My TGA scooter instructions say to leave it on charge when not in use.
So does mine, and I think most do. My experiments with lead acid using a energy meter and smart charger showed a lead acid can take 3 weeks to fully charge once allowed to sulphate, the narrow boat people with continually cruising have a problem in that 6 hours cruising a day is not long enough to recharge the domestic batteries fully, and they go down bit by bit over the month, so they try to find some where to plug in once a month to fully recharge batteries or their life is seriously shortened. And even after 24 hours the batteries are still not full using a hydrometer to test, often takes 48 hours.
The longer the lead acid battery is left discharged the longer it takes to charge up again, so start a car and then use alternator and it charges quickly, but use a scooter and then leave it in the car over a weeks holiday, and not only has it discharged more fully than the car battery, but it has been left discharged for longer, so charge time is dictated by the battery, and how it has been used. But look at a 10 amp CTek MXS charger and looking at £135 they are not cheap,
this one 10A 24V costs £145 so for cheaper items like as I said my hedge cutter to sell at around £50 for the lot, they used a very cheap and nasty charger with instructions only charge for 16 hours. Lidi did a 3.5 amp smart charger at around £14 think Aldi also did one, similar to the CTek but much cheaper, even had a volt meter built in, so clearly if sold in enough numbers cheap chargers can be made which can be left on 24/7 365 days a year, but most scooters use two batteries and are 24 volt not 12 volt, so getting a cheap off the shelve 24 volt smart charger is more of a challenge. However quick internet hunt and
this one at £30 does not say if a smart charger, larger output models have the AH listed so would expect to find they are simply stage chargers not what we consider as a smart charger.
The stage charger has been around for years, milk floats, fork lifts etc have used them, but early models tended to boil the battery a little to ensure the battery was fully charged in 8 hours, and so batteries needed topping up. Latter versions used on narrow boats a lot, have just two stages in real terms but are called 3 stage.
1) Charges as max output, 2) charges at 14.4 or 14.8 volt to 12 volt battery, in real terms this is one stage depending if glass mat sealed or able to top up it charged to 14.4 or 14.8 volt until the current drops to a set amount.
3) When the current drops to set amount normally around 1/20th of AH ratting so with boat batteries normally around 3.5 amp, then the voltage is reduced to 13.4 volt.
There are two problems with this, one with boats the lights can draw over 3.5 amp so mooring up at canal side pub for night, the charger can fail to drop to float charge voltage, the second problem is 13.4 volt does not charge very much, cars use 13.8 volt as a compromise, so can take a few days to put last 10% of charge into the battery.
The pulse charge uses the voltage decay of the battery when taken off charge to work out state of charge, so two 70 amp alternators on the boat are kidded into charging flat out by reducing voltage to under 13.8 volt and the power from both is fed into a charger unit, that supplies a float charge of 13.8 to engine starting battery, and pulse charge to domestic batteries, this means draw from the domestic batteries does not cause over charging, and the three 160 Ah domestic batteries can be charged at full 140 amp after engine first started. The same method often used with solar chargers, it also means the voltage at the solar panel can match what is required to get max output from panel, but voltage to battery is still at 13.8/14.8 volt RMS again very complex chargers.
I would say a mobility scooter not using a stage or smart charger of some type is unusual and points to a very cheap and nasty product. But electric vehicles be it a push bike, scooter or wheel chair are expensive, reasonable electric assisted push bike around £1500, cheap ones start at around £500 and one with mid engine around £2000. Mobility scooters use cheaper batteries, so can be slightly less costly, and wheel chairs are low production quantity so expensive as a result unlikely to find one under £2000. The major problem with mobility scooters is very low resale value, one costing £2000 at 5 year old changes hands for £70, with new batteries around £60 each, and most need a pair, so second hand you can buy one with new batteries for £250 so there has been a move to produce new cheap enough to sell at a price where some one will buy new rather than second hand.
However my mother not light in error drove hers off a curb in error and it did not have any problems with the smaller lighter models however then tend to either turn over or break, not so much of a problem at 4 mph with some one who does not really need one, but with an amputee a much bigger problem.