Preventing Failures:
The Problem
STO-P Solution
Back Up Power
Volume Quotes
Custom/Military Versions
Common Electrical System Faults:
Induced E.M.F.
Reverse Polarity
Land Transport



F.A.Q's About STO-P Protectors

Q. What causes Spikes and Transients?
A. Very high voltages, both positive and negative, are generated whenever a magnetic field collapses around in inductor. That's the technical explanation. But what does it mean? Let's take engine starting as an example, although the same process happens with lots of other things on your boat. When you press the 'start' button to start the engine, what happens? First, the start button activates a 'solenoid'. The 'solenoid' is an electrical relay that can safely handle the large amount of current needed to start the engine. It sends current rushing into the starter motor. The starter motor begins to spin the engine and causes it to spring to life. But, we are not interested in the engine itself, but rather the starter and its solenoid. Because the starter motor must work hard to spin the engine, it requires a large amount of power from the battery. This builds up a very large magnetic field. When you let go of the starter switch, this magnetic field has to go somewhere. It collapses, and for a very brief instant it generates a terrifically high voltage transient or spike. A 12 volt starter /solenoid combination can generate a spike of 200 volts or more! It doesn't last too long but it sure can have a devastating affect on your equipment. In reality, because the connection that the solenoid makes is not 'perfect' but rather quite 'bouncy' a whole series of spikes are generated each time you start the engine. As the solenoid ages this spike generation problem becomes even worse!

Q. Is engine starting the only source of Spike and Transients?
A. No! Spikes and transients can be generated by any sort of 'inductive' load. Here are a few examples of things that we have found that generate spikes and transients: Solenoids, Starter Motors, Electric Anchor Winches, Bilge Pumps, Water Pumps, small DC Relays, Electric Fuel Pumps, Watermaker Motors, Autopilot Motor Drives, Electric Clutches, Electric Valves (for Propane, Butane, etc.), Battery Chargers, Alternator Field Coils, Electric Refrigeration Compressor Motors, Generators, Engine Shutdown Solenoids, Vacuum Cleaners, 12 Volt Tools, Fans, Inverters, Bait Tank Pumps, Electric Air Pumps, Bilge Blowers, Shower Drain Pumps, Electric Toilets! And more! The intensity of the problem varies depending upon the type of device.

Q. What about Overvoltage; what causes it?
A. There are several sources. Your Alternator/Voltage Regulator, Solar Panels, Wind and Tow Generators, Battery Charger, and Generator are all candidates for this problem. First, your alternator is quite capable of generating significantly higher voltages than you might expect. If you were to suddenly disconnect the battery from your alternator its output voltage will skyrocket - reaching 100 volts in most cases! (This is easy to do - just turn your master battery switch off. But don't try it! You will likely damage the alternator as well as your electronics). This disastrously high voltage will be fed to your electronics and other electrical equipment. And, by the time you try to rectify the accident, the damage is done and irreversible. If the voltage regulator fails, it can also send the voltage skyrocketing.

Most marine Solar Panels will generate 20 volts or more when the load is reduced. I have been on many boats where the panels were connected AFTER the main battery switch, i.e., they were connected through the power distribution panel instead of directly to the battery. So, if the master battery switch is turned off, the panels cause the voltage to rise substantially. The same goes with wind and tow generators except they usually put out even higher voltages, generally 50 to 75 volts with transients of perhaps 300 volts or more!Battery chargers that are powered by shore power or by an onboard generator set can cook batteries and send voltages well above the safe limits for your electronic gear.

Q. How safe is it to plug into AC Shore Power?
A. This can be a real hazard to your electronic equipment! AC shore power is a well known source of 'surges'. The term 'surge' refers to spikes, transients and overvoltages that occur on AC systems. Usually these originate from lightning strikes on power poles, or from the operation nearby electrical equipment and motors. They can enter your boat via your AC mains battery charger and affect your equipment in the same way that spikes and transients generated on your boat do. STO.P will prevent damage from these surges!

Q. Is STO.P like a 'Surge Suppressor' that is used on the AC Mains?
A. No! 'Surge Suppressors' clamp damaging voltages from anomalies such as lightning strikes to power poles which cause very high voltages to travel along the line and enter AC mains connected equipment. These devices 'limit' high voltage surges to 750 Volts or more! They do not work very well on low voltage DC powered equipment. STO.P, on the other hand, works on low voltage DC systems. It stops spikes and transients that are as low as 18 volts! It if far more complex than normal AC mains 'Surge Suppressors' too!

Q. Why is 12 volt equipment more susceptible to spikes and transients than AC mains connected equipment?
A. Because A.C. main operated equipment must first convert the AC voltage to DC voltage for use by the electronic components, it provides a degree of immunity from 'surges'. Still, we know that surges are a big problem for this type of equipment. Low voltage equipment is much more susceptible to spikes and transients because it is powered DIRECTLY from the 12 volt source. It has no 'conversion' process to 'filter' some of the problems out before they reach the electronic circuitry.

Q. What will it protect?
A. STO.P is designed to protect ELECTRONIC gear. Don't waste it by connecting light bulbs or other non-electronic equipment. STO-P's come in various power ratings. The most popular is the STO.P-15 model which can handle up to 15 Amps of power. You can protect all of you electronic gear as long as they total power consumed is less that the rated power of the STO.P.

Q. My Autopilot manual says that it uses more than 15 Amps of power, what kind of STO.P should I use?
A. Take a close look at your Autopilot first. Larger autopilots usually have separate electric or hydraulic rams or actuators. These are the big power consumers. Usually, the electronic portion of the autopilot is fed from a separate set of terminals. And, the electronics rarely consume more than 1/2 Amp of power! So, you can use the same STO.P that you use for the rest of your electronics. Just run a power line from the STO.P to the autopilot electronics. Keep the heavy power leads going to the drive unit. These drive units are usually built with very high power and high voltage semiconductors that are relatively unaffected by spikes and transients.

Q. Can I install it myself?
A. YES! Refer to our 'Installation Notes' for more details. But, all you need to do is to install the STO.P in between your 12 or 24 volt power source and your electronics. Usually this is easily done at the power panel. Even if you are not very handy and 'all thumbs' when it comes to electrical work, you will be able to install one quickly.

Q. Where should I install it?
A. STO.P can be located almost anywhere. It is best to keep it as close to the equipment as possible. Usually, it is most convenient to locate it near the power distribution panel. While the STO.P can be placed at the battery, this is actually the least effective place! Locating it near the equipment is best.

Q. Can I add more electronics later?
A. Sure! As long as you do not exceed the power rating of the STO.P.

Q. How many amps does my equipment use?
A. Look in the instruction manual. Most manufacturers will show the power requirements in the 'specifications' section of their instruction manuals. Look for something like: Power Requirements: 12.0 - 14.0 Volts, 500 mA. The '500mA' is the current consumption. 500 mA is the equivalent of 1/2 Amp (1000 mA = 1 Amp). Make a list of the 'current' requirements for each piece of equipment that you want to protect. Add all of these together and make sure that the sum does not exceed the power rating of the STO.P. Note that manufacturers usually specify the 'worst case' or maximum power needed and often the equipment will use 10 or 20 percent less than indicated in the manufacturers specifications. Incidently, equipment fuses are not a very good indicator of power consumption. Fuse values are often 2 or 3 times the actual current consumption. Remember, fuses are there only to prevent fires! If you have an ammeter, you can use it to directly measure the power consumption of each piece of equipment.

Q. Typically, how much equipment can I expect to protect?
A. For example, a STO.P - 15 (15 Amp power rating) was installed on a yacht. To it, the owner connected a 24 miles Radar, two GPS receivers, Depth Sounder, Wind Instruments, Satnav, Fishfinder and Autopilot electronics (not the drive unit). When we measured the total power consumption, it was 7.5 amps when everything was running! So, there was still plenty left for later additions.

Q. Will it protect my electronics if I receive a direct lightning strike?
A. The STO.P is designed to work (and survive) up to about 600 volts DC. Lightning strikes are much higher than this. But, even though your STO.P may be destroyed we have designed it to protect your equipment anyway. The effects of lightning strikes are difficult to predict and therefore we cannot guarantee that your equipment will survive, but it has a much better chance than without a STO.P!

Q. Does a 'battery isolator' help protect my electronics?
A. Battery isolators have been sold as cure-alls much like the 'elixirs' sold by old time medicine shows! They are useful to prevent two or more batteries from being discharged simultaneously. But, when it comes to protection against spikes and transients forget it! Isolators can be destroyed by them!

Q. What about using a separate battery for starting the engine.
A. If you have the ability to use the 'house' battery to start the engine, you are asking for trouble. And, remember that the engine starter is only one of many sources of spikes and transients! The other culprits are already connected to the 'house' batteries!

Q. Can I hookup my SSB radio?
A. SSB and ham radios usually consume 20 to 30 amps. So you must use a STO.P with a higher power rating. The new STO-P UPS40 system is ideal!

Q. My GPS manual says it can operate up to 40 volts - does this mean it's protected from spikes and transients?
A. No! The 'voltage regulator' used in this type of equipment is susceptible to damage by both Spikes and Transients. It will survive some overvoltage conditions but most overvoltages exceed 40 volts. (Typically they are 60 to 100 volts) And, spikes and transients usually exceed 100 volts!

Q. Don't fuses and circuit breakers protect my equipment?
A. They are there to prevent fires! Nothing else. They react much too slowly to prevent damage from Spikes, transient or Overvoltages.

Q. Sometimes I see my equipment doing 'funny' things. Does that mean there is a problem somewhere?
A. There is always a 'cause' when your equipment acts 'funny'. And, it is often difficult to 'pin down' an exact cause for each problem that has been observed. Digital electronics (and most modern gear has some form of digital electronic circuitry) responds to a series of instructions stored as binary 'bits'. A spike or a transient can cause these 'bits' to become scrambled. It takes only one or two small changes to create some really unusual effects! For example, recently I came upon a depth sounder that was showing some 'funny' digits on its display. They were there for a while then disappeared. And, then reappeared a few days later. What was happening was that 'spikes' from engine starting had entered the depth sounder via its power leads and had altered the memory. When we installed a STO.P the problem was eliminated! So be careful, if you are seeing 'funny' things. It could be an indicator that irreversible damage is occurring!

Q. Can I use a STO.P to protect my laptop computer?
A. Certainly! Many laptop computers can be powered directly from a 12 volt or 24 volt battery and as such are very susceptible to damage from power glitches. Either connect the computer to the vessels STO.P or use a separate STO.P for the computer.

Q. When I use my SSB sometimes lights on my power panel will glow. Will a STO.P prevent this?
A. SSB and Ham radios emit a relatively strong signal. These radios cover a fairly wide range of frequencies. When you transmit, the signal is picked up by your boat wiring and fed back into your electrical system. This is why you often see lights on your power panel glowing as you speak! STO-P's also have 'passive' filtering that helps to eliminate this problem from entering your electronic gear. For best results, mount the STO.P as close as possible to your electronic gear.

Q. Will STO.P generate radio interference?
A. No! STO-P's do not emit any form of electromagnet interference. As such they are totally safe and non-hazardous to both other electronic equipment or to its users!!

Q. Can a STO.P be used in non-marine applications - like on cars, and trucks?
A. Absolutely! In fact the same problems we see in marine applications exist in these areas as well. Avionics equipment usually comes with a warning in the instruction manual to keep the equipment off until the engine has started. These manufacturers are well aware of the problem but have not had any way to STOP the problem - until now! With the widespread use of cellular telephones, computers, fax machines and now GPS receivers in vehicles of all types, equipment failure due to spikes, transients and overvoltages are becoming commonplace. Many technicians are just beginning to realize this!

Q. What kind of warranty do you offer?
A. STO-P's have a limited one year warranty. We expect them to last much longer though! We use quality components, careful design and each STO.P is fully tested before it leaves our lab.

Q. Can STO.P be used on 'floating' ground systems? (No pun intended!)
A. Yes. There is no danger of electrolysis in metal boats.

Q. I've heard that you can use a simple Zener Diode or voltage regulator to prevent Spikes?
A. We have tried all of these 'common' solutions with no success. That's why we had to develop STO.P!!!

Q. Once I have a STO.P installed does that mean I will never have another electronics failure?
A. No one can guarantee that! STO.P will reduce or prevent permanent damage from power induced causes. But, remember that if you have had your equipment operating before you installed STO.P substantial damage may have already occurred. And, failures may occur for that reason alone. In these circumstances, STO.P may be able to prevent failures by arresting further deterioration of electronic components.

PLEASE NOTE: If you have a question that has not been answered, please email us!

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