Off grid solar powered washing machine and dryer.

halnet · May 2018

My setup is as follows: 100 watt solar panel charging a 115 amp/hour Deep Cycle 12 volt battery driving an 8000 watt inverter (16000 watt peak) with modified sine wave output. I only need power for the 110 VAC motor for either washing machine or the gas dryer (neither runs at the same time as the other). The washing machine runs perfectly, but the dryer motor's starting surge shut the inverter off. I haven't check it yet, but I don't think the dryer motor HP is greater than the wash machine. My initial thought is to replace the dryer motor with one that will work like the washing machine motor. Can anyone suggest a remedy for this problem?

P.S. I just enrolled in this forum, so I don't know what a tag is. Someone please tell me.

mcgivor · May 2018

More likely the battery voltage collapses when it attempts to start, the battery capacity is extremely small in relation to the inverter capacity, more battery capacity and larger conductors feeding would be a start, but in reality the whole setup would need modification, larger array to now charge the larger battery bank. Using 12V to support larger loads is problematic due to high current which create voltage drop, building a system requires a loada calculation, after which everything else is calculated to support it.

mike95490 · May 2018

A couple (4) things happening:

1) Under voltage, either cables not optimum, or battery going bad

2) Huge oversize inverter, it's tare losses and overhead are going to be huge

3) insufficient solar power: if you really tune things up, 100W MIGHT be enough PV, but I doubt it.

4) Attempting to run a large motor on mod-sine wave. Motor will consume 20% MORE power than from pure sinewave inverter, run hotter and hotter nearly always = early failure. And the 20% more power comes from your battery, which is already weak from running the washer and inverter.

halnet · May 2018

I thank the both of you for your advice, My thinking is that the washer which spins heavy wet laundry several times per washing cycle would have to be a more powerful motor. But neither of your comments explains why the washer motor works perfectly while the dryer motor does not. If my choices are to upgrade the system as you suggest or simply changing the dryer motor, I choose the latter. I guess my question should be to ask if I substituted an exact motor in the dryer (assuming it fits) as the one in the washer, would that fix the problem?

halnet · May 2018

I should also mention the reason for the use of solar is so that we can wash during the day and not have to wait for lower evening cost. So although the system and charging may not be as efficient as it should be, it's use is intermittent - so there's plenty of charge up time and not enough usage to cause overheating.

mcgivor · May 2018

The washer uses gearing as a torque multiplier, to get the machine started, the dryer needs to revolve the damp laundry from stall, or 100% motor torque, to reach its running speed without the use of gearing, belt ratio aside, so the initial load will peak for a longer period of time. This will reveal the shortcomings of the supply used to power the units, hense the responses addressing the solar portion, as opposed to the mechanical proposition. The motors may well be the same, just purposed differently, naturally a wild guess, but the point is, these systems are not designed with inverters and batteries in mind, but rather for grid supply, which can absorb the inrush currents. More advanced machines with direct drive brushless DC motors and inverter technology are less demanding on a solar based supply, but tend to be more expensive. My suggestion is to address the supply shortcomings rather than to re engineer the appliance, another means to address the problem would be the use of a soft start to lessen the effects of inrush, but not sure how they will react to a modified sine wave of unknown quality, modified could mean square wave or stepped, but either way there is harmonic distortion which can cause problens. My opinions, for what they're worth.

Thom · May 2018

My own rule for inverter sizing is 1000w max for 12v battery. Your 8000w is 8 times that with a tiny battery bank. Tag is the text below.

littleharbor2 · May 2018

If your reasoning for doing this with solar and batteries is to save money you are fighting a losing battle. Granted with the tiny pieced together system you have, while it may not have cost much, but as you are finding out it isn't working out too well. To assemble a properly designed off grid system and replacing the batteries every 3-4 years will cost you more than just buying the power from the power company.

Estragon · May 2018

The best solution may be to use solar power directly to dry clothes (on a clothes line in the sun).

Alternatively, using a 12v automotive starting type battery may handle the starting surge for the dryer. They're designed to provide high currents needed to crank an engine and, if fully charged and connected with good sized wire, may allow voltage to stay high enough to prevent the inverter from cutting out. Cycled deeply, this type of battery may not last long though.

Even making sure your existing deep cycle battery is fully charged may help. The panel won't be enough to keep it charged while washing, and if you're trying to start the dryer with an already discharged battery, that may be adding to the problem.

Photowhit · May 2018

I'm quite happy line drying my clothes...

As others have pointed out your system is quite unbalanced. Imaging your 8000 watt inverter trying to run at peak, it would have to draw 8000/12=666 amps! (actually more as it's likely only 85-90% efficient). That would require 1250 MCM wire!

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

That is many times larger than 4/0 wire I use, I tried to find a photo of 1250 MCM wire, I couldn't find one, here's a photo of 2/0 next to 500mcm wire.

Image: http://www.solarwarrior.com/pictures/wire.jpg

I wonder what the inverter manufacturer recommends?

littleharbor2 · May 2018

Photowhit said:

I'm quite happy line drying my clothes...

As others have pointed out your system is quite unbalanced. Imaging your 8000 watt inverter trying to run at peak, it would have to draw 8000/12=666 amps! (actually more as it's likely only 85-90% efficient). That would require 1250 MCM wire!

How about the previously mentioned 16,000 watt surge rating.
BTW , good visual here. pictures being worth a thousand words, sometimes.
Yes, I wonder too, what the Mfg, recommends?

Estragon · May 2018

Makes me wonder what's inside the thing to handle that kind of DC current. I hope there's a fuse/breaker on the battery circuit ;-)

westbranch · May 2018

Have you tried drying the clothes in , say, 1/4 of the washer load? If you get the same problem, switch back to the grid for the dryer...IMHO.. and then change the solar sysem to at least 24 v, better 48V if you intend to go solar

BB. · May 2018

Tags... There are "two types" of tags here. One is the "signature line"... You can put information about your solar power system, what you are powering, etc. in it. Just click on this link (or through your screen name, then a pull down menu of a "person", then signature) to make your own signature:

http://forum.solar-electric.com/profile/signature

The other Tag is a "search tag"... You can put key words in the tag to make searching easier--I don't think anyone here really uses tags (the forum software will sometimes fill in tag key words--I guess).

Your drier. Can you tell us more about the inverter "shuts off" means? I doubt that the inverter is shutting down because the drier is drawing more than 8,000 to 16,000 Watts (A gas drier may draw less than 500 Watts to run the motor, and another ~500 Watts to heat up the gas igniter).

304970 GAS DRYER IGNITOR REPAIR PART FOR WHIRLPOOL AMANA MAYTAG KENMORE AND MORE

It is possible that the gas igniter is drawing >300-500 Watts, and the Motor+Igniter load is higher than that of your washer. Gas igniters will typically draw between 2.5 and 3.6 amps (3.6 amps * 120 VAC = 432 Watts--Possibly more when cold/first turned on).

If so, then possibly what is happening is that the DC input voltage to your AC inverter is falling below ~10.5 volts (typical 12 volt inverter battery cutoff voltage). If the input of your AC inverter is below ~11.0 volts... Then your DC cabling may be too small of diameter and/or too long back to the battery bank (high voltage drop).

Or your 115 AH @ 12 volt battery is simply too small to drive that amount of current/power... For example, I suggest the maximum surge current from a deep cycle flooded cell lead acid battery is around C/2.5 (20 hour capacity divided by 2.5) for reliable operation:

115 AH / 2.5 max surge load support = 46 Amps
46 amps * 11.5 volts = 529 Watts max surge into AC inverter
529 Watts DC * 0.85 AC inverter eff = 450 Watts available to AC load(s)

In summary, your battery (and solar array) is really too small to drive the loads you want to run. And your AC inverter is way to big to be used on this small of DC Battery. If I was to use our design rules... You would need a 3,200 AH @ 12 volt battery bank to run the 8,000 Watt AC inverter at its rated output. Or about 28x of your present battery (not that this is good solution either).

I highly recommend that you get a Kill-a-Watt type power meter so you can measure you AC loads:

https://www.solar-electric.com/kiacpomome.html

For the DC side--Get yourself an inexpensive AC/DC Current Clamp DMM. NOTE DC Current CLAMP function... There are AC only current clamp meters--Which are nice meters, but they cannot measure DC current. Here is an example ($40--Just crazy cheap these days--May take a few weeks to ship from China or overnight via Amazon Prime--depends on who you buy from):

UNI-T UT203 Digital Handheld Clamp Multimeter Tester Meter DMM CE AC DC Volt Amp
https://www.amazon.com/gp/product/B07546L9RT

Or, there are lots of little DC AmpHour/WattHour meters out there these days:

http://rc-electronics-usa.com/

Note that we need to know both how much POWER (Watts, Amp at what voltage) your loads are, and also how many hours per day you run these loads (Watt*Hours or Amp*Hours at what voltage). Sort of like miles per hour vs miles driven.

-Bill

halnet · May 2018

Thank you all for giving me an education. My interest in solar energy was triggered by a successful 400 watt solar system to power two sliding gate operators.. I did this to avoid having to run wiring underground and going through the permit procedure. When a city inspector came out to sign off a cinder block wall unrelated to the gates, he was so impressed with my installation, that he asked my permission to take a picture of it. I thought "wow," this solar stuff is a piece of cake. That's when I decided to get involved with solar energy. I realize that an 8000 watt inverter may be an overkill to power my washer and dryer (include the dishwasher also) but I'm having fun experimenting. Once I get into it with the help of you guys, I will start getting practical and do the proper balancing. I did hook up a watt meter to the dryer and found that it's consuming a modest 320 watts (about 2.7 amps). So as one of you suggested, the dryer must have a huge surge which momentarily drops the battery voltage enough to shut down the inverter.. I just ordered an oscilloscope from ebay which will allow me to check the battery voltage drop on startup (as you can see, I caught the solar bug).
BTW: How do I attach an image like the one above showing the fat cable?

Estragon · May 2018

On my mobile version of the site, the picture attach thingy looks like an icon of a mountain on the right and a cloud or something in the upper left.

westbranch · May 2018

and On a laptop it is displayed about 3 / 4 o the way across the banner , just above this space that you can type in

:

mike95490 · May 2018

Because of grounding issues, you MUST be very careful when using an O'scope to troubleshoot AC circuits. The "ground" clip of the scope probe often goes directly to chassis ground, and if you connect it to a live wire (like measuring the voltage across a resistor as part of an amps measurement) you can easily fry the scope and catch a plasma ball on your safety glasses

NANOcontrol · May 2018

I'll be doing some interesting stuff this summer with a washer running off solar without a battery. Those USB scopes are handy once you learn how to use them. If i were doing this, I would put a delay on the igniter. The igniter is generally in series with the gas valve as a safety feature. I have a gas stove that I don't use the oven on. that takes 400W and has to be powered all the time. It's resistance changes dramatically from cold. Delaying that current till the motor spins up would give you a fighting chance. Your limiting is a result of your battery.

Off grid solar powered washing machine and dryer.

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