Need to charge 2 boat batteries via the boat's onboard charger

[timweidner]

I am new to solar power and just purchased a Sunforce 60 Watt solar 12-volt power generator kit that I think can serve a very modest solar power need, but I want to set it up in a way that I don't see described in the very simplistic manual:

I want to take the power from the panels to the 7-amp solar charge controller, then from there directly to the kit's 200-watt 12-volt DC-to-110-volt AC power inverter so I can run an extension cord from the 110 inverter outlet to the 110 inlet on my boat's on-board battery charger. I would not be storing power directly from the solar panels, but as long as the sun is shining I should be getting some level of 110 AC power to my boat onboard charger, right? I want to do it this way because the on-board charger is designed to balance power to the two batteries and stop charging when they are at capacity. This boat was previously in a garage with access to 110 AC, but is now in a barn with no power.

Will it be safe to have the panels permanently connected directly to the controller and then the controller directly to the inverter at this remote barn? The panels will be positioned such that they should get about 6 to 7 hours of direct sunlight each day. It will not suit my needs if I have to go to the barn twice a day to connect and disconnect the system.

Thanks!
Tim

[SunEagle]

I am new to solar power and just purchased a Sunforce 60 Watt solar 12-volt power generator kit that I think can serve a very modest solar power need, but I want to set it up in a way that I don't see described in the very simplistic manual:

I want to take the power from the panels to the 7-amp solar charge controller, then from there directly to the kit's 200-watt 12-volt DC-to-110-volt AC power inverter so I can run an extension cord from the 110 inverter outlet to the 110 inlet on my boat's on-board battery charger. I would not be storing power directly from the solar panels, but as long as the sun is shining I should be getting some level of 110 AC power to my boat onboard charger, right? I want to do it this way because the on-board charger is designed to balance power to the two batteries and stop charging when they are at capacity. This boat was previously in a garage with access to 110 AC, but is now in a barn with no power.

Will it be safe to have the panels permanently connected directly to the controller and then the controller directly to the inverter at this remote barn? The panels will be positioned such that they should get about 6 to 7 hours of direct sunlight each day. It will not suit my needs if I have to go to the barn twice a day to connect and disconnect the system.

Thanks!
Tim

There should be no issue having the panels, charge controller and inverter always connected if your on-board battery charger has the circuitry to go to "float" mode when the batteries get to the "full" charged condition. Without that circuitry the batteries can get over charged.

The problem comes with the limited amount of power that the 60 watts will generate and the amount of "useable" sunlight that panels will get. Just because you get 6 to 7 hours of sunlight does not mean you get that many hours of "useful" sunlight. Depending on where you are located the amount of "useful" sunlight can range between 2 to 6 hours.

You will need more panel wattage than the 60 you have.

[timweidner]

Thanks much for the reply, SunEagle!

I see what you are saying, but I essentially need this solar system to just continually "top off" the charge on these 2 marine 12-volt batteries. I am in northeast Ohio, which isn't Seattle in terms of cloudy days, but it is pretty cloudy relative to the rest of the country. My usage would essentially be this: I will take the boat out for the day and perhaps discharge 25% of the main battery's capacity and 10% or less of the auxiliary battery's capacity (it is only used to start a small outboard motor that may not even be started on many trips). So then I will return the boat to the barn and hook up the connection to the solar system and usually will leave it connected undisturbed for at least a week.

Before I moved to my current location, I had this boat in an attached garage and hooked its on-board charging system up to 110 AC house current. I generally observed that the on-board charger would indicate that the batteries were back to full charge in 3 to 4 hours and then I would disconnect the charger until I was ready to go out again in one or two weeks and I would plug it back in the day before a trip just to make sure it was "topped off."

Given this sort of usage need, do you still think the 60-watt system will be inadequate? I currently keep the two batteries connected to a 1.5-amp 110-volt AC "trickle charger" in my garage and then lug the batteries to my boat in the barn when I want to take the boat out. The trickle charger is doing a fine job of keeping the batteries charged, but it is a hassle to take the batteries in and out of the boat frequently and causes wear and tear on the boat and the batteries.

Thanks again for your thoughts on this!
Tim

[SunEagle]

Thanks much for the reply, SunEagle!

I see what you are saying, but I essentially need this solar system to just continually "top off" the charge on these 2 marine 12-volt batteries. I am in northeast Ohio, which isn't Seattle in terms of cloudy days, but it is pretty cloudy relative to the rest of the country. My usage would essentially be this: I will take the boat out for the day and perhaps discharge 25% of the main battery's capacity and 10% or less of the auxiliary battery's capacity (it is only used to start a small outboard motor that may not even be started on many trips). So then I will return the boat to the barn and hook up the connection to the solar system and usually will leave it connected undisturbed for at least a week.

Before I moved to my current location, I had this boat in an attached garage and hooked its on-board charging system up to 110 AC house current. I generally observed that the on-board charger would indicate that the batteries were back to full charge in 3 to 4 hours and then I would disconnect the charger until I was ready to go out again in one or two weeks and I would plug it back in the day before a trip just to make sure it was "topped off."

Given this sort of usage need, do you still think the 60-watt system will be inadequate? I currently keep the two batteries connected to a 1.5-amp 110-volt AC "trickle charger" in my garage and then lug the batteries to my boat in the barn when I want to take the boat out. The trickle charger is doing a fine job of keeping the batteries charged, but it is a hassle to take the batteries in and out of the boat frequently and causes wear and tear on the boat and the batteries.

Thanks again for your thoughts on this!
Tim

Unless you have a number of consecutive days of cloudy weather during the week you may be able to get away with the 60 watts. It comes down to not draining your batteries too far if you don't get a full charge. That would hurt the batteries and shorten their life. You can try out your 60 watt system but keep an eye on the batteries to determine if they are getting fully charged after a few days. Worst case would be you having to use your trickle charger to top them off before taking out the boat.

For the future. Those Sunforce panels (I think there are 4 - 15 watt in that system) will not last very long. Before you go replacing them with similar panels you may want to look into a single 100 watt panel. Good luck and I hope it works out for you.

[timweidner]

Thanks much, SunEagle!

[Naptown]

Why run through an inverter at all
Just connect the panel to the trolling motor battery through a charge controller that has a plugs on the battery side and panel side and plug in in the correct order ( battery first panels second

[SunEagle]

Why run through an inverter at all
Just connect the panel to the trolling motor battery through a charge controller that has a plugs on the battery side and panel side and plug in in the correct order ( battery first panels second

I think his existing battery charger requires 110v to run and I wouldn't trust the Sunforce charger to do the job on those batteries. This way he is using his trusted charger and generating the 110v from the Sunforce solar system.

[PNjunction]

Will it be safe to have the panels permanently connected directly to the controller and then the controller directly to the inverter at this remote barn? The panels will be positioned such that they should get about 6 to 7 hours of direct sunlight each day.

Take Naptown's advice and merely connect the output of the solar controller to your batteries.

That 7a sunforce controller is a cheap on/off ping-pong mosfet switch that switches off at 14.6v and turns back on at 13.2 volts or so. It is not designed to be attached to anything but a battery directly.

At any rate, save yourself the headache and just do the standard panel > charge controller > battery. If anything, upgrade beyond that 70's charge controller tech and pick up a small Morningstar 6A pwm charge controller which will do the job faster and more efficiently.

Also note that you do NOT have 6-7 hours of useful daylight. There is a difference between sunrise-to-sunset hours, and *solar insolation*, which are the hours that the energy from the sun is strong enough to actually do any good with a solar panel. Essentially early morning and late afternoon hours are ineffective. I looked up some generic OH solar-insolation hours, and you have 2.5 hrs winter, and 5 hours summer for solar insolation. These center around noon.

Note that like you said, this solar system is merely for *maintaining* a fully charged battery, and not charging one that has any real amount of discharge to it. A maintainer (like this 3a solar system with your two large boat batteries) is definitely in maintenance category which merely keeps a battery in the state it found it in, and not really charge it to any degree, especially with low solar-insolation in winter. Thus make sure you are truly fully charged with an external charger and THEN use the solar maintainer.

[timweidner]

Thanks Naptown and PNJunction. SunEagle's assessment of where I was going with this is exactly right. I really like the idea of using the on-board 110 AC charger that is designed to charge AND maintain 2 marine batteries at the same time. It has 2 banks with readouts that display the charge state of each battery and has performed perfectly for several years now. I understand your recommendation, PNJunction, but would l just add two lines from the SunForce controller (or the Morningstar replacement) that terminate in clips to attach to each battery? At least I would be leaving the batteries in the boat, which was the whole purpose of this exercise, but it sounds like the SunForce system may be too under-powered for my application. If I have to take the batteries out of the boat to charge them back up to full capacity before reattaching them to the SunForce for maintenance, I might as well leave them in the garage on the AC charger/maintainer and I am back to square one.

We have a couple of sunny days this weekend so I will try out a couple different set ups to see how it plays out, but if anyone else has words of wisdom, I'm all ears!

Thanks folks!
Tim

[Naptown]

The simplest thing to do is use the inboard charger but no power in the barn is that correct?
Shy not park it in reach of a cord for a few hours charge it up and put it away
The start battery can sit put the maintainer on the trolling battery or house battery.to maintain it.

[timweidner]

Thanks, Naptown -- yes, that is the situation. And yes, my normal routine would get me back to the house from lake with a few hours of daylight left, so I could take an extension cord to the on-board boat charger, get the batteries up to full charge, then take the boat back to the barn (which is on the property, but far from the house) and hook up the solar system directly to the deep cycle/house battery on the boat. Is the consensus though that I should not trust the 7 amp controller that came with the Sunforce system? Should I upgrade immediately to something better? Thanks!

[Naptown]

I would get something along the lines of a 10a Morningstar pwm.
This way when the harbor freight panels go you fan get a real panel in the 100-120w range.

[timweidner]

Thanks, Rich!

[PNjunction]

Upgrading the charge controller is probably the easiest and most beneficial modification to the typical HF panel kits. But that replacement shouldn't be an ebay cheapie special which puts one back where they started.

While the 6A Morningstar pwm charge controller would do in this case, like Naptown says, if you go for the 10A controller, you have some breathing room for a larger panel - which starts to put you beyond the "maintainer" status into something capable of a real charge - which if taken to the minimum limits, could replace your need for charging it up via the AC charger should you wish to do that and had enough solar time in between boating to do it.

You didn't say if you are using flooded or agm batteries. If they are agm, then solar may not be necessary at all since they have very low self-discharge, and a top off every month or so when idle with the AC charger would do just fine.

[timweidner]

Thanks for the feedback, PNJunction. I have flooded cell marine batteries right now. Is there a 10 amp controller that you recommend?