equal or less than a quarter of their capacity. SLA batteries are standard for ball machine, I do not believe any of them use Li-ion. If your battery is around 9 Ah as some third party sources suggest [12 V, 9 Ah, F2 connectors], the optimum charging current would be about 2.25 Amps. Lower current is not worse but charges slower. Higher might be bad for the battery. Smart chargers drop the charging voltage when battery is almost charged to prevent overcharge at the end of the charging cycle. This can extend the life span of the battery. The 12 V written on the charger refers to the nominal voltage of the battery. SLA batteries are not too picky about charging conditions. You can use almost any charger designed for lead acid batteries, including the 1.5 Amps one, except those which run at a much higher than the current recommended for your battery based on its capacity. OEM charger has the advantage that it comes with the correct connector and is therefore a plug and play solution. And they are not too expensive in OEM version, either.
If you machine is around 10 years old, you probably need a new battery as well. They do not last 10 years, typically. You will be lucky to get 5 years from such battery. Same as with car batteries.
P.S. Just be aware that SLA charger is not the same thing as a power supply for electronics. A power supply for, e.g., external hard disk or something along these lines, may be rated at 12 Volts and will be supplying exactly 12 volts. Lead-Acid battery charger rated at 12 Volts will actually be supplying over 14 Volts, and fully charged battery will have the voltage over 13 volts on its terminals. A power source which delivers exactly 12 volts will never charge your SLA battery to more than half or so. This is a little confusing, but this is how it works. They cannot be used interchangeably.
Batteryspec actually sends adapters for F1 to F2 or vice versa. They are the professionals of sla batteries. Just check out their aftermarket chargers and prices for those too. The charger will save you $100 compared to someone like Lobster.Regarding where to buy a replacement battery, my experience has been that before ordering from a third party site, one should better have a very clear understanding of parameters of the battery which is being replaced: capacity, dimensions, and type of terminals (connectors). I checked out betteryspec, a great resource indeed, but opening the page with replacement for batteries for my Volley, they offer batteries with two terminal (connector) types. They are not interchangeable and only one type of the two would fit into the battery housing. I cannot come with a reason why they offer both types of connectors, other than they have no clue. It is fairly typical across many sites on the web. They want to promote batteries for every imaginable application, but lack information which battery is a perfect fit.