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Power Consumption
Roger Power Consumption Standby: 0.72 WAuto: 10 W at 25% duty cycle(depending on boat trim, helm load and sailing conditions) Go to Raymarine, use Google search or any other search engine, and the complete specs are there for you. This is for the ST4000+
Roger Power Consumption Standby: 0.72 WAuto: 10 W at 25% duty cycle(depending on boat trim, helm load and sailing conditions) Go to Raymarine, use Google search or any other search engine, and the complete specs are there for you. This is for the ST4000+
watts and amps
Stu: thanks for the answer. Went to Raymarine but still not clear. They say 10 watts at 25%. My rough calculation would be about 5 amps an hour at 100%. My setting don't let the boat go off course more that 5 degrees and usually it is about 3. And of course it is working 100 %.
Stu: thanks for the answer. Went to Raymarine but still not clear. They say 10 watts at 25%. My rough calculation would be about 5 amps an hour at 100%. My setting don't let the boat go off course more that 5 degrees and usually it is about 3. And of course it is working 100 %.
So...
Roger If you've done an energy budget (and I assume y0u have a fridge, lights, anchor light, VHF, stereo, running lights, etc.), you've found that the AP may be a significant portion of your total daily energy use. The real load is between 1 and 2 amps per hour. This is because of the duty cylce. 5 amps per hour is extremely high. Depending on how much you use it and your sensitivity settings, hours X amps per hour. What's your question related to? Battery capacity? Stu
Roger If you've done an energy budget (and I assume y0u have a fridge, lights, anchor light, VHF, stereo, running lights, etc.), you've found that the AP may be a significant portion of your total daily energy use. The real load is between 1 and 2 amps per hour. This is because of the duty cylce. 5 amps per hour is extremely high. Depending on how much you use it and your sensitivity settings, hours X amps per hour. What's your question related to? Battery capacity? Stu
Me worry
Stu: Thanks again. At two amps it makes me feel more comfortable in motoring to Cataling, CA, 30 miles with the frig on and have plenty of amps left in my house battery.....so nothing to worry!!!
Stu: Thanks again. At two amps it makes me feel more comfortable in motoring to Cataling, CA, 30 miles with the frig on and have plenty of amps left in my house battery.....so nothing to worry!!!
Back to Fundamentals
This discussion thread suggests there was more to your question than just the autopilot current draw. It appears that you are looking at a total energy management issue. Fundamentals: Batteries (and fuel) are chemical forms of potential energy storage. The amount of a battery's potential energy storage is determined by its size and construction, and usually indicated by its ampere-hour rating. The energy to be stored is supplied by other sources (alternator, solar panels, shore power, etc.). The relative state of the battery's potential energy is assessed (not measured!) by both the static terminal voltage and the specific gravity of the acid electrolyte. When you complete an electrical circuit, you are converting the chemical energy stored to a kinetic form of electrical energy. Energy delivered/used is measured by the power delivered (watts) over time (hours). The electric meters on the side of your house are really watt-hour meters measuring energy delivered. Power (watts) is the electric potential (Volts) x current delivered (Amperes). We often make the simplifying assumption that the battery terminal voltage is constant over all loads (it really isn't) and simplify the energy calculation to Amperes x Hours. If you want precision, you get into the math of integral calculus. Energy Management. For reasonable battery life, we generally don't want the battery no-load terminal voltage to drop more than 25%. That said, you'll never get the full energy delivery (amp-hour rating) of your battery without killing it. Most texts suggest counting upon half of that rating. The key to energy management is then to budget the continuous and intermittant current drains over time so as to not exceed the 1/2 amper-hour rating of your battery. Then, ensure a recharging source is applied to replace the energy consumed. Lights are continuous drains, as are some electronics in the standby mode. Pumps, winches, autopilots, VHF transmitters, etc. tend to be intermittant drains. Refrigeration is intermittant but a heavy load when running (usually, but an initial cooldown of a warm unit might present a heavy continuous load for quite a while). Autopilots generally have a low continuous current consumption to run sensors & displays, with bursts of intermittant consumption to power servos for steering. The rougher the seas, or the more imbalanced the sail/helm trim is (e.g., heavy weather helm), the more the autopilot will be working to correct the steering. Regarding your last post, if you are motoring the 30 miles to Catalina Island, then the charging current going into the battery will likely far exceed the drain from your various gadgets. If you want more info, I would suggest that you consult Nigel Calder's book(s) on the subject. He treats the subject very directly and understandably. --Ron s/v Lady Jane Marblehead, MA
This discussion thread suggests there was more to your question than just the autopilot current draw. It appears that you are looking at a total energy management issue. Fundamentals: Batteries (and fuel) are chemical forms of potential energy storage. The amount of a battery's potential energy storage is determined by its size and construction, and usually indicated by its ampere-hour rating. The energy to be stored is supplied by other sources (alternator, solar panels, shore power, etc.). The relative state of the battery's potential energy is assessed (not measured!) by both the static terminal voltage and the specific gravity of the acid electrolyte. When you complete an electrical circuit, you are converting the chemical energy stored to a kinetic form of electrical energy. Energy delivered/used is measured by the power delivered (watts) over time (hours). The electric meters on the side of your house are really watt-hour meters measuring energy delivered. Power (watts) is the electric potential (Volts) x current delivered (Amperes). We often make the simplifying assumption that the battery terminal voltage is constant over all loads (it really isn't) and simplify the energy calculation to Amperes x Hours. If you want precision, you get into the math of integral calculus. Energy Management. For reasonable battery life, we generally don't want the battery no-load terminal voltage to drop more than 25%. That said, you'll never get the full energy delivery (amp-hour rating) of your battery without killing it. Most texts suggest counting upon half of that rating. The key to energy management is then to budget the continuous and intermittant current drains over time so as to not exceed the 1/2 amper-hour rating of your battery. Then, ensure a recharging source is applied to replace the energy consumed. Lights are continuous drains, as are some electronics in the standby mode. Pumps, winches, autopilots, VHF transmitters, etc. tend to be intermittant drains. Refrigeration is intermittant but a heavy load when running (usually, but an initial cooldown of a warm unit might present a heavy continuous load for quite a while). Autopilots generally have a low continuous current consumption to run sensors & displays, with bursts of intermittant consumption to power servos for steering. The rougher the seas, or the more imbalanced the sail/helm trim is (e.g., heavy weather helm), the more the autopilot will be working to correct the steering. Regarding your last post, if you are motoring the 30 miles to Catalina Island, then the charging current going into the battery will likely far exceed the drain from your various gadgets. If you want more info, I would suggest that you consult Nigel Calder's book(s) on the subject. He treats the subject very directly and understandably. --Ron s/v Lady Jane Marblehead, MA
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