Solar Panel Excess Ideas?

I've just set up my solar panel system, which is working out great. I have 4 100 W panels on my roof connected a Mastervolt solar controller.

The controller is hooked up directly to the battery bank on one side and has an output on the other to provide excess 12 V power. I'm thinking of running this to a standard 12 V plug for availability. Any other ideas?

Also, if anyone uses a Torqueedo electric outboard, do you know if it is ok to plug the 12 V source directly to the battery? I ask as I'm not sure if a regulator is required or if it is built-in.

I presume that you mean that your controller has two outputs: one for charging that hopefully has a three step charging algorithm and another for general use. That second output is probably regulated at 12V.

But is the Torqeedo battery 12V?. I think not. Never try to charge a Li battery with anything other than the manufacturer's charger.

David

djmarchand said:

I presume that you mean that your controller has two outputs: one for charging that hopefully has a three step charging algorithm and another for general use. That second output is probably regulated at 12V.

But is the Torqeedo battery 12V?. I think not. Never try to charge a Li battery with anything other than the manufacturer's charger.

David

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I agree with David but look at what Torqeedo sells.
Charging Cable 12V - Torqeedo

That looks to me like a simple plug adapter for 12v or 24v. That would tell me that it should work just fine from your solar provided that its 12v output is actually regulated to 12v as David surmised.

The controller does use a 3 step charging algorithm for battery charging and has a 12 V output, as noted. I also have a 1800 W inverter, so currently I just plug the Torqueedo charger into my A/C plug.

I use 2 battery packs for my Torqueedo, leaving one in board to charge. To have this work independent of the house battery bank is my goal.

I agree that going with the manufacturers set-up when it comes lithium batteries. Thanks for the Torqueedo link. I can probably order it from West Marine at my next port.

Thanks!

If you are looking to use surplus electricity generated then if you have a watermaker...run it. Install a blower to cool your batteries. Turn on your ice maker. Just thoughts.

What I would do is wait.

Right now you have 400W of max solar Capacity.

You do not know if you have "extra" capacity over your needs or not, on a 24 hour basis

Once you get that figured out you can decide where to use any extra caacity.

If I had excess "free" generation I'd be inclined to add to my house bank, and have a quality inverter to let me decide at a moment to moment basis what if anything extra I wanted to power.

ksanders said:

What I would do is wait.

Right now you have 400W of max solar Capacity.

You do not know if you have "extra" capacity over your needs or not, on a 24 hour basis

Once you get that figured out you can decide where to use any extra caacity.

If I had excess "free" generation I'd be inclined to add to my house bank, and have a quality inverter to let me decide at a moment to moment basis what if anything extra I wanted to power.

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400W is not a lot of daily production with fixed panels. I have 400W, 2 are hinged to take advantage of sun angle when I can, the other 2 are totally portable to keep out of shadows and also take advantage of sun angle.

Even with the added production from sun angle, my 400W just covers average power consumption for a 40 footer snd 2 people. Not even close on cloudy days.

The only use I would consider for that 12V output would be an led light in the electrical cabinet just so I dont have to run longer wire which is silly if it is in tbe electrical cabinet anyhow.....

Let me add my support for using the "excess" power to charge the house batteries. But if the OP is already using the output to charge the house batteries (see his OP) and he has excess power, then he probably needs more house battery capacity. He didn't give the size of the house bank, but unless it is already big, like 800 AH then adding additional batteries will absorb that excess power and make it available for cloudy days.

And then he can use some of that stored energy, an inverter and the Torqeeda charger or the DC adapter to charge up his Torgeeda batteries. FWIW that DC apapter is probably a 12V to 30V voltage converter and it may not have as robust a charging algorithm as the 120V charger. I would use the 120V charger running off of the inverter. The efficiency of the voltage converter may not be any better than his inverter, so why not use what he already has.

David

djmarchand said:

And then he can use some of that stored energy, an inverter and the Torqeeda charger or the DC adapter to charge up his Torgeeda batteries. FWIW that DC apapter is probably a 12V to 30V voltage converter and it may not have as robust a charging algorithm as the 120V charger. I would use the 120V charger running off of the inverter. The efficiency of the voltage converter may not be any better than his inverter, so why not use what he already has.

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That is a good point that I would never have thought of. Thanks.

More info is needed to determine if 400 watt panels provide excess user power. For example, how much power is consumed and where. If at a dock, all the power provided will be excess. If on an anchor/mooring with an inverter powering a decent size fridge, TVs, lighting, laptops and so forth, the panels might just be adequate.

I recently replaced my 4 145watt 12v (18 mvp) poly panels with 4 295 watt mono panels. I sort of screwed up my earlier poly installation by laying them against a contoured hard top instead of flat along with using a PWM controller. NOw have a Victron 150/70 MPPT controller. Never the less, the polys were adequate and we do enjoy the things I mentioned above such as a fridge (self defrost) and the other loads.

My motivation for so called overkill was to minimize the amount of discharge that my enlarged battery bank (460AH to 860AH) will endure at any time. I am trying to double my battery life from 5 to 10 years. Batteries are CG2 Duracell golf carts purchased from Sams.

So... excess power in my opinion is good for extending battery life and not squandered.

foggysail said:

So... excess power in my opinion is good for extending battery life and not squandered.

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I think that is true IF you can actually use that power to bring the batteries back up to 100% and keep them from dipping below, say 70%. To me that would mean enough net positive output to recharge the batteries during the day so you are back to 100% by the time the sun goes down low enough to cut your output.

Any extra capacity above your needs during the day plus the absorb/float charge, would seem to be unused as far as battery health goes. But that is simply my own guess based on ignorance.

The trick is when the sun goes down, did you divert enough to batteries or other?

Isnt it easier to use just use the batteries for power and keep all solar going to them so in the end there is no guessing?

I have just connected my 4 mono panels that have a total rated solar capacity of 1180 watts. Two of my panels are mounted onto our front hard top while the other two reside on the rear hard top. I was careful to be sure the panels were as reasonably flat as possible and not mounted to the contour of the hard tops.

I was rafted with a friend while out and we both suffered genny problems. His needs a fuel pump and mine needs a manifold end plate for cooling. So I allowed him to connect his boat with refrigeration, TVs lights and stuff to my 2KW sinewave inverter as did mine for the 3 days we were out. That power originated from my battery banks. So my guess is that the panels along with the large battery bank will do as planned. Time will tell.

So far I have seen a maximum charge current of 69 ampere; I thought I would do better. I just don't have enough performance history yet. Things were too hectic while on anchor to check the batteries with a hydrometer but I do know that the batteries were in either absorption or float (Victron battery monitor) at each day's end.

psneeld said:

Isnt it easier to use just use the batteries for power and keep all solar going to them so in the end there is no guessing?

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Sure, absolutely agree with you. That is how my solar is connected. But the batteries are at the same time being discharged by whatever load is present unless the charging current is greater than that being demanded by loads

My batteries are floating by noon-ish and the fridge etc runs 24 hours off the panels and I have not run the genset since I connected the panels. I am going to hook up the inverter to run the hot water heater. The controller (Outback) can be programmed to cut the power below a particular voltage setting. 600 watts.

Xsbank said:

My batteries are floating by noon-ish and the fridge etc runs 24 hours off the panels and I have not run the genset since I connected the panels. I am going to hook up the inverter to run the hot water heater. The controller (Outback) can be programmed to cut the power below a particular voltage setting. 600 watts.

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Do you have you solar panels wired in series or parallel.

"I am going to hook up the inverter to run the hot water heater."

Might be simpler to just run 12V solar to the HW heater.

A resistance element will deliver heat , regardless of input voltage .

A good switch is all thats required.

You guys have really nice issues, I wish I had too much power to the extend I was not able to know what to do with it

L

FF said:

"I am going to hook up the inverter to run the hot water heater."

Might be simpler to just run 12V solar to the HW heater.

A resistance element will deliver heat , regardless of input voltage .

A good switch is all thats required.

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Not really. Power P = V^2/R. The heating element's resistance I doubt is constant over temperature so that could a little, very little with power increasing by 4 by doubling the applied voltage.

It is an easy way to dump excess power , so "efficiency" is moot.

FF said:

It is an easy way to dump excess power , so "efficiency" is moot.

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OK, but I understood your method was to get hot water. If you use and inverter between the panels and the hot water tank as you earlier suggested that is a different matter because the voltage supplied to the heating element will be about 9-10 times as great as that from a direct 12v panel connection.

There is another issue with just connecting a 12v (18vmp) panel to a hot water tank. Panels are current sources, not voltage sources. YOu may find there is very little voltage applied to the tank because the load most likely is too great for the panel.