Looks the same as mine, which is fine on my current AGM batteries. It might be worth checking it with a multimeter, when connected to your battery, to see if it is giving a high charge.

 

It, the optimate charger, may charge but is there a float mode on the unit that will monitor the charge instead of quite possibly a continuous 12v charge. I'd check with the manuf. and ask them the question if their charger stay on a AGM battery and not damage it. Remind them of the age of your unit and if possible the model number. The deltran units are quite economically priced and very trustworthy.

 

I think your battery tender is good for any lead acid type battery. It's those lithium batteries that use something different. But as Sir Graham mentioned, check to see if that Optimate is working right.
Looks like the OPs tender says MAINTAIN for the float mode.

 

Measure your output voltage of the tender with a multimeter. Tenders can and do go bad after years of use.
Then check your battery also with the multimeter without the engine running and with it running.
Those are the only ways I know to find out if the battery is bad or the charging system is malfunctioning or if the tender is AFU, unless you take the battery to an auto parts store.

 

Well I put volt meter on bike, 12.6 with bike off and 14.3 at rpm. Doesn't seem to be overcharging. I picked up a new charger/tender today just to be safe, but I'm thinking I had a defective battery.

 

Could be the charger, have a buddy that his charger was actually discharging his batteries, thought he had bad battery, dealer charged it and sent him home said it was good, he never put the tender on a meter, just bought a new one and all was good.

 

Im sure you got a bad battery, with that said I am sure battery tenders/chargers destroy way more batteries then they preserve.

I dont see the reason for them, never used one on any vehicle including my boats. Batteries HATE heat and love cold/cool/room temp storage. Batteries are made to store energy, not have a constant never ending supply of electricity being sent to its plates keeping them warm to hot.

 

I know some GEL batteries do not do well with some battery chargers.
Check the numbers on the battery and the charger (been there done that, back when red tops were fairly new on the market).

 

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I have been wrenching classic cars & bikes & dealt with a lot of batteries for 4.5+ decades and found what alarmdog stated holds a lot of merit being right on the money IMHO.

Thru the yrs since maint chargers with float mode have been around i have seen 1st hand more then just a few batteries toasted resulting in significantly reduced srv'c life when a maint/float charger that was designed to charge the battery it was on 24/7 or often on classic cars & bikes i wrench/maintain for other people. (After that experience they then realize why i had rec they not leave a maint charger on their batteries 24/7 or often.)

Thats why even though i have a maint charger with float mode i never leave it on the battery in my bike or classic car more then a few hrs after it brought the battery to full charge lvl & then dropped back to the lower float mode charge rate and rec to other people they do the same too.

And like already stated just as long as you ride the bike every so often (1x every 1.5-2wks) long enough to decently re-charge the battery there should be no need to leave a maint charger on 24/7.

I have always obtained considerably longer then avg srv'c life out of the batteries in my bike & cars going this route with battery maint.

But for guys with much newer bikes that have quite a lot of draw on battery when bike is off/sitting still may find they need to put a maint charger on the bike more often like 1x wkly esp if the battery is 2+ yrs old & used in a hotter climate.

Again,i rec removing a manit/float charger soon after battery is fully charged & charger has gone to float mode to avoid any chance of possibly overcharging the battery over enough time if the maint charger is left on the battery 24/7 or often.

BTW,for past few yrs i was quietly keeping track of premature battery failures on another motorcycle site i belong to along with a classic car site too and guess what,i found approx 8 of every 10 premature battery failures i investigated questioning the owner online that responded said they had in fact used a manit/float charger either 24/7 or often on their battery that failed prematurely in 1yr , 1.5yrs & or 2yrs or so when the same battery & mfg has been lasting 4.5-5yrs on avg with some getting 6.5-7+yrs srv'c life for others in same try cond & vehicles not using a maint charger a 24/7 or often.

Thats what backed up what i had already experienced in the past 4.5 decades wrenching cars & bikes that in some cases maint/float chargers can & do in fact lead to premature battery failure even though mfg's of float chargers claim that can't happen when it can & does happen in some cases.

Happy motoring!

Scott

 

Sounds like you're thinking of a trickle charger. Today's tenders use circuitry to watch the battery condition and only charge when needed. I can say that I have had batteries last for 7 plus years when using a battery tender on a regular basis. All modern vehicles draw a small amount of juice and will run a battery flat if left connected. I currently have 5 battery tender Jr. I spend a lot less on batteries nowadays.