I have a 98 sportster 1200. 30k miles.
Last fall just before riding season ended my battery took a $#1t.
I debated replacing then or parking then and waiting for spring.
(Warranty only 6 months on those)
I decided to take a chance that I had some good riding days left last fall and replaced it then. I think I rode it one time after the battery replacement.
I put a tender on it around Christmas time and left it on. Only rated at 3/4 of an amp.
I did start it up and warm it up a couple of times over the winter no problem.
I have ridden it to work once this year (70 mile round trip) about 2 weeks ago.
I didn't put the tender back on. I've let this bike sit a couple months without a tender connected many times and when ready it fired right up without issue those times.
I went to start it last night and Stone dead.

I jumped it (my bench top charger wasn't enough boost, has to get the big snap on wheeled battery charger out)
And it took a good while even on hi boost to do more than click click click. I finally got it going. I let it run about 10 minutes (battery charger disconnected as soon as it started) and my headlight was pulsing, which it has never done before. It finally stayed on solid for a few minutes then it and the tail light just died. Dash lights brake and turn still work.
I put a multimeter on it after the lights died and got 13.89v while running so it is charging.
Shut it off and battery had 10v.
Took battery out and without being hooked up to the bike it was at 6.some volts. I put it on the bench top charger, and it's an "automatic" charger. Shortly the red 'frown" lit up indicating a bad battery. Reset it and left it on all night. Went out this morning the red frown was on again on the charger, and battery was at 4.some volts.
I took it back to interstate and the guy was gonna "loan" me a battery and charge mine, told me to come back Monday. He put it on his charger while we were there and about 10 minutes later decided to swap it out with a new one. (He initially said he can't warranty it, it's just run down. When I asked him what difference his charger might make when it had been on mine all night already) it seemed to go over his head but he finally gave me a brand new one.
I'm about to go put this latest new battery in and see what it does.
I'm worried I screwed something up running it with that bad battery and fried something related to the lights. I don't see any fuses on this bike. What do you guys think? I've never seen the lights flicker nor have I ever seen them "not" work anytime the key was on.

I've heard motorcycle electrical systems are more delicate than automobiles, and there is a chance you could've hurt it if you used a normal car charger on high boost to get it to start. I've definitely been told to never jump a bike from a running car or anything that can produce automobile charging system levels of amperage.

Your battery for sure failed, and you may have lucked out and the taillight just died from the voltage spikes. The flickering can definitely happen because of your battery.

If voltage was rock steady at 13.9 with it idling, I think your stator and regulator are ok and it's just the battery that needs to be replaced.

I go through batteries every two years no matter how much I spend on one. I did have my charging system crap out and replaced, but batteries are pretty much junk anymore. I gave up trickle charging them, I just budget for a new battery every two years, sometimes get three out of them but it isn't worth the worry...

First question is your new battery an AGM battery? If not then you're doomed for failure again. Normal lead/acid "flooded" batteries can only last in a sub-two G (vibration) environment. Most motorcycles are subject to that and as high as 4-5 G's during most riding. AGM batteries can withstand up to and a little over 6 G's of vibration. Use a battery charger that is for an AGM battery and one that has a "desulfating" mode and charges at 2-amps. A battery "tender" mode is built into some AGM battery chargers or the usual battery tender will work just fine. I was just in an Autozone store and saw a rack with nothing but AGM motorcycle batteries so the battery industry (and motorcycle manufacturers) know the benefits of absorbent glass matt batteries and motorcycle application.

Mike

Rhino,
is this on your daily drivers or cars that sit? I started just disconnecting the batteries when parking for extended periods and have gotten 7-10 years out of them. That may no longer be true though as I have heard the Battery MFr's (mistype 🙄) have been cutting costs by decreasing the internal pates etc.

I was specifically talking about my 91 Softail Custom Harley-Davidson I have owned since new. I have tried every imaginable battery made for these bikes, lead acid, AGM, and whatever new technology that has come out since I bought it and still have to get a new one every couple of years. Like I said before, no matter what I do or use that is the fact, they just do not last...

Yeah the battery I took out was an AGM, my son bought when he first got this bike, which was inherited from an uncle that died of cancer, said uncle had owned since 2003. My son then rode it 2 years, but can't no more because car seats for a 2 yo and an 8 month old, don't fit on a bike. So with gas at $5/ gallon last year and my 70 mile a day commute now I have it
My son had put on a battery that came from a federated auto parts store lasted about 3-1/2 years, "almost" 4 riding seasons
The first one I put in was bought 10/4/22 and lasted 1 ride last fall,2 starts/warm-ups over the winter and 1 ride 2 weeks ago. Went to start it last night and it was stone dead. I did have it on a battery tender all winter, but didn't plug it back in 2 weeks ago after that 1 ride. I just got another just like it from the Interstate place this morning, guy put a tester on it and claimed 500-amd-aome CCA. Both the one I bought in October and the one I put in this morning are both AGM. I know I haven't had the luck out of interstate batteries in my cars/trucks nor do we at work, but they were the only place of many I called last fall that had one for that bike in stock. So I bought what I could get

I was amazed when my battery took a charge last month and the bike fired up! I charged it and it is holding for now, going on a long ride today, supposed to be 85 here...

Try "east penn battery", made in the USA. not sure if they have bike batteries. The "intimadator" for your diesel pickup trucks is a great battery.

Jim what brand battery?

I will have to look, went on a 50 mile ride today with the wife and no issues. Will check it out tomorrow and let you know...

Thought you said you were going on a long ride (85 degrees). Lol