Duracell Marine Deep Cycle Battery, Group Size 31

Bought battery for trolling motor, seemed to work fine. Hard to tell how much actual capacity, but used trolling motor for 5-6 hours.

I'm on year three with these batteries while running a part of my home electrical system. It is charged by 800 watts of solar panels. I chose these lead acid batteries for specific reasons: 1.) price; 2.) this was the first solar system that I designed, so I expected to have a learning curve; 3.) and, availability. First, let's be realistic; these are lead-acid batteries.If we were to design a lead/zinc battery that could mach the storage and cycles of lithium (or others), the cost would be astronomical. As it is, I calculated that the same storage capacity in lithium would cost five times or more as much as lead. All batteries have a life expectancy, and they all can meet a quick demise through human error. So we have a trade-off. The one-year warranty is a clue. However, the company must account for the people that strait-up ruin batteries. Most manufacturing defects should be found well before a year. And, I've used dozens of these batteries in other applications (cars, trucks, and tractors) and always get four year plus, but they do require maintenance. I have an applied science degree in controls technology. Before you build, design your system. My requirement was a system capable of running a flat screen with DVC (4 hours per day), a laptop (4 hours per day), one small refrigerator, and a microwave oven on high for 10 minutes a day. I got the appliance specs from the labels (the average refrigerator from google). The second specification was that the batteries could run the system for 48 hours from full charge down to no less than 70% with no sun. The last detail was that the maximum instantaneous draw would not exceed the 205 minute rating for the Duracell 31DCX. To match this, I then needed 31DCXs. With lead acid, battery maintenance is critical: Design your system to draw no more than 25 amps (300 Watts) per battery. Build in enough reserve. I have drawn mine below 90 percent no more than three times. A secondary problem is that lead-acid batteries a prone to sulfiding when left uncharged. Reference the following: % charge voltage 100 (full) 12.7 90 12.5 80 12.4 70 12.3 60 12.2 these can run a bit different in practice, mostly due to temperature. Again, many (most?) voltage controllers account for temperature. Some inverters shut down somewhere between 50 and 70 percent. It is best to put all batteries on line at the same time. Fully charge all batteries before hooking them up. Allow them to sit on slow charge for at least a day. Never hook up directly to a solar panel. Panels will put out way too much voltage. Use a voltage controller that has a flooded battery setting and a float setting. Note that these batteries are already filled, contrary to what some may state.Do not fill these to the top. assure the plates are covered. If you need to add to a new battery, do not use water. Use battery acid solution. Use distilled water to refill. With a controller, it is unlikely that you will need to fill often (I have never needed to add to mine). Have a de-sulfiding or battery conditioning charger on hand. Some charge controllers have this function built in. As I rarely run my system down below 90%, I can get by running a de-sulfiding protocol every 2 to 3 months. If you don't, your batteries will first begin charging and discharging quickly lowed by them not taking a full charge. They will appear dead. That being said, lithium batteries are worth considering. You still need to match them to your system. If you mess up, you've lost more money. However, they can also be more forgiving. For example, for the above system I would not run my refrigerator and microwave at the same time because it would be beyond my specifications, potentially reducing the life of the batter. Lithium is more resilient. I calculate that the cost of lead-acid starts to break even with lithium (and others) between 4 and 5 years. The lead option requires a lot more attention, but mine is a hobby.