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Soo...I have been asked by a few boat owners if installing a second battery is a good idea. My safe, usual, canned response to that question is absolutely yes.
However the necessity of having a second battery onboard is not the same for all boat owners. Therefore, I've created this entry to provide some assistance to those on the fence considering this addition.
First, I need to say that any information provided by me is solely just advice. Additionally, this writeup is not a guide on battery installation. There are a number of great articles on second battery installations within the forums and throughout the net.
The largest stress placed on the battery comes from cold starting. Therefore, keep in mind the main purpose for another battery onboard is to have a backup starting source when the primary source has been compromised or depleted. Any other puopose is ancillary.
Before going any farther, I strongly suggest anyone relying on battery power for starting purposes to pickup some type of voltage monitor. Knowing your battery voltage is crucial when out on the water, and is the best tool available when determining battery charge and what steps to take as the voltage changes.
Very affordable voltage monitors can be found on EBay. I prefer the 12V automotive style monitors solely for their ease of use, and the near ubiquity of 12V sockets found in all watercraft. A link to a decent low cost monitor is provided at the end of this entry.
Now with all of that out of the way, lets discuss some battery specific details. I've generated a check list of important factors that should be considered when determining if a second battery is really necessary.
Only one motor onboard?
Increased motor(s) compression?
Supercharged intercooled (4tec SCIC)?
More than two speakers onboard?
Auxillary stereo amplifier onboard?
Any additional lights onboard?
Anyone who answers yes to three or more of these questions should seriously consider an additional battery source. A yes to two of these questions may also benefit from an additional battery. I will discuss why each one of the questions are important factors.
1. Only one motor onboard?
Some people may be confused as to why having only one motor is even a factor. The answer is simple. Two motors provide twice the charging capacity on a battery, leaving additional charge on the battery when the motors are not running.
2. Increased motor(s) compression?
3. Supercharged intercooled (4tec SCIC)?
Both of these questions lead to the same point. High compression motors require more torque from the starter to fully turn over. Greater torque load on the starter results in more battery "juice" required during starting. A nominal battery charge capable of starting a stock motor may have trouble turning a modified engine. The more powerful SCIC 4tec motors run at a higher compression vs their internally intercooled cousins, and therefore will require more energy during starting.
4. More than two speakers onboard?
5. Auxillary stereo amplifier onboard?
6. Any additional lights onboard?
The last three questions pertain to battery loading while the motor(s) are off. Unpowered (engine off) battery loading cause more people to end up stranded out on the water without enough stored power to start the motor. This most often occurs when the battery voltage is allowed to fall below its safe starting threshold voltage. Yes, the newer boats have low voltage monitors. However, most owners will not be aware of potential low voltage conditions until it is too late.
There are real time battery recovery options available, but I don't suggest jump starting on the water. Of course it can be done when there is no other option available at times when its absolutely necessary. However, it is very important to know that jumpstart conditions may stress the electronics beyond their ratings. For example, many of the mobile jump start modules use voltages double the nominal battery voltage.
On another topic, damaging load dump conditions can be created when jump starting others from a single battery connected to a running motor, and is another reason why it is important to have an additional battery that can be isolated when starting others. Some load dump conditions can generate voltage surges as high as 100V. Additionally, to prevent self induced load dump, never move any battery switch to the off position while the motor(s) are powered. Unfortunately, many have damaged their MPEMS due to this.
There are a number of dual battery voltage monitor systems specialized for marine use, that will automatically switch between the two batteries. However, those systems are usually expensive and unnecessary especially when a simple dual battery switch and an informed user will provide the same functionality.
In order to better understand what the current battery voltage truly means, I've provided the following excerpt from an automotive battery site online. It is important to only read the voltage with the motor(s) off, when no other axillary functions are running (ie lights radio).
Voltage reading: description
12.8V and above: brand new or lightly used battery
12.67V - 12.8V: fully charged battery
12.45V - 12.67V: 75% charged
12.24V - 12.67V: 50% charged (may not be capable of starting a high compression engine at this point)
12.06V - 12.67V: 25% charged (may not start a unmodified standard compression engine)
11.89V - 12.06V: no charge
11.89V and below: (dead)
These numbers have to be adjusted -0.01V for every 10 degrees below 80F.
Feel free to provide questions, or corrections. I will respond/update as required.
EBay link
http://www.ebay.com/...DefaultDomain_0
However the necessity of having a second battery onboard is not the same for all boat owners. Therefore, I've created this entry to provide some assistance to those on the fence considering this addition.
First, I need to say that any information provided by me is solely just advice. Additionally, this writeup is not a guide on battery installation. There are a number of great articles on second battery installations within the forums and throughout the net.
The largest stress placed on the battery comes from cold starting. Therefore, keep in mind the main purpose for another battery onboard is to have a backup starting source when the primary source has been compromised or depleted. Any other puopose is ancillary.
Before going any farther, I strongly suggest anyone relying on battery power for starting purposes to pickup some type of voltage monitor. Knowing your battery voltage is crucial when out on the water, and is the best tool available when determining battery charge and what steps to take as the voltage changes.
Very affordable voltage monitors can be found on EBay. I prefer the 12V automotive style monitors solely for their ease of use, and the near ubiquity of 12V sockets found in all watercraft. A link to a decent low cost monitor is provided at the end of this entry.
Now with all of that out of the way, lets discuss some battery specific details. I've generated a check list of important factors that should be considered when determining if a second battery is really necessary.
Only one motor onboard?
Increased motor(s) compression?
Supercharged intercooled (4tec SCIC)?
More than two speakers onboard?
Auxillary stereo amplifier onboard?
Any additional lights onboard?
Anyone who answers yes to three or more of these questions should seriously consider an additional battery source. A yes to two of these questions may also benefit from an additional battery. I will discuss why each one of the questions are important factors.
1. Only one motor onboard?
Some people may be confused as to why having only one motor is even a factor. The answer is simple. Two motors provide twice the charging capacity on a battery, leaving additional charge on the battery when the motors are not running.
2. Increased motor(s) compression?
3. Supercharged intercooled (4tec SCIC)?
Both of these questions lead to the same point. High compression motors require more torque from the starter to fully turn over. Greater torque load on the starter results in more battery "juice" required during starting. A nominal battery charge capable of starting a stock motor may have trouble turning a modified engine. The more powerful SCIC 4tec motors run at a higher compression vs their internally intercooled cousins, and therefore will require more energy during starting.
4. More than two speakers onboard?
5. Auxillary stereo amplifier onboard?
6. Any additional lights onboard?
The last three questions pertain to battery loading while the motor(s) are off. Unpowered (engine off) battery loading cause more people to end up stranded out on the water without enough stored power to start the motor. This most often occurs when the battery voltage is allowed to fall below its safe starting threshold voltage. Yes, the newer boats have low voltage monitors. However, most owners will not be aware of potential low voltage conditions until it is too late.
There are real time battery recovery options available, but I don't suggest jump starting on the water. Of course it can be done when there is no other option available at times when its absolutely necessary. However, it is very important to know that jumpstart conditions may stress the electronics beyond their ratings. For example, many of the mobile jump start modules use voltages double the nominal battery voltage.
On another topic, damaging load dump conditions can be created when jump starting others from a single battery connected to a running motor, and is another reason why it is important to have an additional battery that can be isolated when starting others. Some load dump conditions can generate voltage surges as high as 100V. Additionally, to prevent self induced load dump, never move any battery switch to the off position while the motor(s) are powered. Unfortunately, many have damaged their MPEMS due to this.
There are a number of dual battery voltage monitor systems specialized for marine use, that will automatically switch between the two batteries. However, those systems are usually expensive and unnecessary especially when a simple dual battery switch and an informed user will provide the same functionality.
In order to better understand what the current battery voltage truly means, I've provided the following excerpt from an automotive battery site online. It is important to only read the voltage with the motor(s) off, when no other axillary functions are running (ie lights radio).
Voltage reading: description
12.8V and above: brand new or lightly used battery
12.67V - 12.8V: fully charged battery
12.45V - 12.67V: 75% charged
12.24V - 12.67V: 50% charged (may not be capable of starting a high compression engine at this point)
12.06V - 12.67V: 25% charged (may not start a unmodified standard compression engine)
11.89V - 12.06V: no charge
11.89V and below: (dead)
These numbers have to be adjusted -0.01V for every 10 degrees below 80F.
Feel free to provide questions, or corrections. I will respond/update as required.
EBay link
http://www.ebay.com/...DefaultDomain_0
- Kevin Leclair likes this
