Haven't ridden the bike all winter. Battery flat. WHat kind of charger do I need to buy ?

Batteries must be charged at no more than 10% of their rated ah rating. A 2A charger will be fine on a 19Ah battery.
I haven't been in a modern HD, I have a 1965 XLCH1000.

Remove the seat to access the battery.
A loose battery connection will prevent charging, Tighten if loose.
If tight, start the bike.
Use a multimeter set on d/c volts or just a volt meter.
Hook red to positive and black to negative.
should read 12.50 volts - 13.50 volts at idle.
Anything under 12.50 means not charging at idle.
Rev motor to 2000 rpm. the meter should read 13.50 - 14.8. If the volts do not change, then your bike is not charging, Anything Higher than 15.0 means that your bike is overcharging, which usully fries the battery and blows the headlight fuse and/or main fuse.

If over/undercharging, this means that the voltage regulator is bad.
Before you buy another one, make sure the one you have is plugged in all the way and that the connectors are clean.
I had a GSXR 750 that sat for a while and i had to clean every connector on the bike before it would run/operate like it should, so a dirty or loose connection should be checked first.
Saves you a lot of money too because voltage regulators are usually over $100.

If you do not ride for months at a time, your battery will discharge over time.
a battery tender or battery charger is needed to keep the battery charged when the bike is not in use. Motorcycle batteries are not like car batteries, that seem to last forever. 4-5 years is about all you'll get out of a motorcycle battery on a motorcycle that is ridden alot.
On a motorcycle that is barely ridden, won't last much more than 2 years if your lucky.
Hope this information was helpful
Best regards
Big Al

Battery not holding its charge if you rely on your bike for transport then just buy new battery as this will never get better just worse and more unreliable it will even not start after you have ridden only few minutes ago eventually
If you want cheap fix then hook up to battery charger few hours before you need to use it but this option would annoy me after first few times personally just get new battery ASAP

sounds like the battery doesn't have enough power.
Battery may be bad, or your charging system is bad.
If the bike was sitting for a while not being ridden (longer than 3 weeks) then the battery is probably dead.
go to a local powersports shop and ask them about a "trickle charger" this is what you plug the bike into when you park the bike for a long time like the winter. You can dfind a cheap charger for about $20. It has to be a trickle charger not a regular battery charger otherwise it could overcharge and the battery could explode or even catch fire. This will keep your battery from dieing everytime you park the bike for an extended period of time.

Battery is not good, does not have enough amperage, try connecting car battery with jumper cables or use battery charger with engine start if bike starts, buy new battery

Hi, Do you have an alarm & Immobiliser fitted on your bike as these drain the battery on your bike very quickly? If so i would recommend removing your battery and fully charging it with a decent amp-age charger. If you have your garage attached to your house then i would definitely recommend purchasing a trickle charger and when not using your bike keep this plugged into the mains and you should not have this problem again. all motorbike shops sell these chargers If after this the battery goes flat again i would suggest purchasing a new battery. This is a common fault as most motorbikes sit in the garage through the winter months and if not kept on charge will deteriorate. Hope this helps.

sounds like its the safty cut out switch on the stand to me as well, you should see it by looking under the bike by the stand,,,its just a push in switch,,,
as for leaving the bike over winter with out charging the battery up,,,well smack your legs! you will soon need a new battery for that!
il give you a tip here!!!! get yourself a cheap solar charger of say 2.5 watts hook that to the bikes battery and leave the charger in good light,(sun light is good) but good day light works as well, this will keep the battery fully charged up all winter and can double the life of the battery,,,cheap power?

any battery that has been completely flat can often get whats called sulphated plates if this happens the battery may never recharge and if it did take some charge it wont be much good after, the battery has had it realy the only this you could try is a very slow long charge but even this may not work,,,as a last dich try putting an asprin into each sell,,, yes thats right an asprin it dose work some times but for the life of me i dont know why, it just dose! as for whats the best battery,,,its all down to price at the end of the day, if its a cheapy type battery it wont last very long but il give you a good tip,,,,buy your self a 12 volt solar charger of say 2.5 watts a 1.5watt will just about do for a small battery,, when your going to lay the bike up the next time hook up the solar charger to the battery and forget it,,, the solar charger only needs daylight to work but sun light is better, and it will keep the battery toped up all winter i use them on my bikes (BMW 750cc 35amhr battery fitted) put on at the begining of winter took off in spring and they start first time every time,,,free power,,good huh!

when you charge the battery make sure that its cable is is loosen from the motor coz it can damage your charging system. on your case you have damage it already that's your light dims whenever you rev the rpm up. so change your voltage regulator of your charging system, charge the battery and it is done easy.

I have the same bike that you do. To get at the battery you need to remove both the seat (2 bolts, 1 screw (at back)), AND also remove the tool kit housing. The battery sits behind the tool kit, and so to slide it out you need to remove both halves (front and back) of the tool kit housing. You have to take the seat off in order to get at one of the screws holding one of the battery terminals in place.

When I do this, I find the hardest parts to be to get at the screw attached to the battery on the side of the bike opposite the tool kit; not such an easy fit. The other part I find hard for some reason is getting the tool pack to fit back into the tool kit housing once you reattach it to the bike.

I am seriously thinking about attaching a "pigtail connector" to the battery for easy charging during the winter. I understand that most trickle chargers come with this kind of accessory.