Newbie questions building emergency power setup.

[mattro]

I am new to solar. I have researched some but have some basic questions.

I am wanting to build my first solar system to be used primarily as emergency power in the event of long term power outage to charge cell phones, recharge AA batteries, run small dc tv and radios, laptop, etc. I have to do this on a very tight budget and not throw money away with mistakes or have a system that has costly annual upkeep.

For the first panel, I am considering an Instapark 30w mono for around $128 off Amazon. I considered a cheaper Amorphous panel, but I am limited on full sun space on my roof and I like the higher efficiency of the mono over time.

For the controller, I know a small simple controller will handle this panel (and more panels later), but my concern is I want a meter to know the charging current (how the panel(s) is performing) and the status of my batter bank. Therefore it makes sense to buy a controller with meter built in. This has me looking at something like the "Sunforce 60031 10 Amp Digital Charge Controller (mixed reviews)", or the "30 AMP SOLAR CHARGE CONTROLLER by Missouri wind and solar (not sure it shows charging current)". Am I thinking smart, or would I be better with a bulletproof controller like the "SunSaver 10 Charge Controller 12V 10A" and install various meters for charging current and battery bank charge? I will enjoy accurately monitoring how the system produces and reacts so having something more than a blinking light for charging and a green light for fully charged is important to me. It may be important for the controller to handle AGM batteries, I am not sure.

For the battery (s), I am looking at starting with a "12V 35Ah AGM Sealed Lead Acid Battery" from ChromeBattery.com. They are located in my area and I will not have to pay shipping. I figure after I play with the system, I could easily and affordably add more of this same battery to increase the storage capacity. They sell 55ah batteries, but two of the 35ah batteries are almost the same price as one 55ah. One question I have on batteries is: is starting with this small of a battery a mistake? If I want to grow the system later (say 200-400 AH), it seems I will be very limited by starting with this small of a battery. Can I mix different AH batteries later without degradation? Should I be looking at high ah 6 volt golf cart batteries instead (which are non-agm and costly)?

I figure I will leave everything 12volt to keep it simple and increase my options for cheap inverters and accessories.

Sorry to be so long winded. I would appreciate any advice and input that could be offered.

[Mike90250]

1) you will need more power than you expect - others will want to charge their phones, laptop..... Plan on building 2, or 1 oversize one.

I used the venerable Trace (now Xantrex) C-12 controller, has blinking lights that indicate state of charge.

My rig the Solar Monolith:



Update pictures/information here.

[mattro]

Thanks for the quick reply. Are you saying I will likely wish I had more battery, or more solar. Obviously both would be nice, but I'm on a crazy tight budget. Does the system I detailed out lack more in the capacity (batteries) or in the recharge (panel).

Thanks

[Mike90250]

Your system lacks known loads. How much power does your ___ need for a recharge ?

Nobody ever promised solar was going to be cheap, and you are better off overbuilding a bit, because it does not destroy batteries. Chronic undercharge can destroy a battery in a month. Sealed batteries can be overcharged and boiled dry, unless the charger has a AGM setting. (don't use a GEL battery).

laptops run on 50-100W, and more when they are recharging. A 30W panel can't handle that. You can use a small battery as you describe, but not at nightime, your 30w panel does not have enough to both recharge a low battery, AND charge the laptop which is charging the iDevices.

You need to know your nighttime loads in watt hours, to properly size the battery, Once you have battery sized, you discover the sun hours in your area, for whatever season you chose to base your system on. Then you can chose the PV panel size to meet both loads and battery charging .

read Sunkings "How To" on this.

http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design&p=33092#post33092

[peakbagger]

Just for reference a 1500 watt Xantrex Portable Power system is $396. It has the battery box, wheels, handles, charge controller and AC inverter (Modified square wave) battery and all the interconnecting wiring. It is set up for charging from the wall or you can plug a 12 volt solar panel in or plug it into a car.

Granted its a good learning experience to build your own, but unless you have the parts hanging around it would be hard to assemble something equivalent out of individual pieces for less. It also is probably going to be a bit more robust compared to buying individual parts from E-Bay especially if they are made in china unknown brands.

[SolLady]

handy load & battery calculator

Mike90250 is giving very solid advice. You must know your nighttime needs and reverse design the system from there. This website has a super helpful calculator to help you determine your load and battery needs. http://www.civicsolar.com/resource/o...ry-sizing-tool

To answer your Q re: batteries, yes, you are starting way too low. Use the above calculator and size as needed. To give you an example, I live off grid and use solar for minimal electricity much like you describe. We also live with low roof:sun exposure like you. We're getting by on 200 amp hrs of battery storage.

Re: the Xantrex system that peakbagger mentions. I had one of those and it is severely under powered. The Xantrex does not include a panel, so that adds to their cost. The onboard battery is only 50amp hours. I used it with an 80 watt panel. In full, all day sun, it barely provided enough juice to charge a cell phone & run a 12v cooler for 8 hours.

Good luck with your project!

[russ]

Westinghouse has come out with all-in-one DIY Solar Panel Kits that have less "stuff" to set up, the ad says 80% fewer parts. The inverter is built into the panel so you have safe AC power.
Powerful, reliable, clean and affordable.

Sorry but that ad is nothing but trouble - their claims are false and misleading and you have no idea what is in the package.

[mattro]

Thanks for the replies. Those load and battery calculators are really handy. I can see how it can be real easy to undersize a system and I appreciate the words of caution.

Tell me this: When building a small system like this, is it better to build with
fewer large batteries (say 1- 125ah battery or 2-55ah batteries),
or more smaller batteries (say 4-35ah batteries)?

Also, if these batteries were still in decent shape in a few years, could I add them to a bank with batteries with much larger capacities or would I want to leave this as a standalone system?

[Wy_White_Wolf]

the larger the individual battery the better, less cells to maintain or go bad. Always try to build your battery bank with 1 single string instead of multiple strigs in parallel.

The age difference in the batteries would make them drag down a new batery and destroy it in short order. Keep old and new bateries on seperate systems.

WWW

[john]

hey, are you learning yet? Lots of confusing advice,isnt there. I started just like you, power for eme rgencies, the only thing is you start looking at the power just sitting there (batteries) and you want to use it for something else. You need bigger batteries. I use 100ah (easier math) . They are cheap and available.You need a bigger panel.I like mono(I have both) .About80-100 watts is good. They are battery chargers, you need to watch amps. You cant charge a car battery with a 2 amp battery charger,so that is not going to charge any battery well.5-8 amps per battery is minimum. Buy a tester for checking outputs.Way cheaper.Good Luck

[conntaxman]

panel

1) you will need more power than you expect - others will want to charge their phones, laptop..... Plan on building 2, or 1 oversize one.

I used the venerable Trace (now Xantrex) C-12 controller, has blinking lights that indicate state of charge.

My rig the Solar Monolith:



Update pictures/information here.

.
Mike very nice on the panels, quite a few. nice to see.