Inverter choices for my rv

big D

I'm new to solar and this site so I hope I'm not asking stupid questions, so here goes.
I'm building a solar house down in Baja (to be completed in 2011) hoping anyway, and I need to put solar on my motor home until then. I'm buying my own hardware (to save money) and so far I found Sun 130 watt panels-335 each, the Rogue mpt 3024-295$ (read the threads yesterday and decided to try it. My problem is a inexpensive but reliable Inverter.

Does anyone have any info on the coleman power express pure sine 2500 sold by Top sale depot. cost 495$ I'v been trying to find user info but so far Nada.
As my motor home has a Converter already, I will have parts installed hopefully by some one like our host(if they do this kind of work).

Any info would be great.

mike95490

Re: Inverter choices for my rv

big D wrote: »

I'm new to solar and this site so I hope I'm not asking stupid questions, so here goes.
I'm building a solar house down in Baja (to be completed in 2011) hoping anyway, and I need to put solar on my motor home until then. I'm buying my own hardware (to save money) and so far I found Sun 130 watt panels-335 each, the Rogue mpt 3024-295$ (read the threads yesterday and decided to try it. My problem is a inexpensive but reliable Inverter.

Does anyone have any info on the coleman power express pure sine 2500 sold by Top sale depot. cost 495$ I'v been trying to find user info but so far Nada.
As my motor home has a Converter already, I will have parts installed hopefully by some one like our host(if they do this kind of work).

Any info would be great.

Pleas explain what your existing "Converter " is. Charger? DC-AC inverter ?

big D

Re: Inverter choices for my rv

When my motor home is plugged into shore power my Converter converts 120vac to 12vdc. Other wise its sleeping. I also have on board 2 trojan 105's

BB.

Re: Inverter choices for my rv

I would recommend that you size your AC loads first before purchasing an inverter.

5,000 watts peak at 12 volts? Assuming 85% efficiency, and 10.5 volts minimum voltage:

5,000 watts * 1/0.85 * 1/10.5v = 560 amps maximum

That is a huge amount of current to bus around.

Frankly, I don't know anything about the inverter you have asked about--but I have my doubts about how well it will work at rated power and if it is really a true sine wave inverter or really just a modified square/sine wave inverter.

In the end, I would not expect much from a 12 volt inverter at >2,500 watts. The amount of batteries you have probably would not sustain anything near this rating.

I would suggest looking at your loads and pick a reasonable load (battery capacity / 10 or / 20 would be a good start). Based on your current system--I am guessing that 30 amps * 12 volts - 360 watt maximum average power output would be about it (thinking laptop computer, small radio/tv, couple CFLs, small fan).

For 12 volts--that would map very nicely onto a MorningStar 300 watt 12 volt pure sine wave inverter (600 watts peak). Very efficient and clean power at a reasonable price.

Assuming you decide you need more power (for building your home)--take a look at a generator. For small, quiet and very fuel efficient, the Honda eu2000i (1,600 watt continuous) is hard to beat.

Most generators are pretty fuel efficient above 50% load--however, when they run at less power, they tend to suck down the fuel at a 50% rate. The Honda will go down to 1/4 load (400 watts) at 1/4 fuel flow... Very hard to beat. And easy to put away when you are not there (50 lbs).

If you need a larger genset--you might get a second "cheap" 5kW unit to run your table saw, pumps, etc. when you need the higher power.

However, if you decide that you want to run your loads off of solar--then you will need to know your peak and average loads (Watts), how much power they use in a day (Watt*Hours) to size your inverter, battery bank, solar array, and backup genset.

Lastly, if you decide you need high power--I would humbly suggest that you look at a 48 volt system... At least with 4x the DC input voltage, you only need 1/4 the DC current to run your inverter.

You can build a bigger than you need system--but at ~$10-$15 per watt generated costs (2,500 watt average power could be a $25,000 solar off grid system)--you don't want to build a bigger system than you will use. And if the power usage is sporadic (a few weekends a month)--you are probably better off setting up a nice generator system for power until you move in full time. Solar is most cost effective when you are using it 9+ months out of the year.

Use the small solar panels and battery bank to power your RV for quiet, smoke free, evenings.

-Bill

john p

Re: Inverter choices for my rv

You would need about 20 x200 ah 12v deep cycle batteries to power that inverter
That would give you 2200 watts inverter output for about 14 hrs a day. Thats a LOT of weight and then you going to need a truck load of solar panels to recharge them....:grr

dwh

Re: Inverter choices for my rv

john p wrote: »

You would need about 20 x200 ah 12v deep cycle batteries to power that inverter
That would give you 2200 watts inverter output for about 14 hrs a day. Thats a LOT of weight and then you going to need a truck load of solar panels to recharge them....:grr

I think the point is that he wants a cheap sine wave inverter.

There's no law that says he has to draw 2500 watts though it - he could just as well use it to power a 100 watt load.

BB.

Re: Inverter choices for my rv

Generally, running a smaller inverter to power smaller loads is more efficient.

And I am still not convinced that it is a 2,500 watt true sine wave inverter for $495 (I have no knowledge of the product--so it is certainly possible that I am wrong).

-Bill

dwh

Re: Inverter choices for my rv

BB. wrote: »

Generally, running a smaller inverter to power smaller loads is more efficient.

And I am still not convinced that it is a 2,500 watt true sine wave inverter for $495 (I have not knowledge of the product--so it is certainly possible that I am wrong).

-Bill

Yea, I never heard of it either. But if it's true, then I'd certainly be willing to ignore a few % of efficiency for that price.

john p

Re: Inverter choices for my rv

Running a 2500 watt inverter is very wasteful if only going to be used to supply say 100 watts.
standby of inverter at 12 v will be about 2amps for 300w inverter about half an amp.. a difference over a 24 hr period of 36 ahr. now that is going to reduce his available battery use by that amount. and the inverter is going to be also less inefficient than a smaller one at providing the 100 watts.
its kinda like using a 20 ton Mack truck to go collect the family groceries each week.

dwh

Re: Inverter choices for my rv

john p wrote: »

Running a 2500 watt inverter is very wasteful if only going to be used to supply say 100 watts.
standby of inverter at 12 v will be about 2amps for 300w inverter about half an amp.. a difference over a 24 hr period of 36 ahr. now that is going to reduce his available battery use by that amount. and the inverter is going to be also less inefficient than a smaller one at providing the 100 watts.
its kinda like using a 20 ton Mack truck to go collect the family groceries each week.

Of course...but that's not the point. The point is that is you can get a Mack truck for 50 bucks, then no matter how inefficient it is, it's still gonna be cheaper to use it to get the groceries.

niel

Re: Inverter choices for my rv

bb,
i did a simple search.
http://www.topsalesdepot.com/bwapusiwapoi.html'
mind you that it is not made by coleman, but it only says it's from the same factory and i would be leary too.

john p

Re: Inverter choices for my rv

Of course...but that's not the point. The point is that is you can get a Mack truck for 50 bucks, then no matter how inefficient it is, it's still gonna be cheaper to use it to get the groceries. BUT IT IS THE POINT .. its going to consume a lot of your stored battery power. mabe you have an unlimited battery bank.. mabe he does not .mine is only 400ah so every amp counts . that is why I use 2 inverters 1 is 300 watts for all house lights as it consumes 280 mw on idle and have a 1000 w one for other uses but its only turned on "on demand."
And another thing a mack truck even for 50 bucks is NOT going to be cheaper to go get groceries unless you have free fuel or can buy it at 10 cents a gallon.

mike95490

Re: Inverter choices for my rv

niel wrote: »

mind you that it is not made by coleman, but it only says it's from the same factory and i would be leary too.

Wow, and with 6 high speed cooling fans, what could go wrong?

westbranch

Re: Inverter choices for my rv

Wow a right hot topic...


for $$ comparison, here is what the Canadian tire is selling for $299 Cdn...

http://www.canadiantire.ca/AST/browse/4/Auto/SolarPortablePower/Inverters/PRD~0111892P/1%252C000W%2BPure%2BSine%2BInverter.jsp

definitely NOT in the same category. Has a 2.15 amp standby draw, but it shows there are lower cost units out there, but as the Q & A states: you get what you pay for.
If cost is a limiting factor, or differential, then you can go that route.

cheers
Eric

niel

Re: Inverter choices for my rv

my 2 cents on,
"Running a 2500 watt inverter is very wasteful if only going to be used to supply say 100 watts."

in general this may be true as the efficiency of the 2500w inverter operating low power will have the effect of a larger load due to efficiency and base operating needs. the basic operating requirements during low power are often larger for larger inverters. one does have to be careful and read specs to do an actual comparison for some small inverters have really bad efficiency losses too making the larger inverter a possible better option.
when shopping for an inverter some leeway is good for possible expansion, but if an inverter has power that will not ever be used this may make it better to go to a lower w rated inverter observing comparative losses for each, as one does not want to cheapen specs, while saving a few bucks on extra fets or even fans. this needs to be a case by case evaluation imho with many inverters to compare with.

big D

Re: Inverter choices for my rv

Wow...great info from everyone...Thanks so much.

I think that to figure usage in the Motor home is important but due to space limits on everything from PV's to batteries, I think I would want to max out my space as much as possible and try to configure to most effective system based on that.
I know that seems wrong because everyone wants to design systems based on usage.
My point is we've been full time in the motor home for 7yrs now so we no how to conserve our available power. So all we really want is to power the entertainment center(DVR,surround sound,flat screen x 2) in the evening without using the Generator(oh yea Onan 5000 watt). We don't need to Micro much,fridge is dual(propane/electric) Perc the coffee on the gas stove and hot water is gas as well.
All lighting is 12v.
So now 3 120 watts on the roof (no more space). Sun-hs-120 from u know who in Florida. But for 335$ ?????
only space for 2 t105s ( hopefully i can mount 2 more in the slide right next to battery compartment with some modifications(venting and what not), that just leaves the inverter/ charger/controllers to make it all work. Also the PVs of choice seems to be 24v.Not sure if that's a problem as I'm a newbe at this.My next trip to Baja is in October and will be for about 8months. So I have still a month or 2 to figure this out. I'm contacting our host today for their input on the Inverter/charger/controller issues and install prices from them. What with the converter,generator, trickle solar charger, already installed,integration is probably best left for the expert.

As you guys are so good at this..I would like to know your recommendations for the rest of the puzzle...Inverter/charger/controller sizes.

I'm I completely off base here in my thinking?

BB.

Re: Inverter choices for my rv

If you where to replace your flooded cell "house batteries" with AGM (less venting, can mount on side, draw down further, etc.) be worth the 2x cost of AGMs?

-Bill

mike95490

Re: Inverter choices for my rv

BB. wrote: »

If you where to replace your flooded cell "house batteries" with AGM (less venting, can mount on side, draw down further, etc.) be worth the 2x cost of AGMs?

-Bill

and you pick up 10% or more on the recharge efficiency. With a smallish solar array, and a good controller, and BTS, AGM, should be nearly a no-brainer

BB.

Re: Inverter choices for my rv

You can figure out how much power you will get from your system by using the PV Watts website... For off-grid with AC inverters, use a derating factor of 0.52 (flooded cell) or 0.59 for AGM. Set for zero tilt if they are mounted flat to the roof (note, 1kW is the minimum the program takes--so you have to do a little math if you have less).

While down in Arizona a few weeks ago, saw a nice RV that had solar panels set up to be like an awning--folded flat against the side of the RV for travel and would tilt out (I am guessing) like an awning. Looked like a good way of getting 600+ watts of solar panels out there.

Basically, those 360 watts of solar panel will probably give you, roughly, 1,000-1,300 Watt*Hour useful power per day for 6 months of the year (obviously, less in winter)...

It is up to you how you slice and dice that power (+genset)--If you assume a 200 watt load, the solar array would power about 5-6 hours per night... Much closer to a 300 watt inverter vs a 2,500 watt one.

Of course, with more genset and batteries--you can choose to make the power go longer (but remember that a genset charging batteries is only going to be ~60% efficient too because of charger/battery efficiencies vs just running the load of the generator).

By the way, do you have some sort of battery monitor? Highly useful to ensure that you are not taking your batteries to an early death with overloading/undercharging. Just about required if using Sealed AGM's since you cannot measure their specific gravity with a hydrometer.

-Bill

westbranch

Re: Inverter choices for my rv

Big D, on the conserv front:

have you changed over the LED or CFLs to shave a bit of power use ?
I would drop the Microwave, as it is a power hogggg. Use the propane for heating food and drink.
hot java please?... use a thermos...

Another idea that was covered before on this board is to use more than 1 inverter and have the loads balanced appropriately though this may not be possible in an RV.

How often do you run the genset, apart from recharging the batts ? must be minimal...
Can you playback the DVDs on a laptop to use less power? Not quite as good as a 42 inch LCD but...

cheers, HTH
Eric

big D

Re: Inverter choices for my rv

Good morning Westbranch

Hope your staying warm up there.

Will be changing to LED's on the most used locations first.
The micro is already a rarely used item.
We will have a 500 liter propane tank in Baja for use so all good there.
In RV's without a Inverter and only a Converter,all that is available for use is the 12v system (overhead lights) and gas appliances. Our Batteries have never been fully used. The last 3 months in Baja during the house foundation build we used about 80 gallons of gas to use the Generator. We only turned it on in the beginning to run the DVR to record on time. That turned into extended run times because why not run the AC as long as your running the gen anyway, turned to to be 6 to 8 hrs a day. The bigger issue is the noise of the gen. Not actually real bad in the desert, it seems twice as bad due to the extreme quiet of the place (which we miss)!!
Our plan is to not have to run the Gen at all except to recharge if needed
I think that I have decided to go with the following
4 120 PV's for 480 watts at 26 amps.
the 30a rogue mpt 3024 mppt controller charger.
1000-1500 watt inverter (brand undecided)
4 trojan t105 batteries. 225AH so 900AH
AS previously stated- space determines power parts above has maxed me from roof to battery location. Would love to go AGM but to t105's I have are new and so makes cents to purchase 2 more at 200$ as they are relatively cheap and small to boot.(must build battery box in slide next to current location). I figure the entertainment center should pull about 600 to 700 watts when all on (just a guess). we plan to live within our means what ever the power draw.


Hope to spend most of the time pool side with the ever popular DOS xx's to cool
Thanks for the input eric

westbranch

Re: Inverter choices for my rv

Hola BigD, sounds like you are getting there... if you don't already have one on order, get a Kill-a-Watt meter. It will tell you exactly what your 110 loads are, especially since you are running very close to the wire , so to speak...

Another K-a-W use is to fine tune the output of your genset if needed, as you can check the cycles. Mine were a hair low and I could hear it in the electric motor sounds, just a slight oscillation, ever so slight, a few more rpm and the cycles went up and under load they stabilized at 60, all to be watched with the K-a-W meter.

Don't forget the ever useful Battery Monitor either. It will let you know if you have a problem and assist in diagnosing it. Well worth the peace of mind.

PS weather is good, but all mixed up this year. A week ago we had temps in the 30 * C range, this week it is a high of 15 * C and down to 4* overnight

enjoy those cervesa.

Eric

big D

Re: Inverter choices for my rv

Hey Eric;
Planning on one of those kill-a-watt thing a ma bobs already before final decisions are made.Thanks

PS 85 sunny and warm here in Julian Ca.

talk to ya...Don