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Old 01-23-2019, 12:15 PM   #1
Mini-Skoolie
 
Join Date: Oct 2018
Location: Ogden utah
Posts: 67
Year: 2002
Coachwork: Bluebird
Chassis: Tc2000
Engine: 5.9 24v
Rated Cap: 27
Inverter options?

Hi,

I'm specing out an inverter for my bus.

Here are the details on what i'm looking for and what I have already.

Appliances to run,

Microwave (1100 W)
Electric griddle (1300W)
T.V (~~ 70 W )
Laptop ( ~~ 150 W )
9000 BTU air conditioner ( Draws 900W )
(https://www.sogoodtobuy.com/9000-btu...ner-senl-09cd/)

Obviously Im not going to be able to run all this at once, but the big hitters here are going to be the microwave, and the Airconditioner.

For my thoughts on the A.C skip to the end.


What I want is about 700-900W of solar power.
2.5KW of battery storage
Charging from the bus alternator would be nice but not essential at this time.
24V system

I already have several batterys out of a totaled Fiat 500E.
These are 6 cell Li-Ions and rated at 65AH each. I plan to use two ( 130AH @ 25.2V )

What I need now i the inverter.
Cost is obviously a factor here, but I also want a unit with good longevity, as a 300$ inverter that dies in two years is less valuable to me than a 800 inverter than lasts 10+ years.

Here are the options I am looking at.

Cotek 2000W
https://www.ebay.com/itm/Cotek-SP200...t9HR:rk:6:pf:0

Chinese 5000W ( Obviously over rated )
https://www.ebay.com/itm/LF-Pure-Sin...Igg:rk:17:pf:0

3KW "FuelZero" ( Never heard of them ) Low Frequency inverter

High Power, High Output Pure Sine Wave Inverter, Low Frequency, AC Charger, 24v Input, 110v Output, 3000 watt Continuous, 9000 watt Peak

Those last two are Low Frequency inverters.

The word on the street is that the LF inverters have longer longevity because they are more resistant to large surge currents, and use a single large heavy transformer rather than high frequency small transformers.

The Cotek is the only one with a reputation, the other two are unknowns.

Im looking at a Pure Sine Wave inverter, Mostly for that microwave, but people have run microwaves on Modified Sine Wave successfully so if you have a suggestion and it's not PSW then I'll still take it into consideration.


Other details for consideration.

Most of my non-appliance stuff is going to be run of 24VDC ( Fans, lights, water circulation pump, USB charger for phone, etc )
These items are irrelivant to my purchase of the inverter

Im O.K with having to often replace MOSFETS in an inverter if they die. So if you know of an inverter that eats a few mosfets now and then requiring a bit of soldering skills to replace them that's not a big deal to me at all. If the motherboard dies or it blows up capacitors often that's not cool.

I live in Utah. It's sunny every day and often over 100 degrees. I need A.C, not negotiable.


**
Thoughts on the A.C. The unit in the link is a VFD driven air conditioner. This means that it's more efficient than a regular A.C, and likely has a way lower, if any start up current.
If you are not familiar with VFD ( Variable Frequency Drive ) it takes your AC, converts it to DC, then uses a variable frequency drive to deliver power to the motor.
This DC stage means that the high inrush current that typically faults out your inverter wont be there. What this also means is that I can probably hack the electronics and feed DC directly into the DC bus of the VFD and bypass the AC Inverter stage altogether. This would mean I can run the airconditioenr directly off the DC batteries using just a DC to DC boost converter.
The DC bus is probably 200+V but Im a electrical engineer by trade and have experience with VFD's Motor's and DC conversion circuitry. I have wanted a DC run Airconditioenr but those things are several grand. Forget it, The VFD units have potential to be direct DC operated and I think I can make it work.
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Old 01-31-2019, 12:47 AM   #2
Mini-Skoolie
 
Join Date: Dec 2018
Location: Mt Vernon, WA
Posts: 65
Year: 1996
Coachwork: Bluebird
Chassis: G30 Bluebird Microbird
Engine: 1995 Chevrolet 350
Youve likely already considered a 24 vdc to 12 vdc converter. I’m placing my 30 amp converter where I can have both voltages available to fuse blocks. The 24 vdc will be less regulated as it’s before the converted. I have a nice 24 volt circulating pump and some 24 volt muffin fans I want to run.
Good idea to bypass the AC on the VFD inverter. Please let me know if that works. Thanks
Doktari is offline   Reply With Quote
Old 01-31-2019, 03:12 AM   #3
Bus Nut
 
Join Date: Apr 2010
Location: Lebanon, IN
Posts: 250
Year: 1998
Chassis: TC 2000 bluebird
Engine: 5.9 cummins
Rated Cap: 66
I have been very happy with myMagnum inverter. And it puts out both 120vac and 240vac

I went with a 24 Vdc battery bank as it reduces wiring size, increases inverter efficiency, and there are lots of good marine accessories that use 24vdc.

It is also a good voltage for charge controllers.

Bill
miltruckman is offline   Reply With Quote
Old 01-31-2019, 01:03 PM   #4
Bus Geek
 
Join Date: May 2016
Location: Eastern WA
Posts: 4,570
Year: 2002
Coachwork: Bluebird
Chassis: All American RE (A3RE)
Engine: Cummins ISC (8.3)
Rated Cap: 72
Quote:
Originally Posted by Doktari View Post
Youve likely already considered a 24 vdc to 12 vdc converter. Iím placing my 30 amp converter where I can have both voltages available to fuse blocks. The 24 vdc will be less regulated as itís before the converted. I have a nice 24 volt circulating pump and some 24 volt muffin fans I want to run.
Good idea to bypass the AC on the VFD inverter. Please let me know if that works. Thanks
I am running a 24 volt house battery bank as well.

I have found a number of items that will run 24 volts.

For some typical 12volt loads, such as lights and fans, I have tinkered with running them, from 24 volts, in series pairs. I have had good success so far.
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