Matching solar panels to batteries to consumption

[Littlechay]

Originally Posted by Adelie

Purchase costs aside, PWM controllers are more efficient than MPPT controllers for small installations. The electrical self demand of the MPPT controller itself exceeds the extra power produced. In larger installations (400-500w) the MPPT is ahead.

Don't think so. It would have to be one hell of an inefficient piece of electronics design for that to be true!

[StuM]

Originally Posted by Sauntress

x

VHF XMDSC 0.6amps (say)

Ta

Assuming you VHF is on standby at all times (which it should be) , it is going to take up to a couple of Amp hours per day if no one in transmitting anywhere near you. If you're in an area with a lot of traffic, you could well double that.

Apart from that extra few Amp hours, the rest of your figures look OK.

But it took a while to make sense of because of your conflating Amps and Amp hours.
You may like to take a look at this: http://www.cruisersforum.com/forums/...ml#post1933764

[mitiempo]

Originally Posted by newhaul

......on most of my customers boats as well as my own much over a 100 watts is over kill. So it makes little sense to spend more on a controller than the cost of the panel.

If the space for panels is limited all the more reason to choose a good MPPT controller. Your customers deserve to get the watts they are paying for with the panel purchase.

[newhaul]

Originally Posted by mitiempo

If the space for panels is limited all the more reason to choose a good MPPT controller. Your customers deserve to get the watts they are paying for with the panel purchase.

I agree once you max out your real estate the next step is mppt however as I said in my post more than 100 watts is overkill for most of my customers boats and power needs. Maine and I had a discussion a year or so ago and we agree on this point max space then add a new mppt controller.

[mitiempo]

Originally Posted by newhaul

I agree once you max out your real estate the next step is mppt however as I said in my post more than 100 watts is overkill for most of my customers boats and power needs. Maine and I had a discussion a year or so ago and we agree on this point max space then add a new mppt controller.

Makes sense if budget is your main concern - some solar charging is better than none.

On a 24' boat isn't 100 watts close to max?

[newhaul]

Originally Posted by mitiempo

Makes sense if budget is your main concern - some solar charging is better than none.

On a 24' boat isn't 100 watts close to max?

Depends on the boat on mine I have 100 watts on the pushpit however if I rotate it 90° I could mount an.aditional 100 there but I only use about 12to 15 ah on an.all nighter 100watts is more than enough power. Figure 100by 6 hours is a out 600 watthours or well over 40ah apossible charging on a sunny winter day here in seattle.
(Pictures on my profile albums)

[mitiempo]

Originally Posted by newhaul

Depends on the boat on mine I have 100 watts on the pushpit however if I rotate it 90° I could mount an.aditional 100 there but I only use about 12to 15 ah on an.all nighter 100watts is more than enough power. Figure 100by 6 hours is a out 600 watthours or well over 40ah apossible charging on a sunny winter day here in seattle.
(Pictures on my profile albums)

A Superball win is possible too.

In your (and my) latitude we figure on 5 hours a day at full output. You have to be further south for 6 hours a day at full. And with your controller you cannot count it as 100 x 6. The best you will get is the amperage of the panel - about 5.5 - with a Pwm controller. For a full day that equals about 27.5 AH on an ideal day. And ideal days do not happen in winter.

An MPPT controller can get you a hair under 7 amps in bulk. Total in ideal conditions about 35 AH in ideal conditions.

[newhaul]

Originally Posted by mitiempo

A Superball win is possible too.

In your (and my) latitude we figure on 5 hours a day at full output. You have to be further south for 6 hours a day at full. And with your controller you cannot count it as 100 x 6. The best you will get is the amperage of the panel - about 5.5 - with a Pwm controller. For a full day that equals about 27.5 AH on an ideal day. And ideal days do not happen in winter.

An MPPT controller can get you a hair under 7 amps in bulk. Total in ideal conditions about 35 AH in ideal conditions.

The next.two days are supposed to be perfect. Clear sunny and cold.

We won today so get a bye in first week of playoffs superbowl dream dint to far from being a reality.
Even with the 5.5 hour estimate of.27ah is well above my 15ah estimated max with an all night sail. Becides im feeding it into a 4Dd with 180 ah rating

[Sauntress]

Originally Posted by newhaul

Why do you assume that a person can't afford to spend a hundred bucks on an item just because they choose not to. I spent 14 because the controller does what I want it to and that saves me the extra 86 bucks. That will purchase a spare controller and a few extra prefilters for my water maker. Which means I won't have to try to source them in some far corner.

All most illuminating. As a matter of fact, being as how my boat has no engine, top of my spending list is integrity of the rig, meaning spars, standing and running rigging, sails and all that keeps her moving. Then preservation of her hull, then the wind vane self steering, charts etc etc. And right at the bottom of the list, electricity (I am ashamed to say). Thus this thread, or discussion has proved most educational and enabled me to get to grips at least with the basics and pay attention to something I have chosen to ignore and shove in the bilges (now to be removed) on the basis that "I don't understand electricity". My motto would be simple, robust and reliable, the last implying reputable makers, but without spending silly money.

[Sauntress]

Originally Posted by StuM

Assuming you VHF is on standby at all times (which it should be) , it is going to take up to a couple of Amp hours per day if no one in transmitting anywhere near you. If you're in an area with a lot of traffic, you could well double that.

Apart from that extra few Amp hours, the rest of your figures look OK.

But it took a while to make sense of because of your conflating Amps and Amp hours.
You may like to take a look at this: http://www.cruisersforum.com/forums/...ml#post1933764

Sorry about that. Yes I will look at that thread. And I know I am supposed to have the VHF on all the time.............but

[thomm225]

Originally Posted by socaldmax

I'm of the opinion if someone can't afford to spend $100 on an MPPT controller, they've got bigger problems than what size solar panels to install.

I paid $12.00 for my PWM Controller. (and bought two)

I didn't trust them for the first 3 years so I connected to the batteries with alligator clips and rarely left the controller plugged in long when I wasn't aboard.

One of the alligator clips has broken so now it's semi-permanent. I wired that side to one of the battery terminals. (I'll buy a proper lug for it one day)

My 100 watt panel was $76.00. (solarblvd)

I found some old 14 gauge wire at work and installed the whole thing in about 10-15 minutes. My panel lays on top of the aft lazarette locker.

I do believe I will go ahead and fuse it soon and leave it plugged in since I have seen the warning about order of connection.

I've probably connected and disconnected in various ways though maybe 75 times. Sometimes panel from controller. Sometimes controller from batteries etc

The system works great......all for less than $100.00.

[socaldmax]

Originally Posted by newhaul

OK max here goes on most of my customers boats as well as my own much over a 100 watts is over kill. So it makes little sense to spend more on a controller than the cost of the panel.
Now your 208 watt panels are 24 volt units which need an mppt controller for the average 12volt system. On the down side they take up a lot of real estate on a small vessel (most of my customers are in the sub 30 range)
( the biggest array I had a customer want was 200 watts. ) and all I install are mono panels with an efficiency in the 20% range.

Then you promptly waste 20 - 25% by using a PWM controller instead of an MPPT.

Most people don't understand that they're never going to get the advertised output from a solar panel even if it's mounted on a solar tracker, much less on a moving vessel that's heeling over. Then you reduce that output by another 25% by using a PWM controller and one would be lucky to get 60 - 65w watts of actual power out of that setup.

Now we apply those same "lack of efficiency" numbers to this guy's situation, everyone is telling him a 50w panel will do, but after he installs a PWM controller on it he's lucky to get an actual 30w out of it. Was that factored into everyone's calculations?

[socaldmax]

Originally Posted by thomm225

I paid $12.00 for my PWM Controller. (and bought two)

I didn't trust them for the first 3 years so I connected to the batteries with alligator clips and rarely left the controller plugged in long when I wasn't aboard.

One of the alligator clips has broken so now it's semi-permanent. I wired that side to one of the battery terminals. (I'll buy a proper lug for it one day)

My 100 watt panel was $76.00. (solarblvd)

I found some old 14 gauge wire at work and installed the whole thing in about 10-15 minutes. My panel lays on top of the aft lazarette locker.

I do believe I will go ahead and fuse it soon and leave it plugged in since I have seen the warning about order of connection.

I've probably connected and disconnected in various ways though maybe 75 times. Sometimes panel from controller. Sometimes controller from batteries etc

The system works great......all for less than $100.00.

I don't know about great - it could work considerably better if you increased the size of the wire to 12 or 10 ga and sprung for an MPPT controller.

I'll never understand this "works good enough" mentality. It's like saying your fuel tank sprung a leak 5 yrs ago and you patched it up with bubble gum and it's been holding fine. Never mind the correct way to patch a fuel tank, or the ever growing puddle of fuel sloshing in the bilge.

[newhaul]

Originally Posted by socaldmax

Then you promptly waste 20 - 25% by using a PWM controller instead of an MPPT.

Most people don't understand that they're never going to get the advertised output from a solar panel even if it's mounted on a solar tracker, much less on a moving vessel that's heeling over. Then you reduce that output by another 25% by using a PWM controller and one would be lucky to get 60 - 65w watts of actual power out of that setup.

Now we apply those same "lack of efficiency" numbers to this guy's situation, everyone is telling him a 50w panel will do, but after he installs a PWM controller on it he's lucky to get an actual 30w out of it. Was that factored into everyone's calculations?

Not really how things work in the real world. The mppt only really benifits in the last. Ten or so percent of charging. Btw I guess you missid the part from the op that he is looking to update a bit from his.current pair of 11watt panels that are over 30 years old.

[Sauntress]

And cross the Atlantic.
Now, we have 10 Amp per twenty four hours estimated of which 6Amp for the masthead tricolour and the compass. I actually question whether people 1,000 miles from land religiously run with nav lights. I suspect the answer is no, just when something hoves in view. The suggested setup is a 50 Watt panel, which theoretically, and if I have understood your discussion, should knock out 4Amps at peak charge, over 5 hours= 20 but I am sure that is not right for all the reasons you two are talking about. One view says the MPPT squeezes 20% more. The other says it ain't worth it, or words to that effect. This seems key and the cost differential given all the rest, possibly academic. I did write up all of this properly but cannot attach the Word document.