Solar Power System

Step 7 Some final thoughts.

I originally made this set up as a back up power source for when the power went out. But, I think I will use it more often than that. I don't think the solar panels are powerful enough to charge the batteries after depleting them every day. I will use it for a few days and update how well the system charges with constant use.

I originally tested out a single battery and was able to run a lamp and my laptop for about 5 hours before I finally shut it off. The good thing about this inverter is it will shut off automatically if the voltage drops too low to prevent depleting the batteries. I'm pretty confident that with the three batteries I will be able to power larger items for an extended period of time.

Also, this is a pretty expensive set up, about $650. My costs (with out tax or shipping charges) and where I got things.

Solar panels $250 (used from craigslist)
Marine batteries $240 (for 3 from Walmart)
2 AWG Cable $5 (for about 2 feet from Lowe's)
Lugs $8 (for 8 from Lowe's)
1200 W inverter $130 (Amazon.com)

I had the rubbermaid container, battery charger, and the charge controller came with the solar panels. I don't think it unrealistic to spend around $700 or so, possibly more depending on how you set your system up.

Depending on how this works I will most likely upgrade to some better solar panels, increase the solar panel array size, and get some more batteries.

If anything is unclear please post comments/questions and I will be more than happy to update.

Comments

[cooltogo]

I share buildem4me's comment: batteries WILL emit hydrogen, a VERY flammable gas. The slightest spark, or even over-heating, can EXPLODE the batteries. The only exception to that is AGM sealed batteries - and they are WAY more expensive. Furthermore, your battery container must be protected from too much heat or too much cold. A frozen battery is a DEAD battery, an overheated battery is a dangerous battery. In order to prolong battery life, don't discharge them too much. Keep them at 80% 'full', and they'll last a LOT longer. This applies for this type of battery, unlike some 'electronics' batteries, where you "teach them a memory" by completely charging and then completely discharging them. An alternative to the marine battery is the golf cart battery. It is actually better suited to the demands of a constant gentle flux of charge/demand. A well-known brand name is Trojan. I've lived off the grid on solar power for ca. 5 years. Never mind the critique, however. You DID put together a very nice instructible, and having the guts to publish something like that is great.

[michaelusa1]

With excellent service at wal mart you can get your deep cycle marine battery replaced very well up to three years at any wal mart in the country. They are pro rated at 4 to 5 years so use em every day and dare them to go bad. just take em back to wally world and get a replacement for cheap.

[michaelusa1]

ATTENTION. For "the best" batt/solar set up and installation as well as what to stay away from can be found over at backwoodshome.com. A 6 part discussion and info on battery types, inverters, charge controllers, solar arrays for the small off grid system (or big if you expand it) This is a must see for a more complete understanding!! The author is a licensed electrician and already has been using solar/batt setup for years.

[aztecaa]

Just read your post after posting. What kind of setup are you running? I am looking to do a setup soon and not go broke doing it. I have a setup on the motorhome at this time but read that higher volt system is much more flexible in running appliances. If you have any pics for review please send me. Thanks

[Angus06]

So the batteries seem unsafe indoors and useless outdoors... What would you reccomend for this setup in terms of providing maximum safety as well as maximum usefulness? And by the way, thank you for pointing that out; that may well have saved me from blowing the house to smithereens.

[cooltogo]

I did not intent to say that the batteries are 'useless' outdoors. Their useful function depends on your ability to place them into an environment where they are neither too hot nor too cold.
An example of outdoor housing for batteries could combine a surrounding structure that is well insulated. It could incorporate passive solar heat by exposing a southern wall to radiant heat via a glass panel.
It could employ a venting system that makes use of the convective heat flow: a louvered opening near the bottom, and another louvered opening near the top of the structure, for instance - where the bottom opening would face the direction that absorbs the most heat: the south.
Such openings could be closed off in winter in order to contain the radiant heat that is absorbed through the southern window (but, SOME ventilation MUST be present in order to prevent the accumulation of hydrogen gases that emanate from the batteries).
My own solution was to buy AGM (aggregate glass mat) batteries that are maintenance-free and do NOT release any gases. I keep my battery bank INDOORS, and safely so because of the nature of the batteries. I got mine on sale 4 years ago, but usually, AGM's are much more expensive than regular wet-cell batteries.
If I had to replace my battery bank at this time, I would probably NOT buy AGMs again. I would buy a number of wet-cell batteries, (compare the brand Trojan), and I would build an add-on to my house, well isolated by a firewall, to house the new battery bank. I would also, at that time, put the add-on to additional use as a garage, fire-wood storage, workshop, etc. I would move my solar panels from their present location on the roof of my house to the roof of the add-on (which, of course, would have a south-facing roof slope).
If I were to seek a building permit for my plans, it would most probably result in a code requirement to have a distance between the 'battery building' and the house. If I chose to actually get and satisfy such an intrusion to my personal choice, I would most probably seek to use the 'distance' space as a walkway, or try to put it to some other good use.
The only reason why I WOULD deal with a permit would be because I would consider my property as something I will eventually sell off and move on, thereby having to satisfy inspection by the new owner's government watchdogs.
I am not planning to sell my place, so it is more likely that it will be left behind as leftovers of my life - kind of like the lifeless physical body that will also be a 'remains' - unless, of course, a being appears in my presence who loves the place as much as I do and wants to keep caring for it. I mean the place, NOT the body. The best that can happen to IT is some coyotes or crows finding an easy meal.
So, let's look at 'what is' and chuckle a little bit about it :)
And keep finding options. Rarely is there EVER a problem that has only TWO choices for solutions. We're just conditioned to not LOOK for the other choices :)

[lilykoart]

can we expect to see an instructables from you soon? :) thanks for the insight!

[Angus06]

Wow. Thank you!

[Biker-74]

Connecting batteries in parallel is not the very best idea. The internal resistance of the batteries are slightly different. One of the batteries will deliver more current than the other one(s) and over time it's resistance will change, thereby adding to the unbalance. One battery will then wear out before the other battery/ies. Difficult to know which one is bad and needs replacing. At the least, make sure that a multi-battery setup consists of "twins" or "triples" by choosing the same brand, bought together, and if available check serial numbers to be as close as possible. You seem to have followed this, which is good, but it's not clear in the instructable that it should be done. The best is to connect batteries in series. This, of course, gives a different set of problems. You will either need a higher voltage source, or some kind of DC/DC step-up transformer. 48 Volts panels may be difficult to find and may be more expensive. A DC/DC step-up will have less efficiency and the loss may be discouraging. 48 Volts charge regulators may be more expensive too. Then you need either a DC/DC step-down or 48 Volts consumers. Not very practical. Having a single, very high capacity, 12 Volts battery is probably the best compromise for combined efficiency and life-time. It also makes it easier to know when the battery is ready to be replaced, since you know exactly which battery is getting bad. On the whole, a very nice instructable. Should inspire a lot of people to get into home power production.

[TFrosty]

Why not connect the batteries in series/paralell. That way you raise your total voltage and amps output.

[suptclark]

In the parallel connection,no current would pass from one battery to the next. Each would contribute to the 12 volt total as it was capable. Large trucks and buses use this type of connection all the time with no problem.

[hemant_saraf]

I have two clarifications... one, I have an inverter at home which charges the batteries from the grid electricity. It is a 24 v inverter at battery input with a 1400 watts power rating. What I wish to do is charge the batteries through solar power and not through the grid electricity. So if I connect a separate charge controller to the batteries for solar charging (as you've advised), then will it get mixed up with the charging circuit that is inbuilt in the readymade branded inverter that I have. Would you be able to advise as to what possibly could happen there ? second, what is the distance (length of the wire) between the solar panel and the charge controller you maintained and what is advisable? I am a newbie and based out of India. Would very much appreciate your inputs and knowledge that you share. Thanks in advance. PS : Being in India only means we operate on 230v, 50 Hz AC, Sun is good and very bright and so it makes sense to go solar here. Also I will be able to size the solar panel requirement based on the required voltage and also be able assemble them correctly for panels to be able to provide adequate charging current and input voltage for the battery bank that I have. Just fyi, I have two 12 v batteries in series to provide a 24v input to the inverter. Each battery is 160 AmpHours.

[riverreaper]

wallyworld sell car solor batt chargers cant recall exact price around 80.00 i think i belive by the pick it shows you can do it without pulling the battery outa your car even , it might be cheeper just to bank them rather than build a monster set up with all theses do`s an becarefulls ,dam they closed the junk yard down i could been rich .

[Mr. Chicken]

Personally, I wouldn't use both methods to charge the batteries. I would use solar or from the grid, but not together. I would connect to solar panels and disconnect from the grid. I don't think it would be a problem, but I'm not 100% sure. I'd be more concerned about charging from the grid unnecessarily. As for length of wire from the solar panels to the charge controller, make it as short as you you can to lower resistance and loss. Mine is at about 10 ft. Good luck.

[TheIronHobo]

does it matter the size of the solar panel? i have 1 12 v and 5 watt solar panel. can i build your exact rig with one two or three batterys and still have it work with my solarpanel?

[TFrosty]

How are you panels wired? Parallel, series parallel, or parallel/series?

[TFrosty]

Where did you get the charge controller?

[awang8]

It came with the solar panels which were from craigslist.

[dusts]

I was wondering what you were able to run from this solar kit. I plan on building my own setup that can run a low power PC or maybe even a gaming pc if that's even possible.

[ahmedirshad]

I have a UPS (220V grit connected) with a battery qhat I wish to do is charge the battery through solar power.what possibly could happen in this case can i use my UPS with any change with the solar panel. I have no knowledge of electronics and solar electricity. but i like this to be done. Can you guide me in this regard?

[renet123]

Biker 74 is correct - but for this simple case parallel battery setup is the best choice. The rule of thumb would be that parallels keep the same voltage, and combine the amp hours of all the batteries. A series battery setup does not combine the amp hours, but combines the volts. In this case you are trying to squeeze as many amp hours as possible before the batteries lose charge. Curious that you left out photos of how you wired the multiple solar panels.. and wondering how that update is coming. - how long is it taking your solar panels to recharge the batteries? how many sun hours are you getting? How long is the lamp and/or laptop lasting on all 3 fully charged batteries?

[basmith526]

Your instructions were well written and the pictures did a great job showing what to do.

[buildem4me]

Aren't you concerned about hydrogen gas buildup inside of the container???

[steadmanjon]

Great job. You explained it very well.