my solar plan

[VanKitten]

First, my philosophy is to get the most I can afford now, and try to have some capacity to expand in the future.   

I have decided on two Panasonic 350W panels.   They will fit side by side on the roof with room for the passive solar hotwater too.  They are 24V mono

I am looking at the 80mppt outback flexmax charge controller.   I would like an opinion on this device.    I hope to add a windmill to this system in the first year or two.  Maybe a third panel that is one of those portable types in a suitcase...eventually if I need supplimental.

I plan to run an inverter for the laptop, printer, scanner (once a week, or so for about an hour)  Also a 1800w dual induction cook top (about 1 hour a day), and a 1000w microwave a few minutes a day.

I plan to have A 200ah 12V battery.    2000 amp inverter.   Are these sized correctly?   

No A/C.  All the rest will be 12v.  Water pump, Led lights, fans, refrigerator.    Charging for internet hotspot, 2 iPads, 3 iPhones, 1 iPod with speakers,  nav system, backup camera.

I never watch TV.   If I must have news...I can read it via wifi.

If I find myself in cold weather...I will use a 12v heated blanket   Failing that..a Mr Buddy

Ok....what is wrong with the plan?

 

[highdesertranger]

just by glancing over it seems the weak point is your battery capacity. have you done the math to add up your daily usage? highdesertranger

 

[John61CT]

The small computer stuff will run direct off DC 12V, easy peasy get the voltage specs and tip polarities, find the charge/adapters on Amazon or eBay. Get spares, they're cheap.

The induction is IMO too close to rated max.

Cook with propane, no inverter needed at all, lots of budget for another panel, gadgets like a SoC monitor.

 

[VanKitten]

just by glancing over it seems the weak point is your battery capacity.   have you done the math to add up your daily usage?  highdesertranger

Maybe I am thinking that since the battery is charging all the time, and the drain is of just a short duration...the recharge would compensate for the daily draw?    It isn't really a fill once a day only and then use and run out........?     The actual dynamic of the charge and use flow all day long is not something I have seen any calculation on....it is best to just assume one drain a day..followed by one charge?    Meaning I figured that the morning draw of 1800 W would be replaced before dinner...if I don't use it again till same afternoon.

Guess the real question is how fast will 80mppt convert 700 W of solar power into usable battery.   Any place you know of where I can find a calculator for that?

Would 700w panels be able to charge 250ah batteries?   The question is ... is there excess capacity in the solar to support larger battery capacity?

Lastly...I do expect to be mostly in the Southern USA.   So, my idea of actual useful solar is based on that.

 

[John61CT]

Timing is important. For battery longevity, there should be a point in the cycle where they hit full, true 100%. Not 98%, but 100.

The smaller solar will likely handle that last top-up portion just fine at relatively low current, but it does take several hours. The high-current needed from 50% to 80-90% is what requires high current to get finished quickly, either big solar or a little quiet generator and high-amp charger, running an hour or two in the **morning** before solar takes over.

Big banks means more leeway and less draw-down, but bottom line is you need to put back what you take out, as promptly as possible for bank longevity.

 

[John61CT]

The induction and microwave are really driving your sizing here, designed for cheap grid power.

Give those up - or fire up your genny to feed them - and you will be much better off with half the size panels/batteries..

 

[SternWake]

How long 200Ah of battery capacity could power your large loads, like induction cooktop/microwave when there is no sun shining, will make or break your system.

If it were not for those huge loads, i would say 700 watts of solar is excessive for your other loads, but 200Ah capacity is good.

 

[minimotos95]

I had 300w of solar through a PWM charging my 225AH battery bank, I found I was generating much more power than I could use even with a fridge so I sold off one panel to get down to 200w.

That is definitely an undersized battery bank for 500w, let alone 750w+wind. But I think if you were to rethink the induction cooktop You would be fine with a 500w or 750w / 250ah or 500ah system even in a few days with no sun.

On using the induction cooktop as a daily, the research I did of the 1500-1800w units didn't show any shorter boil times than a gas burner and less control just like an electric range. Yes it's free energy from the sun but I would default to a gas stove and maybe back that up with a way to utilize any extra solar power like a crock pot or hotplate.

One major downside to cooking off PV power is when you want a warm meal the most(days when the sky is gray) is when you should be careful about your power consumption.

 

[Trebor English]

Do you want electricity on a rainy day? You might want enough battery for a day.

 

[Optimistic Paranoid]

I plan to run an inverter for the laptop, printer, scanner (once a week, or so for about an hour) 

I plan to have A 200ah 12V battery.    2000 amp inverter.   Are these sized correctly?   

First of all, I think you meant to say a 2000 WATT inverter, as I have never seen inverters described in terms of amps.

Now, watts = volts X amps, so amps = watts/volts.   2000 watts divided by 12 volts equals 166.66 amps.  So if your inverter is running near maximum, it's going to be trying to pull 166 amps out of your 200 ah batter bank.  No way is that going to work.  It might work in bright sunlight, pulling most of it's power from the solar panels, but it definitely isn't going to work at night or on cloudy/rainy days. 

In short, too much inverter, not enough battery.

My WAG (wild ass guess) is that you're going to need at least **6**  six volt golf cart batteries, wired as 3 pairs in parallel for about 660 amp hours at a minimum to be able to routinely use an inverter that size, not to mention an induction cooktop and a microwave.

 

[John61CT]

Solar electricity is not free, just that all the up front expense has an unknown amortization life.

Smart conservation choices pay off bigly, both in reducing the up-front and lengthening the bank lifespan.

Personally no inverter needed at all by using say $10 a month of propane, probably needed for heating anyway, would be smart.

Or run the gennie for the big consumers if they're really "needed".

 

[highdesertranger]

I have said it over and over, it is very inefficient to heat things with electricity. no matter the voltage or being AC or DC. highdesertranger

 

[VanKitten]

I have to find another answer instead of induction cooking, that is obvious to me now.

Thank you all for your answers. I appreciate the time you all took to look this idea over.

I am going to look into 250ah batteries too.

I have heard that 12v cooking...ovens, rice cookers, etc. do not stand up to nearly constant use. I heard this from a couple of over the road truckers. Anyone have recent experience with them?

So...the blackboard has been partial erased....to be filled in...

 

[GotSmart]

Figure 3 monthe use tops on the truckstop lunchwarmers.   

 

[jimindenver]

Kat

I do a lot of cooking, heating water, even run a small A/C with the kind of power you have available with a system of that size. The thing is I also have all of the things people normally use to back it up in the event the weather doesn't co-operate. I added a huge panel to the truck to compensate for the lower sun and shorter days of winter. I have three times the battery bank you are talking about and my appliances are all low draw, nothing like a power hungry induction heater. Almost everything I use is below 500w besides a coffee maker and the microwave. Those are used for minutes, not hours.

The things I use that are within the output of the solar system without dropping the banks voltage are...

The small burner on a Elite two burner cooktop using 470w
A Hott rod in my water heater pulling 450w
A 400w oil filled heater
A 200w bathroom heater
A 5000 BTU A/C that pulls 450w except for a momentary surge at start up.

I picked these things to save me on propane and gas when the weather is right. They fall within the output of the 750w roof system in the summer and my complete 1185w system in the winter. I even use a solar cooker and two solar ovens when I can, the power is free once you make the initial investment. It also means my bank cycles less and for what it cost to replace, I want it to last as long as possible.

So my answer is yes you can do it but not all of the time and it's not cheap.

 

[akrvbob]

I think you have an excellent plan! Having used a microwave off solar a lot I think you almost have it right. 700 watts of panels is excellent, but you need at least 4 golf cart batteries (at least 400 ah) to run the microwave or induction stove. It'll run it no problem at all!!!!!! It draws over 100 amps an hour, but that is only a bit over 2 amps a minute, which is very high but for 5 minutes would be only 12 amp hours total.

So double your batteries to 4 or even 6 and you can use the microwave no problem.

It does require a Pure Sine wave inverter though, modified will work poorly. This inverter ran my 750 watt microwave no problem for many years:
http://amzn.to/2lK7fze

The problem with the induction stove is how long it takes to cook, It draws much more than the microwave and also it will take longer to cook something. I think you'd be better off with propane.

 

[VanKitten]

Once again, thank you all for the leads.

I wish I could get more solar power, but the roof top is full now.
350w is the biggest panel I could find that still fits and meets my criteria: reliable manufacturer with long history.

I will create a roof top passive solar hot water ... black hose on snap fittings that I can pump water into, wait, use gravity to shower or wash dishes. A good friend in N. Carolina does this at her home....works great...have to be careful..it gets really HOT. Even in the winter...when there is sun, there is hot water. It is only about 3 gallons...but combined with cold water..it is more than enough for shower and galley. I am going to but a manual foot pump for the water. This is commonly done on sailboats (which is where I know them from). Not going to get wasteful with water when you are using one of these....and zero watt usage too.

I am completely happy with just fans. I was last year in FL..from Oct through April. Temps got into the 90s ...fans were just fine for me. Even with that high humidity, it worked fine. But, I don't plan to spend that much time in high temps again.

As for heat. I will use a 12v blanket if needed. If I get caught somewhere really too cold..then I will break out the Mr Buddy, and move.

So really, only need is cooking and coffee.

Bob, do you have a link from here to the elite 2 burner you talk about?

 

[John61CT]

Yes, matching usage to constrained power availability is a great way to go.

Note also if you do find you really want more solar and have space to carry them, the "suitcase" style folding panels can add a bit more capacity, but they do need unpacking and setting up each stop, easily stolen, can be too much hassle for many, but a good option for some. Can be placed in the sun when the van's in the shade is on the plus side, especially with a controller that allows serial stacking to get to high voltages to minimize power loss from longer cables.

 

[Optimistic Paranoid]

For solar water heating, you might check this out:

https://www.amazon.com/EZ-37-Solar-...1487777230&sr=8-1&keywords=solar+water+heater

http://www.heliatos.com/

 

[VanKitten]

For solar water heating, you might check this out:

https://www.amazon.com/EZ-37-Solar-...1487777230&sr=8-1&keywords=solar+water+heater

http://www.heliatos.com/

Could not find where it says how many gallons of water it will hold.

I got the impression this is for solar assisted heating...using a tank and hotwater heater..this supplements the heating of the tank??

I will have no hot water tank. Nor heater. Passive solar will be all I use.