Need help sizing a portable solar system

[Tkreger]

I live in Miami, Florida and want to build a portable solar system that will fit into a large storage bin with wheels, like the "Husky 37 inch Mobile Job box."

For batteries I am considering either two Trojan T105 AGM that are 6 volt, 217 amp-hour capacity wired for a 12 Volt system, or two Trojan 31AGM that are 12 volt, 100 amp-hour, wired for a 12 volt, 200 amp system. And I was thinking of purchasing one Eco-Worthy 200W 12V foldable Poly solar suitcase.

Questions: Wanting only one portable panel, is this solar panel a good power match choice? What is the better battery choice? And finally, what size inverter is a good match for this set up?

Thank you!

[Xringer]

One thing to consider with some batteries, is venting. To prevent hydrogen built-up. (It can explode).
It's a super light gas, so having the top of the Job-box open should work.

Before you can 'size' a system, you need to define the loads. How much power are you going to need?
Do you want your PV power output to be high enough to charge the battery bank, while at the same time, be able to take care of your day-time load?

I could not find any reviews on that 200W folding array. I did see a review of their 100w folder, that questioned the power out spec.

I own some good 200W panels, and they only able to put out the full 200W on the very best days.. Like when it's very cool (or freezing cold) and very sunny.

In my opinion, if you need a full 200 watts of PV power, you might want to buy 250 to 300 watts of PV.. Conditions vary. Sometimes it's hazy or partly overcast etc..

One other question.. Is this system going to stay at home? Stored in garage?
Or does it need to be portable enough that you can take it camping?

[Tkreger]

Thanks Xringer.
I was going to use sealed AGM batteries so that I would not have to vent. I thought only flooded lead acid batteries need maintenance like that.

Miami is rated at about 4 1\2 peak sun hours per day, (though it seems like more!), and I just want the unit as an emergency power source for some lights, laptop, charging iPad,etc. in case power goes out from a hurricane or other event. I live in a condo and would store the unit on my balcony (which faces South), and not use it really for anything else than emergency power.

The goal is to build the unit with as much capacity possible in that space, and be the most efficient possible. I don't have a specific power load need, and i'm not worried about budget.

I was thinking of a 1000watt inverter though I know it's more than I need.

[oil pan 4]

Get an MPPT charger.
If you want an inverter to charge consumer electronics stuff get a pure sine inverter. The cheap modified sine wave ones fry chargers or don't charge your electronics at all.
Most of the laptops I have had will not charge off modified sine wave.

[Xringer]

Re: venting.. Found this: https://www.altestore.com/forums/ind...ic,1319.0.html

Yeah, I would say get an MPPT charger. It will get the most out of your panels.
But, one thing you might want to have is a Battery Tender. To trickle charge the bank.
I have a car that gets little use, so I have to keep it connected to a battery tender.


Instead of buying a sinewave inverter to make 120vac,
you might want to get a car-charger for your phone or Ipad..
Not that you'll have wifi during a blackout.. (Unless you use a Pirate Box).
For lighting, just use 12VDC LED lighting. With car type 12vdc plugs..
Less power wasted in conversion.

You want your PV to have enough power output to be able to fully charge a few phones,
at the same time you are charging the main bank..
Which could be used to power lights and low drain devices at night.
Some people like a small 12vdc fan.. (Women mostly).

[creeky]

A lithium battery would be a better choice. You avoid the need to trickle charge during idle periods. Simply charge to 60% and then leave it until you need it.

I would invert the power. Get a 300 watt inverter like the morningstar. Very low idle draw and it makes the power more useful for lights, etc. You can 12v it. Quite a few appliance options (lights, stereo etc), but a.c. will make life easier. Pure sine is the way to go.

A good rule of thumb is 1w solar per 1 amp storage. With lithium that drops a bit. Not knowing anything about the panel you're looking at. Size wise it should suffice.

[Xringer]

One advantage of using old-tech batteries is their availability.
If your high-tech rig fails during a four day power outage,
Amazon isn't going to be delivering any new parts to your door..

But, you can most likely find a used car battery, if your sealed LA pack fails.
Or, you can hook up to your car battery. Which can be charged during a totally overcast sky..
If you were worried about the MPPT charger failing, a cheap PWM charger could be in your spares box..

As nice as having a Pure Sinewave AC source sounds.. Do you really need it?
If you don't foresee needing 120vac, you could still buy a low cost 100W to 400w unit, just in case..
I think COTEK has them on Amazon.. Just need to have the Amp hours to feed it..

[creeky]

You can also keep a horse and buggy ready if your car fails. Kerosene lamps if the power goes out. A box of ice etc.

The advantage of quality new tech is its more reliable. For a small power outfit meant to be portable, redundancy is probably not essential.

Btw. The morningstar inverter draws milliamps on idle. Pure sine is the way to go as its more efficient with a variety of appliances. Battery chargers. Motors. Etc.

Lithium batteries deliver the same usable power at 1/4 the weight. Far more suitable for storage/back up as well.

[oil pan 4]

LiFePO4 batteries are a waste of money in this application.

For a stand by power application I recommend AGM deep cycle marine batteries. They have excellent stand by life.

Put a fuse or breaker in line with the inverter and sever the power when not in use and draw 0ma. That's what I do.

[jjackstone]

Originally Posted by Tkreger

Thanks Xringer.


...I just want the unit as an emergency power source for some lights, laptop, charging iPad,etc. in case power goes out from a hurricane or other event. I live in a condo and would store the unit on my balcony (which faces South), and not use it really for anything else than emergency power.

I agree with xringer. As long as you aren't running anything with a motor there is really no need for AC at all, hence no inverter. For lights use directly powered DC LED lighting or battery backed LED camping lamps(very low power usage). Charging any phone or tablet should be possible with just a car charger connection. I did this on a cross country bicycle trip a couple years ago. Here's a picture.

https://www.crazyguyonabike.com/doc/...545&size=large

On the left hand side of the photo below the trailer light there is a one inch piece of PVC with four lithium batteries in it to make a 12 volt supply. I used this to power the LED trailer light, charge my cell phone when no other power was available, and charge my laptop/tablet. You should be able to see the car charger connector there too. That's how I got power from the battery pack. Unless you just want to spend a lot of money on batteries, I agree with the lead acid or AGM packs in this app. While the lithium products will use less space, they problably cost three to four times more than lead acid.

However, if you are concerned about losing food in a refrigerator, then you should most certainly get a full sine wave inverter to keep it running. Motors don't usually like modified sine waves.
JJ