They’re very water resistant, but they aren’t built to be submerged. Millertech Sport Series batteries are built with marine usage in mind. Yes, they are waterproof but not submersible or to be used in a direct spray of water for an extended period of time.

The batteries are very water resistant, with an estimated IP67 rating. This means they can handle rain, spray, and short-term exposure to water, like when washing a boat, but they are not fully waterproof. As long as they aren’t submerged or continuously sprayed for long periods, they should be fine.

Yes.

Yes. A solar panel can stay connected to keep your Millertech battery topped off while your RV is parked. Set your solar charge controller to its lithium setting, or use a user-programmable setting set up for lithium. Turn off or disconnect everything else, so detectors and other small loads can't slowly drain the battery. Not sure how to set your controller? Call our Support Team at 855-MAX-LITH.

Yes. Millertech batteries perform “extremely well in cold conditions during discharge.” Sport Series batteries are rated to run from -4°F to 140°F. The limit is charging in the cold, not fishing in it (see question 25). Greg Hackney ran his while breaking ice: “nothing but raw power, the same as if it was 90° every day.”

Almost none: there’s no watering. Three habits prevent most problems:
• Keep the battery out of standing water.
• Use a lithium charger.
• Keep connections tight: ring terminals, torqued to 10 ft-lb.

To winterize:
• Charge the battery fully.
• Disconnect every load and cable.
• Store it with nothing attached.
LiFePO4 loses only about 1–3% of its charge per month, so it holds charge well over the off-season. Millertech’s “How to Winterize Your Boat’s Millertech Batteries” video walks through it.
How to Winterize Your Boat's MillerTech Batteries

Keep the battery plugged into the charger whenever it’s not in use. For long-term storage (1 month or more), fully charge the battery, remove all loads, and store it with nothing connected. Following these steps will help maximize the lifespan of your lithium deep cycle battery.

For long-term storage, fully charge the battery, remove all loads or connections, and store it with nothing attached. This preparation helps maximize the battery’s lifespan during extended storage periods, such as over the winter.

Something is always on. Propane and carbon monoxide detectors, stereo memory and control boards draw a little power around the clock, and over weeks that adds up. Before storage, charge the battery fully, then flip the battery disconnect or remove the cables. A Millertech lithium battery loses only about 1% to 3% of its charge per month on its own, so once it’s disconnected it’ll be ready in spring.

Sport Series batteries are rated to operate up to 140°F. The built-in BMS also protects against internal over-temperature.