Can I plug my battery tender into the heater plug
 

Will it work

Why wouldn't it? Make sure polarity is correct!

whats a heater plug? would polarity even matter if its AC?

I have a YUASA battery tender. The connector is un-marked as to polarity. Last night I hooked it up to charge a Gel Cell battery on my workbench. The first try, I had polarity reversed. I just touched the lead briefly... and noticed the charge LED lit RED (instead of the normal green) to alert me that I had to reverse the polarity of the lead extensions. I swapped them, and it started charging the battery. :-)

If your battery tender is as smart as my YUASA unit - it should tell you if polarity is incorrect.

Red usually means its charging or that it needs charging and green means its done.

I know charge is DC, but I simply do not know what a heater plug is...

Acualy I'm not sure what the plug is for that sticks out beside the seat. I assumed it was for a heated vest or something

o ok, now i got a much better idea about what ur saying... yea keep polarity correct and ur good, assuming the funky thing is hooked up right n such, i know my bike doesn't have a plug hanging off stock lol.

The thing that sticks out under the seat is for a battery tender. Lucky you someone pre-wired the bike for ya.

So all 09's don't have that? :o
I got the bike with 200kms without a scratch on it in what I thought was completely stock form.
It works with my heated vest also but that kills the battery.

Mine unit has 3 LEDs. Red for power, yellow for charging, and green for charged / float charging. It was the last LED (charged/green) that lit red when I had the polarity reversed. When I swapped the wires, the yellow (middle) charging LED came on. When I got home, the green (charged) LED was on. :-)

I waffled between the Battery Tender and the YUASA unit. The YUASA was higher current, and cheaper, and came with ring connectors and alligator clips. I've since bought a second one...

Might have missed it, but I didn't see it mentioned whether the "plug" was wired "hot"...that is directly to the battery. I'd guess that if the plug was on a switched circuit to the key/ignition unit, then it wouldn't charge. As long as the plug is connected hot to the battery and the polarity is wired properly, it should charge.

Brings up a good point....anyone know how many amps our little bikes put out and how much power is available for accessories?

See, I'm not such a lazy git!
 

from another thread:

For the 2009:

16 A-14 V @5 000 r/min (rpm)

For the older KLXs:

14.5 A/14 V @7000 r/min (rpm)

Do the math on the lights and CDI power draw, and you'll find out how much you have left for accessories. I would imagine not much extra watts left since the stators were only designed for what they needed to power to make the bike as light as possible. There's probably not much margin built in. But hey, put a penny in the fuse clip and anything is possible!

Or better yet, if you know all this, put a clamp on ammeter to the positive terminal of the battery with the bike running at 7k RPM with the bright lights on, a turn signal, and the break light illuminated. That will give you a good guesstimate.

Cheers,

Anthony

The 09s did not come stock with this plug you speak of. Somebody added it. I would not use it until I verified where it goes and besides, when you buy a battery tender it will come with a new one.

Don't assume it was installed properly. Take off the sidecover and check it.