What do I buy next ???

Re: What do I buy next ???

One suggestion... Monitor the charging voltage & current from your wall charger. Also, get a good temperature compensated hydrometer too (assuming this is a flooded cell battery).

The typical wall charger will boil the battery dry in a few months as they do not typically have a very sophisticated charge profile--but tend to just "trickle charge" the battery. And unless there is some load (or the trickle charger is quite small compared to the size of the battery), you may not be too happy with the results.

Personally, I and my in-laws' have a couple cars that are not driven too often and because of on-star, low-jack, keyless entry systems, and such--they need a trickle charger to keep the batteries from going flat.

In one case, the draw on the battery is about 0.185 amps--That works out to ~4.4 Amp*hours per day. Inside of two weeks, the battery is already being significantly discharged beyond recommended margins (about 20% discharge maximum is recommended for an automotive style starting battery--or typically around 20 amp*hours).

My problem was the the "maintenance chargers" you get from the local auto parts store does not properly float charge the battery--but instead boils it dry.

So, I just used a lamp timer to turn on the charger (in the in-laws' case) ~4-5 hours per day... Makes up for the load, and the battery does not boil dry (supposed to be a Maintenance Free battery). My car, I have set it to ~1 hour per day.

One of the most difficult things to imagine is the amount of "work" it takes to keep a battery (and battery bank) happy. Seven years ago, I certainly did not realize this (and have had to replace more than my fair share of lead acid batteries).

Regarding where to go next--basically, with solar and renewable energy--conservation is the number one goal. In virtually every case, it is worth spending the money first to ensure that you have the most efficient/lightest load(s) possible for your system...

So, that usually means, with small systems, starting with 12 VDC appliances. Radio, small LCD TV, lighting (LED, CFLs, etc.). Just enough to survive the emergency (I would plan on 5 to 14 days of being "on your own"). Try not to plan on cycling your standard flooded cell storage battery to more than 50% discharge (~50 amp*hours in your case). And try to recharge the battery relatively quickly after discharge--the longer it is stored with less than full charge, the quicker it will sulfate and lose capacity.

As you get a larger system, a good energy star rated refrigerator would be a nice load to add (keep food fresh instead of going bad within a day or two). But, that will be a good size system (~1kWhr per day--or probably ~500 watts of solar panels+more batteries+DC to AC inverter).

Then you will need an inverter--and you will probably have to get a "true sine wave inverter"... Yes, the Modified Square Wave Inverter (usually Modified Sine Wave Inverter in marketing speak) is much smaller and cheaper--but some appliances do not work on them very well (electronic loads work great, or overheat and die--and you can't tell which will do what).

And electric motors (like refrigerator/freezers) don't like MSW inverters at all... So, check with a reputable supplier (like Wind-Sun's inverter page) for more information about good, reliable, and efficient models.

When you start looking at actual solar panel useful ratings (vs data sheet ratings), battery charging losses, and inverter losses, you quickly find that you will need almost twice the wattage of panels that you thought--Nothing is wrong--it is just the nature of collecting, storing, and inverting energy with a solar system. Hence the first recommendation about conservation.

-Bill

Re: What do I buy next ???

Well.... You have to add up all the loads (in watts), multiply by approximate inverter efficiency of 1/80% (1.25), then divide that into the 50% capacity of your storage battery... Say this is a 100 amp*hour 12 vdc battery, your TV is 100 watts, and your three CFL's are 60 watt equivalent (about 3 x 13 watts):

Load = 100 Watt + 3x13 Watts * 1.25 (inverter losses) = 174 Watts

12 volt battery * 100 amp*hours * 50% (discharge) = 600 Watt*hours

600 Watt*hours / 174 Watts = 3.4 hours of normal operation before recharging

So, you decide the load and the time--that sizes the batteries. If 3+ hours of emergency power is enough--then this setup will nicely handle it. If not--then you have the choice of more storage and/or alternative power to meet your planned emergency needs.

If you want solar charging, you can back calculate the amount of sun and other losses.

Or, plan on a generator or utility power to recharge your battery bank.

Turns out, that Lead Acid Storage Batteries are pretty big and heavy for the amount of energy they store--versus what people are used to using in their normal lives.

For an emergency system, if you want 5-10 days of independence (in moderately sunny weather), then you have to cut down your loads or increase the size of the system.

And you have to weigh that against an emergency where you will need that power... In areas that have hurricanes, ice/snow storms, tornadoes, and such--a good size system sized to provide a couple weeks of emergency power (and a good food/water supply too) using batteries and solar is a good thing.

Here, where I live, it has been 50+ years since the last multi-day power outage--and earthquakes (the biggest fear) come only once every 100 years or so (last "major" one in our area--1906).

I chose Grid Tie solar (for power, no back emergency power) and a small 2kW inverter/generator plus siphon hose (gas from my couple of cars will provide several weeks of power for my fridge and a few lights).

Your choice(s) may be different.

-Bill

PS: MSW inverters are much cheaper than true sine wave inverters--but are probably NOT worth the cash for an emergency--possibly blowing out your CLF's and/or TV/Radio in an extended emergency with a MSW is probably not part of your plans.

PPS: forgot the "NOT" in the previous PS...

Re: What do I buy next ???

Mad,

Well, the bigger issue is what are you going connect the input of that 1kW inverter too? Loaded up, imagine how long your car battery would crank (5-10 minutes?)--roughly the same load as that inverter (roughly 100 amps).

For an emergency, the Honda inverter series is hard to beat. I got the eu2000i for around $900 shipped. Runs for ~4 hours on 1.1 gallons of gas at 1,600 watts--but what I liked, runs about 15 hours on 1/4 load (400 watts). more than enough for my fridge/freezer plus a few lights and such. 20 gallons of fuel (couple of car fuel tanks) and you are good to go for several weeks.

The normal 2kW generators for $200 really suck the fuel down and are noisy as sin... Good for a short outage (hours/day?)--but not really friendly to use for outages that will last a week or more...

-Bill

Re: What do I buy next ???

Probably 80% of your day to day appliances will run OK on the inverter... Items with motors will tend to run hot (because of the square wave). TV's and Radios may run OK, or have background noise, or a few may overheat and die (no way of really knowing without trying).

Overall, the inverter will probably be OK for emergency/fun use. For long term off-grid living, it is questionable how long the inverter and appliances connected will last, plus there will be a loss in efficiency due to wasted power as heat (I forgot, but it may be something like 20% lost energy).

One of the guys here does use a large MSW inverter to run a water pump for an off-grid cabin (large inverter is not expensive, water pump does not often, so wasted power much less of an issue).

Again, the biggest issue will be the batteries/source of power to run the inverter.

You really should size the inverter also on the size of your batteries too (besides the load you are going to drive). A large inverter running a small amount of load can be inefficient (need to know the inverter's idle power).

Certainly, at $150 for 1kW, the inverter will work for you--but there are issues which can limit its usefulness. And without knowing how much load you have, how long you need to run them, and how much battery bank supports the inverter--have no idea if it will meet your requirements.

But most people really don't have a good feeling for how little power a "car sized" 100 AH storage battery contains... For example, you can run a typical TV for about 2 hours before you need to recharge the battery... It will run the TV for 3-4 hours, but if you run the battery flat, the battery will have a very short useful life because of the damages sustained from over discharging.

-Bill