Inverter question - newbie

medic29

Good evening. I'm a newbie at all of this and have several questions, but the one at hand is in reference to inverters and charging a set of batteries.

My eventual plan is to have a solar setup to power my cabin. As of right now, I need to hold off on getting the solar panels, but would like to get a battery (or batteries) and an inverter so that I can power my cabin. It is a small cabin, less than 400 sq. ft. The only things I plan to power are a fan or two during the night and maybe a small radio during the evening. This may grow later to powering a few lights, but as of right now the lights are powered via propane.

It has been suggested I look at the Morningstar 300 inverter. It has also been suggested I look at a 100Ah AGM battery.

The question I have is about charging the battery. I would like to charge the battery for now by utilizing a generator. Will the Morningstar inverter also charge the battery when plugged into the generator? I know there are some inverter/chargers out there in which they sense AC power and automatically start charging the battery, then when they loose the AC power they automatically switch and make power from the charge in the battery. I don't know if the Morningstar inverter is this type of inverter or not; or if I would need to purchase a seperate charger as well, then when running the generator I would take the inverter out of the loop and charge the battery and supply power to the cabin; then later when the generator is off, put the inverter back in-line and it can get power from the battery, convert it to AC and power the cabin.

I hope this makes sense. Any help would be appreciated.

icarus

Re: Inverter question - newbie

First,

The Morningstar inverter is a very nice, very efficient unit. It will not, however, charge the battery. What you need to do is get a good battery charger,,, (I recommend the Xantrex tc series or the Iotas http://www.westmarine.com/1/1/1363-truecharge-20-plus-battery-charger-from-xantrex.html) . The Xantrex works especially well with cheap, smaller floating neutral generators.

Then you would wire in a transfer switch to switch between generator and inverter power. Your battery charger would be plugged into a dedicated outlet that is served ONLY buy generator power. http://www.iotaengineering.com/its30r.htm

As for the battery size,,, as with everything,,, do your math. Calculate your expected loads, and provide a battery of such size that you can run up to 3 days without charging (solar design standard) without drawing the battery down more than 50%. (I personally don't like to draw the battery down more than 20%).

Depending on your fans,,,lets say 1 amp for 12 hours= 12ah. Radio 1 amp for 4 hours=4 ah. Lights,,,15 watt cfl,,say 3 might be 3 amps,, 4 hours=12ah. Total then would be 24ah/day (12vdc) Three days would be 72ah. That would mean that them minimum battery size for this application might be in the 150ah range,,, assuming you don't want to charge it more often. You will seriously shorten the live of any battery if you leave it in a discharged state (under ~75%) for more than a couple of days.

I suggest you read some of the following regarding battery health and sizing.:http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
http://www.batterystuff.com/tutorial_battery.html
http://www.batteryfaq.org/

Hope this helps,

tony

PS The other word of caution I would give you is that loads WILL increase with time, as you discover how nice it is to have these little luxuries. Also, since battery strings really can not be added onto once they are installed (see the links above) make sure you start with a big enough battery. Also be advised that you will, in all probability cook a set of batteries as you learn how to use them properly. (This forum helps greatly in reducing these dangers, but it doesn't totally eliminate them). I would consider not using an agm, since they are fairly easy to cook and when you do, your done,, so I understand. Others chime in with your opinions.

niel

Re: Inverter question - newbie

these items can be 12v rather than 120vac. inverting will add a step that will deplete the battery faster and lessen overall efficiency. if you still want to use the items on 120vac via an inverter, you need to know the total power that all of these items will draw and round up for start surges on the electric motors and future items that may be added to the inverter. there are inverters out there with built-in chargers, but running a separate inverter and charger is fine too. be aware that the charger should not be the cheap automotive types as they aren't regulated and could overcharge and cook your battery. 3 stages of charge or more should be utilized in the charger. these would be bulk, absorb, float, and the 4th possibility may be equalize. the 4th you may skip for one battery.
btw, i believe you meant to say a 100ah agm and not 100ma.
one more side-note is that electric motors do not like modsine inverters as they will use more power than a normal 120vac source that is sine wave. sometimes the modsine will also cause failures in such electric motors due to this extra power dissipating within it. some 120vac wall adapters, sometimes called wall worts, have been known to fail quickly on modsine especially for battery chargers for some tools.

medic29

Re: Inverter question - newbie

niel wrote: »

btw, i believe you meant to say a 100ah agm and not 100ma.

Thanks!!


Thanks for the input; I was thinking about an inverter/charger type of setup, are there any brands I should shy away from, or others that fair better?

Also, I have read that I may experience the "joy" of burning up a set of batteries as I get things figured out and that it may be well advised to hold off getting the AGM batteries until I get things worked out. Could I get by with using some regular deep cycle batteries off the shelf?

I was also thinking about getting probably 2 batteries and wiring them in paralel to give me a little more capacity.

Thoughts??

icarus

Re: Inverter question - newbie

The Morningstar 300 is a real true sine wave inverter,,,

You could start with an off the shelf deep cycle, or move to a pair of t-105 golf cart batteries,,, ~220 ah. As I suggest,, consider doing your math and try to figure your loads, before you figure out your battery needs.

T

niel

Re: Inverter question - newbie

as both tony and myself have said. find out what you power needs are. sizing your inverter and your batteries are dependent on the power you draw during a day. i'm guessing you still want the ac from an inverter by how you have responded so get yourself something like a kill-a-watt meter to measure that power need.
http://store.solar-electric.com/kiacpomome.html
after that you can look at some inverter chargers and discuss both that aspect and the battery aspect. you can see the inverter chargers in the following link by sifting through these inverters as not all are inverter/chargers and they do cost a good deal,
http://store.solar-electric.com/inverters.html
separate inverter and charger may be cheaper for you, but that's dependent on factors yet to be determined.

BB.

Re: Inverter question - newbie

I would not always avoid AGM for first time use... But, you want to spend the time and money up front to understand your power needs/system capabilities well enough to not needlessly "abuse" your AGM batteries...

For example, when you look for charging devices (solar, 120 VAC, etc.)--look for ones with remote battery temperature sensors. The sensors help keep the battery fully charged (instead of 90% or so sometimes), and can prevent thermal run-a-way (cold controller and hot battery--battery voltage drops with temperature, but cold controller tries to increase battery voltage).

Also--I highly recommend a true Battery Monitor. The Trimetric has users here that like it (good for "lower cost" applications). The Xantrex units have a programmable output that can be used to set an alarm or turn off the inverter if battery falls below 50%--great for those spouses and guests that may just turn things on--like they do at home.

For your application an AGM would be very nice. They have low self discharge and are not as susceptible to cracking the case if frozen (electrolyte is in "mat"--no a column of liquid. AGMs (at least one brand claims) less susceptible to sulfate hardening (storage below ~75% state of charge). And lastly, very "clean" battery operation (no water spills, no need to bring distilled water, etc.).

Put a small solar panel (may be a single 10-20 watt) on the roof (or south facing wall if you have snow--that you can tilt/remount for summer use) with an AGM capable solar charge controller--and it will keep the battery charged throughout the season (assuming you bulk charge the battery before you leave the genset).

Bring a Honda eu1000i or eu2000i--small, quiet, and very efficient at low loads (25% load run time is nearly 4x longer than 100% runtime when using "ECO" throttle). The eu2000i (1,600 watt) will run ~15 hours with a 400 watt load on 1.1 gallons of fuel. Don't use the inexpensive 3.5kW or 5kW generators--they are noisy and fuel hogs at lower power levels (which I assume your cabin would be).

-Bill

medic29

Re: Inverter question - newbie

Okay, I played with my Kill-a-watt meter and found the fan I looked at using uses 45 watts on low and 67 watts on high. The lights I'm looking at using pulls around 15 watts.

I'm looking at getting a 100Ah battery.

I'm trying to figure out how long I can expect to be able to use these? The plan is to use the fan for probably 10 hours and maybe use the light for 2-3 hours.

Another question is I would like to run some wire through my cabin to a couple different outlets and to a couple different light outlets, will having this wiring ran and all of it connected to the inverter cause drain on the battery? even if nothing is on?

mike95490

Re: Inverter question - newbie

You have to look at the standby draw of the inverter. The morningstar suresine has a very low idle draw. As to your 100Ah battery, only drain it 50%, with 50ah.

A 100W load (at 120V) is about 110W draw thru a 90% efficient inverter.
110W @ 12.5V = 8.8A

50AH /8.8a = 5.6 hours of 100W load, and then you have to shut down to save your battery.

This is a VERY rough way to calculate, but it gets you a ballpark figure.

a 50W ac load would run for 11 hours off the battery/inverter.

medic29

Re: Inverter question - newbie

Wow, so it sounds like I could only run the fan on low through the night, then would have to fully re-charge the battery again the next day before the following night. It sounds like I need to look at a fan that draws a lot less.

Any information about the wiring and whether this would cause a draw on the battery?

homerramirez

Re: Inverter question - newbie

here my two cts. on inver charger, I have a new Samlex S-2024A (24v true sine wave 2000w continuos), probably B.B. will not recomend a $749.00 invercharger for such small Ah. battery, (you will need 2-12v-100AHea. to make 24v-100AH). the inverter works very good to the full rated capacity BUT when I tried to charge my battery bank with my ETQ TG 4000 generator the transfer relay on the invercharger did not switch to charging mode :grr , however, when I pluged to the grid the invercharger transfer switch worked within the 5 seconds of delay mode, I called Samlex regarding this problem and they explain that the frecuency on my generator(63.7Hz) coudn't syncronize with my invercharger(60Hz) therefore, the transfer switch will not operate and WILL NOT START THE CHARGE CYCLE, now I'll try to regulate the governor on the generator to stabilize the frecuency to 60Hz. so equal to the invercharger, if I can't do it, I might buy a 2nd. better brand generator (Honda)that is a true sine 60Hz. within the rated capacity of the invercharger.

if still do not work, it will be like buying a tv/dvd on same unit, tv breaks, can't watch dvd's, dvd breaks, can't watch dvd movies.......got the point?

medic29

Re: Inverter question - newbie

homerramirez wrote: »

if still do not work, it will be like buying a tv/dvd on same unit, tv breaks, can't watch dvd's, dvd breaks, can't watch dvd movies.......got the point?

Good point.

It's just hard to fine a decent charger. I feel like I'm walking around in a dark room, no lights, and trying to find a charger.

homerramirez

Re: Inverter question - newbie

I think Tony/icarus has a very good recomendation, make it simple and plan for your future needs within the solar power and budget limitations.

Good luck. :cool:

by the way, get used to the dark room with no lights lol

BB.

Re: Inverter question - newbie

Tony / Icarus likes the Xantrex TC charger family... There is a new set of models the TC-2.

From a paper point of view--the Xantrex TC family have a very solid design. Power Factor Corrected front end (great for use on a generator--older style battery chargers take very high peak current and can cause generators to overheat). Also, they have a remote temperature sensor option--get it... Much better battery performance over the long term (will tend to charge batteries closer to 100% capacity over the entire temperature range).

However, it looks like they are not in the store at this time--hopefully with in weeks they will be there.

-Bill