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Old 09-05-2021, 07:50 PM   #1
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Solar question

Does anyone know if a larger inverter will use more power to operate if it does not have a large power draw. In other words, is there a disadvantage to having a 3000 watt inverter if you are typically only going to be using 1500 - 2000 watts of power?

I am thinking about putting together a setup with 4 250watt panels a 40A Mppt charge controller and 10 100A agm batteries. Trying to decide how big of an inverter to get. Only running dc lights, water pump, a microwave a little bit, and maybe a little tv. Fridge and water heater are lp gas. 12v stuff wouldn't run through the inverter. Inverter would be pure sine wave.
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Old 09-12-2021, 02:16 PM   #2
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I ran a xantrex 2000watt inverter charger with 1200watt of solar and the biggest draw was my Samsung convection oven on 4 agm batterys cook time max 30 min

No Air conditioner on

all led lights

55in led tv

small dorm refrigerator110v AC for drinks


2 rv 9.6 CF dometic on propane and water heater on propane and Furnace on propane early morning for couple hours
3 months unplugged worked fine

You should be fine

Never ran out of power
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Old 09-12-2021, 03:40 PM   #3
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Quote:
Originally Posted by Dallasrules View Post
Does anyone know if a larger inverter will use more power to operate if it does not have a large power draw. In other words, is there a disadvantage to having a 3000 watt inverter if you are typically only going to be using 1500 - 2000 watts of power?

I am thinking about putting together a setup with 4 250watt panels a 40A Mppt charge controller and 10 100A agm batteries. Trying to decide how big of an inverter to get. Only running dc lights, water pump, a microwave a little bit, and maybe a little tv. Fridge and water heater are lp gas. 12v stuff wouldn't run through the inverter. Inverter would be pure sine wave.
Typically a larger inverter only means that the current capabilities of the solid state device is larger (example: a 25 amp IGBT or a 100 amp IGBT) all semi-conductors operate in the same manner, with the same (essentially) losses, which means that a small inverter or a large inverter will not have any significant difference in operation current draw.

Also I do not believe that there is ANY inverter on the market that produces a "Pure" Sine-wave. All inverters produce what is called (at least where I live) a "Synthetic" sine-wave. Without big long detailed instruction, the inverter turns the DC on and off for varying times (on then off, then on for longer then off for shorter) this produces a group of pulses that eventually replicate 1/2 of the sine wave, the DC is then inverted and the process starts over. This gives the other half of the sine wave now an upper portion has been produced and a lower portion has been produced which is 1 cycle of the sine-wave (the on/off time is in the 0.000001 time frame (Nano-seconds) 1 cycle of a sine wave of 60 Hz (standard North American frequency is 16.67 milli-seconds)

These pulses are not smooth but due t their on/off time ration it replicates a sine-wave but is certainly not "Pure"
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Old Yesterday, 07:52 AM   #4
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Ok, so how can they get away with advertising them as "pure sine wave" vs modified sine wave?

Also, I see a lot of no name charge controllers at ridiculously low prices. I know these must be junk, but how do you know?

I currently have a setup with 4 x 250w panels going through a morning star 45a charge controller, charging 8 vmax tank agm 125ah batteries wired for 24v.

I want to set up another system with 4x 250w panels and 10 x 100ah agm batteries. The panels are 8.?amps, so a 45 amp charge controller should work, but someone said I would need 2 of them. What would be the other limiting factor on the charge controller. I know there are other numbers, but I don't know what they mean.
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Old Yesterday, 08:53 AM   #5
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One would need to talk to government regulators as far as "False Advertising".

IMHO most of this stuff comes from China and just because it is "ridiculously low prices" does not equate to junk. Many products sold at the likes of Canadian Tire, Home Depot are also for sale at Uncle Verns, same product much lower price at Uncle Verns. We, as North American consumers, are buying Chinese products almost every place where we shop. Several years ago I was looking to a BBQ, found one at the local store ($2500.00) went searching on the inet found same BBQ from a Chinese supplier (a little over $250.00, exactly same one including the recipe book). Problem is I would need to have bought 2, shipped them, and pay Duty & GST, as I remember the estimated landing costs at my door was right around $1000.00 and but I would have had 2 BBQ's. My story on Chinese VS what we consider other brand. Chinese units MAY not have all the bells and whistles but doesn't mean they are junk.

Since your panels are connected in Series you are limited to the 8.?? amp output therefore a 45 amp charge Controller should be good.

My bigger concern is: Do you have proper Fusing? Do you have a proper Disconnect?

You are talking massive Short Circuit current capabilities which present possible, lethal voltages and currents, which could also result in destruction of your RV. I say this out of concern for life and limb.

A battery bank is not simply connected to a charge controller nor is the PV (Photo-Voltaic cell = Solar Panel) simply connected to the CC and on to the load, although many wiring diagrams would lead us to believe that.

There needs to be means of disconnection and fusing. This system once installed is similar to a house electrical system and needs to have protection.

Lastly you have (will have) some serious power capabilities. I assume you are a boon-docker and need that sort of power. (225 ah of battery power)
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Old Yesterday, 10:34 AM   #6
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Yes, I have all the proper wiring and fuses in between the major components plus my panels come into a combiner box with individual fuses on those as well. The current set runs to a pedistall and we plug the rv directly into that. Our problem right now is that the setup is 24v due to the inverter and we can't run directly to our batteries. Everything is running off the inverter.

On the second setup will be split. The panels, controller and batteries will be in one place where the sun is. The rv will be in another. Vwhen needed I plan to pull a few batteries, take them to the rv. Have the inverter there. If I run them down, I can swap them out with fresh batteries from the solar setup.

Property is off grid. No utilities at all. Sunlight is limited to a few hours a day in one clearing surrounded by 200' tall oaks. Thus the large battery banks. We don't go very often, every couple of weeks for a few days, so there is usually plenty of recharge time.
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