Exide - The Oldest and Best Battery Company in the USA.
Selecting batteries for your Ray Electric outboard.
Golf cart batteries provide the ideal size and weight of lead acid batteries for your motor. They also provide the greatest capacity, edging out 12V trolling motor batteries in this regard, and in longevity. Automobile starting batteries should not be used because they have a short life when deep cycled repeatedly.
Wet cell (standard) vs. absorbed electrolyte (sealed) and gel cell batteries:
Generally the wet cell battery provides more capacity for equal weight. The gel cell tends to be significantly more expensive. The wet cell edges out the absorbed electrolyte type, but not necessarily the gel cell, in longevity. We recommend the standard battery unless there is an unusual application where a sealed battery is needed to prevent spills.
There are generally two ways of stating a rating. Golf cart batteries are typically rated in minutes. Specifically, the number of minutes the battery will supply 75 amps before it is run down, run down being when it will only supply 5.25 volts for a 6V battery.
The other type of rating is the ampere hour rating. The most common amp hour rating is based on 20 hours. "How many amps can it sustain for 20 hours", then amp hours = sustained amps X 20. Any number of hours can be used and obviously the shorter the hours the more amps (flow) that can be sustained. However, batteries cannot produce as much energy when they are more rapidly discharged, so the ampere hours produced for say 8 hours will not quite equal the ampere hours for 20 hours.
The Exide battery data (below) for their four types of Golf Cart batteries provides example of both minute and ampere hour ratings. No matter what rating is used, ampere hours or minutes, each is a measure of battery energy where the voltage is understood to be the same for the batteries being compared. A 6V battery will have an ampere hour rating approximately twice that of a 12V battery of equal weight because the 6V battery will sustain approximately twice the current of the 12V battery for an equal number of hours. The energy of each battery is equal.
6V Battery Energy = 6V x 6 amp x 20 hrs. = 720 watt hrs.
12V Battery Energy = 12V x 3 amps x 20 hrs. = 720 watt hrs.
Amp Hours = 6 amps x 20 hrs. = 120 and 3 amps x 20 hrs. = 60 respectively
In the golf cart 75 amps/minute rating, both the amperage (75) and voltage (6) or (8) are constant and the minutes are used as a measure of the total energy capacity of the battery. This rating is more suitable for electric vehicles because it gives a better estimate of how long the vehicle will run, than does the ampere hour rating.
Very well, but what do I need?
It depends on your system. Specifications show the number of batteries you need depending on whether your system is 36, 48, or 60 volts. The specifications also give the total system weight. So, you can influence the number of batteries and weight by your choice of system.
The system you need will depend on the battery storage and weight capacity of your boat, and the performance you expect. Performance needed will be influenced by the size and type of water on which your boat is used. Also, don't forget, performance depends on the boat itself as well as the motor system.
The different battery banks can be used: System 200 (36V), six batteries, System 300 (48V), eight batteries and System 500 (60V), ten batteries. Specifications show that three different capacity batteries can be chosen for each system, the E-145 (145 minutes), E-135 (135 minutes) and E-110 (110 minutes). For system 300 (48V) an additional selection is possible consisting of six 8V batteriesfor small boats or small waters 3,4, or 5, depending on System voltage. Size 27/12 Volt trolling motor batteries may be used. These selections provide variations of weight and running time within each system, also battery space required.
You can also make major upgrades by doubling the number of batteries. Two chargers are required. This means the choice is extended to twelve 6V batteries for a 36V system, to sixteen 6V batteries (or twelve 8V batteries) for a 48V system or twenty 6V batteries for a 60V system. Doubling batteries cuts individual battery current in half, and more than doubles your running time. For example: For a top speed running time of two hours with the Exide 135 battery, running time will be 4.7 hours with two sets of batteries (80 amps vs 40 amps discharge time - figure 2 - Article Performance Electric Boats).
For more on power, running time, and type of boat suitable for different waters see Performance Electric Boats.
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