Solar Panel Wiring query

[bony]

G'day everyone,

I recently purchased a Projecta SPA400 5watt solar panel to maintain a trickle charge to my boat batteries. The panel comes with an inbuilt blocking diode and the owners manual says the unit has "smart control unit prevents solar discharge at night".

Here is the dealer I got it from -

Projecta SPA400 Amorphous 12V 5W Solar Panel

The SPA400 comes with just a red and a black battery clip on 2 metre leads so that the panel can be connected directly to a battery.

My question is - Does it have to connect this way or can I cut the clips off and wire the leads directly into my boat's wiring system?. If so where would be a suitable place to connect to in order for the panel to function efficiently?

I have a dual battery setup and I was thinking of connecting the charger to the (+) and (-) leads of my BlueSeas fusebox, would this be ok?

I woulld be grateful for some advice on this please.

bony.

[MBWhite]

OK I'll give my standard disclaimer first- I live in the midwest so the only salt water I deal with is what I soak my chicken in for a couple hours before it goes on the grill....


Anyway, the short answer is that yes you can cut off the battery clips and hardwire it in but there are some good reasons why you should consider putting some sort of terminal there to allow for a means of disconnection.

The longer and more involved answer starts at the panel, and begins by pointing out that the wire used for most inexpensive panels leaves a bit to be desired and should be replaced with a reasonable quality wire. Another item that you should be aware of is the purpose of the blocking diode. When a solar panel is in sunlight it produces electricity, which can be used to charge a battery. However, when the sun stops shining instead of being an electrical producer it becomes an electrical load and if the diode were omitted it would drain the battery it was connected to.

Now, if the panel is hooked directly to the battery and the wiring gets electrically compromised either through bad insulation, seawater getting into connectors, or something more drastic like cuts or shorts in the wiring you will still get this backflow unless that diode is installed at the battery end instead of the panel end.

So yes you can snip the clips off and wire it direct, but a much better approach is to remove the diode and wiring, and install it with a quality wire and put the diode between the wire run and the battery.

Whether or not a 5 watt panel should have a charge controller is a topic for a different thread, but good luck and best wishes for your project!

[bony]

Hi MBWhite,
I have some good quality tinned marine wire left over so I'll see if I can get into the guts of the panel to change it over.

Many thanks for the good advice and the clear explanation, it's a great help.

bony.

[pesarsten]

You may also want to consider installing a small inline fuse ( 2 Amp )

[bony]

Thanks pesarsten, I will do that.

Cheers.

[socaldmax]

I agree with all of the advice above.

I don't know if 5 watts is really going to do much good for you. I built a cheapo battery maintainer for my truck, and I used 2 x 5w epoxy panels. It sits on the dash and does ok. Consider ebay for these cheap panels, I got them for $15 ea, free shipping. I did have to replace the wiring, but they do work.

Do you have any CO, smoke or propane detectors? These things can pull a little power that adds up over time.

[bony]

Hi socaldmax,

I only need the solar panel to maintain my batteries charge when the boat is sitting on it's mooring. Before I bought this unit I found some posts on other forums which led me to think that 5 watts would do the job. I guess it remains to be seen, but I s'pose I could add more panels if I need to.

Thanks for the advice.

bony

[MarkJ]

At 5 watts you just wire it directly to the battery. I doubt youd even need a fuse.

I seriously doubt a 5 watt panel would charge a AAA battery for Mums hearing aid so its gunna do bugger all for your boat.

[Ex-Calif]

The fuse protects the wire. The fuse should be there and it should be at the battery end of the wire run. You are protecting against a short.

If connected for a long time even a small panel can damage batteries. I think week to week you are OK. If I were going to leave this setup for months I would consider a controller. I left 20 watts connected week to week with no controller but the panel was always working with a battery that I had depleted by day sailing.

You should have no issues wiring direct to batteries but you should consider wiring in a plug in case you want to disconnect them. Do not lose track of the positive and negative leads when you add the terminals.

[socaldmax]

Originally Posted by bony

Hi socaldmax,

I only need the solar panel to maintain my batteries charge when the boat is sitting on it's mooring. Before I bought this unit I found some posts on other forums which led me to think that 5 watts would do the job. I guess it remains to be seen, but I s'pose I could add more panels if I need to.

Thanks for the advice.

bony

The easy way to tell is to wire it up, and use a multimeter to check your battery V just before you leave, write it down.

When you get back, check the battery V again and see if it went up or down. Depending on your batteries' self discharge rate and any other parasitic loads you may have it might be enough, or it might need a little more power.

To give you an idea how little 5 watts is, my cell phone charges at 4 watts, my tablet charges at 11.4 watts. Anyways, measurement is the only way you'll know for sure.

[bony]

Just a quick reply to thank everyone for their advice in this matter. I guess I'll find out in the long run if 5 watts is not enough, in which case iit'll be easy enough to upgrade to a highar wattage unit. Thanks again for the replies.

bony.

[MBWhite]

Good luck!

[bony]

I wonder if someone can take a look at the Solaring wiring circuit I've drawn up and tell me if it is correct.

I have incorporated a solar charge controller but also wanted to install an On/Off/On Toggle switch into the system to allow me to switch the solar charge to either of my dual batteries. I don't know if I have set it up correctly, I'd appreciate your opinions on this please.



bony.

[Lake-Effect]

Your circuit looks ok.

if it's just the 5W panel, and you will be checking on your boat at least once a week, I agree with the others that a charge controller is probably not necessary.

We have a small solar panel almost identical to yours with a similar output, which i use to top up our single group 24 deep-cycle battery. I have it on a 12v lighter plug (with fuse in plug) and i just plug it in and confirm charging before leaving the boat.

Only once have I seen it take the battery up to 14.5v (close to overcharging) at which point I simply unplugged it.

[socaldmax]

Originally Posted by bony

I wonder if someone can take a look at the Solaring wiring circuit I've drawn up and tell me if it is correct.

I have incorporated a solar charge controller but also wanted to install an On/Off/On Toggle switch into the system to allow me to switch the solar charge to either of my dual batteries. I don't know if I have set it up correctly, I'd appreciate your opinions on this please.



bony.

You have your wires reversed on the bottom battery. That usually results in a blown fuse.