Hi-my battery box has room for a second battery--any problem with just adding another, same size battery? Dont know how old the current battery is but it still seems strong.

thanks
dennis

You'd be better off to add two, new, identical batteries. Yes, you want them both to be the same size, but you also want them to have identical electrical characteristics, such as the Amp hour rating.

If you pair a new battery to an older battery, you risk damage to the new battery if the old one fails, which it probably will do fairly soon.

Make sure your new batteries are deep cycle.

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew

thanks for the info