I have a trailer battery (Marine starting ? maintenance free) that sits in my basement all winter. What’s the best thing to do to gain the most life out of this battery? Should I leave a trickle charger on the battery 24/7, or should I just charge it every now and then when I think of it? OR is there something else that would be best for a battery like this one that sits for months at a time? Over the past couple years it has sat for 11 months straight without use.
Thanks in advance for any advice on this…Bob
Trikle charge is about the best you can do. If you put a charge on it whenever you remember, it could loose it’s charge completely and that is usually the end of that one.
Store the battery in a cold place and top off the charge every 60 days.
I would recommend an automatic type trickle charger - the kind that turns on and off automatically as needed. There used to be a model by Schumacher for about $25 . There are some other switching type models that will do the same thing but also charge a full sized battery. But make sure it is the type that will turn back on as needed instead of just turning off.
Store that battery on wood, not on the concrete. Don’t charge it at all during the winter if the temperature stays above forty. It won’t need it. If you keep charging unused batteries once a month, they could explode. Every six months could be helpful if you don’t put it in use.
Batteries don’t mind concrete at all, They LOVE being stored at 10 degrees, and charging them will not make them explode…
It is important to remember that there are different types of batteries and the rules that apply to some don’t apply to all. Car batteries are not the same as cell phone batteries, laptop computer batteries, and other similar batteries. Letting your cell phone batteries drain completely every once in a while is good form them. However, letting a car or marine battery drain completely is harmful and will often lead to failure and replacement.
I have heard that storing a battery on wood is better than concrete, but I don’t think it has anything to do with the charge. I think it has to do with the fact that older batteries would sometimes leak acid and the wood could prevent the concrete from being exposed to the acid. In that case, the wood might be a good idea, but probably not necessary.
The exploding automotive battery phenomenon depends on the charger. A normal automotive battery charger could make a battery explode if left on too long, but most of the newer ones are smart. They can tell when the battery is charged and can shift automatically to a trickle charger. As long as your battery charger has this feature, there is very little chance of the battery exploding.
The type of battery you’re talking about is a deep cycle marine battery. Unlike with an automotive starting battery, these type of batteries are designed to be completely discharged and recharged many times. So, I would just store it at whatever state of charge it’s in, and recharge it when it’s time to put it back into service.
Putting a battery on concrete isn’t an issue anymore. It used to be that way when the battery casing were made from hard rubber. But now that they’re made from plastics, batteries don’t discharge when placed on concrete.
Tester
The best way to go on any conventional wet cell battery (cranking or deep cycle) is to keep it somewhere that gets some ventilation (because it generates explosive hydrogen gas) that stays above freezing (in case something happens and it doesn’t get the charge it needs). Then get yourself something called a “float charger”. These are NOT the same as trickle chargers. Float chargers monitor the battery’s voltage and connect themselves automatically when charging is needed. Most importantly, they DISconnect themselves internally when the voltage is that of a full charge. As mentioned elsewhere in this thread, you can buy one for about $25. To maximize the life of your battery, any automotive battery, deep discharge it as INfrequently as possible. As a battery ages, its quiescent voltage naturally declines, as does its total capacity. But deep discharging it accelerates this condition. Deep cycle batteries are constructed in such a way that they’re less susceptible to this, but it still affects them. Letting it discharge fully in your basement (unused batteries discharge without any external loads on them over extended periods) is not the right thing to do. By the way, the temperature at which a battery will freeze is a function of its state of charge. A completely dead one freezes at the same temperature that ordinary water does.
Folks THANKS! Lots of great information here, and things I hadn’t considered. I will look into one of those “float” chargers and put it to use.
With all this information it brings me to ask one more question of this knowledgeable group. Can I hook up a lawn tractor battery ?and? the deep cell battery on the same float charger, or is that not a good thing to do? They are both 12 volt but obviously of different physical size, rating, age, etc.
Thanks again ? great feedback???..Bob
You want to use separate battery “tenders” for each battery, they only cast about $30 each.
BUT, be careful what trickle charger you get. Some of them claim to trickle charge but actually deliver a constant charge without monitoring the state of the battery. These can damage the battery and in worst case scenarios cause the battery acid to leak out and eat through whatever the battery’s sitting on. Yes I have personal experience with that. Yes countertops are expensive. Yes significant others get very angry when this happens 
The OP states it is a marine STARTING battery not a deep cycle. Big difference in usage and charging requirements. Most smart chargers have a switch to differentiate between the two. Neither likes to remain in anything but a fully charged state. They both will sulfate if left partially charged.
The trouble with smart chargers is that there is more to go wrong with them. I prefer to monitor the state of charge with a hydrometer and charge them when they need it. This requires some knowledge of battery basics, presence of mind and discipline that the general public is not up to. An timer to shut off the charger after some hours is a good thing to since my presence of mind seems to be deteriorating.
The cheapest thing to do is connect the battery to your car with jumper cables for a few minutes while the engine is running. Do this once a month or so and the battery will be fine.