battery bank ?

[joshuafarmer]

if I were to purchase the new 200 watt kit from renogy what would be best for a battery bank Im thinking 2 12volt but what size should they be whould 2 100 ah be too much or should I go smaller idk

 

[scottorious]

Certainly wouldn't be too much. You might get advice to get get 2 big 6 volt true deep cycles and link them in series. I suppose the an important question is, what do you want to power?

 

[joshuafarmer]

Certainly wouldn't be too much. You might get advice to get get 2 big 6 volt true deep cycles and link them in series. I suppose the an important question is, what do you want to power?

I would be powering a computer, cell phone, crock pot or pressure cooker maybe sometimes and a vent fan

 

[joshuafarmer]

ANY RECOMENDATIONS ON INVERTER SIZE

 

[becida]

I've been using two 122 ah 12v batteries I picked up at Walmart for around $86 each. I believe they were labeled marine batteries.
Smaller batteries are not the way to go.

 

[Trebor English]

ANY RECOMENDATIONS ON INVERTER SIZE

What is the wattage of the things you want to power?

 

[jimindenver]

You have to think of your full system as a balancing act. Each part affects and is restricted by another. You chose a inverter by what the draw of the largest item you will use. The inverter is limited by what the battery bank can handle. The battery bank in turn is limited in size to how much power your solar can put out and 200 watts is not a lot of power especially in the winter time. You should not run a big load on the batteries and leave them partially discharged for long as the solar tries to replace the power even while you continue to use more. So a crock pot or pressure cooker might be too much.

 

[Weight]

If your plan is a crock-pot, plan on a mains feed connection. If a microwave or a coffee pot, four six volt golf cart batteries would make a good bank. You will need something like a 2000 watt sine wave inverter.

 

[DLTooley]

You'll want to do the math for your specific needs. Generally you can estimate power based on a label on each device. That rating will most likely be high, but that is good for estimating.

You can go with a smaller battery system if you time your heavier loads, like charging a laptop, when there is excess solar power available. This will generally be after your battery system has absorbed it's initial recharge. That math is a bit trickier, but 2-3 hours after reaching full solar in the morning should be good.

My system is designed for a 20% draw down. This means I can generally go for two days without sun, after which I like to do a drive into town to charge up. 50% is the general minimum, but it is the average that matters most. Going low rarely has a cost, but it is minimal, unless you completely drain the battery.

 

[user 37446]

I think the heat producing appliances on 120V are too much of a draw with your present thoughts. You'd need much more storage capacity, a bigger inverter than most, and a better way to replenish your batteriues than 200 watts of solar, especially given shorter winter sunshine hours and cloudy days.

If you dump the 120v heating/cooking idea, stick with either 12v appliances (Roadpro is a brand truckers use) or use propane, then you can do what you want with either the two 12v marine batteries or better yet, the two six volt golf cart batteries (which are true deep cycle as opposed to hybrid batteries like the marine style). Either way you need to read up on the electrical forum threads for cooking appliances and decide if the big investment in equipment is what you want compared to easily used propane.

 

[joshuafarmer]

I think the heat producing appliances on 120V are too much of a draw with your present thoughts. You'd need much more storage capacity, a bigger inverter than most, and a better way to replenish your batteriues than 200 watts of solar, especially given shorter winter sunshine hours and cloudy days.

If you dump the 120v heating/cooking idea, stick with either 12v appliances (Roadpro is a brand truckers use) or use propane, then you can do what you want with either the two 12v marine batteries or better yet, the two six volt golf cart batteries (which are true deep cycle as opposed to hybrid batteries like the marine style). Either way you need to read up on the electrical forum threads for cooking appliances and decide if the big investment in equipment is what you want compared to easily used propane.

yeah I always planned on having propane stove I don't no how two live without one other than roastin over a open pit fire, I dam sure wont be usin a microwave unless I get a burrito at the quickie mart, at any rate I will be basing everything off 12 volt the crock  pot was just a thought I suppose I could just shelf that idea for now thanks

 

[John61CT]

It is best to learn specifically how much power each of your devices consumes.

In the meantime get to know relative ranges, sm/med/lg for the different categories.

Anything producing heat is large, only OK with a big system and even then only used a few minutes per day.

 

[geogentry]

I did some math for you.  The numbers are for ideal conditions in areas like Ehernburg and they are an AVERAGE of what is available with the panels tilted directly at the sun.  Your still going to have to monitor the batteries and your usage.
Best case scenario your going to get about 700 watts of power to use per day out of your solar setup. This assumes you use an MPPT solar charge controller.
This has to be divided between what you use and what you have to stuff back into the batteries.
Your going to need  221 ah of battery so round it nicely to 250 amp hours of battery.  This takes into account limiting to a 50% drain with a 2 days supply of power.

You can do all kinds of mix and match on what you power but you get only 700 watts to play with for the whole day, use it wisely.  ALWAYS  assume that there may not be sun tomorrow for you to use the power from the panels.  So dont use up your batteries - keep them as full charged as you can.  That way if there is no sun you can still use your laptop etc off the batteries.

If your panels are not pointed at the sun, and they probably wont be, your going to get less energy from them.  Take that into consideration.  If you let them get dirty your going to get less power.  If your not down south (like Ehenburg) your going to get less power.  A good solar charge controller will tell you how much power your getting from you panels.  Make plans based on what you see.  I could only give you a basic ballpark set of numbers.  I will give you the math if you want to have it.

As for the Inverter.  Get a good one.  And get the biggest your budget will allow.  Why?  You'll eventually want to upgrade to more power.  Everyone does eventually unless they are already maxed.  If you get a very small one now you will have to buy a bigger one in the future.  And if you pull 200 watts through a 1000w inverter no harm no damage, but if you try to pull 1000 watts through a 200 watts inverter you get to buy a new inverter much much sooner than you planned.

 

[John61CT]

Watts are not a per day, or per any time, measurement.

Watt-hours yes, so panels putting out an average of 700W over 5 hours (best case in winter? ) would be 3500 wH per day.

Assuming high efficiency charging at 14+V that would be 200+AH in theory available for replenishing the bank. Lots of other real-life factors make the power actually absorbed much lower.

Just as an example explaining the measurement units, no idea if that's in line with the actual scenario here.

 

[DLTooley]

200 watts of panels. At actual operating efficiencies 700wh is a reasonable rough calculation during the winter.

 

[geogentry]

Watts are not a per day,  or per any time, measurement.

Watt-hours yes, so panels putting out an average of 700W over 5 hours (best case in winter? ) would be 3500 wH per day.

Assuming high efficiency charging at 14+V that would be 200+AH in theory available for replenishing the bank. Lots of other real-life factors make the power actually absorbed much lower.

Just as an example explaining the measurement units,  no idea if that's in line with the actual scenario here.

[font=Roboto, arial, sans-serif]Power is the rate at which energy is generated or consumed and hence is [/font][font=Roboto, arial, sans-serif]measured [/font][font=Roboto, arial, sans-serif]in units (e.g. [/font][font=Roboto, arial, sans-serif]watts[/font][font=Roboto, arial, sans-serif]) that represent energy [/font][font=Roboto, arial, sans-serif]per[/font][font=Roboto, arial, sans-serif] unit time. For example, when a light bulb with a power rating of 100W is turned on for one [/font][font=Roboto, arial, sans-serif]hour[/font][font=Roboto, arial, sans-serif], the energy used is 100 [/font][font=Roboto, arial, sans-serif]watt[/font][font=Roboto, arial, sans-serif] hours (W. h), 0.1 kilowatt [/font][font=Roboto, arial, sans-serif]hour[/font][font=Roboto, arial, sans-serif], or 360 kJ.  So yes watts are indeed a per day or per anytime measurement.[/font]

[font=Roboto, arial, sans-serif]-two 100 watt panels will create 200 watts of power per hour.[/font]
[font=Roboto, arial, sans-serif]-at 5 hours per day tbat would be 1000 watts for the day generated.[/font]
[font=Roboto, arial, sans-serif]-resistance, dirt or snow on the panels, angle of panels to the sun and power loss in the charger will all reduce this amount.  To arrive at a conservative estimate of what can be generated into the system that number is multiplied by 0.70.  If you get more than that fine but this number will result in a fairly safe estimate.  So we end up with 700 watts generated  per day.

If your looking to generate 700 watts to the battery per hour - as in your example yes you would end up with 3500 watts.  This would require you to have 10 each 100 watt panels.  Or 3 each at 330 watts.  At 330 watts each you would not generate the needed 1000 initial watts to achieve the 700 watts out but only 693 but that is close enough for your example.

The number 5 you used in your example was calculated as an average per day over the period of a year based upon climate, and other conditions, for a particular area and will of course vary depending upon weather conditions.  That is an overall average per day.  The actual amount will vary, sometimes widely, depending on factors occurring during each particular day.[/font]

 

[geogentry]

200 watts of panels.  At actual operating efficiencies 700wh is a reasonable rough calculation during the winter.

That is per day production - you know that right?

 

[John61CT]

font tags

I can't decipher all the pseudo HTML there, so I'll just say

Watts are an instantaneous power measure, the unit already internally represents a flow rate with a time element included, just like amps.

Per hour or per day representation requires wH or AH.

So "consumes 3600 watt-hours per day" or "3 AH per hour" is correct.

"Watts per hour" or "amps per hour" is very common, but actually makes no sense.

Yes 5A "for an hour" or "over an hour" does come out to 5AH.

But a device that consumes a variable amount, or is cycled on and off by a thermostat etc, you would have to say either consumes

an average of 5A at that temperature

or, more clearly

5AH per hour, 120AH per 24 hours etc

 

[John61CT]

That is per day production - you know that right?

Yes I agree 700wH per day is a reasonable output guesstimate for 200W rated panels. But optimistic to say enough to replace 40-50AH average daily usage if that's the only charge source and you're trying to get the bank back to 100% full.

Charge efficiencies greatly decrease as SoC gets higher.

 

[geogentry]

I can't decipher all the pseudo HTML there, so I'll just say

Watts are an instantaneous power measure, the unit already internally represents a flow rate with a time element included,  just like amps.

Yes I know that the term watts or amps is inclusive of a time factor and assumed when discussing those terms.  When  a motor is rated as needing 5 amps rarely do you see that it will have a much larger amperage draw when it initially starts, unless you read the technical specifications.  As for the constant draw and the cycling effects - a 1200 watt heater will not draw any amps when it cycles off -which it is assumed people know- but is still rated at 1200 watts.  And the hour tag is also assumed.  It will use 1200 watts per hour while operating.  They abbreviate it to 1200 watts for simplicity.  Mathematically it is an instantaneous measurement but for practical purposes it is a durational time element.  
I copied and pasted a definition out of being lazy.  All the HTML tags didn't show on my screen.  Sorry bout that.