For the last year I have been using a Battery Tender to maintain my batteries on our boat. I leave it on indefinitely when the boat is stored. Usually it works great. Everything charged, no problems. Lately (last two times I've pick up our boat) I have noticed when I pick up the boat the volts are a little low. I don't know if I just so happen to be picking up the boat when the tender is on its "decharging" mode or if my charger is kaput! I'm thinking about an onboard charger.
What's the deal with onboard chargers?
Do they only "charge" your batteries when in use?
What about in the winter when the boat is stored, do they save some amps to get you going?
Can you hook them up like my "tender" during the winter time to maintain the juice?
Anyone use them?
Thanks in advance.