Category Archives: Smart Battery Switch
An aerator pump is a specialized water pump used on fishing boats.
Part of a livewell system, in which a fisherman keeps his catch alive, the aerator (or livewell) pump helps to “aerate” the water and put oxygen into it. This is most often done by re-circulating
the water in the livewell through the pump and back to the well via a sprayer that agitates the water and induces oxygen. These are typically known as “recirc” pumps.
Another use for this pump can be as a “pickup”, where it draws in the outside water to fill the livewell or refresh it. The pumps come in a variety of pumping capacities and are powered by 12V DC.
Aerator pumps are manufactured by several well know companies, including Attwood Marine. The Attwood Tsunami Series features innovative engineering and compact design, that delivers high output from a small package.
Attwood aerator pumps are famous for using the most advanced material available, including the best quality bearings and state-of-the-art brushes, alloys and magnets.
They offer three high-efficiency aerator pumps that move water at output capacities of 500 gph, 800 gph and 1200 gph.
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Batteries are a common power source for many household, industrial and transportation applications.
There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times.
Rechargeable batteries are what are used in automotive and marine applications. They can be recharged by applying electric current. Devices to supply the appropriate current are engine alternators or chargers.
The most common form of rechargeable battery is the lead-acid battery. This battery is notable in that it contains a liquid in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas produced by these batteries during overcharging.
Battery management is the efficient monitor and control the outflow of power from your boat’s batteries.
The “prime directive” of marine electrical battery management to to avoid the overuse of this finite power supply, which may eventually compromise an important function, like starting your engine. 
Marine electrical battery management can be as simple as monitoring a voltmeter to determine battery voltage; to the use of switches to turn on certain batteries, while isolating others from use ; to having sophisticated voltage sensitive relays that will do the job of monitoring levels and switching batteries on and off automatically – often called a Smart Battery Switch.
Any boater that will be spending time at anchor running electrical accessories, like stereos, will need to maintain some awareness of the condition and level of their battery supply and life. The inability to restart an engine (which is a key source of recharge for the batteries), or to lose the use of a boat’s navigation lighting, boat horns or bilge pumps because of dead batteries is a situation to be avoided. Thus the importance of battery management.
The VSR, or Voltage Sensitive Relay, is a very handy little box that solves a load of traditional charging problems on marine electrical systems. It essentially serves as a smart battery switch deciding automatically when either one or two batteries are charged – or discharged. It works great on almost any boat with multiple batteries – and eliminates all of the guesswork that used to come with manual battery switches.
What a VSR does
The VSR is installed between two batteries. Many people are surprised to learn that it is NOT connected to either the alternator or charger output wires! Its setup is much more clever.
- If either battery goes above 13.7 volts (due to either alternator or charger output), the VSR connects both batteries together. Both batteries are now charging – without the boater ever having to throw a switch.
- Alternately, when the system voltage drops back below 12.6 volts, i.e., no more charging, the relay opens and the batteries are separate. This means that both batteries now discharge independently.
How a VSR changes real world boating
Let’s say that a fishing boat has a two battery setup. As is often the case, one of the batteries is dedicated to an important job – starting the engine. The other battery is used for other operations, including trolling.
- As the fisherman runs the boat from hole to hole, the engine alternator elevates the voltage to the cranking battery above 13.7 volts. This triggers the VSR to automatically connect the starting battery and trolling battery together. Both are now charging.
- Upon reaching his destination, the boater kills the engine – and, the alternator output – and begins trolling. Because of the lowered voltage, the VSR now disconnects the batteries. Because he is now discharging only one battery, our fisherman is going to have starting power when he needs it later – no matter how long he uses the trolling motor and depletes that trolling battery.
- Once underway again, the alternator power causes the VSR to reconnect the batteries and begins replenishing the trolling battery.
- Back home, the fisherman powers up his onboard battery charger. This increased voltage causes the VSR to once again link the batteries. This means that even a single output battery charger would now be charging both batteries!
- Our fisherman has had a great day on the lake, getting to and from his fishing hole, trolled for hours without killing a battery and never once had to worry about the settings on a manual battery switch.

