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Old 06-03-2019, 14:36   #46
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Power draw on autopilot and general cruising

Actually any good controller whether it be an MPPT, alternator or shorepower Charger, should maintain voltage and let the amps go where they may, which means of course slowly decrease, until it’s time for float, which is often a simple timer.
Then of course the voltage resets to float voltage.
I sometimes have as many as four different independent charge sources running, two shorepower powered by the generator, Solar and the alternator, and they all play well together and share the load.

However it seems that my Outback 80 will lead. I presume that is because 14.3 V to it is actually 14.35 (I’ve measured it), but 14.3V for my Magnum and Balmar 614 is 14.0.
It amazes me that these things can be so precise, I grew up in an analog world where 14 ish was acceptable for a “good” regulator.
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Old 06-03-2019, 15:12   #47
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Re: Power draw on autopilot and general cruising

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It amazes me that these things can be so precise, I grew up in an analog world where 14 ish was acceptable for a “good” regulator.
I used a slide rule in HS, and that was cutting edge!

As to being precise, that Victron is very precise. I spoke to the rep in Seattle this morning about how to connect one of the MPPT controllers to three batteries just to keep them topped (engine start, genset start, and watermaker). He said Victron makes a battery isolator that works with their MPPT controllers that do that. I'm still looking into it.
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Old 08-03-2019, 08:37   #48
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Re: Power draw on autopilot and general cruising

I believe you said you have an atomic 4 inboard. With a 55 amp alternator.

Moyer marine sells an accessory drive pulley for the Atomic 4 which has been machined for a 1/2" belt, it's a good upgrade from the original 3/8" belt.

I suggest upgrading your alternator to a 1/2" belt. Adding a battery monitor and taking the time to understand your actual loads.

Next i'd upgrade the alternator to one capable of putting out 70-100 amps, and with a 3 stage external regulator.

Then i'd replace your two group 27's with two 6v golf cart batteries, which will give you approximately 225 AH of capacity.
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Old 08-03-2019, 11:16   #49
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Re: Power draw on autopilot and general cruising

I got a BlueSea Mini OLED Ammeter which has a resolution of tenths of an amp. Using my Raymarine auto-pilot in typical conditions I find the auto-pilot uses 1A. More if it has to work hard. This is substantially less than I thought it would take.

Lesson is: Get some monitoring gear like a digital ammeter or battery monitor system and it will pay off in many more ways than you think!.
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Old 08-03-2019, 12:16   #50
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Re: Power draw on autopilot and general cruising

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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.
I think you've mentioned that you bought the lecomble and Schmitt drive with the Eco solenoid controller.... but if not, here is how we reduced the clutch consumption. Our lecomble and schmitt used 12 watts continuously for just the clutch. So, before installing the drive, I played with it and found it held just fine against the spring with only 1 watt. A company called Elactis.com supplied a driver that gave full power for the valve movement and then reduced power by a factor of 9 to 1.33 watts after 300ms. It connects inline from the computer to the clutch, and I added quick disconnects to make sure it can be removed from the circuit if it fails, but we now have a little over 7,000 miles on it so far with zero issues... and much happier batteries. This is much lower priced option compared to L&S version, but not as elegant.

A64Pilot- The hydraulic linear drives sold for autopilots are not continuous hydraulic pumps. They shouldn't use an power unless operating the ram.... at least ours doesn't. But, when they do run, they use so much power that they average out pretty high.

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Old 08-03-2019, 13:42   #51
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Re: Power draw on autopilot and general cruising

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Hi,
Only in my 3rd year cruising (Chesapeake bay), wanted to run this by you guys. I was on a weeklong trip to Baltimore and annapolis and on the last day, my batteries were discharged quite a bit (showing 11.9V). It worried me. We only spent the first day sailing for about 8-10 hours, then 4 days at anchorage. Even at winter, my 100W solar array will output from 0.5 amps to 1.8 from sunup to sundown even in some overcast weather (I have silicone polycrystallaine panels). It turns out my alternator belt was broken at some point, so when I ran the engine at anchorage for about 30 mins, it might not have charged anything. (55amp alternator running off of an atomic 4).

I actually don't know how well my amp meter is reading. The panels should top out at something like 5 amps. With suboptimal angle to the sun and my boom/sail covering some of the panels, I figured I should see 2.5 amps in the summer. I use the Wattsup device hooked up between the MPPT and the chargers.

I want to map out my hypothetical daily usage on an open passage as I am planning on trying a delmarvar penninsula circumnavigation this year. Does the below sound right to you guys? The number for the CPT autopilot, I mainly pulled it out of my a** based on what I read on different forums on the CPT autopilot power draw.

Batteries- two group 27 80AH AGM batteries in parallel. I also have a 90AH deep cycle lead-acid starter bank.

Use:
CPT autopilot - 72 AH capacity needed
- assuming 3 amps on average, 24 hours

charging cell phones via microUSB - 6AH capacity needed
- 2 devices, 0.3 amps, 10 hours (my primary nav device)

VHF - 0.5 amps - 24 hours

nighttime running lights - 12 hours - 33 AH capacity needed
- 0.6amps x2 (bow lights)
- 0.1amps x1 (stern light LED)
- Spreader Lights 2 amps

Total: 133AH capacity needed

Charge
Solar - assuming spring/fall use - 2 amp output @ 7 hours - 14AH capacity provided
Engine - at low RPMs, assuming 20amp output at 1 hour a day - 20AH capacity provided

Areas to save - switch spreader lights to LED (+18a). change bow lights to LED (+12a). Change pulley ratios on alterator to bump up output (+10a)

I'm getting a new mainsail soon and adding a bunch of mainsail controls (vang, outhaul, possibly cunningham), and hoping that'll cut down on the power draw of the CPT unit as well.

I should get a load tester to get a better idea of my battery usage as well, even just for bay cruising.

Even with that I'll be drawing down a third of my batteries every day.
I guess I better add a windgen. I don't really have any room to add another solar charger - I had to construct a dodger frame to mount the panels.
I understand this is not enough for extended cruising, but wanted to see if you think my assumptions are correct. I'd appreciate any tips as well.
If you are using Lead Acid and AGM Batteries in the same electrial charging
system it will never work properly. They are designed to charge at differnt rates. If you change the pully size on your alternator it will only get you to a quicker initial charge and then drop off to where the regulator tells it to be. Best bet is to get a smart charging system and change to one type of battery. I have found that golf cart batteries make a good house system. Also gettin your sails in proper trim will help greatly in AP power draw.
Hope this helps.
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Old 14-03-2019, 07:56   #52
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Re: Power draw on autopilot and general cruising

Thanks. The alternator will only charge whatever batteries are selected in my switch. And my solar is only connected to my house batteries. The only thing that is hooked up to both is my shore power charge controller, which supposedly will do an AGM and lead acid no problem, just won't do an AGM and gel or LA with gel.
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Old 17-03-2019, 00:53   #53
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Re: Power draw on autopilot and general cruising

Few updates -
I actually have amorphous silicon panels, not any sort of crystallaine panels.
The charging current typically has been reading: 1.5-1.8amps @ 18-19 volts under sail, a bit lower @ 1 amp at 19-20 volts when mainsail is down. I imagine the difference is from shading - I will have partial shade on 2-3 panels when my sail is down since the boom is centered, and when I am sailing, I will have clean light on 2 panels.

1.8 amps at 19 volts - is that going to have the same effect as charging my batteries at 2.4 amps at 13 volts? I really need to do the reading that was suggested on this thread.
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Old 17-03-2019, 04:02   #54
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Re: Power draw on autopilot and general cruising

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Originally Posted by svsonora View Post
Few updates -
I actually have amorphous silicon panels, not any sort of crystallaine panels.
The charging current typically has been reading: 1.5-1.8amps @ 18-19 volts under sail, a bit lower @ 1 amp at 19-20 volts when mainsail is down. I imagine the difference is from shading - I will have partial shade on 2-3 panels when my sail is down since the boom is centered, and when I am sailing, I will have clean light on 2 panels.

1.8 amps at 19 volts - is that going to have the same effect as charging my batteries at 2.4 amps at 13 volts? I really need to do the reading that was suggested on this thread.
Amorphous silicone is not a Good choice for a boat, because of efficiency. You need at least twice the area than for crystalline cells.

Your last computation is basically correct, but depending on controller
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