Energy Options > Solar Power

solar power to keep a battery up

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mountainmoma:
I think I've got thsi right.

I bought 2 used 140W 12V used panels very cheap off a re-roof.  Then A morningstar charge controller, 20amp 12V is in the mail via Amazon.

Likely I only need one of the panels, not sure

The travel trailer has 2 100amp hour gel batteries.  When  I run this thing not on hook ups, ie end of this week maybe or next week (  if I can hook up the truck brake controller in the truck and drag it up the mountain, or someone at teh fair will do it just to get rid of us :)  )  There is alot of sun at my place, DC is only needed for sure for igniting propane to run fridge, second will be if I have enough power the DC lights,  3rd will be water pump, but I can shower elsewhere and I will be hauling water and can just as well set the 5 gallons on the counter by the sink as dump it in the fresh water holding tank

Anyways, I also ordered cables and I think all I have to do is hook a panel to the charge controller  and that to the battery

OK, I just noticed I did not order wire to go from charge controller to battery.  But, I bet the charge controller instructions will tell me what to get at the hardware store.

SO, those of you that connect solar to your trailer or RV -- does this sound right or am I forgetting something ?

Bradbn4:
>> I bought 2 used 140W 12V used panels very cheap off a re-roof.  Then A morningstar charge controller,
>> 20amp 12V is in the mail via Amazon.

Mounts or stand for Panels.
Water proof location for controller hardware
12V - one panel 140 watts + one panel 140 = (1.167 amps * 2) = 2.334

My guess is that the batteries are in parallel  to simulate one large 12 volt battery.


------------
Fun thoughts .. .

1) You will never get 140 watts per panel - even at high noon
2) You will never point the panels at the perfect point in the sky to maximize charge rate.  It is very rare to have sun tracking hardware in a fixed location, let alone on a mobile.
3) every thing seems to use more power than expected
4) it will always be overcast when you need power the most
5) where all possible, run DC appliances (pump, light, etc)
6) The longer the power wires are, the more power you lose
7) The thicker the power wires are, the less power you lose
8 ) A 12 volt batter does not have 12 volts  8)  Fully charged it should be around 13 volts?



Fixit:
In general you are right . Now. 140watts÷  12 volts=11.06 amps so you will only want to hook up the1 panel as your charge control isn't rated to handle both. Above post gives reason why that may no be a problem. Getting max  power is rare. It is easier to save power than to make more so switch all lights to LESs if they aren't already.
Just my 2 ends worth.

mountainmoma:

--- Quote from: Bradbn4 on September 15, 2020, 05:07:08 PM --->> I bought 2 used 140W 12V used panels very cheap off a re-roof.  Then A morningstar charge controller,
>> 20amp 12V is in the mail via Amazon.

Mounts or stand for Panels.
Water proof location for controller hardware
12V - one panel 140 watts + one panel 140 = (1.167 amps * 2) = 2.334

My guess is that the batteries are in parallel  to simulate one large 12 volt battery.


------------
Fun thoughts .. .

1) You will never get 140 watts per panel - even at high noon
2) You will never point the panels at the perfect point in the sky to maximize charge rate.  It is very rare to have sun tracking hardware in a fixed location, let alone on a mobile.
3) every thing seems to use more power than expected
4) it will always be overcast when you need power the most
5) where all possible, run DC appliances (pump, light, etc)
6) The longer the power wires are, the more power you lose
7) The thicker the power wires are, the less power you lose
8 ) A 12 volt batter does not have 12 volts  8)  Fully charged it should be around 13 volts?

--- End quote ---

yep, my thought too on unlikelihood to have too many amps -- and I like that brand so I ordered the 20 amp as I dont think they make a larger one, at least I couldnT find a larger one right now not much time to research.   

Yes, of course the batteries are in parallel, they are in a box, it is thick plasTic with a lid and a padlock and a disconnect to dissconnecT batteries from the trailer when not in use I guess

lights appear to be LED

Water pump is I think overly large and likely also then overly power consumptive, why I think it is oversized is that it has to cycle on and off when I run  a tap at the pressure I like

Bradbn4:
yea, it looks like I did a typo on the conversion (or went to the wrong website  :o )

While I don't think you would max out real word on amps - it is way to close to consider it.    On some hardware I would like to make sure I have lots and lots of headroom as I can afford to make sure the equipment is not run at its max capability.

https://www.rapidtables.com/calc/electric/Volt_to_Amp_Calculator.html

There are a bunch of different hardware options available from Morningstar that might fit your need.   However, once you go up in amps the price of the hardware go's up.   There is a lot of cool hardware out there since the last time I looked at anything solar.

PS-30 might work, or the simple answer is you only need one panel and the controller you picked up will do just fine.

Real world testing would be needed to see if one panel configuration will meet your needs.

And you are right, the water pump will be the highest peak load; but if that happens during the middle of the day it should not be too much of an issue. 


Some of the higher end charge controllers will show you a current display on the health of the batteries.

Some solutions can be 'cheap'.  i need special mounting gear or - I only use the hardware a few times a year, maybe my saw horses can do the work for me.

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