One question though. I was told with my purchase of a 2016 Mercury 4 stroke not to use a deep cell battery ever as the main source of power because it can damage the computer onboard the new motors.
Tony,
Here is some information I'll pass along. This has been a topic well discussed on several fishing forums.
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Here is some more information from CDI concerning the use of flooded lead-acid batteries for regulator/rectifier outboard motor charging systems:
The article simply discusses the use and effects of the starting battery. The outboards that use a belt driven alternator are not included in this article as they are basically an automotive style charging system.
On a safety note: Always disconnect the battery’s negative post first and reconnect it last. Questions are consistently arising about the use of cranking batteries with outboard engines. These questions do not take into consideration the differences between most outboards that do not have a belt driven alternator and the ones that do use a belt driven alternator. Most of today’s (and yesterdays) outboards use a flywheel with magnets inside it, a stator assembly containing multiple posts wound with wire and either a straight rectifier or a rectifier/regulator combination. A common misunderstanding regarding the use of maintenance-free or low maintenance batteries with engines that do NOT have a voltage regulator on the engine is the battery acts as the voltage regulator.
It is not uncommon for the battery to reach as high as 19 volts on an engine having only a rectifier when using a maintenance-free or low maintenance battery. An outboard using a stator and regulator/rectifier will usually maintain the battery voltage between 14.2 and 15.5 volts. Make sure the battery you are using has enough capacity to do what you and YOUR ENGINE want it to do. Remember the engine manufacturer has certain battery requirements that have to be met in order for the engine to perform properly.
Also, if you are using the cranking battery to run other devices (aerators, radios, etc), make sure the battery can deliver the amperage you want (as long as you want) and still have enough energy to start the engine. A couple of interesting facts I found out when doing the research is:
1. Heat is harder on a battery than cold (as long as the batteries are fully charged).
2. Batteries are manufactured slightly differently for Northern than for Southern climates.
3. Most aftermarket batteries are built by just a few companies. The differences come into play due to the requested specifications of the retailers.
Common questions include:
Why does my boat engine over-charge?
Why did my ignition pack fail when I ran the engine at WOT (wide open throttle) for an hour (on battery ignition engines)?
Why can I not use an automotive battery in my boat?
Today, typically there are four types of batteries being used in boats with outboard engines. (1) The traditional lead acid flooded cell, (2) AGM (Absorbed Glass Mat) lead acid, (3) Gel Cell and (4) Dry Cell. As long as the batteries are used correctly, there are generally few problems. A reminder – outboard engines that do not have a belt driven alternator generate voltage/amperage that varies with RPM and reaches a peak at a specified RPM (usually 3500 to 5000 RPM). The output is NOT a straight DC voltage but is a pulsating DC voltage where the pulsation frequency increases with engine RPM. This is drastically different from an automotive style alternator charging system.
Traditional marine lead acid flooded cell batteries are the most common type and require the user to periodically check the electrolyte level in the battery, refilling as needed. If the caps on top of the battery cannot be readily removed in order to check the electrolyte level, the battery may be a maintenance-free design. Remember to only use distilled water when adding fluid to a battery. Use extra care as the acid will cause severe burns if it comes into contact with your skin and it will form chlorine gas if it contacts seawater. These types of batteries can leak if they are turned over or if the case gets broken.
Additionally, during charging, the battery will give off hydrogen gas, which can collect in the boat and explode if any sparks are present. The difference between most marine and automotive lead acid flooded cell batteries is the internal construction. The marine batteries are constructed with heavier lead plates in order to withstand the vibration and pounding common on the water.
Older engines typically used only a stator and rectifier to charge the battery and the battery acted as the regulator. Keep in mind that these engines usually had a battery powered ignition system which was susceptible to damage if the battery voltage exceeded 16 volts or if the voltage dropped below 9.5 volts during cranking.
Gel cell batteries use a thick jelly like substance as the electrolyte in the battery. The batteries are sealed and cannot be refilled with electrolyte by the consumer. This type of battery is very sensitive to the charging voltage and charge rate. Too much charging voltage or amperage will likely damage the battery. The charging voltage for the gel cell is usually less than the voltage for the flooded cell type, therefore the charging system has to be adjusted to compensate. Most gel cells require a constant voltage, current limited charger instead of one that changes amperage and frequency. The charging voltage is usually more than the float voltage. In other words, if the battery is charged at 14.4 volts until it is fully charged, the voltage should drop to approximately 13.5-13.8 volts after the battery is fully charged. The current should be limited according to the specifications of the battery manufacturer.
High battery temperatures (normally above 77 degrees F) require the charging voltage and amperage to back off as the battery temperature increases. Installation needs to be in an upright position as the cells within the gel battery can create internal air pockets and cause damage or premature failure if mounted incorrectly.
AGM (Absorbed Glass Mat or Advanced Glass Matting) lead acid batteries (also known as Valve Regulated Lead Acid or VLRA)This type of battery uses a fiberglass like material to hold the electrolyte between the plates. The bonding between the plates, fibrous material, and the case make the AGM virtually spill-proof. These batteries can be mounted in virtually any
position. Since they are sealed, the charging has to be carefully controlled or the battery can be damaged. The AGM requires the charging rate and the charge voltage to be controlled. Also, if battery temperature exceeds 77 degrees F, the charging values need to be adjusted accordingly. With an unregulated charging system common on older engines, there is no control of the charge rate or amperage. This unregulated system can cause damage to the battery and any electronics connected to the battery. It is not uncommon to see voltages approaching 20 volts on the battery with an unregulated charging system. Such high voltage can cause severe damage to depth finders, radios, etc. The AGM batteries are also limited in the charging amperage rate because the outboard engines typically (without a belt driven alternator) have a charging system similar to a battery charger. The AGM batteries typically require a
charge rate (from a battery charger) of approximately 13.8-15 volts with a maximum of 10 amps for up to 12 hours as a limitation. Please refer to the individual battery manufacturers instructions regarding your battery. The AGM battery restrictions are totally different when using a belt driven alternator charging system.
Dry Cell Batteries use more than one type of material in their construction. The industry uses a variety of chemicals when manufacturing these batteries. Depending upon the actual manufacturer, the chemicals can include lead-acid, Nickel-Cadmium, Antimony, Arsenic and Calcium. Like the AGM and Gel Cell batteries, true dry cell batteries require proper care when recharging to prevent over-charging or damaging the battery. In conclusion, it is not recommended to use any battery other than a traditional lead-acid flooded battery with an outboard engine that does NOT have a regulated charging system.
Maintenance-free batteries are not considered to be a traditional lead-acid flooded battery. The AGM or Dry Cell batteries have given mixed results when used with the regulated charging systems
