Battery plates start to calcify after 6 months in a discharged state. There is no reversal for calsification. My spelling is horrendous I know.
A smart tender is the way to go. Not just a tender.

My sons 06 softail however still has the same battery in it and he could give a crap less about tendering it. It still fires up! Go figure.

 

My 2007 Road King was built in9/06 still same battery use tender in winter.

 

I ran a tender on my Deuce for 10 years, occasionally during riding season but constantly during winter storage. During the 10 year period I replaced 1 battery and NEVER had a starting problem. My tender is the el-cheapo $30 Harley model I bought with a sporty in 2002. Still using it on my new RK.

Your unit (battery tender ) might well be defective!

 

i had the same problem tender killed the battery i just ride it a few miles in the winter to charge it about once a month.

 

Right on dannyZ71! I have used the BATTERY MINDER PLUS - not the Harley version or the Battery Tender - for 6 years. Original battery and still going strong. A "smart" charger is the answer.

 

Many bikes and old cars on tenders for many years. I've used both Battery Tender and Yusa brands with never a problem. Good luck resolving the problem.

 

I bought two of these a couple of years ago and couldn't be happier with them.



http://batterytender.com/motorcycle/...t-1-25a-1.html

 

+1 on that. I never tender my battery unless it is removed for the winter.

 

BatteryMINDer Charger/Maintainer/Desulfator is the way to go for me.

 

If your tender is a deltran float tender something is wrong with it. Usually they have a light that flashes while charging and you get a solid green when it's at idle.
You can leave them plugged in forever and it shouldn't ruin a battery.

If yours is showing green but cooking batteries something is wrong. I'd probably just buy a new one as they're 30 bucks give or take.

I use them year round and my batteries last for years.