STO.P Installation Notes

Despite its small size, STO.P is a precision instrument that had been specifically designed for applications requiring a 'clean' power supply to operate a moderate number of small electronic instruments. STO.P is completely sealed and can be used in harse environments which makes it perfect for all Marine, Transport and Industrial applications.


(Models 051224AP)

The STO.P 5A+ will handle loads of up to 5amps continuously. Enough to power all of the electronic equipment found on a small pleasure craft: GPS (0.2A), Fish Finder (0.1A), Plotter (0.4A), Knotmeter/Log (0.1A), Instruments (0.1A), Autopilot Electronics (0.5A), Cellphone (0.1A) and VHF Radio (0.2A Receive, 3.5A Transmit). Check the power requirements in your equipment manuals, or measure the actual current using a suitable ammeter.

STO.P 15A+

(Models 151224AP)

For larger loads, the STO.P 15 A+ will handle loads of up to 15 Amps continuous. Which means that it can power all all of the equipment mentioned above, plus the heavier loads of a Radar or other equipment.

UNDER Voltage Fill In

Bonus feature! With the addition of a small user supplied rechargeable battery, it will provide 'fill-in' voltage during engine starting. Low voltages encountered during cranking are the number one reason for memory loss in marine and automotive/transport navigation systems.


Installation can be as simple as cutting an existing power lead and fitting the STO.P between the equipment to be protected and a suitably 'fused' power source. But, to utilize the STO.P to its maximum some thought needs to be given to the installation.


STO.P should be placed in a location away from heat sources such as the engine. It will be most effective when placed as close to the equipment as possible. Generally, a position somewhere in or near the existing electrical panel will suffice.

Diagram showing STO.P Wiring


You will notice that there are 7 wires emerging from the bottom of the STO.P. There is also a white wire that loop back into the STO.P - cut this wire if you are using your STO-P on 24 Volt systems. The following instruction are for 12 Volt installation:

INPUT SIDE (Power Source):

OUTPUT SIDE (Equipment):


The STO.P must be connected through a suitable fuse or circuit breaker. You can connect your STO.P through an existing electrical panel or directly to a 12 volt battery. Fuses should be the 'standard' quick blow type rather than the 'slow blow' or 'time delay' type. If using a circuit breaker, it should trip within 2 seconds at twice its rating.

Connecting the User-Installed Batttery


Adding a small standby battery to your STO.Pallows it to provide 'fill-in' voltage when main battery dips during engine cranking. This will prevent memory loss in your GPS and other sophisticated equipment. While, STO.P is designed to use a multitude of different batteries, the best choice is to use a rechargeable type. Sealed lead acid (or gel) batteries are inexpensive, readily available and are a good choice. But, you may also use a series of 10 NICAD batteries or even standard 'D' sized Alkaline batteries. Each of these types has different charge/discharge characteristics and their performance will vary. For most applications, choose a battery rated between 1 and 4 Amp-Hours (AH).

The battery will recharge automatically while the engine is running. The recharger built into the STO.P is designed to cut off when the voltage drops below 12.8 Volts to reduce the drain on the main battery while the engine is off.


If you wish to use non-rechargeable batteries such as standard 'D' cell Alkaline batteries, you may do so. Note however, that these batteries are suitable for light loads only. We recommend that you limit the equipment load to between 0.5 and 1.0 amps maximum. You should check these batteries often and replace them when they begin to deteriorate slightly.

Place 8 Alkaline 'D' cells in series in a suitable battery holder and connect as shown. DO NOT CONNECT THE BLUE WIRE! Tape up the end of the blue wire so it does not touch anything.

Connecting to Equipment


Your electronic equipment can be divided into two groups:

  1. Equipment NOT AFFECTED by low voltages during engine cranking. Your VHF radio is a typical example.
  2. LOW VOLTAGE SENSITIVE EQUIPMENT. Your GPS fits into this category.

Connect Group I equipment to the GREEN (+) and BLACK (-) leads of the STO.P. This provides protection but does not provide fill-in voltage.

Connect Group II equipment to the YELLOW (+) and BLACK (-) leads of the STO.P. This provides protection plus 'fill-in' voltage from the standby battery.

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