oldspark battery bank w/possible solar

First I want to say I hope this is in the right forum and I will try to keep this organized and to the point but there is a lot to explain. Situation - I could write a lot here, if anyone is interested I can expand more. Simply put I am buying a van to live out of for the next year while cramming almost 2 years of classes in less than a year so I can transfer into an Electrical Engineering program. Money and time are limited so I have to make sure they are used where it counts most. Summer starts June 6th and I need to figure out how to provide power to the van for small appliances and a computer. The vehicle - 1991 Ford E 150 extended conversion van, comes with a 13,500 BTU A/C on top and a 2,500w industrial power inverter. The inverter was meant to replace the small generators on big rigs for power while they are camped and supposedly costs a couple thousand new, apparently it can power the A/C unit. My goals - - Stealth - Be self sufficient - Power small appliances and computer, ie a mini mini RV - Be power efficient as much as possible, ie don't run the 5.7L engine a whole lot just to recharge batteries Electricity use per day - expected/max - A/C (1800w) - 0hr/1hr - 0w/1800wh Mini fridge (42w) - 24hr - ~1000wh PC w/monitor (~350w) - 2hr/4hr - 700wh/1200wh Hot Plate (1500w) - 1/4hr/3/4hr - 375wh/1125wh Toaster Oven (1500w) - 0hr/1/2hr - 0wh/750wh Other - ??hr - 200wh/400wh The rest of the stuff would be some lighting, cell phone, cordless power tool battery chargers, AA/AAA battery charger, occasional car vacuum etc. Total per day - 2275wh/6275wh Average use per hour - ~95w/~262w ---------T-105--------------T-145----------T-105---T-145---T-105-----T-145 ------------------Capacity---------------------C/10 Amps--------C/10 Watts 2-(225AH/2700w)-(245AH/2940w)---22.5A---24.5A---310.5w---338.1 w 4-(450AH/5400w)-(490AH/5880w)---45A-----49--A----621w------676.2 w 6-(675AH/8100w)-(735AH/8820w)---67.5A---73.5A---931.5w---1014.3w The plan so far - -Purchase 2-6 used Trojan T-105(225AH@20hr)($55ea plus core) or T-145(245AH@20hr)($60ea plus core) 6v deep cycle batteries for an effective 1-3 12v deep cycle batteries. -Possibly upgrade the alternator to a 130 or 160 amp along with the "Big Three" wires. -Move some existing loads to the battery bank such as the radio, power inverter and lighting. -Run most non essential vehicle loads off of the inverter, ie A/C, PC, mini fridge etc. -Potentially install smaller secondary inverter for the PC - see questions. Questions - - Do I need to worry about the safety of the PC if I turn on the A/C while the PC and mini fridge are on? Those 3 items are very close to the inverters rating. - Do I need to do anything special for the PC to protect it from start up current when other items are turned on or when the vehicle is started? - How many batteries should I get? I think 4 of the T-145's should work so long as I have a way to recharge them, I don't see the electrical load draining the batteries more than half of their capacity from any one peak usage which would be cooking times or when the A/C is used. - Should I avoid the used batteries I have mentioned? - Will a UIBI set up work or do I have to worry about the battery bank pulling the starting batteries charge down to unacceptable levels once the van is started since I will only be driving short distances? - What are the thoughts on Wal Mart deep cycle batteries since it would be very easy to exchange when they crap out and most likely not cost much? - What are the thought on adding a solar panel or two? I see three options - use the engine, buy and use a generator or buy and use solar panels. Solar seems the best option since it will probably be no more expensive than a generator, probably cheaper than a purpose built quiet generator, cheaper in the long run over running the van, and would be the quietest option of all. The down side is limited space, limited daylight and power recharge capacity. - What are the thoughts on DIY solar panels over pre-made regarding total cost, time invested and functional benefits? Other Thoughts - I've worked at a car audio shop briefly when I was about 17, I've worked as a field tech for a cable company for a few years and as an electrician apprentice for a few years plus I had some electronics training in the Air Force. I'm not very good with designing electronic circuits but I can do all of the basic stuff, just need some help figuring out what I should be doing to accomplish these goals.

Without going into great investigation.... I'd probably forget solar... 92W/hr means at least 400W of panels assuming 50% daytime and 50% of "full power" (cloudy etc). Then the battery capacity to be able to be charged at those rates... And assuming a few dark and rainy days.... I'd suggest get rid of your hotplate and toaster. Electricity is not efficient for heat - unless using a reverse cycle aironditioner! Use gas (propane etc) or petrol or wood or engine/exhaust heat instead. And reduce your fridge power unless it is large and a compressor type. (Forget Peltier & 3-way fridges off battery power! I bought a >$1000 40L fridge rather than another >$750 of panels etc for my $145 heating/cooling Peltier fridge - but now I can have ice-cream in 45°C (115°F) heat running 2.5A max but probably only 1.5A cyclic.    I also bought a 2.8kVA petrol generator (a used "CHonda") for $220 after deciding a >2kVA inverter and the battery drain wasn't worth while for my girlfriend's chainsaw (electric; ~1100W).     Plus of course a generator has essentially infinite reserve time compared to batteries (depending on petrol supply). And it has a 12V 10A output (in addition to the AC 2.8kVA). I'll let you consider that before detailing further. As to batteries, one tries to avoid series batteries, but parallel even more. Hence a big 12V battery is ideal, otherwise 2 series 6V. If a choice between fore x 6V in series/parallel and 6 x 2V in series, I'd go the 2V route. But I'd also consider several parallel 12V batteries merely to keep to standard and interchangeable batteries because I know what's required for max life - but that might still not be IMO practical. And battery sizing... A deep cycle may last 300 cycles to 80%; 1200 cycles to 50%, and 2500 cycles to 20% discharged. It will last longer if charged slower, and if discharged slower, and if kept cooler. And one has to decide what reserve time - ie, how long between full recharges and at what current drain... Then details like max current draw and max recharge current come into it. Also flooded (wet cell) batteries are probably the best (also economical) battery provided they are suitable... (ie, not "indoors" etc).   

I'd really like to examine the possibility of solar a bit more simply because I don't feel totally comfortable having a generator on the outside of the van and having it run while I'm in class. I understand it normally makes more financial sense and has more ability to charge the batteries but I would be worried about drawing attention from security, possibly having my vehicle towed or having the generator stolen. Before getting into the solar you recommended doing away with the electric hot plate and toaster oven, how safe do you think that would be to run propane inside the van? If that is viable I am welcome to it although I don't know of a toaster oven that will run on propane which I would only have for pizzas and bagels. The hot plate I think would be fine to replace with a dual cook top propane burner. Again setting up camp to any extent outside of the van is very undesirable because there are a lot of stuck up people here who are entirely too privileged and wouldn't want someone doing that plus I have to worry about too much attention for the sake of not getting the van stolen. There aren't any places reasonably close where that sort of stuff is appropriate such as the beach so cooking with fire is out of the question unless you have some very creative suggestion on the logistics of that, same goes for cooking with exhaust gas! As for the fridge I read an article somewhere that talked about using a thermostat to control when the compressor was turned on which was supposed to help reduce the electricity usage so I planned on looking into that but 42 watts seems small. The mini fridge would be in the 3-4 cubic foot range with a separate freezer door top just like a normal fridge so I can use the freezer for actual food storage instead of just ice cube trays. Regarding batteries I am all ears, what would be some real world suggestions as opposed to putting 2 6v batteries in series and then paralleling pairs to get more capacity? Should I look into 12v Wal Mart deep cycle batteries? Why is it good to avoid series batteries and parallel even more so? Are you saying that the worst situation is to have a mix of series and parallel, the next worse is parallel, then series and then ideally in a perfect world a single battery of correct voltage and capacity? I was leaning towards the Trojan batteries because I've read they are better than the Wal Mart batteries but I like Wal Mart for the fact that they are everywhere and if one craps out I can take it back easily but I'm not so sure about the Trojans. On to the solar, if I build them myself there are 40 cells putting out 1.8w each at .5v for about $47 on ebay. They are 3"x6" so if I strung 40 in a single column and had 4 columns that should easily fit on the van roof. That would be 288w @ 20v which I was reading should be used with a SMPS charging controller to make best use of the available solar power. Southern California is sunny most of the time so on the occasion that it is cloudy I will have to make up for it by running the van or some other means. I'm sure this calculation isn't perfect but I figure it's close. Right now there is about 14hrs of sun, so integrating 144sin((pi*x)/7)+144 from -3.5 to 10.5 yields 2016watts, figure we're getting about 85% of full potential based on the max angle of the sun being close to 78 degrees which yields about 1750w over the day. So that leaves between 525w and 4525w to recover. 288w * 14hrs = ~4030w, 1750/4030 = ~43% efficiency based on usable sunlight, does that sound like it's in the ballpark? If I can add a circuit to the fridge so it only kicks on based on the thermostat that sounds like I could save some energy. Actually this this describes getting a chest freezer to run on about 100w/day so I will look into that alternative so long as I can meet my size requirements. I could replace the toaster oven with that Presto Pizzazz pizza maker since that's really the main thing I would want a toaster oven for, the pizzazz uses 1200w and supposedly cooks pizza's in 10-15min which means 300w savings off the top and reducing about half the time. I could take your suggestion for the cook top using propane, my main reason for the cook top is boiling water and making the basics for burritos. I can reduce my time on my computer as much as possible and try to get away with a simple dvd player for now, eventually I will build a new computer and because of the situation I'll factor in making it low power. I could probably do without the A/C but I want to factor it in just in case, any thoughts out how long it would have to run to drop the temp in such a small space? I'm hoping that I could run it for 5min bursts here and there if absolutely needed. So far that sounds like I could significantly reduce the energy required which I realize is going to be the most valuable aspect of this. Also I think it's safe to say that my max energy consumption can not be my max, I must make do with less. I would still like to know what your suggestions are regarding batteries in terms of actual products and places to find them along with why you said that basically series and/or parallel set ups are undesirable. Also the issues I mentioned before about negatively impacting the starting battery when the bank is connected while driving short distances and whether I need to worry about protecting the PC from additional loads being turned on. Thanks for the quick reply and the help! I don't mean to sound rude or anything, just trying to understand why you are suggesting some of the things over others.

Just park the van close to a light post... Have you checked whether or not parking your van where you are intending to and living out of it will be "legal".

awdeclipse - Not to be rude but I don't see the relevance to what you are saying. I'm not sure if it is legal but knowing this area it probably isn't, these are the same kind of people that would outlaw being homeless, most of them really only care about keeping yuppie ville up to snuff. There is a good reason I've listed stealth as a main goal, minimize confrontation in all forms. I am really curious as to what you were trying to get at with the light post...

Light posts are a source of power, just plug your van into it.

Not really possible around here unless you tear open the electrical panel and add in receptacles.

Maybe if you were Apprenticing for an electricians job. But since you are aiming towards electrical engineer keep away from the high voltage stuff. Good luck with school, all I can say I am glad I am done with all that.

I don;t see the issue with liquefied gas in a dwelling or camper - it is the common cooking method here. I don't know if some caravans etc have electric cookers, but they would be limited to powered sites and generators. (I'd almost suggest batteries are more hazardous than gas...) Fridge-wise, the question is what type is it. Compressor & 12V? If not, reconsider getting a 12V fridge - and not an absorbtion type (unless you intend to run that off gas) nor a Peltier type (ie, an electronic food cooler/heater). As to batteries, a single monobloc battery is always the preference because all cells are co-manufactured and share the same history & temperature etc. That sums up the undesirability of series & paralleling batteries. Series is undesirable due to charge inequality, but tends to be minimised due to equal thru-current, and easier to overcome. Parallel is more undesirable for the same reason but has the disadvantage of unequal current distribution and mutual destruction if a cell or battery fails - which in turn can be a hazard. There should be design tools available to give you an estimate of panel size for your locale and provide optimum mounting angle and direction. The use of an MPPT should be well worth it. Like I said, I'd suggest a minimum of 400W based on half of 24 hours of daylight and 50% efficiency (of the sum - ie, clouds, rain etc).

Well unfortunately I just found out that the van I was going to get was given to the owners brother who lost his job yesterday so it's back to the drawing board with finding a van. There is a 1983 dodge extended van but it doesn't have any of the extras that the first van does plus it's older by almost a decade. At any rate regardless of the van I end up in I now have to deal with the power inverter since the nice power inverter I've been talking about went away with the first van. I may buy one large power inverter or I was considering purchasing a few smaller ones to get to about 2400w. Reason being is I have a cobra 800w power inverter that I bought for about $45 and 3 of those is cheaper than an equivalent single inverter. A lot at this point depends on how much I can get the van for. Oldspark - I understand what you are saying about the batteries, do you know of a single battery that has the capacity I would need? What about batteries that could be joined in series only with no parallel connections? Would another alternative be to put blocking diodes inline so that the current only goes one way? I'm just asking because I don't know of any single battery that would work or any large capacity 2v batteries for series only like you mentioned.