Modified Sine Wave vs Desktop Computer

Hi to all,

I was able to achieve this year the purchase of 10 x 100 watt solar panels for what looks like its going to be an off-grid tiny house. The controller I have came with a 200 watt kit its kind of dinky and I am sure is not up to the job so that will need to be replaced. As for converters I bought this: YSOLX 1000 watt converter. I suspect I did badly. I have a desktop that is my workstation and entertainment center .  I can cook with fire and heat water with sun, but Im NOT parting with the laptop. Yet the converter is a "modified sine wave" type. Will my computer and monitor work with this device?

As for batteries Im just going with local Walmart golf cart batteries. No muss no fuss.

The converter issue is troubling me however. Any thoughts?

thanks..M

PS thats a typo below..it should read "1000" instead of "100".

Michael Littlejohn wrote:Hi to all,

I was able to achieve this year the purchase of 10 x 100 watt solar panels for what looks like its going to be an off-grid tiny house. The controller I have came with a 200 watt kit its kind of dinky and I am sure is not up to the job so that will need to be replaced. As for converters I bought this: YSOLX 1000 watt converter. I suspect I did badly. I have a desktop that is my workstation and entertainment center .  I can cook with fire and heat water with sun, but Im NOT parting with the laptop. Yet the converter is a "modified sine wave" type. Will my computer and monitor work with this device?

As for batteries Im just going with local Walmart golf cart batteries. No muss no fuss.

The converter issue is troubling me however. Any thoughts?

thanks..M

PS thats a typo below..it should read "1000" instead of "100".

Michael, in my experience laptop power units are DC as in they take ac power and convert it to DC to run the laptop. Usually those types of power units are ok with modified sine wave. You will get in trouble if you try to charge up most cordless tools though.
As for the charge controller get yourself a good mppt type with 1000 watts of array for better charging on cloudy days.

Hi David thanks for that but what does mppt stand for? M

It's sort of a crapshoot. I have run a laptop using a cheap inverter, though not for extended periods. I figure that the power supply takes most of the abuse, and I have spares.

Other electronics will let you know that they dislike the dirty power from a MSW inverter. All sorts of noise and grumpy behaviour. I haven't had one actually fail, but they are clearly unhappy.

So, in my unscientific opinion, a desktop PC and monitor will run off a cheap inverter -- in a pinch. If it was a system I cared deeply about, I would be looking for other options. My 2c.

BTW, uninterruptible power supplies are pure sine wave inverters, using an internal battery. I have a couple of spare ones but never got around to hot-wiring a car battery in there. I would have to kill the warning beeper too, since they pester you when on battery power.

Michael Littlejohn wrote:Hi David thanks for that but what does mppt stand for? M

maximum power point tracking...
The inexpensive chargers that 12 volt panels come with are pwm or pulse width modulating... basically a charge don't charge switch. The problem is if it's cloudy or the sunisnot pointed right out them you get very little of the panels rated capacity. Mppt charger combine several panels into a higher voltage string and convert it down to the battery's voltage at the controller. You get better charging in cloudy conditions and can use thinner wire from the array to the controller.
https://en.m.wikipedia.org/wiki/Maximum_power_point_tracking

I suggest doing your sensitive electronic devices a big favor by using a full sine wave inverter for them. Modified sine waves are fine for hot plates & light bulbs, etc. Things like power tools may or may not work. If they do work check their temperature now & then. They might work for a while then overheat. The excess heat buildup is clue that it's not happy.

Modified Sine Wave inverters are horrible for Desktop Computers, I don't expect to last more than a few months, maybe even less. If you were given those solar panels and devices. I would have been okay with it but hopefully you didn't spend too much money on them.

$600 Solar Panel 1000W (4solar panels at 250W each or 3panels at 333W each) Each about 3ft by 5ft and 10Amp by 30V
$500 MPPT Charge Controller 100Amp  (could handle 6000W of solar panel)
$1000 Perfect Sine Wave 4000W

It might be better to use a laptop because then you will only have to replace the charger. And if you only plug in the charger when the laptop is off. It should last even longer.

I am going to echo what S Bengi said.  A Modified Sine Wave causes electronics to suffer early death, but not instant death.  MSW probably will work for a time but is definitely not recommend for any long or even medium length of time.  It is possible to get a line conditioner that smooths out a Modified Sine Wave into a Pure Sine Wave safe for electronics, but they aren’t cheap and buying a Pure Sine Wave inverter from the get-go is probably cheaper and better for the electronics.

so with what y'all are saying.

Something like this would fit the bill? correct?

https://www.amazon.com/Inverter-POLAR-Power-Cigarette-Lighter/dp/B08JCRT8BJ

Or is the pure sine wave part of that inverter questionable?

Something like this might fit the bill better?

https://www.cdnsolar.ca/shop-wholesale-solar-products/kisae-sw-1210-power-inverter/

This looks like a good product

https://www.amazon.ca/dp/B00H8N97E2

Howdy, search before you buy,


https://www.amazon.com/product-reviews/B08JCRT8BJ/ref=acr_dp_hist_1?ie=UTF8&filterByStar=one_star&reviewerType=all_reviews#reviews-filter-bar

This is the pure sine wave inverter I bought for charging electronics.

https://www.amazon.ca/GIANDEL-300Watt-Inverter-outlets-Smartphones/dp/B07H32N3ZD/ref=mp_s_a_1_3?dchild=1&keywords=giandel+pure+sine+300&qid=1634147535&sr=8-3

It's cheap, but it's a reputable brand. Ive only had it a few months, but I haven't noticed any problems so far. You need a 12V cigarette lighter type outlet off your batteries to plug in that particular model.

I don't know about a desktop, but if you have a laptop you don't care about running off the battery, you could use that. I just replaced my 13 year old macbook that was finally getting too old to run any useful operating system. I bought three or four batteries over the last few years for that thing, cause they kept dying from our modified sine wave inverter. I finally stopped buying batteries and just ran it off the house battery bank all the time, since the laptop battery only held about five minutes of charge. My new laptop has a much longer battery life so I haven't had to charge it all that much - one a week usually, sometimes more. Would take a while longer to show any issues. I ran my old laptop with unusable battery through a modified sine wave inverter for well over a year with no problems, though.

With 1000W of panels, I think you are better off going with a 24V system instead of 12V.  At 12V what you can realisticly expect out of those panels is (1000W/13Vcharging) X 85% fudgefactor = 65A.
You'll need a rather expensive controller that can handle that many amps.  With a 24V system however, the amps will only be (1000W/25Vcharging) X 85% fudgefactor = 34A.

Take a look at this Epever controller.

Epever MPPT Solar Charge Controller 12V/24V Solar Regulator 150V 40A/30A/20A/10A

It's an MPPT type, so you can wire 5 of your panels in series to reduce wire resistance losses, and you'll also save money on thinner copper wire (10 gauge).  If you use all ten panels you wire two parallel strings of 5 panels each, so each string will put out ~ 5.5A at 90VDC.  Two parallel strings put out 11A.  You would write that out as 5S2P.  When the controller receives this raw high voltage solar power, it transforms it down to the voltage the battery wants, which will be about 25-26V for bulk charging.  For a lead-acid battery, charging tops out at ~29VDC, but amperage goes down as the voltage goes up.

If you want something higher powered, then this one.

Epever 60A 80A 100A MPPT Solar Charge Controller Set 12/24/36/48V 150V US Stock

A good quality Sine-Wave inverter is this Samlex for 539$.  Samlex also makes a 2000W version for 6something.
https://ressupply.com/inverters/samlex-pst-1500-24-pure-sine-wave-inverter

With four 6V Walmart golf carts in series, assuming you don't want to drain the battery less than 50% for long life, you'll get 210Ah X 24V X 50% = 2520Wh of useable power, that's 2.5kWh

It's important to add up all your loads first. The PC, monitor, printer etc. will have power consumption (max.) stamped on them. Volts x Amps = Watts. I would then add a safety margin for surges (perhaps 25%) and that will tell you the wattage output your pure sine wave inverter should have. (Note that some inverters will have a surge capacity in their specifications, which may be enough for the safety margin.)

Modern desktop computers have a type of power supply known as switching power supplies. Things with that type of supply don't do well with modified sine waves. Laptops typically use a much simpler type of power supply that generally do better with modified sine waves. I still wouldn't risk my laptop though. Even some of the laptop battery chargers are rather complicated. And about the same price as a small pure sine wave inverter.

Can you confirm/correct/update my following recap of your situation.

200W Solar Array (over sized to 1000W)
200W Charge Controller
800W Inverter (oversized to 1000W)
3,200WH Battery Bank
800WH Daily Load

Daily Usage = Daily Production  = 4x Solar Array = 4x ChargeController = Inverter = BatteryBank/4 = Peak Load
800WH      = 800WH(200W x 4H) =     4x 200W     = 4x 200W(12V*16.8A)   =  800W    = 3,200WH/4

I like your setup because it mostly follow my self-made rule, with a few exception.
Daily Usage = Daily Production  = 4x Solar Array = 4x ChargeController = Inverter = BatteryBank/4 = Peak Load
Your solar array is oversized (10panel vs 2panel) so you probably get 2x the amount production because you still get 200W (vs 1000W) even in the early morning/late afternoon/cloudy days. But you will lose 800W of the 1000W during mid-day sun, hopefully that doesn't damage your charge controller. Your inverter is a bit oversize at 1000W vs 800W but that just gives you a little extra surge juice to start up motors/etc.

I have a feeling that your daily load isn't fully flushed out and you plan on running more than just your PC on the solar system. Can you give us an itemized list of appliances that you will use. How many hours of usage per day. Daily Load = Desktop +Monitor +TV +Phones +Lights +microwave +blender/vacuum +Fridge +etc and with each one running about 4hours per day.

Here is my idea of a version2 of your system:
1,000W Solar Array
1,000W ChargeController (48V x 20A)
4,000Wh Daily Production
4,000W Inverter (48V x 80A)
16,000Wh BatteryBank (48V x 320Amp-Hour)
(with a Lithium batterybank it can be smaller because you can do 1C charge/discharge aka just 4,000Wh)

Daily Usage = Daily Production  = 4x Solar Array = 4x ChargeController = Inverter = BatteryBank/4
4000WH      = 4KWH(1KW x 4H) =     4x 1000W    = 4x 1000W(12V*83A) =  4000W  = 16000WH/4

Could you avoid converting to AC entirely? You can buy "Car chargers" for most laptops, which convert 12 VDC to the charging voltage of your laptop. Desktops are a little bit trickier, but you can buy DC-DC power supplies for those as well. If you can avoid the extra load of an inverter, it might be worth it.

https://www.amazon.com/Output-Computer-Connect-Suitable-Mini-ITX/dp/B07TY121LT

I appreciate all the help with this.  I was curious and so I came up with a short resource on what NOT to use with a modified sine wave inverter. Hope its helpful to others as well.  thanks, this has been educational.

Laser Printers, photocopiers, anything with an electrical component called a "thyristor"
Anything with a silicon controlled rectifier (SCR) (sometimes used in washing machine controls)
Some laptop computers
Some florescent lights with electronic ballasts
Some battery chargers for cordless tools
Anything with a microprocessor control
Digital clocks with radios
Medical equipment such as oxygen concentrators

An SCR is a type of thyristor. They are often used in power control circuits. Light dimmers are probably the most common use in homes.

Thanks everyone for their part of the puzzle.

I have graphiced my components below. I havent bought the controller or inverter yet, I have one of each but they unsuitable and will be used as backup components in an emergency.
Since I want maximum power for what I have I will probably do a rooftop mount and keep the cable as short as possible.

See attached.  And thanks again.M

Glad we could help, sort of, piecemeal.

It looks like you have a plan: great! Before you pull the trigger, I will just add one proviso, which I have learned the hard way over and over: if you buy cheap, you buy twice, and you pay a lot more in the end.

Luck!

I'd keep your panels, and revise other components to include mppt charge controller (approx $100 to $200), pure sine wave inverter ( approx $300 to $500), and skip the golf cart batteries in favor of one (or more) 100ah LiFePO4 batteries (approx $300 to $500) each.

The goal is simplification, and FLA batteries won't simplify your life ... they will add complication. They are maintenance intensive, messy, fume-dangerous, and come with a 50% capacity penalty (buy 4 to get the capacity of 2). They are possibly inexpensive in a golf-cart scenario, where they can take the abuse of minimum-wage employees handling 100's of them, but have little place these days in a RE system. Most folks kill their first set of FLA batteries, for many reasons.

It's the total opposite with LiFePO4 batteries ... little to no capacity penalty, way more lifetime cycles, no maintenance, much less heavy and therefore easier to work with and accommodate, and more. It's the future technology, available now.

Otherwise, the FLA batteries will pile up on your property like dead cars on concrete blocks.

If you stay 12v, then get one 12v LiFePO4 battery ... if you move to 24v, as others have discussed, then get two 12v's, placed in series for 24v operation.

Thanks JT. I was thinking in that general direction regarding the batteries. And simplification. I am daunted by the cash out aspect of a startup from nothing, but yes it hurts to buy cheap and then have to buy the  right thing later on.

Best. M

Jt Lamb wrote:I'd keep your panels, and revise other components to include mppt charge controller (approx $100 to $200), pure sine wave inverter ( approx $300 to $500), and skip the golf cart batteries in favor of one (or more) 100ah LiFePO4 batteries (approx $300 to $500) each.

So just for a reference for me up here in canada a 100ah Lifepo4 battery which is 12v is 1599$CAD plus tax. https://www.modernoutpost.com/product/rb100-100ahr-12v-lithium-battery-by-relion/

I am so curious where these 300 to 500$ batteries are. I will take 2 of them! Do you have any links or sources?

It would be real nice to have one of them..

We use smaller SOK 100ah batteries (metal cases, easily modified) for the more mobile projects, and larger Ampere Time 300ah batteries (sealed ABS cases, so no modifying possible)  for the house battery bank.

The SOK's took longer to get here, but the A-T's got to us within a week or two, right off Amazon. Both brands are on Amazon, and we can vouch for both now ...

I know nothing about conversion rates or availability in other countries, but in your case, we can possibly meet at the wilderness border and toss them across to you, if you can't get these up there?

Finally, perhaps build a battery or two yourself, with all the fine knowledge from the forum folks over at diysolarforum?