Power draw on autopilot and general cruising

[a64pilot]

Originally Posted by svsonora

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

No, not as long as everything is adjusted correctly.
However just as an example if you have a stock alternator it’s likely to only output 14V or thereabouts, assuming you absorption voltage is much higher, it’s entirely possible that as soon as you Solar can exceed 14V, the alternator’s output will drop close to zero.
However up to the time that the bank makes it to 14V, the alternator will help charge.

[CptCrunchie]

Originally Posted by svsonora

I'm wondering if 2 solar charging systems will trip up the alternator.

Your alternator is connected to your battery bank. Your MPPT controller is also connected to your battery bank. Your alternator will top out at between 14.2-14.6V. This won't effect your MPPT except to stop it from sending solar power into your battery bank, because its sensors will pick up that there is more than enough power in the system already. As long as everything is connected directly to your battery bank, it cannot back-feed.

If it were me, as long as the panels are all the same size and rating, I would connect all of them in parallel to one Victron MPPT controller. You can find the calculator here. This link will tell you which controller will work for your array and battery bank.

[CptCrunchie]

Originally Posted by a64pilot

No, not as long as everything is adjusted correctly.
However just as an example if you have a stock alternator it’s likely to only output 14V or thereabouts, assuming you absorption voltage is much higher, it’s entirely possible that as soon as you Solar can exceed 14V, the alternator’s output will drop close to zero.
However up to the time that the bank makes it to 14V, the alternator will help charge.

It really depends on which has the higher charging voltage. Either way, running both at the same time won't speed up charging.

I'm not sure what you mean by "as soon as you Solar can exceed 14V." The MPPT controller output is a set voltage, no matter what the array is producing.

Here is an excellent article on it.

[svsonora]

Thank you everyone.

I'll have to get another mppt controller. I'm planning on getting a mono panel this time to hang off my pushpit. Probably rig it up so that it rotates down when not in use. I'd have to design it so that it clears my outboard storage mount as well.

[waterman46]

Originally Posted by 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

Wish I could sail a lot more than I do. Wind being so fickle, usually too light, or just so very strong and on the nose, having to fight current, etc, that use of engine is a lot more than I enjoy, but this is reality. We are talking about coastal, not long distance ocean crossing.

Why I mention this, to the OP is that does he expect to sail this entire distance? Reality means that if you have a schedule, job, friends or appointments waiting, whatever, engine use is, for many, a significant part of the charge power available.

Therefore, it is important to use that engine to get more than just 20 amps charge, as the OP has presently. If you have the bucks, a much better way, and pricier, get a Balmar charge controller. For what you need, the stock alternator will be just fine, it will put out about 40A without problem, when properly regulated. So only two hours of engine use per day will take care of at least 50% of your needs, solar the rest. And as others have said, get a battery monitor so you will know what you are doing.

Your power budget for the AP sounds a bit high for upwind or beam reach conditions, but about right for anything downwind in seas.

[a64pilot]

Originally Posted by CptCrunchie

It really depends on which has the higher charging voltage. Either way, running both at the same time won't speed up charging.



I'm not sure what you mean by "as soon as you Solar can exceed 14V." The MPPT controller output is a set voltage, no matter what the array is producing.



Here is an excellent article on it.

Most MPPT’s can’t I don’t believe exceed panel output voltage.

[a64pilot]

Originally Posted by CptCrunchie

It really depends on which has the higher charging voltage. Either way, running both at the same time won't speed up charging.

Well, it can. If your only making 10 amps out of Solar, and crank the motor and bring the 165 amp alternator online, well then most likely your very soon past the bulk phase and into absorption, and that can in fact shorten charge time.

[CptCrunchie]

Originally Posted by a64pilot

Well, it can. If your only making 10 amps out of Solar, and crank the motor and bring the 165 amp alternator online, well then most likely your very soon past the bulk phase and into absorption, and that can in fact shorten charge time.

Not so. The MPPT does not monitor amperage, it monitors voltage. The MPPT controller merely raises or lowers the voltage coming from the array so it can be used to charge the battery bank. So, in human terms, as long as the MPPT is sized correctly, the MPPT doesn't care how much amperage is being produced, it only cares about sending the correct charging voltage. Amperage is a concern when dealing with line size, but even that depends on the voltage being used.

Bulk or absorption, once the voltage going into the battery bank reaches beyond the MPPT set point, the MPPT will shut down,....because MPPT's monitor voltage, not amperage.

Case in point: Ignoring the alternator for a moment, .... Your batteries register 10.5V. The Victron controller shifts to bulk charging. No matter what voltage your array is producing, it will charge at whatever voltage the MPPT is set at, and it will feed it whatever amperage the array is producing (as based on the array's generated voltage). Most MPPT output set points are 14.2-14.6V, though some are much lower.

As your batteries fill, moving to absorption, they are still receiving 14.2-14.6V, but the MPPT is clicking the flow on and off so the batteries don't overheat. Once it reaches the float stage, the battery feed is still 14.2-14.6V, but the connection time will have become extremely short.

The moment you add any outside charging source, your MPPT will read it as the battery being fully charged (or overcharged) and it will shut down the power it is sending. And this is what you want it to do.

For this reason, I highly recommend the new Victron MPPTs with their new Smart Sense module. You can stick one of them onto one of the batteries to monitor the battery voltage and temperature. This too can shut down the MPPT feed, which is want if you want your batteries to have the longest life.

[CptCrunchie]

Originally Posted by a64pilot

Most MPPT’s can’t I don’t believe exceed panel output voltage.

All due respect, but it appears you don't understand what an MPPT controller does. The algorithm is a charging means that takes what is being produced and converts it to what can be used. On bulk charging, it inputs the maximum amperage your array is producing at whatever you set the MPPT to charge - AMG, Lead Acid, Gel, .....inputing the voltage of the system (12v, 24V, etc.) Your absorption rate is something you can set, and this will be the same rate for float.

Watts = Volts x Amps

You have a 130W array. That is its maximum output.

First example: When you put a meter on what your panels are producing, it reads 17V at 4.6A. The MPPT controller wants to maximize the feed ....which is what MPPT stands for (Maximum Power Point Tracking). Based on the algorithm, it converts the 17V into 14.2V. When it does this, the amps respond inversely and accordingly.

The math is easiest when you put it into watts, then divide by the voltage needed.

17V x 4.6A = 78.2W.
78.2W / 14.2V = 5.5A

Remember, your panels are not outputting a consistent voltage. So, the MPP tracks the panel output voltage so it can properly convert it to the 14.2V your battery needs. To maximize what the panels are producing, your batteries are now receiving 5.5A.

Second scenario: You have 130W 12V panels and a 24V battery bank. Lets say your meter reading shows the panels are producing 17V at the same 4.6A.

Again, look at the wattage being produced, 78.2W.

Your MPPT output is now set for 26.8V to feed your 24V bank. What now?

Same, same. Your MPPT will convert the 17V to the 26.8V needed to feed your bank. This means your 17V @ 4.6A is now 26.8V and as that exact moment, the maximum going into your bank is 2.9A. In the next moment, your panels could be providing 18V at 4.5A. However, the voltage entering your battery bank will remain at whatever you set it at, but the MPPT will convert what it is receiving to maximize the amperage it can receive from it.

So, your statement that your battery bank cannot exceed your panel output is incorrect.

[rsn48]

Efoy 210 with Firefly batteries, minimal of 4 (can be abused and not brought up to full charge, much like a lithium, but not a lithium), this route is expensive but will allow you to be out substantially longer on the hook using microwaves and smaller convection ovens (the one I have is 1380 Watts - cooking a small chicken for 50 minutes will consume 100 amps).

[noelex 77]

Originally Posted by CptCrunchie

Same, same. Your MPPT will convert the 17V to the 26.8V needed to feed your bank. This means your 17V @ 4.6A is now 26.8V and as that exact moment, the maximum going into your bank is 2.9A. In the next moment, your panels could be providing 18V at 4.5A. However, the voltage entering your battery bank will remain at whatever you set it at, but the MPPT will convert what it is receiving to maximize the amperage it can receive from it.

So, your statement that your battery bank cannot exceed your panel output is incorrect.

MPPT controllers can generally only reduce the solar panel voltage. There are only a very few, specialised, controllers that can increase voltage.

It is also important to understand that the output voltage of the MPPT controller is determined not only by the controller, but also the battery and potential solar panel output.

[CptCrunchie]

Originally Posted by a64pilot

Well, it can. If your only making 10 amps out of Solar, and crank the motor and bring the 165 amp alternator online, well then most likely your very soon past the bulk phase and into absorption, and that can in fact shorten charge time.

I'm revisiting this post, hoping we are on the same page.

If you are saying that firing up a 165A alternator will speed up charging, or course it will.

But if you are saying firing up this alternator will add 165A to the 10A from your MPPT, unless your MPPT output is set higher than your alternator, it won't.

[CptCrunchie]

Originally Posted by noelex 77

MPPT controllers can generally only reduce the solar panel voltage. There are only a very few, specialised, controllers that can increase voltage.

Just need to get one that has 'Booster' on it.

[a64pilot]

Originally Posted by CptCrunchie

But if you are saying firing up this alternator will add 165A to the 10A from your MPPT, unless your MPPT output is set higher than your alternator, it won't.

It will if the bank is at a SOC that will accept the amps.
First thing in the morning my AGM bank will accept more than 200 amps, later in the afternoon it will accept well less than 10, and is considered charged when it will accept only 3.

What the bank will accept determines charge rate, assuming of course that your programmed voltages are correct.

[CptCrunchie]

Originally Posted by a64pilot

It will if the bank is at a SOC that will accept the amps.
First thing in the morning my AGM bank will accept more than 200 amps, later in the afternoon it will accept well less than 10, and is considered charged when it will accept only 3.

What the bank will accept determines charge rate, assuming of course that your programmed voltages are correct.

I agree with you. My point was using them both at the same time doesn't mean the battery bank is receiving power from both. Bulk, absorption or float, the moment the MPPT controller senses voltage over its set points, it will drop to the lowest set point. Even if your amperages were reversed, the moment the MPPT controller senses that higher voltage, the same would happen.