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Solar "Generator"

Since I've always wanted to do something like this and I found this site, it's about to happen! I found a smaller version with what I wanted to do at Popular Science but I want to do something on a larger scale. I do have some questions though that I'm hoping someone can answer or point me in the correct direction.
I'm going to describe what I'm doing with what and what I have questions with.

I'm going to be buying this solar panel and charge controller kit.
Sunforce Solar Panel With Charge Controller
A deep cycle 115 AMP Hour 12 V marine battery from Wal-Mart with Plastic Battery case
Salvaged wood Toy Box
Meter
Question: How to meter how many amp hours I have left or how charged the battery is? What kind of meter to buy? Where? (not too expensive <20 bucks or so) how to hook it up.
A 12 V accessory outlet with on off switch
Question: I'm putting an inline fuse before the switch, 15A the line fuse goes on the + (positive) side correct?
A 700 Watt 6.25 AMP DC to AC converter with 4 outlets connected to it.
Question: can I put a breaker or fuse between the 4 outlets I'm going to be plugging into on the outside and the plug being plugged into the DC to AC converter? If so how?
USB ports for charging with on off switch.
Question: how do I convert the 12V to 5V in an easy way? I've seen some creative ideas on here for charging VIA salvaged USB ports but I don't want to have to hook it up to my power inverter if I don't have to.
Cooling/ventilation for the entire thing.
Any ideas how I might cool/vent it? Currently I'm thinking of using old computer fans and put them on both sides of the toy box and have 2 blowing and 2 blowing out. Having the fans run off of the solar panel during the day and either have a switch to change it to battery at night (if it's too warm in the house) or maybe photo sense it? Temp sensor to turn it on and off? Or a switch to turn it off completely. I'm just looking for idea's to keep the battery (and to expand to be more than one battery) cool/ventilated. If you have examples or detailed description on how to do it that'd be great.
I'm not one to steal ideas so I'll credit the idea's I'm given if I use them =)
I'm going to see how much I can run off of this and how long. Hopefully save some big time energy also!
Thanks all!


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NachoMahma9 years ago
> Question: How to meter how many amp hours I have left or how charged the battery is? What kind of meter to buy? Where? (not too expensive <20 bucks or so) how to hook it up. . Most of the cheap "state of charge indicators" I've seen are just voltmeters across the battery. Just about any decent voltmeter (15-24V range) should work. . There are more complicated systems that look at the current draw and voltage and compute a "% charged"/"% left" figure, but that's probably going overboard for your project. A lot of UPSs use this method to derive "remaining time until shutdown." . As far as I can tell, it's impossible to accurately judge the state of a battery without a measured load on it, but for most DIY projects a simple voltmeter is "close enough." . > Question: I'm putting an inline fuse before the switch, 15A the line fuse goes on the + (positive) side correct? . Theoretically, it doesn't matter if it's on the + or - side (although there are safety concerns), but, since most systems are - ground, the positive side is usually fused. I'd get a breaker, but I tend to blow a lot of fuses. . > Question: can I put a breaker or fuse between the 4 outlets I'm going to be plugging into on the outside and the plug being plugged into the DC to AC converter? . You can put as many breakers/fuses as will fit. Using a separate b/f for each receptacle will work, but would be overkill. I'd use a GFI (ground fault interrupt) breaker on the 120VAC for the added safety - more expensive, but well worth it. . > If so how? . In series with the supply. Ie, in the hot wire from the battery to the switch. Physical placement (at source, switch, or in between) is unimportant, but the closer to the source, the safer. . > Question: how do I convert the 12V to 5V in an easy way? I've seen some creative ideas on here for charging VIA salvaged USB ports but I don't want to have to hook it up to my power inverter if I don't have to. . I'd use a 5V regulator (7905?). You only need 500mA (all USB allows). . > Any ideas how I might cool/vent it? . Since you've got 12VDC, I'd use "computer" fans. How much fan will depend on how much heat the inverter has to get rid of. I'm guessing four fans will be overkill, unless they are really small. I'd try to rig something that would run the fan(s) at very-low-speed when the inverter is off (to vent the battery) and kick to high-speed when the inverter is on. . Or, if the battery will get enough ventilation just sitting where ever it is, use 120VAC fan(s) that are connected to the inverter output.
oddie1212 (author)  NachoMahma9 years ago
Here are some images of what i'm trying to do with the cooling to hopefully give you a better understanding on what i'm trying to do. I'm hoping to put a fan on each end to blow air through the box (from left to right) I also want to use the 7805 positive for the 5V regulator correct? I'm most likely going to get this from Radio Shack.
F:\My Documents\My Pictures\Solar_Project\DSC00220.JPGF:\My Documents\My Pictures\Solar_Project\DSC00227.JPG
. I'd put some holes in the lid and a few more low on the sides to take care of venting any gases. If you are recharging after a deep discharge, you might want to prop the lid open until it fully charges. I don't think you will _need_ a fan in a box that large (modern batteries don't produce as much Hydrogen as older ones). Of course, I wouldn't put the box next to a water heater. ;) . Where will the inverter be mounted? If mounted on the outside of the box (or through a hole in the box so any heatsinks are exposed), you may not need a fan there, either. If the inverter will be mounted inside the box, a 700W inverter shouldn't need that much air, except maybe under full load. . Maybe mount the fans so they exhaust through the holes in the lid (see above)? I'd use 120VAC fan(s), wired to the inverter output. Or 12VDC fan(s) wired to the inverter input (on downstream side of switch from battery). Some ductwork from the side holes to the inverter might help. . > I also want to use the 7805 positive for the 5V regulator correct? . You better check with somebody else on this one. If all you want is 5VDC, the regulator ought to work; for USB, I dunno.
oddie1212 (author)  NachoMahma9 years ago
>> Where will the inverter be mounted? From the picture on the right, it will be mounted right infront of the battery box. Eventually, there will be another battery box in there to the left of the current box that's pictured. The inverter is a standard one you'd buy for your car. I purchased this one at wal-mart, it is acutally a Black and Decker 400 WATT inverter with one fan in the back of the inverter plastic case. So there are no heat sinks exposed on this unit. >>> I also want to use the 7805 positive for the 5V >>regulator correct? >>. You better check with somebody else on this >>one. If all you want is 5VDC, the regulator ought >>to work; for USB, I dunno. I will try the 5V regulator unless someone else can tell me different. I've seen some other instructables where they just use the 5VDC regulator you stated after poking around some more.
. If you can mount the inverter so the built-in fan is pulling/pushing air in/out of the box, you should be good to go. Probably won't need any other fan(s).
if you felt like doing some maths an ammeter and voltmeter could tell you a percentage of of power left but the best test would be running the battery down from full charge with the maximum intended draw with the ammeter and voltmeter attached to a computer attached to a graphing program from a computer making a cross reference graph which could be put in to a logic chip and read as a percentage or just have the guages and the graph beside them
uguy NachoMahma9 years ago
I believe the 7905 regulator you recommend is a negative 5 volt device, the 7805 is a positive 5 volt regulator.
NachoMahma uguy9 years ago
. Oops! Thanks
oddie1212 (author)  NachoMahma9 years ago
Thanks NachoMahma! Especially the idea about the GFCI i never thought about it. Do you know where i can easly get the Reglator you describe? Thanks! I'm still looking for ideas on how to control the fans speed. If any one else has idea's or comments please let me know.
> Do you know where i can easly get the Reglator you describe? . Should be available at just about any electronics supplier (DigiKey, Radio Shack, etc). . > I'm still looking for ideas on how to control the fans speed. . If the battery is sealed or in a well-ventilated area, then you will only need a fan to keep the inverter cool. Just hook the fan to the inverter output. . If you want to run fans while the inverter is off, it will require a 'shutdown on low battery voltage' circuit to keep from draining the battery.
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