This is about sealed lead acid batteries. For lithium batteries see our blog on lithium batteries.
When it comes to SLA (Sealed Lead Acid) batteries there is more than one quality of battery. Some are actually designed for general purpose things like an alarm panel or an electric gate or a computer back up system. They have a very similar part number that designates something like 12 volts 20 Amp Hours. A true scooter battery will say the same thing, but is designed to last longer under much heavier load.
For example if you put those general purpose 12 volt 20 Amp Hour batteries in a scooter, it would likely run out of juice after about 10 kilometres. Conversely if you put the actual scooter batteries marked 12 volt 20 Amp Hour in the same scooter, it would go more like 50 kilometres before it ran out of juice.
So how do you tell them apart? Generally speaking the scooter batteries will have the words deep cycle on them, and the term AGM (Absorbed Glass Mat) as opposed to just the words sealed rechargable battery. The cost difference between the two is around $60 for the general purpose ones, and $110 for the actual scooter batteries.
Also the general purpose ones have about a 100 cycle life span. That means you can discharge and recharge them about 100 times and then their life is over. The true deep cycle ones have about a 400 cycle life span. So while the genuine ones cost more, they are superior in the long run, and will actually provide your scooter the power it needs to get and keep going.
Now to the charging of the batteries. It is best for the batteries to recharge them when they are about half way drained down. While the scooter manufacturer will give the maximum range possible, they don't mention this is very hard on your batteries. As a rule of thumb, it it says it gets 70k on a single charge, going 35k and then recharging them would be much healthier for the batteries.
In fact if you do drain them down 90/95%, it is likely your charger won't even recognise the batteries and simply show charged right away, or just blink, when they are clearly not charged. You can try to take the batteries out and charge them one at a time on a 12 volt charger to restore them, but this doesn't always work. So to be safe, follow the 50% drained down rule best you can.
Another thing about charging is you should always plug the charger into the scooter first, then the outlet. This makes any spark that occurs happen at the wall end, and not on your scooter charging port which can damage it, or the charger.
Keep in mind your scooter and batteries are just like a car and gas, the faster you go on your scooter, the faster you will wear out your batteries. The more you deeply discharge them, the more likely you are to hurt them. This is why most scooter batteries only carry a 3 month warranty. Some people will drain them right down twice a day, every day of the week, and drive as fast as possible everywhere they go. That can kill the batteries in as little as 3 months.
A weekend user doing moderate speeds and charging appropriately can get years out of them.
To get the most life out of your scooter batteries, buy the right ones, recharge them appropriately, and use moderate speeds.