When it comes to replacement batteries for the Polaris ACE, most riders will tell you to get the biggest sealed battery that can fit. A particularly popular ACE battery is the Duracell UTV battery from Batteries Plus. It is taller than the stock battery and the posts are opposite as well. It might take a little maneuvering to get it snug, but it works great. AGM batteries also work great as well. With an AGM battery, your machine can sit all winter in seriously cold temps and fire up in the spring first try no problem. You can even put a 2013 Ranger battery in the 2014 and other years of the Polaris ACE. It is larger than the stock battery, so you have to move some cables do run the positive wires on the opposite side, but you don't have to buy anything extra. It is a 220 CCA (cold cranking amps) capable of producing an output of 30ah (battery amp hours).
Upgraded your ACE battery but still experiencing issues? If your rig is showing signs of an excessive draw when riding, battery drainage when the machine is off, or voltage regulator malfunctions, there are a few things you can do. If your regulator has gone out, you should see signs such as meltage on the plug that goes into the stator. If you see that the plug is melted, then there is likely a lot of resistance in the wiring -- a bad connection will do that. Start by checking all connections and the stator output as well. Good practice suggests starting at the ground connection on the frame as well as the positive connection -- both of which are located down on the frame by the battery. If the plug connection is bad, it will create heat and cause meltage. Some people add wire to the leads on the battery side and place the unit right inside the cab on the back panel to give it airflow and prevent mud build up. This makes sense as there is plenty of room. You should also rinse the mud off the regulator after every ride for a preventative measure.
If your ACE battery is dying after a few days of inactivity, you can run a parasitic draw test and you will find your draw. Anything over .024 draw will run the battery dead in short order. Any aftermarket switch can make a draw also when the switch is off. The alternator and/or regulator could be the culprit, as too could be a bad cell in the battery; sealed batteries are the best, and dry cell even better. Whatever battery you go with, however, it is highly advised to run a battery shut off and a trickle charger to extend the life and prevent failure in the battery as well as other electrically powered Polaris ACE accessories.