Simple camping solar generator

braneri

So I am becoming an active festival goer and want an off grid simple set up to allow me to power my camp.
My needs are getting beyond simple usb battery backups as more people are coming and we need to power lights, fans, and small appliances.

I have a basic idea in mind but the technical issues are what I don't know. I know I need to be able to power a blender, and about a 20watt max speaker amplifier as my most demanding items. Most of the other appliances are phones or usb powered anyway and I plan on using DC to DC power regulators(cigarette lighter usb chargers) to provide USB power.

I plan on using a marine grade deep cycle battery. Cheap one but I know it can power a trolling motor for 7+ hours no problem. What is the recommended watts for a solar panel to keep this charged to a reasonable amount? It will probably be in use for most of the day and only a little at night.  Also with most of these controllers people seem not to use the load terminals when creating a solar generator, is this common? is it possible to power an inverter off the load side during the day if the battery is fully charged and then switch automatically to the battery during the night? Is this an inherent feature of load circuits?

BB.

Welcome to the forum.

$1,000 question is how much power do you want.

An inexpensive system would be 2x golf cart batteries in series (6 volt @ ~200 AH).

50% discharge x 12 volt x 200 AH = 1,200 watt*hours (over 1-2 days of storage).

Get a 300 Watt Morningstar 300 Watt tsw inverter, about 400 watts in solar panels, and a charge controller would my low cost starting system.

400 watts X 0.52 system eff x 4 hours of sun = 832 watt*hours per day ~ 9 months of the year

-Bill

braneri

Well have a 1000W PureSine inverter that was given to me, and a 12v Deep cycle battery that is new and I planned on using for the battery bank. Its not sealed but I am ok with that and will never be tipped.

I know I do not need the 1000W inverter (I could probably do with a 450W 25A) but since I have it and its free I planned on using it. It will have an inline off switch and will be turned on only when needed and only for as long as its needed. The rest of my power needs a will be 5v dc 1.5 to 2.5 amps for usb powered devices and will be using dc to dc regulators (cigarette lighter adapters) for usb power, and possibly making a regulator to run a 20 watt amp for running a small set of speakers from a 3.5mm jack or Bluetooth adapter that will happily run off usb power.

I hope that was enough information, but again I know very little about this subject. Also I would rather not put batteries in series unless its really needed or provides some other benefit over using a single 12v battery. I would be far more comfortable doing two 12v batteries in parallel to extend my time when the sun goes down, however Its more about making sure the thing will get charged during the day and keep me moving into the night.

BB.

The two golf cart batteries (2x 6 volt) in series is (probably) going to be the best bang for the buck, more forgiving, and cheap "when" you make your first few mistakes (practically everyone "murders" there first battery bank or two). Start cheap, then look at "higher tech" batteries in the future.

For various reasons, I would suggest that you do not want two 12 volt 100 AH batteries in parallel. Two 6 volt @ 200 AH batteries will be the same size/weight, but easier to connect, maintain, and probably cheaper/more rugged than their 12 volt counterparts. We can discuss the details more when we get to that stage.

In  general, lead acid storage batteries are almost all the same volume and weight for equal energy storage. Configuration changes (physical size of cells, number of cells "per battery", how they are wired in series/parallel) comes from your requirements (actual system size, available batteries/hardware/space/costs/etc.).

We try very hard to design systems that meets your loads and charging sources. Sometimes, that is very difficult to know (no experience, requirements change over time, etc.).

So, we got several ways we can proceed... First is measuring your loads. We work best with Watt*Hours measurements

• a 100 watt light running 8 hours = 800 Watt*Hours
• You can use Amp*Hours (typically for DC Battery loads)--Similar 10 amps * 8 hours = 80 Amp*hours.
  
• To convert AH to WH, simply multiply by the voltage--80 AH * 12 volts = 960 Watt*Hours

You can measure Energy with (web links just suggestions of what to look for):

• DC Watt*Hour/Amp*Hour meter (for smaller loads)
• AC Watt*Hour meter (Kill-a-Watt)
• DC Current Clamp DMM (no "time" measurement)

Once you know your power needs, we can quickly design a system to support those needs (need the location, season, peak power usage, any size restrictions, etc.).

Another way to go is "pick" a piece of hardware. Say you only have room for one 12 volt 100 AH lead acid battery. Then that is what we design the system around (and understand its limitations).

Or, say you can only fit 280 Watts of solar panel, then design the system around that (and its limitations).

In general, it is not a great idea to design, for example, around a 1,000 Watt AC inverter... Larger inverters can consume a relatively large amount of power just to 'turn on" (say 10-20 Watts for a 1,000 watt inverter). If you only need 100 Watts, then a large percentage of your energy is just going to make the inverter buzz and get warm.

Also, there are options in inverters to go into standby if there are no loads, or remote on/off switches (no big switch or relay needed to turn on/off inverter, etc.).

There are other options too... For example, people that have weight/size constraints for batteries are starting to use LiFePO4 (lithium iron phosphate) batteries... They have some very nice characteristics--But the details on how to use them are very different (and the batteries are much more expensive). AGM type batteries are a nice version of sealed lead acid batteries (and support higher surge current for their weight) and much cleaner. However, they are more expensive than flooded cell lead acid batteries and a bit more easy to damage if not carefully used (vs flooded cell).

Anyway--A few thoughts.

-Bill

scrubjaysnest

BB, makes some good points. Also the "trolling motor" marine battery isn't typically a true deep cycle so you won't get the life out of it.
It makes a good starting point if you already have it.

oil pan 4

Maybe something like I built.

http://ecorenovator.org/forum/solar-power/4544-home-made-solar-inverter-generator-hybrid.html

braneri

I appreciate the feedback, however to what I will chalk up to pure ignorance on my end and because of recent medical issues no budget whatsoever to speak of(this is a recent change as of the past few days). I think I am going to go with my original plan of using free and obtained stuff and just follow simple instructions on assembly and hope for the best.

This plan will be scoffed at I am sure, even laughed at by most here. However I am not an enthusiast or an expert so I am going to use that as my excuse.

What I have.
1) 80W solar panel and charge controller.
1) Deep Cycle Battery 12V (new)
1) 1000wPS inverter
1) DC 12volt battery meter
1) large wooden box
2) 12v Fans (for cooling when needed)
1) Temperature regulated switch (for automatic fan activation)
+) an absolute crap ton of automotive wiring, buss bars, fuse panels, fuses, 12v 'cigarette lighter' sockets and accessory switches rated for 24v DC

My plan is to pretty much secure all parts into box and wire according to plans as normal and hope for the best.
Will this system support continuous load all day? NOPE! (not that it needs to)
Will it charge phones, tablets, and power DC powered LED lights? YEP...for a little while any way
Will the solar panel help keep the system going all weekend? Most likely(as long as the inverter is only used if absolutely needed or not at all).
This is going to be used in Summer in Michigan, so not equator levels of sun but enough to get effective use to keep the battery charged when no load is attached.

Most of all right now its free, it will fit in the back of a car, and will be lift-able by 1-2 people. It wont have any more inherent issues (other than not using sealed batteries) using a single 12v battery over 2*6v in series. I may have to splurge a bit and get a better charge controller, however I don't plan on using it for the load circuit as that will come directly off the battery and will be monitored with the volt meter.

I feel this will accomplish my goal of allowing to have a few more creature comforts than otherwise available from simple battery packs for charging phones as well as a replenishing way of obtaining power for phones instead of depleting over the weekend with no hope of recharging. It will be easily upgrade-able over time and will be a learning experience I am sure. Its not a perfect plan by any means, but it should work for a 3-4 day stint out in an open field in the middle of June.
 

oil pan 4

An 80 watt panel will likely give you less than 4 amps of charging power with a PWM charge controller.

A good MPPT charger (not a $20 made in china knock off) will get you an extra 2 amps out of an 80 watt panel.

The best I can figure MPPT give you as much as 50% more power than PWM. When in full sun they give around 30% more power over all and MPPT can produce some power in conditions where PWM chargers can not.

For example my MPPT charge controller start applying power to the batteries with panels that are laying flat before the sun is even up. The MPPT charger will produce some power on heavy over cast days where the PWM does not.