Is your trolling battery sitting in the corner of your garage? Whoa. There are a number of things that need to happen in the off season to keep it in top condition. Since I messed up a battery last year, I checked a few sites to get the right info on what to do.
There are a number of sources - the Battery Council is one, but I found the information posted on exide.com to be the most helpful. Another super reference is Marine-Electronics.net.
Here are the top questions I had and the answers from Exide and Marine Electronics:
Proper Storage: Store in a cool, dry place and check the charge every 45 days. Add water if needed. Obviously, keep the battery someplace where your kids or pets cannot get at it. Be aware that, even though you are not using the battery, it will discharge between 1% and 15% each month it sits in the corner. If you let your battery get below 80% charged, you are basically hosed and need to follow special procedures to get it back up to snuff.
Maintenance: Check the water level every 30 days.
Charging: You can overcharge a marine deep cycle battery. You should either disconnect your charger when the battery is fully charged or use a charger that is fully automatic. A fully automatic charger will sense the charging level of the battery and turn itself off when the battery is fully charged. Exide discusses all the horrible things that will happen from a technical perspective if you overcharge - you should read about them there.
Here's the step by step from Exide:
"What is the best way to charge my deep cycle battery?
1. The electrical capacity of the battery charger determines how long it will take to charge your battery. In most applications, a 10-25 amp charger is recommended. First, determine the battery's state of charge using a hydrometer, voltmeter or state-of-charge indicator.
2. Check electrolyte level before charging. Add distilled or good quality drinking water if the electrolyte level is below top of the plates.
3. Follow the instructions provided with the charger. There are many chargers on the market, each with their own features.
4. Be sure the battery is completely recharged. Use a hydrometer to determine the percent of charge, following the manufacturer's instructions.
5. Recharge within 24 hours after each use. Discharged batteries can freeze.
6. Do not overcharge your battery. Overcharging causes grid corrosion and reduces battery life. A charger with a timer switch is best.
7. Do not use a fast boost charger. A slow charge is best for a deep cycle battery.
8. Unhook the charger when the battery is fully charged"
Marine Electronics makes the key points:
- Recharge only in a well ventilated area
- Wear eye protection
- Do not smoke or cause sparks or flame anywhere near the battery
Bottom line: Go look at your battery now and make sure it is OK and that you pay attention to it during the off season.