I use a float charger every nite on both scoots. Thus, I have a fresh battery every morning, no matter how little I ride.
The only time I had an issue was with a certain brand of headlight modulator on my SYM. I pulled it out of the garage after having ridden that day (no battery tender) and it would not turn over. Hooked up a battery booster for about 10 seconds and fired right up.
I replaced that battery the next day, and the modulator unit with a different brand. No more problems, and the old battery is actually good. I think the modlator drew it down.
I also replace every possible bulb with LED. That gives back 21watts just for the brake light. you can pick up as much as another 20 for the position lights. And if you convert your turn signals to LED, WOW. When I plug in my tender, it goes red as soon as I activate a turn signal on the S200 - they seem to draw a lot of juice.
Here is another trick:
Energizer sells a portable battery (about the size of a pack of cigarettes) that puts out 5V USB, 12V, and 20 V.
The 12V output is 2800 Mah.
So I have one of those Peak cigar lighter - cigar lighter charger plugs, three of those batterys, and a power cord I rigged up for 12V.
I can report that ONE of those batts with start a scoot with a mildly discharged battery in just a few minutes.
Remember, the standard battery is around 7-9 amps, this thing puts out 2.8 amps. so it can work pretty good as a charger. It is good insurance against a dead battery on the road!
And you can buy a new battery for your scoot at Wal-Mart for around $55 - that is for a Taiwan, NOT a China battery.
so the first time mine fails, I just install a new one.