Solar Charge Controller debate

This debate rages and rolls in marinas across the planet. Seems just when a guy (or gal) figures out whats available and educates themselves.... the technology bumps up.

I have a fairly basic electrical system on board and am leaning towards augmenting it with new solar.

Simple... prob 600w on a 24v feed. Im inviting this debate. Let it walk and wander. We can see what sticks. Each of our needs is different. Spitballing can bring out some great ideas.

My simple approach this far is to stay with Mono panels. Yes, I know mono vs poly it its own debate... but it is what it is.

Qt 4. 150w (600w total) Mono panels feeding my qty 9. 8d batteries through a basic mid level digi charge controller. 2 on each engine. Isolated single for generator, then 4 more for house.

With recent price drops in the solar market I have shopped and found my little system to be had for approx 700.00. (Installing it myself)

Questions-

Charge controller recommendations?

House bank swap from the 8D's to true deep group 27s? They are only 6 months old. Ouch

Let the games begin.

Why are you use 2 8Ds per engine? Seems like a waste of battery capacity that could go towards your house bank.

Sorry. Good point as I myself look at it often and ultimately come to the same conclusion. Although it is a lot of weight and space, it sure is nice peace of mind.

My optional configuration I have considered is to isolate only two for engines. And plumb the rest into growing the house bank to 6. Keeping the remaining one in reserve. This would allow my admittedly smaller than optimal solar system to further catch up, or rather keep ahead with the deeper bank. Figure approx 1400ah or 700@50% cycle.

Capt.Bill11 said:

Why are you use 2 8Ds per engine? Seems like a waste of battery capacity that could go towards your house bank.

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Not only a waste, but probably not the best for them.

When we acquired Dauntless it had two 8D's to start and house, the other two 8D's to House, with a Perko switch to combine.

I made one house bank of Four 8D's and bought one Grp 31 for start. Works great and I can still use the Perko if need be.

I did indeed invite the topic of this thread to wander so I am not trying to corral it...

The starters were just replaced recently and I could be mistaken but I believe they are 24v systems.

Oooops...but If I were you...2 8Ds for starting both should be plenty...either separate or in series for the 24V start.


Now you have opened up the whole discussion on how much of your boat do you want to keep 24v such as windlass, thrusters, starters....


Solar is only part of a whole boat power design.....


what is yours?

I forgot the question.

Tuesday said:

I did indeed invite the topic of this thread to wander so I am not trying to corral it...

The starters were just replaced recently and I could be mistaken but I believe they are 24v systems.

Click to expand...

If that is the case, it would explain why you have two start batteries per engines.



Is the rest of the boat 24v as well? Or do you have both 24v circuits and 12v circuits?

Have both 12v and 24v

Capthead said:

I forgot the question.

Click to expand...

Question was posed to the group: Which charge controller did they recommend?

Tuesday said:

Question was posed to the group: Which charge controller did they recommend?

Click to expand...

MorningStar MPPTs seem to enjoy a good reputation. So too for Outback.

Do not be surprised if a MPPT costs almost as much as your panels.

With an MPPT controller, you'll get an extra 10 - 20% current out of your panels; even more on cloudy days, or when your batteries are lower than normal voltage (when you really need it).

IMHO, it's worth the extra hundred bucks, unless you have unlimited real estate for panels.

Thats what I wanted to hear. Also going with the 24v input feed is a good sized capture for panel's output.... or so I have heard.

"I forgot the question. "

The question is always the same,

How can the house loads be reduced so the House batt set is seldom drawn down to 50% SOC.

Solar is as good as it gets , no noise , no stink , no PM or replacement .

But only if the loads are reasonable enough to exist on the limited power.

Once the loads are low enough the batts hover at 100% and live long and you prosper. (sorry Spock)

Unless you have a very different boat configuration than everyone else, the key to solar is to get the most Watts out of the limited space available for panels. This typically means:

- Get the most efficient panels you can.

- Get panels who's shape and size allows you to best fill the available space

- Use an MPPT charge controller to extract as much out of the panels as possible.

Unless you are a real miser with power, they will help, but not provide all your power needs. When it's sunny out, our panels will carry the boat's typical power load while at anchor, but it's not enough to recharge the batteries from the night before. But it definitely extends the time between generator runs.