POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS content (soft water) is fine for batteries; some is terrible. The best bet is to check with a local battery shop and ask about their experience with the local water.
Keep tabs on both your engine’s alternator and your boat’s 110-volt battery charger, if you have one. Overcharging or undercharging is damaging to any battery. Overcharging will boil the electrolyte and rattle the lead off the plates. Undercharging will allow the lead sulfate to permanently harden, reducing the surface area of the plates. A sulfated battery will not develop full power and will eventually have to be replaced.
Battery Installations There are a number of ways to hook up and combine batteries. For the small, open boat, the choices are fairly simple and easy to understand. But, if your boat is a medium-sized cruiser with twin engines and both a bank of starting batteries (for starting the engines) and a bank of house batteries (for supplying your needs while away from the dock), the battery systems can get fairly complex. I will only attempt to present the most common systems here. First, refresh your memory on series and parallel wiring hookups as we discussed back in chapter 1. These two methods of connecting battery cells and batteries are the primary methods builders use to alter system voltage and amp-hour capacity. Also, you need to know a little more about battery characteristics. To create a 12-volt lead-acid battery, manufacturers connect a series of six cells, which each produce a little more than 2 volts, to attain the 12 volts in batteries used by most boats. Larger boats might use 24-volt systems, and some boats even use a combination 12- and 24-volt system, but these are just 12-volt batteries connected in series to get the higher voltage. When battery cells are connected in series, the voltage is multiplied. Thus, multiplying the number of cells in a lead-acid battery by two gives the final system voltage. If we hook these cells or batteries up in parallel, the voltage stays the same, but the amperage of the system is multiplied. Thus, if you have 76
two 6-volt batteries with 25 amps each, wired in series, you’ll end up with a 12-volt bank having 25 amps of current available. If you wire these same two batteries in parallel, you’ll have a 6-volt system with 50 amps of current available. The majority of recreational boats today operate on 12-volt battery systems, so we’ll stick with those. Figure 5-8 shows two pairs of 12-volt batteries. One pair is connected in series, the other in parallel, and the resulting amperage and voltage of each arrangement is shown. This is very important. I’ve seen more than one boater trying to connect batteries in the spring, and they just can’t remember how they were attached when they took them out. Here’s a quick tip to prevent this confusion: Simply mark the cables when you remove your batteries in the fall so you’ll remember how they go when you’re ready for your spring launch. Remember that connecting 24 volts to a 12-volt system can be a very interesting but very expensive mistake. The parallel hookup is not what you’ll find on your boat, as a bat-
Parallel Batteries
Series Batteries Fig. 5-8. Two 12-volt battery pairs, one in series, one in parallel. Remember that series connections combine the voltages of the batteries connected; parallel connections combine the available amperage but do not change the voltage.
