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Old 07-24-2020, 02:33 PM   #1
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Help with inverter size

Using 700ah battery pack and 80amp dc charger to run fridge, microwave, coffee maker, lites, fans etc and calculated about 3169watts continuous assuming all components running at same time and looking at a 4KW pure sine wave inverter to run all mentntiined minus lites and fans on 12vdc.looking at several in $500 range which seems like most are made in China and reviews are concerning about premature failure of unit.am I looking fir the correct size and any recommendations on brands.? Any ideas would be appreciated.👍
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Old 07-24-2020, 03:15 PM   #2
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Using 700ah battery pack and 80amp dc charger to run fridge, microwave, coffee maker, lites, fans etc and calculated about 3169watts continuous assuming all components running at same time and looking at a 4KW pure sine wave inverter to run all mentntiined minus lites and fans on 12vdc.looking at several in $500 range which seems like most are made in China and reviews are concerning about premature failure of unit.am I looking fir the correct size and any recommendations on brands.? Any ideas would be appreciated.��

Inverters are one of those items, where to a large degree, you roughly get what you pay for. That said, you can get by with a budget inverter just fine in many cases, just don't expect to push it too hard, particularly regarding high surge loads (most often "inductive loads" like motors and fridge compressors).


You need to determine the max current that may be running at one time, taking into consideration startup surge. Samlex (a high quality inverter manufacturer) has a useful cheat sheet for some common loads:




Full document here


What inverter brands are you considering?
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Old 07-24-2020, 04:12 PM   #3
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Thanks fir the info! I was looking at aims and reliable but some of the reviews are concerning and very recent in time. The chart tells me that my fridge at startup would be around 4250 watts��. Microwave at 1400 etc. I don’t think I would have everything in the bus running simultaneously and my stove, space heater, and water heater are on propane.my AC unit will be strictly shore power So I may need to look at a 5kW inverter??
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Old 07-24-2020, 05:16 PM   #4
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Thanks fir the info! I was looking at aims and reliable but some of the reviews are concerning and very recent in time.

Of the two, Aims would be my choice based on your loads if you are talking about the big boxy aims inverter. Its a value oriented low frequency inverter. Low frequency inverters are much more capable of handling large startup surges and just generally more robust (also, heavy, big, generally more expensive, with higher idle power consumption). If it matters to you (or to your insurance company, Aims sells UL listed inverters (not all of them are). If you want to pinch a few more pennies and don't care about UL listing, there is another brand sells a virtually identical or identical inverter from the same manufacturer--Sungoldpower. I believe Sigineer is the OEM for both companies (you could also buy from Sigineer directly).



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The chart tells me that my fridge at startup would be around 4250 watts��.

That sounds pretty extreme. I'm sure the estimates are on the conservative end so as not to underjudge, but still. 4250W/5 = 850W. Are you sure your fridge compressor draws 850W continuous?



Quote:

Microwave at 1400 etc. I don’t think I would have everything in the bus running simultaneously and my stove, space heater, and water heater are on propane.my AC unit will be strictly shore power So I may need to look at a 5kW inverter??
If you get a high frequency inverter like the Reliable, I would err on the safe side and go with 5kW or 6kW (if your fridge calculation is correct), if you go with a more robust low frequency inverter, you could probably get by with less. But this is certainly not an area I have a ton of expertise.




With a high frequency inverter (most cheap inverters on amazon are) the surge rating is for a few thousands of a second. A low frequency inverter can handle a much longer surge (300% for 20 seconds for aims, 200% for 2 minutes for Victron).
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Old 07-24-2020, 06:52 PM   #5
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Ive had a couple high frequency inverters burn out so I donít like them anymore. Ive got 3 low frequency inverters that have been in service for years with no problems, knock wood. Adequate ventilation helps. Any moisture is of course asking for disaster. I had water drip on one causing a $800 repair.
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Old 07-24-2020, 07:16 PM   #6
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10 cuí fridge says 292kw/yr avg draw. I think I overcalculated amperage so maybe itís 850W /24 hr??these numbers sometimes throws me for a loop.dies this sounds more reasonable?
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Old 07-24-2020, 07:20 PM   #7
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That sounds pretty extreme. I'm sure the estimates are on the conservative end so as not to underjudge, but still. 4250W/5 = 850W. Are you sure your fridge compressor draws 850W continuous?
First off, if that fridge is 110V, and it really draws 4000W+, its going to trip any residential 110V breaker on the market. So no, that's not correct.

Second off, I went the budget/off brand inverter route after lots of research. I was about to settle on a $1200 AIMS 6000W when I discovered Power Jack through Sean @ Genetry Solar's YouTube channel:

https://www.youtube.com/channel/UCS2...FcEfS5ebgHyw2w

He services these inverters as a contractor for PowerJack. He's working with an electrical engineer to make his own variant with IoT-style controls built in, and enhanced cooling capabilities.



What won me over was the low pricing (below) and transparency Sean offered.




I use several PowerJack brand low frequency inverters. They are versioned and come in 12V, 24V, 48V configurations from 1500W through their most recent releases of 30,000W. These inverters also come in split phase, allowing you to use residential load centers and both 110V and 220V appliances. I have an 8000W 48V (version 10.3) and before that an 8000W 24V (version 8 ). I think I paid $460 for each the 24V and 48V. In Version 8, each leg was off by around 8-10 volts. Not a deal breaker for my uses, just annoying. Version 9 and above PowerJack started to wind their own transformers, in my 48V V10 both legs are within 0.1V of each other, and are adjustable 110V->125V.



As for how well these perform, my V8 8000W would do 2000W continuous on each leg, or 4000W between the two. The V10 8000W can do 4000W continuous, even on a single leg. Microwaves, vacuum cleaners, mini split and residential fridges, all at the same time. I frequently have the AC, Microwave and toaster going at the same time. Of course you need a battery bank capable of putting out the amperage required (4000W = 333A at 12V, 166A at 24V, and 83A at 48V).



The real problem with these inverters, I think any low frequency inverter for that matter, is that they're quite big and heavy at the higher ratings, and thus hard to ship safely. They have gigantic transformers in them that becomes a wrecking ball in the hands of couriers. If they arrive intact, I'd say chances are they will work and work well.



In my build thread, 48V upgrade:
https://www.skoolie.net/forums/f11/k...tml#post379462
Inverter final setup/cooling:
https://www.skoolie.net/forums/f11/k...tml#post386394


Best of luck. If I were going for a premium inverter, I'd be leaning towards either Magnum or Victron, probably Victron for the total system integration.
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Old 07-24-2020, 08:01 PM   #8
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10 cuí fridge says 292kw/yr avg draw. I think I overcalculated amperage so maybe itís 850W /24 hr??these numbers sometimes throws me for a loop.dies this sounds more reasonable?

Yeah, what you are looking for here is the instantaneous Watt rating.


What you did extrapolating watt-hours per day from kilowatt-hours per year is useful for sizing your battery bank. But its a measure of energy consumption over time, not power.



But for inverter sizing you need to know how many watts it will draw. You can get this by looking at the fridge, it will the volts (120) and amps (TBD) multiply those together to get Watts. Then if you want to use Samlex' rule of thumb, multiply that times 5 to get the startup power.
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Old 07-24-2020, 08:08 PM   #9
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. If you want to pinch a few more pennies and don't care about UL listing, there is another brand sells a virtually identical or identical inverter from the same manufacturer--Sungoldpower. I believe Sigineer is the OEM for both companies (you could also buy from Sigineer directly).






.
I ordered a sungoldpower inverter (48V). After about 5 weeks with no word from them and no updated tracking info, and two emails, I finally heard back from the company. They were having trouble finding people to work. I was expecting it to be some customs issue, but this sounded like a manufacturing issue. After another three weeks and still no update on shipping I cancelled the order.

This was partially because of the 48v inverter, and getting a 12 or 24v inverter might not be a problem. But I figured I would note my experience at least.
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Old 07-24-2020, 09:16 PM   #10
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I ordered a sungoldpower inverter (48V). After about 5 weeks with no word from them and no updated tracking info, and two emails, I finally heard back from the company. They were having trouble finding people to work. I was expecting it to be some customs issue, but this sounded like a manufacturing issue. After another three weeks and still no update on shipping I cancelled the order.

This was partially because of the 48v inverter, and getting a 12 or 24v inverter might not be a problem. But I figured I would note my experience at least.

Woah that's not good. Was this recently? Where did you order from?
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Old 07-24-2020, 09:36 PM   #11
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Woah that's not good. Was this recently? Where did you order from?
beginning of june. I ordered from them through Amazon. Got my money refunded.

Ordered another one from Fuelzero. 4000Watt 48v inverter/charger. Cheaper than the sungoldpower. I cannot find anybody online who has bought an inverter from them. They sell batteries and panels and things. People say the owner responds well at least.

I got the inverter in two days lol. After waiting six weeks for the other! But no manual, and the one he sent me in email doesn't match mine, and doesn't really go through much. I think you're supposed to know what your doing when you order one of these. I don't. But he's answering questions in email for me. Once I power it up I will be adding it to my build thread.
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Old 07-24-2020, 10:37 PM   #12
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beginning of june. I ordered from them through Amazon. Got my money refunded.

Ordered another one from Fuelzero. 4000Watt 48v inverter/charger. Cheaper than the sungoldpower. I cannot find anybody online who has bought an inverter from them. They sell batteries and panels and things. People say the owner responds well at least.

I got the inverter in two days lol. After waiting six weeks for the other! But no manual, and the one he sent me in email doesn't match mine, and doesn't really go through much. I think you're supposed to know what your doing when you order one of these. I don't. But he's answering questions in email for me. Once I power it up I will be adding it to my build thread.

I imagine COVID is significantly F*ing up supply chains, possibly more so for companies like Sungoldpower or Aims who rely on someone else to manufacture the core product and then tweak it to their specs.


I also heard additional tariffs have recently come into effect which apply to inverters among other things being shipped from Hong Kong. A member of another forum I belong to just had an extra 28% tacked onto his $5000 order, he said when all was said and done the new tariffs on top of the existing tariffs added roughly 50% to the total cost.


This wouldn't be an issue for the buyer if buying through Amazon, but it may well have been an issue that affected the seller or importer.


Crazy times..
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Old 07-24-2020, 11:33 PM   #13
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It does sound crayzee.
This inverter price on Amozon is $300 less than on eBay.
https://www.amazon.com/SUNGOLDPOWER-...5651043&sr=8-9
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Old 07-24-2020, 11:41 PM   #14
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Wow and the more expensive ebay listing won't arrive until mid September.
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Old 07-25-2020, 07:15 AM   #15
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Wow and the more expensive ebay listing won't arrive until mid September.
Lol don't count on the Amazon listing to come any sooner though. Regardless of what Amazon says.
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Old 07-25-2020, 06:23 PM   #16
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KAZETSUKAI: thank you for responding and turning me on to POWER JACK inverters. I am going with them based on price point and your experience with them seems to be reliable units.looking at 4KW 12V unit which should be enough to handle my 10CUí fridge, 700W micro, 1000W Keith coffee. Rest is either propane or 12V.
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Old 07-25-2020, 06:34 PM   #17
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KAZETSUKAI: thank you for responding and turning me on to POWER JACK inverters. I am going with them based on price point and your experience with them seems to be reliable units.looking at 4KW 12V unit which should be enough to handle my 10CUí fridge, 700W micro, 1000W Keith coffee. Rest is either propane or 12V.
Neato. One of these guys?https://www.ebay.com/itm/4000W-LF-sp...kAAOSwDtRe8rfY


The stainless steel case ones are the newest units available and should have quite good transformers. Always inspect and test these things upon arrival for damage- shipping is where these are the most vulnerable due to how heavy they are.
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Old 08-01-2020, 09:30 PM   #18
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That inverter is a great price. For that price point I might try one out myself.
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Old 08-02-2020, 12:42 AM   #19
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Quote:
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Using 700ah battery pack and 80amp dc charger to run fridge, microwave, coffee maker, lites, fans etc and calculated about 3169watts continuous assuming all components running at same time and looking at a 4KW pure sine wave inverter to run all mentntiined minus lites and fans on 12vdc.looking at several in $500 range which seems like most are made in China and reviews are concerning about premature failure of unit.am I looking fir the correct size and any recommendations on brands.? Any ideas would be appreciated.👍
Bought my Low Frequency Pure sine inverter from ebay in 2017. It features a heavy copper transformer for true analog pure sine conversion. I have be abusing it for more than4 years now. I demand a lot from it and have only had on issue with it all this time. The cooling fan failed a few months ago. Easy fix.

I run an 8000 BTU air conditioner 24 7 throughout the hot months in New Mexico. Small fridge, Deep freeze,microwave, coffee maker, lights, 50" TV, 30A MArine charger for our backup system, 3 Vornado clone fans, Portable swamp cooler, various phone chargers, etc...

we never have brown outs and the is plenty of power to start air conditioning compressor and fridge ans freezer compressors.

This is not the same seller i bought from but it is the same manufacturer.
https://www.ebay.com/itm/8000W-LF-SP...AAAOSwF4Ney5Z3

THis inverter is split phase so you can wire your distribution the same way you would wire a home with two 110V legs. This gives you the option of being able runappliancess that require 220. I have even run my mig welder with no problems.

The price is right and performs as well as the Magnum inverter I had in 2012 which I paid about 1500 for.
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Old 08-02-2020, 12:56 AM   #20
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Any of you guys know how the Go Power IC3000 stacks up? It’s an expensive inverter and I bought it without looking around much. Normally I research thoroughly but in this case I just picked it. I’ve had a few annoyances with how it was designed but I have no idea if it’s better than cheaper models.
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