SAILFISH 276 DC | VSR BATTERY SYSTEM - “THE SMART BATTERY SWITCH”
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 alterna-
tor or charger output wires! Its setup is much more clever.
It 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 boat 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.
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 house 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 low-
ered 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 recon-
nect 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!
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