Power draw on autopilot and general cruising

[stormalong]

A wind generator needs a minimum wind of 15 knots to produce power. In Chesapeake Bay I doubt it would be effective very often.

Does your on engine alternator have a smart regulator? Stock internal regulators are very ineffective at producing power. A larger alternator with and external smart regulator would be a big improvement. Be sure to get an alternator that is capable of long time high amperage output. One question here is just how big of an alternator can an Atomic 4 drive.

I agree with others that a good battery monitor would take the guesswork out of managing your batteries. A voltage check is an ineffective way to monitor battery condition unless you let the battery sit without being charged or discharged for at least 12 hours. A glance at a battery monitor while the engine was running would have given you an immediate indication that your alternator wasn't working.

A small portable generator is a good alternative to running your main engine. You will also need a battery charger designed to charge gel cells.

[beetle]

You shouldn't need to make any assumptions regarding electrical power consumption, all the information needed is right there in the manufacturer's manuals.

What you want to do is write a power "budget" that will show all the expected loads over a 24 hour period. Once you have that then you solve for how to replace the power consumed.

Do pay attention to battery charge curves, particularly as regards how much time it takes to push power back into a battery (battery charge acceptance rate is not linear) and the efficiency losses in charging a battery.

You're biggest bang for the buck is usually to upgrade the alternator to a hot-rated hi-output alternator mounted on the engine,. 105 AH alterator is typically the largest alternator that can be operated on a single 1/2" belt; if that will work for you given the alternator location and space inside the engine box then you can avoid the cost of a dual-belt setup to drive the alternator (plus you cut down on crankshaft bearing wear from an off-axis load - the alternator belt).

A convenient approach for me was to time charging to coincide with twice-daily SSB schedules - I use the SSB when the alternator is putting out current and therefore the radio is receiving full voltage (SSB radios like lots of voltage). Everything on my boat is sized for an hour engine charge morning and again evening during passages; the solar panel pays for the refrigeration and nav station laptop, the wind generator is an extra goody that solves the problem of enormous autopilot loads when close reaching in 20-35 knots, and as a complete backup in case of engine failure I have a Honda EU2000 that produces enough AC power to re-charge via the regular AC battery charger - that has worked out great at anchor when I don't want to run the main engine just to spin an alternator.

But first thing is get your energy budget in place, second thing is to size the alternator to suit a charging methodology that suits your cruising style. You may decide that a third house battery in parallel with the existing two will help significantly with power management - one big battery is more efficient to charge than two smaller ones.

And how did you run the engine for 30 minutes with a broken alternator belt and not notice? A broken belt usually means a non-working water pump">raw water pump, and a non-working pump will cause the engine to overheat.

- rob

[gmakhs]

Depends on what kind of sailing you gonna do I suggest you get another 100 watt of solar , average 3 amp for the autopilot are too.mucj you should try to balance the boat better , my boat but s 1 amp when it's unbalanced and 0.30 during ocean crossings or when I bother to spent time to balance the sails .
Depends.on how the autopilot is connected try to make easier for him and it will save you a lot of amp .

Wind vane is a solution but it might be out of your budget .
Your batteries seem quite small I would like to have 200 am/h (my boat has 300ah) and in general the bigger the battery bank the less impact it has .
P,s whatever route you choose to take try not to really on engine for charge , it's not nice to the engine .
I believe after the trip you gonna have a very clear image of what you need

[CptCrunchie]

Originally Posted by beetle

And how did you run the engine for 30 minutes with a broken alternator belt and not notice? A broken belt usually means a non-working raw water pump, and a non-working pump will cause the engine to overheat.

I believe the alternator is a single pulley and the water pump is a double.

[Mike Banks]

The hydraulic pump on an autopilot can draw ten amps--and I suspect the ones that use a mechanical drive probably as much or more depending on the gear ratios chosen.

If you are going to rely on an autopilot at sea for long voyages in overcast conditions, you had better have wind generators as well as your solar array of at least 200 watts--preferably two of them.

Which is why most ocean crossers rely on a monitored wind vane system for most of the journey. It is only when things get nasty that a wind vane, with a monitor is not sufficient.

[stormalong]

Originally Posted by Mike Banks

The hydraulic pump on an autopilot can draw ten amps--and I suspect the ones that use a mechanical drive probably as much or more depending on the gear ratios chosen.

If you are going to rely on an autopilot at sea for long voyages in overcast conditions, you had better have wind generators as well as your solar array of at least 200 watts--preferably two of them.

Which is why most ocean crossers rely on a monitored wind vane system for most of the journey. It is only when things get nasty that a wind vane, with a monitor is not sufficient.

1) If you read the op you will see that the boat in question here has a CPT autopilot which is very stingy on electric power usage.

2) All electric motors draw higher loads at startup than they do running. The average power draw is far less. The wiring is sized on that initial load not average load. Just like wind vanes the better balanced to boat the less correction is needed and less power is used. The average power draw for a Raymarine type 2 linear drive is six amps.

3)Look around. Most cruising sailors today use electric autopilots. Having done dozens of ocean crossings myself and spending a lot of time with other ocean voyagers I can tell you that wind vane usage is definitely on the decline.

[thomm225]

Running the engine for electrical power or having a generator seems to go against all the reasons many of us sail.

Invest in more solar and an MPPT Controller like Victron

[svsonora]

Just to answer the question on the alternator belt breaking -- there are no other belt driven appliances on an atomic 4. Water pump is a gear driven pump on an a4.

[CptCrunchie]

Originally Posted by svsonora

Just to answer the question on the alternator belt breaking -- there are no other belt driven appliances on an atomic 4. Water pump is a gear driven pump on an a4.

Gear driven. Certainly answers that question. Guess it is raw water cooled?

[Stu Jackson]

Electrical Systems 101 Electrical Systems 101


Read up, educate yourself.


Good luck, but luck should have nothing to do with it.

[svsonora]

One more question - 100w mono panels are so cheap now. If I bought one and mounted to the pushpit and got a dedicated MPPT panel, could I simply wire it to the bigger bank, while my existing bank is still hooked up to it?

[CptCrunchie]

Originally Posted by svsonora

One more question - 100w mono panels are so cheap now. If I bought one and mounted to the pushpit and got a dedicated MPPT panel, could I simply wire it to the bigger bank, while my existing bank is still hooked up to it?

Not clear what you are asking, but I'll give it a go.

Bigger bank: You have 2?

MPPT panel: An MPPT is a controller like this. This one has bluetooth so you can monitor and control it with your iPhone.

...while your existing bank is hooked up to it? While you can hook more than one MPPT controller to one battery bank, you should never connect one MPPT controller to more than one battery bank. Since the MPPT controller monitors the bank for the level of charge it has, as the bank reaches a full charge, it opens and closes the connection so it will never overcharge.

That means, if the MPPT controller is hooked up to more than one bank, unless the banks are the exact same level of charge, you could fry the higher level bank.

Also, if you connect the MPPT controller to more than one battery bank, you will fry the wires or the fuse, because the banks will use the wire as a bridge, and that bridge ain't big enough for that much traffic.

While an MPPT controller can be connected to more than one solar panel, it is a dedicated unit to only one battery bank.

[a64pilot]

Originally Posted by skipmac

Never had a wheel pilot, always below decks units but at the end of the day, I think the same amount of work would have to be done so power consumption similar based on similar performance.



Off the wind is where I see the problem of power use. It's been years so I don't remember the exact specs but at least a few amps draw by the motors when working. More when farther off the set course to move the wheel faster, less when making small correction.



Depending on the boat and conditions and exact course I recall at least 30% duty cycle. One trip, downwind in 30-35 kts and 8-10' seas I think well over 50%. That was after playing with boat trim and AP settings for days, adjusting dead band width, correction speed, delay times, etc. Assuming bad but not worst case scenario of 33% duty cycle, and 5 amps motor draw that's 40 amp hours a day. In a built in unit add another 0.5 amps for the clutch so now that's over 50. Based on tests done by Practical Sailer 30-40 years ago that is not unusual. So, would really love to learn how to get AP power draw down to 11 ah/day, especially since my clutch would draw that much.

No, at the end of the day the same work is done but one done by an inefficient hydraulic system and the other by a direct mechanical system that is way more efficient.

Taking a rotary mechanical motion and importing it to a mechanical wheel and driving it in a rotary motion is way more efficient than compressing oil passing it through lines and imparting it to a linear motion that is converted to rotary via an arm.

For one thing the mechanical electric motor draws no power at all until a correction is desired, then it will pulse for way less than 1 sec and move the wheel and stop, it may of course then later pulse again.
However assumption is that a hydraulic system maintains constant pressure?

The “right” way for me to do a below decks autopilot on my IP is to put a sprocket on the backside of my pinion shaft and drive it by an electric motor, that has been shown to draw way less than half what a hydraulic system does.

Here look at this screen shot from CPT.com
It says average current draw is .4 amps
Well .4 amps times 24 hours is 9.6 AH?
Less than 11, the CPT is extremely miserly in power consumption

[svsonora]

Originally Posted by CptCrunchie

Not clear what you are asking, but I'll give it a go.

Bigger bank: You have 2?

MPPT panel: An MPPT is a controller like this. This one has bluetooth so you can monitor and control it with your iPhone.

...while your existing bank is hooked up to it? While you can hook more than one MPPT controller to one battery bank, you should never connect one MPPT controller to more than one battery bank. Since the MPPT controller monitors the bank for the level of charge it has, as the bank reaches a full charge, it opens and closes the connection so it will never overcharge.

That means, if the MPPT controller is hooked up to more than one bank, unless the banks are the exact same level of charge, you could fry the higher level bank.

Also, if you connect the MPPT controller to more than one battery bank, you will fry the wires or the fuse, because the banks will use the wire as a bridge, and that bridge ain't big enough for that much traffic.

While an MPPT controller can be connected to more than one solar panel, it is a dedicated unit to only one battery bank.

Clarifying my question. I already have 100ws of panels mounted on my bimini roof with their own MPPT controller (x1, 4 wired in parallel)

If I got another solar panel, I don't have enough room on the bimini nor anywhere else on the boat to mount a panel. The only spot is at the stern end. If I got that panel, do I simply wire it to another MPPT controller than to the house bank, while my existing panels and controller are hooked up to it?

EDIT: I just saw you answered it. Thanks. I'm wondering if 2 solar charging systems will trip up the alternator.

[svsonora]

Originally Posted by a64pilot

No, at the end of the day the same work is done but one done by an inefficient hydraulic system and the other by a direct mechanical system that is way more efficient.

Taking a rotary mechanical motion and importing it to a mechanical wheel and driving it in a rotary motion is way more efficient than compressing oil passing it through lines and imparting it to a linear motion that is converted to rotary via an arm.

For one thing the mechanical electric motor draws no power at all until a correction is desired, then it will pulse for way less than 1 sec and move the wheel and stop, it may of course then later pulse again.
However assumption is that a hydraulic system maintains constant pressure?

The “right” way for me to do a below decks autopilot on my IP is to put a sprocket on the backside of my pinion shaft and drive it by an electric motor, that has been shown to draw way less than half what a hydraulic system does.

Here look at this screen shot from CPT.com
It says average current draw is .4 amps
Well .4 amps times 24 hours is 9.6 AH?
Less than 11, the CPT is extremely miserly in power consumption
Attachment 187028

Also would like to add that the standby current draw is almost non existent because it doesn't integrate to anything nor does it do anything aside from tack and hold a magnetic heading.

the 0.4amp draw figure is kinda useless to me, without knowing sea state etc. I'm imagining 4-5 foot seas in the chesapeake bay. Anything more than a reach, the autopilot is constantly working. I imagine its up to 5 amps (its fused at 10 or 15 if I remember correctly).