A few muddled comments above. I have three battery tenders/minders, which are all many years old and have never killed a battery. All are quietly working as I write, despite them being in a freezing cold garage. A trickle charger is NOT a tender and is only suitable for short-term use, whereas tenders can be used on a long-term basis, as all mine are. Starting a bike engine at regular intervals during storage is not wise!

Before condemning your tender, follow Zanthamos's advice above at post #3. We can't move on until we check and diagnose the condition of your battery. Once that is restored or replaced, then we can check your tender to see if that seems OK.

 

[QUOTE=jbarr1;18000369][/QUOTE



Now that was an naive answer I did not expect from an experienced rider. Your engine is designed to efficiently handle a lot more heat than is going to be generated by idling from a cold start for 20 minutes two or three times a month.

How long do you normally let your bike warm up before riding off after it has been sitting in the cold for a few days? Is idling 15-20 minutes uncommon for you at any time? It is ridiculous to be concerned to let your bike idle 15-20 minutes a couple of times a month, about the time it takes to cold crank and recharge cycle your battery. Tenders are fine and all that, but the best way is the way it is designed. I regularly ride in Houston rush hour traffic in the summer when the road surface temp is over 100 and traffic snarls you cannot get out of can tie you up at 5 mph for a lot longer than 20 minutes. We get hot and I get concerned, but me and my Harley have made it out alive so far with no harm done. And, how about those big bike meets like Sturgis or Lone Star or Daytona where the parade is 5 mph for miles...

Tenders are not meant to charge batteries, just maintain a charged state temporarily. That does NOT guarantee that your cold battery can deliver the current to crank the cold bike and take a good hard rush recharge cycle from the system. They will, however, cause you issues if you believe they are all the upkeep you need on your battery for 4 months...

cheers!

 

I do not live where the temperature gets below freezing often so maybe there are issues with that kind of cold that keeps you from cranking your bike on cold days but this just doesn't make sense. We have forum members who ride in this weather all the time, are you suggesting that they are damaging their engines every time they crank it in the freezing cold? Exactly how is starting your cold engine and letting it idle at regular intervals during winter storage is bad for the engine or electrical system...It is just not logical from the standpoint of how engines operate.

A tender or minder or trickle charger or whatever you want to call these maintainers, will not charge a battery but it will give you false confidence in your battery's charge state and will damage it over the long term if the battery is not deep cycled occasionally. That is the OP's question, and that is my experienced and learned opinion.

Peace, out

 

A 'trickle charger' is a very particular, old fashioned device, namely a low output charger which provides a constant electrical charge at a 'trickle'. It does not monitor the condition of the battery while connected and should not be left connected for any great length of time. In no way is it a suitable alternative to a modern 'intelligent' tender, which does monitor battery condition and can safely be attached for months on end. I've been using them for many years.

 

 

i have had both scenarios happen to me, a tender killed a battery and a battery killed a tender. most of the modern battery tender style charges will not or stop charging the battery if the unit doesn't sense at least 3 volts in the battery. In the OP's case it seems like it could have gone either way, like the battery failed and the charger killed it's-self trying to re-charge/maintain it or the charger committed suicide and took the battery with it. Seen both happen.
Modern AGM batteries should NOT be deep cycled, as it WILL cause damage and shorten battery life. That being said and confirmed by more than one manufacturer, exercising the battery periodically IS a good idea. Not to the point of what is actually a deep cycle event, but cranking up a bike 2-3 times to get it started doesn't qualify for that. Also most bikes will not recover the energy used in a cranking event when run at idle for just 15-2o minutes. They need to be run faster than idle speed or you can actually discharge the batttery even MORE.
I don't have any issue with starting a bike and running it for a bit during times of storage, i actually like the idea of distributing some oil through the engine to help keep things lubed up, but if you are going to just start it and let it idle, over the long term you do more harm than good. Start it up and run it for a bit, then put your tender back on and go about life till it's time to really ride again.
m

 

Not saying Tenders have not ruined batteries or visa versa but the new tenders have a few features to help prevent this from happening.
The Battery Tender brand has a safety feature in it's program. Read step 2 about the "current time limit". Other steps have time limits as well. YMMV
http://cdn2.hubspot.net/hubfs/215471...=1472056163665

 

I would agree with Jbarr1. Get one of those IR heat guns and put it on the cylinder head after that period of time an see what you get.. Personally you won't find me parading a bike.. Don't want burned up stator, seals/O rings or motor. 15 minutes at idle is not enough to burn moisture off the oil but enough to heat the head above ideal operating temps. Shut the motor down and the crankcase will air enter from the outside.. Hope that air is real dry.

As far as exercising an AGM, they like it, pulling current out and shoving it back in. It's best to keep the total discharge to less than 10% of the AH rating for life.

Also most tender are smart chargers, the have bulk, absorb and float modes. The 2 big weaknesses are that bulk is limited to lower amperage and they won't charge a dead battery. IIRC they need to sense a voltage to put out current.

I don't use a tender on my bike but then I get to ride them year round and if ridden, it's almost always more then 20 miles. Typically 50-200. The batteries don;t get low.

Tenders can dry out an AGM battery if they malfunction. If they die, so can the battery.