Reputable Inverter brands?

NeedMyTVNeedMyTV Registered Users Posts: 4
I am designing a small emergency power system to run a TV, a small fan, and the occasional microwave oven, so we are not sitting in the dark the next time there is a big storm (Florida).   I have an (old) degree in Electrical Engineering so I understand all the principles. I have decided on all 24v parts, all pure sine wave, which helps narrow the field.  There will be a small 300W inverter for the TV and fan (60W and 20W respectively) because I read that the smaller units are more efficient for small loads, and this is what we will be using most of the time.   Later on I will need a separate 2000W inverter for the microwave.  But the last time I did this exercise, in 1999, the choices were different - brand names come and go and it is hard to tell the reliable brands from the cheap ones that will let me down.  For the smaller unit, they are all cheap enough it is not too big a worry, but the big units are expensive enough to do more study.

I know the name TrippLite.  Is Trace now Xantrex?  Who is GoPower?  I assume they are mostly all manufactured in China regardless of the quality.  Is there a list of the "good" ones?
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  • westbranchwestbranch Solar Expert Posts: 5,114 ✭✭✭✭
    In the field of inverters, the price is a fair indicator of quality.... a good one at 24 V 2000w should be above ~$600..  also the more data you find available, generally > better quality... 
    To me most important were, idle draw, sleep mode draw (consumption), overall efficiency rating at different  loads than just its sweet point ... and surge capacity and duration...

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.BB. Super Moderators, Administrators Posts: 28,172 admin
    edited October 2016 #3
    My suggestion would be to get a Kill-a-Watt type power meter. You can plug your 120 VAC devices in and see how much energy they use.

    For a "good" solar off grid power experience, you really need to reduce your loads (conserve) as much as possible. And, realistically, solar can be difficult to justify for emergency/backup power vs just getting a small genset (like a Honda eu2000i or eu1000i) and some gasoline siphoned from the car. Batteries age just sitting around, and do need charging (flooded cell either need to "float", or need to be charged for ~24 hours every month). A Honda eu2000i will provide ~1,600 Watts for 4 hours on or 400 Watts for 9 hours on ~1.1 gallons of fuel (for ~$1,000). Note--You can buy cheap/larger backup gensets, but their fuel consumption can be very high (5 kWatt genset can use ~0.5 to 1.0 gallon or more per hour).

    Get a small multi-fuel stove (gasoline, diesel, Coleman fuel, propane, alcohol, etc.).

    For lighting, get some LED flashlights--On low, they can go for days on a pair of AA batteries. --Pretty much more like camping. For fans, there are some DC fans (ceiling, RV) that do not use much power.

    Usually, designing a small/cost effective emergency power system precludes using a microwave oven/full size refrigerator and other large loads--Both because of high starting surges (induction motors), and because of extend power draw over time (Watt * 24 hours per day=Watt*Hours and a large battery bank).

    More or less, if you power LED lighting, TV (LED type), Radio, Cell Phone charging, laptop computer use, small RV water pump from cistern, etc... A 500 WH or 1,000 WH per day system is usually sufficient for enough power to keep everyone happy (laptop computer use + water pump--more towards 1,000 WH per day).

    Also, using a smaller solar power+battery system for nighttime/small loads, and a (smaller, fuel efficient) genset for daytime loads (cooking, running washer, well pump, recharging battery if no sun available) is not a bad combination.

    But--energy usage is a highly personal set of choices... I will go through a system design that will run a 2,000 Watt inverter so you can see what is involved--And make your choices from there.

    Nominally, I would start with your loads (peak Watts, hours of day for loads--Watts*Hour for days for each appliance) to design the battery bank. However, since you have a 2,000 Watt AC inverter in mind--I will start there and work out the specs. from there. For a battery bank (flooded cell lead acid battery), you need a minimum of ~200 AH per 1 kWatt of inverter rating (to supply ~2,00 Watts of surge current/max continuous power of 1,000 Watts for a period of time). So that puts in the 400 AH @ 24 volt battery range. Roughly, 4x 6 volt @ 200 AH golf cart batteries in series (for 24 volts) and 2x parallel strings for 24 volts @ 400 AH battery bank (golf cart batteries are cheap, fairly rugged and forgiving, and a good starter bank for folks to learn with--An 8 battery GC bank is around $800).

    To charge such a battery bank--Recommend 5% to 13% rate of charge. 5% for emergency/weekend/seasonal usage. 10%+ for full time hard core off grid system. 10% rate of charge is recommended current for a lead acid battery bank--For many reasons. Plus, 10%+ makes "managing loads" much less of a daily task.
    • 400 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 753 Watt array minimum
    • 400 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 1,506 Watt array nominal
    • 400 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,958 Watt array "cost effective" maximum
    Now, based on hours of sun near where you live (guessing near Jacksonville FL):
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Jacksonville
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 60° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.94
     
    4.48
     
    5.16
     
    5.78
     
    5.67
     
    5.01
     
    Jul Aug Sep Oct Nov Dec
    5.17
     
    5.00
     
    4.62
     
    4.68
     
    4.26
     
    3.84
     
    The various array options would supply (long term solar average), for December (worst case, "break even month"--perhaps use genset some):
    • 753 Watt array * 0.52 typical AC off grid System eff * 3.84 hours per day = 1,504 Watt*Hours per day (December, long term average)
    • 1,506 Watt array * 0.52 typical AC off grid System eff * 3.84 hours per day = 3,007 WH per day
    • 1,958 Watt array * 0.52 typical AC off grid System eff * 3.84 hours per day = 3,909 WH pr day
    And if you assume 2 days of stored power and 50% maximum discharge (for longer lead acid battery life):
    • 400 AH * 24 volts * 0.85 AC inverter eff * 1/2 days of storage * 0.50 maximum discharge = 2,040 WH per day storage
    A 400 AH @ 24 volt with 1,500 Watt array is a very capable system and should meet your needs (guessing) as you have given them. Now the question is this how much you want to spend (and install solar array, battery bank somewhere with good ventilation, etc.). Replace batteries every 3-5 years (for "golf cart" batteries, in warm Florida weather--Keeping batteries cool will help extend their life--For every 10C rise over room temperature, ~1/2 battery aging life is lost).

    Or $1,000 for a small(ish) genset plus a siphon hose (and/or 10-20 gallons of stored fuel with fuel stabilizer, rotated into car every 6-12 months will run the genset for 5-10 days at least ~12 hours per day). Or--if you have propane/natural gas for a genset?

    Either are perfectly good options--And even with solar off grid power, a backup genset is usually a good idea (if you have many days of dark clouds, you will not harvest much solar, or if the wind storm damages your glass solar panels with wind blown debris, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NeedMyTVNeedMyTV Registered Users Posts: 4
    Thanks for all those detailed numbers - I can use them in my spreadhseets.   This is not really an 'off-grid' system;  it is for use when the power goes out so we are not sitting in the dark.  (We just had Hurricane Matthew, and the power was out for 3 days)  This system will be plugged in all the time with a smart charger to preserve the battery life.  I see some inverters even include that function.  So it does not need to have massive solar panels to begin with.

    It looks like the batteries should not be in the garage!  In the summer it gets up to 100 degrees F in there.  We have a spare bedrrom where it could go.  I was planning on a couple small wheeled carts.

    We already have plenty of flashlights.  We do not expect this thing to power the whole house, and I am working up a power budget spreadsheet.  ("Microwave at 1000W for 6 minutes" etc)  The main thing we do in the evening is watch TV and for that we have a small LED TV with integral DVD player and a quite large library of movies.   The fan is to make the bedroom less stuffy without the AC running.

    The microwave is the second phase of all this, which is why I am designing around 24v in the first place.   The big inverter would be running only when we need that so tons of battery AH capacity should not be required..   Cold Chinese food got a little old...  I forgot to mention that my wife really dislikes generators, but I am thinking that a small one that is just used to recharge the batteries in case of another really long outage like this last one could be a good compromise.  Stored without gas in it to prevent clogging up.

    It is an all-electric house, so if we went with a propane generator (such as we had in New Hampshire) we would have to add a tank for that.  That was a monster - 6KW, but it had to power the whole house otherwise we would have no heat (oil furnace and water heater) and no water (deep well).  But we had a 5 acre lot then.   Now we are on 0.5 acres and the neighbors are a lot closer.  There is limited room for such things.  In NH the problem was ice storms.  In FL it is wind that is the hazard.
  • BB.BB. Super Moderators, Administrators Posts: 28,172 admin
    edited October 2016 #5
    The "quiet generators" are really quite nice... The Honda eu2000i sounds like an idling Honda Electroglide motor cyle. And if you are on a city street (food carts, street musicians), you cannot really even hear them until you are top of one. There are propane conversion kits for the eu2000i (and others) if gasoline storage is an issue. With oil changes and air filters, people get something like 2,000 to 6,000+ hours out of them (crossing fingers). Yes, store without gasoline (dump tank, run dry, there is a small drain screw on the carb for the Honda).

    Put it on a 50' extension cord out back (genset changed to tree for security, some people make plastic handle metal guard plate to make cutting more difficult--if needed). And a carbon monoxide detector in the home--Just in case. You can also get/make a fuel cap + hose to pull fuel from a 5 gallon gas can (or outboard tank)--No more refueling several times a day.

    https://www.amazon.com/s/ref=nb_sb_ss_i_4_19?url=search-alias=aps&field-keywords=honda+extended+run+fuel+system&sprefix=honda+extended+run+,aps,529

    My suggestion would to run a 500-1,000 WH per day system with a 12 volt MorningStar 300 Watt TSW inverter, and use the genset when time for cooking/other loads. Use 2-4 6 volt @ 200 AH golf cart batteries.

    And get an RV 12 volt fan for the bathroom. We have some threads like this one:

    http://forum.solar-electric.com/discussion/10865/most-efficient-12v-dc-fans

    Much smaller system, will give you quiet power at night. And the ability to run larger loads via genset when needed.

    Flooded cell lead acid batteries--Not really a good idea for bedroom installation/storage. They out gas hydrogen (and oxygen), and many times a bit of electrolyte (sulfuric acid+water) when charging. AGM batteries generally do not out gas and are much cleaner--HOWEVER, AGM batteries will overheat/out gas/catch fire with the best of them when they get old and/or being over charged.

    Assume pretty much all batteries will out gas/leak and are potential fire hazards and treat then accordingly. I will leave it to others here that have hot weather/Florida experience on their suggestions for best battery / best installation practices. For a suggestion, a battery box on the north side/under shade should be a start. Ground contact is not bad (earth average temp is less than hot summer day). However, if you get standing water, ground contact may not work for you.

    Set up for permanent / fixed installation of the battery bank/charge controller/solar array... I assume it would get old if you had to push your battery cart to the garage once a month to recharge for the other 9 months of the year you don't need backup power.

    -Bill "my two cents" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdownsoftdown Solar Expert Posts: 1,928 ✭✭✭✭
    Getting a 2000 watt inverter for the microwave screws up the equations. Get the smallest microwave you can. I have seen 800 watt units for about $60....all over the place. So they take 4 minutes instead of 2 minutes.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • NeedMyTVNeedMyTV Registered Users Posts: 4
    Yes, AGM batteries are a given.   For now the compromise is to design the DC system for 24v of AGM batteries, consisting of 6, in plastic battery boxes, of 35AH each (U1 size).   This makes them manageable weight (25lbs each) if we have to move them separately (us being over 65 years old...).  That gives a useful capacity (50% discharge) of 35*3/2*24=1260 watt-hours.  Running the 60W TV would give a continuous run time of 17.85 hours, assuming 85% inverter efficiency.  Add the fan and we can still get a couple evenings on a charge.

    A portable generator will be used both to power a small microwave when necessary, and to recharge the batteries in case of a long outage.   There is always the option of adding solar charing and/or a big inverter later.  Since we need the generator anyway for recharging, and the microwave is only used intermittently.

    Killawatt meter also on order...
  • BB.BB. Super Moderators, Administrators Posts: 28,172 admin
    Can you give a link/specs for the batteries... 8 volt batteries (3x 8 volt = 24 volt) are around, but not very common. Typically 12 or 6 VDC.

    I am not sure I understand your math--So, the way I format it:

    If these are 35 AH @ 12 volt batteries (2x series * 3x parallel = 6 batteries):
    • 35 AH * 3 parallel strings * 24 volt battery bus * 0.85 inverter eff * 0.50 max discharge = 1,071 Watt*hours "recommended usage"
    • 1,071 WH / 2 days of stored energy = 535.5 WH per day (no sun)
    • 535.5 WH per day / 60 Watt TV 120 VAC load = 8.9 Hours per day
    For emergency systems using good quality AGMs like the Concorde series--You can use up to 80% of battery capacity--As long as you get them recharged right away (lots of sun, genset, etc.). Most likely, in a standby type usage, they will age out before they cycle out.

    Make sure these are not "UPS" type batteries... Those tend to be only for float service and not have very much deep cycle life (UPS batteries are typically replaced every 2 years or after a couple of major power outages).

    I understand you do not want heavy batteries--But for the above system, I would be suggesting a single 12 volt battery or 2x 6 volt batteries in series of ~210 AH (equivalent to your 24 volt bank) with a 12 volt Morningstar 300 Watt TSW inverter....

    I do not like large arrays of small AH batteries.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NeedMyTVNeedMyTV Registered Users Posts: 4
    The batteries are Universal UB12350.   35AH AGM batteries in U1 size.  They are apparently often used in wheelchairs.
  • BB.BB. Super Moderators, Administrators Posts: 28,172 admin
    High quality agm

    1x https://www.solar-electric.com/concorde-sunxtender-pvx-2120l.html

    Or

    2x in series https://www.solar-electric.com/concorde-sunxtender-pvx-2240t.html

    Or flooded cell golf cart batteries, 2x in series 6 volt @ ~220 amphr batteries for around $100 each (good "training battery bank", cheap and forgiving).

    The batteries you linked to would be more expensive than flooded cell golf cart batteries for the same capacity (6x wheel chair batteries).

    Trojan batteries are mid range quality. Shipping can be an issue (batteries are heavy, flooded cell can only ship by truck).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ThomThom Solar Expert Posts: 185 ✭✭✭
     We use Ryobi 18v fans at night if needed . They last 8 hours . Inverter is off at bed time. Saves a lot of power. 

    Thom
    Off grid since 1984. 430w of panel, 300w suresine , 4 gc batteries 12v system, Rogue mpt3024 charge controller , air breeze windmill, Mikita 2400w generator
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