For our 12V batteries, set the bulk and absorption stage between 14.2V and 14.6V, and never above 14.6V. Lithium doesn’t need a float stage, but a float of 13.5V to 13.8V is fine when you’re plugged into power. With several batteries in parallel, let absorption run at least 20 minutes per battery so they balance.

A standard Sport Series battery won’t take a charge below freezing. Built-in low-temperature charging protection stops it, which protects the cells. Store and charge it above freezing, or bring it inside the night before. If you charge on the boat in the cold, choose a heated model. Millertech offers several options that are heated.

Yes. Make sure your solar charge controller is compatible with lithium.

Yes, the batteries can be charged using solar panels. Please make sure your charge controller is compatible with lithium.

No, when you have three 12V batteries in series, they must be charged individually with a 12V charger. Attempting to charge the entire 44.1V series configuration with a single 44.1V charger is not recommended. Each battery needs to be charged separately.

It may work, but it could overcharge the battery or not have sufficient voltage to fully charge it. Before you hook it up, call Millertech at 855-MAX-LITH. A real person will tell you whether your charger fits your new batteries. We promise to never try selling you something you don’t need. Our goal is simple: you get exactly what you need and nothing you don’t. When you’re happy, we’re happy.

No, the lithium deep cycle battery has built-in overcharge protection, and the MillerTech chargers also have a cut-off voltage to prevent overcharging. Even if the charger continues charging for any reason, the battery has its own protection mechanisms. These safeguards ensure overcharging should not be an issue.

Yes, use a lithium-compatible charger. Lead-acid and AGM chargers may charge a lithium battery, but they usually stop short of a full charge. The wrong charger is the most likely way to cause a problem.

Plug in the battery charger that comes in the box. Need a second charger for the cabin or the truck? The 12.6V 3A AC Charger (Item #1123) and the 12.6V 2A AC Charger (Item #Z3085) are sold separately.

Yes, we recommend charging the battery right away when you receive it. Due to shipping restrictions, batteries are not shipped fully charged, so an initial charge is necessary.

During your active season, yes. Keep the battery on the charger whenever you’re not using it. The BMS and the charger’s own cut-off together mean it can’t be overcharged. For storage of a month or more, follow the instructions on this video:
How to Winterize Your Boat's MillerTech Batteries

A dual-bank charger charges your 12V starting or house battery and your 24V or 36V trolling motor battery at the same time, from one plug. If you run one cranking battery plus one trolling motor battery, it’s the simplest setup. Millertech offers:

• Dual-bank: 12V/24V and 12V/36V
• Three-bank: for boats that add an electronics battery
• Four-bank: 12V, waterproof, mounts on the boat