Interersting, but that is not the post I dreamed of. Post was on this forum, advice was not to leave your boat plugged in. My Xantrex 2000 SW calls it float, but it puts out 3/4 amp or so into a 600+ A/H battery bank, whick accoridig to that thread is a "trickle", not a "float".
I would ignore that thread. There is lot's of misinformation in there. Good float chargers also do not always "shut off". Most simply maintain a voltage and the current flows as the bank accepts it. At times the current may be as low as 0.2A or so to maintain the voltage. Batteries don't naturally rest at 13.4V + so you need some current flowing to maintain 13.4V+. Some may pulse it some may apply it as the battery accepts it.
There is much misinformation out there around float charging 24/7 so it is hard to discern what is really true. The charger manufacturers say it's ok and with a good one this is mostly true. Real world experience tells me another story though as there are many factors involved.. I often see shorter life from banks left 24/7 on chargers than I do from banks "topped up" and then disconnected. Banks on solar that only see a few hours per day of "topping up" seem to do very well.
In the winter our batts are left on-board the boat. Cold weather benefits and can extend the life of lead acid batteries. It dramatically slows self discharge and can also slow the sulfation process way down. The batteries must be topped up to prevent freezing and if they are they can be good for 8 weeks plus in-between charges if the winter temps stay cold.
Last winter I charged them to full in early November and did not put a charge on them again until early April. The batteries were still at a resting open circuit voltage of 12.68 volts. Full on this bank is about 12.73V. If they had been in my basement I would have needed to top them up every three to four weeks due to the much higher temps.
I am not a big fan of 24/7 charging UNLESS you have loads that need that support like a fridge or you have some phantom loads that can't be shut off like a propane sniffer, stereo memory, ACR or Echo charger, electric bilge switch etc. etc. and this draw amounts to 0.2A or more.. For a fridge I might consider a dedicated power supply to avoid the constant charging of the batteries.
There are also vast quality differences in chargers so you need to be careful who's "float charger" you're using.. Good float chargers should always have battery temp sensors as increases in battery temp affect what the voltage needs to be. I have one customer with a flag blue hull. His bank sits behind the settee and the compartment gets VERY hot. I have measured it at over 105F at 8:30 am once the sun has hit the hull. Keeping his float charger at the same voltage when the banks get hot can easily lead to over charging despite the rather low "float voltage".. He gets about two years from his bank, likely due to this heat..
