Solar Help from EEs and Others Please

[blodn1]

This is the diagram I've come up with for the solar system I want to put on my trailer. Any help from people who know more about this than I do is GREATLY appreciated!

[padlin00]

I'm an Other not an EE so I could well be wrong here.

From the diagram I saw at the Trimeteric site, all negative leads from the converter, inverter, and the solar controller, go to the shunt. I believe you need fuses at the battery end of positive leads for the converter, solar controller, and the battery monitor. What are you going to use as your disconnects at the solar controller?

[blodn1]

Hi Bob - I'm another other. This is so confusing, because every diagram I see has different configurations. Planning to use 60 amp breakers for the disconnects. What size fuses would you recommend for those battery end positive leads?

[multi-task]

Using that many panels you might want to research 'Blocking Diodes'. Some install them on each panel, some don't bother. I've never used them so I can't really comment much further on how well they work/don't work.

Your controller temperature sensor should be at the battery. If that's where your shunt is you're good. If it's like my ts-mppt-15 it carries no current and can be attached to positive or negative or neither and just be in the box.

[blodn1]

Thanks Drew - The drawing is pretty, but was difficult in Publisher. The sensor is at the battery (tiny dotted line to controller) - I have it at the negative, but I suppose with some sort of attachment, that would work, too.

Blocking diodes...another electrical expression I'll have to *try* to figure out. Hardware, I can understand, though.

[Briantb]

Relabel output from panels to DC first off.

[blodn1]

Just looked up blocking diodes. Seems the two reasons to use them are to compensate for cells that are blocked from shade or whatever, and as resistance to keep energy from flowing backward when the sun isn't shining.

I won't have anything on the roof but the panels and their components, so unintentional shading will be minimal, and I think the controller would cancel the problem of backward energy flow.

I also read that higher-quality panels have higher resistance, anyway, and they have bypass diodes to allow for under performance of some of the cells.

[blodn1]

Hi Brian - not sure what you mean. What/where should I relabel?

[Mike Magee]

Your legend shows black line as "AC neutral", red line as "AC hot". It's DC. But hey, we know what you meant.

See what you get when you show us your diagram?

[Briantb]

You're colour coding.. Or at least on my tiny screen it looks like you are using the same colour for AC as well as your your DC output from the panels.
I'm not good with the schematics but it looks to me like you are planning on being able to hook up either shore power or generator to run your big loads.. example air or microwave but running through your battery bank all the time??? .. Not sure the small battery bank could keep up with the drain even with external power hooked up

[blodn1]

Ya get so close to something, you can't see errors. That's why there are editors. Thanks Michael and Brian - probably saved me some more embarrassment :-)

[Briantb]

The best diagrams are done on paper with a black pencil and no labels.. Then everyone assumes you know what you're doing

[blodn1]

Brian - I don't think I'll ever use a generator, but I thought planning for it would be a good idea. As an ME, I'm not really good at all the electrical stuff, and don't know colors and symbols. In fact, I hid under my desk for most of the electrical courses. Have to figure out how to re-route that big drain to use only shore power for big loads, but would like to have the option to charge while on shore power.

[blodn1]

Then everyone assumes you know what you're doing

Geezz - I know I can't fool anybody. And I have to live with the outcome, so I really want this done right!

[Bob Miller]

It looks like your ac outlets, air conditioner and microwave all have to run off of the inverter/battery bank. As mentioned above, there is no way an inverter/battery will be able to keep an a/c on for long, even with an huge charger. You might want to incorporate running the a/c off of the shore power only and have pairs of outlets, one from the shore cord & breakers, the others from the inverter, for your utility ac use.

BTW: Just how big are those 100 watt solar panels?

[blodn1]

The flexible Renogy panels are 41" x 21", and the Lil Snoozy roof is plenty big - might even be big enough for 6, but I think that would be WAY overkill.

Since I have lots of time to plan, I'll figure out a way to bypass the batteries when on shore power, though I doubt I'll need it that much.

[Bob Miller]

duplicated from above

[padlin00]

Fuses... a quick look on line shows max circuit amperage rating times 1.35 = fuse size, bumped up to the next common size. Your 45A controller x 1.35 = 60A. Make sure they are rated for DC.

http://assets.bluesea.com/images/products/20010.jpg

[blodn1]

Thanks Bob - good formulas!

[peterh]

I'm afraid there's a lot in your picture that doesn't make sense, like having a 12v fuse panel that doesn't connect to all your 12v devices, missing things like your solar controller and inverter, and an inverter circuit that feeds all your 120V appliances as well as a shore power connector that doesn't. Perhaps a better approach for you -- and us -- would be to tell us what you're looking for and thinking of buying, and asking someone here to draw it up for you.

As for the solar set up:
* You've got four panels on your drawing and an MPPT controller, but it looks like all four panels are wired up in parallel. To get the biggest bang for your buck out of your MPPT controller, you really ought to wire them up as two sets of two panels in series, what many people would call a "24 volt" setup. Wiring them up this way will make maximum use of your MPPT controller's capabilities while still minimizing the effect of having a panel or two parked in the shade. It'll also allow you to use a smaller, lighter, lower-cost, 30-amp controller.

* You should ask yourself this question: Do I really want to run my A/C off my 12v system? In most cases, the answer to that question would be no, because you'd need a lot of both batteries and solar panels to actually be able to do that. The system you've described isn't up to the task.

* Even a microwave is pushing it. Deep cycle batteries work best when their discharge rate doesn't exceed 50% of their rated capacity, e,g, a 100AH battery shouldn't be asked to provide more than 50 amps of power at any given time. To run even a 900w microwave you need a battery bank with, at the very minimum, 150AH batteries.

If you decide you only need these appliances when you have hookups, youll need some wat to switch between shore and inverter power. You can use a simple A/B switch (ours is a standard "3-Way" light switch), which is very simple and inexpensive, or you can get an inverter that does the switching for you.

One thing you don't really need is a "transfer switch." Most trailer owners don't have one; they simply plug their shore line into their generator when they're using it.