[LadyDraco]

You both have been very lucky ....

My buddy has killed/blew up a few batteries that way..
He now makes sure that the battery is full before he puts a tender on it...

There are a few kinds of tenders ~ trickle chargers~ floaters...

I use one that will charge the battery up first then it will maintain it...

If you read the pamphlet on them some will say make sure the battery is fully charged first....