I have about 5 tenders. They're almost always in use. If anything sits for more than a couple weeks, it's getting one on it.
Another note: Check your batteries to see if they have caps. When I went for new batteries yesterday, I took 4 with me to get them tested. One was a large deep-cycle that I use (with an inverter) for emergency electric power. I thought it was sealed as there was no visible caps. He told me to read the sticker on the top. It says to remove the sticker and fill the cells now and then. DOH! Took it home, removed the stickers, opened the caps. They were way low. Added about 1/2 gallon of distilled water then put it on a 10-amp charge.
Another note: Check your batteries to see if they have caps. When I went for new batteries yesterday, I took 4 with me to get them tested. One was a large deep-cycle that I use (with an inverter) for emergency electric power. I thought it was sealed as there was no visible caps. He told me to read the sticker on the top. It says to remove the sticker and fill the cells now and then. DOH! Took it home, removed the stickers, opened the caps. They were way low. Added about 1/2 gallon of distilled water then put it on a 10-amp charge.