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pianotuna

Regina, SK, Canada

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Posted: 11/27/20 11:34pm Link  |  Quote  |  Print  |  Notify Moderator

Start with an energy audit in watt-hours. Divide that number by five. That will give a good guideline to how many watts of panels would work well.


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My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

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Posted: 11/28/20 10:12am Link  |  Quote  |  Print  |  Notify Moderator

Adding to KD4ULP - Larger panels cost less in terms of cost per watt, less roof space per watt and less installation cost. For my installation in 2014 a 12V panel system with PWM was only $100 less than a 24V panel system with MPPT. So 24V panels were a no brainer for me.


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Devocamper

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Posted: 11/28/20 10:20am Link  |  Quote  |  Print  |  Notify Moderator

We use a Renogy 200 watt suitcase. Has its own weatherproof controller and cables and is portable for times we are camped under trees the panels can be moved into the sun . Renogy also has a 100 watt set up lighter and smaller have also used that one both very well made and reliable


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valhalla360

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Posted: 11/28/20 10:28am Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Start with an energy audit in watt-hours. Divide that number by five. That will give a good guideline to how many watts of panels would work well.


YES!!!!!

Before just randomly installing as much stuff as you can fit, figure out what you are trying to do and what you really need.

No point in installing a 2000w solar array if all you need is to keep a 12v fridge going over night a few weekends per year.


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obiwancanoli

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Posted: 11/28/20 12:08pm Link  |  Quote  |  Print  |  Notify Moderator

Start with an energy audit... determine typical power needs (in watts) by looking at the back panel or bottom of your appliance, and add them up, inflate 25% for unanticipated needs, then convert to Amps (Watts = Amps X Volts; Amps = Watts / Volts.

Then, after determining how many batteries you have (or need/want), add up the total Amp Hours all batteries produce in total. If your batteries are flooded or AGM, safe to consider using NO MORE than 50% of bank before recharging (otherwise, you'll severely shorten their lifespan). If instead you have Lithium batteries, you can generally get as low as 10% SOC, perhaps more, before recharging, thus, you'll have more usable amp hours, longer lasting power, and they also recharge much faster.

Once battery type and amount are known, with a completed audit, you'll know how much power you typically need for a day. Once that is known, then consider the wattage of the solar panels you'll need. They come in a variety of sizes, just know that typically, a 160W panel might produce - at peak performance and circumstance - about 8 amps (or about 5 amps for a 100W panel). From here, you can determine how many panels you'll need, and where to mount them on the roof.

You'll likely benefit by having an MPPT Solar Controller, get one with more capacity than you think you'll need down the road (should you want to add more panels, you won't have to buy a new controller). A 30A controller will handle about 500 watts (panel) and is typical of an initial solar installation, but I've seen up to 1200+ watts of panels on some RV's, likely someone who does a lot of boondocking, where such volume comes in pretty handy.

My most recent boondocking experience has shown me that I'll need more than the 480 watt, 3-panel solar net. I have Lithium batteries, and in the low Arizona sun, with 3 fixed 160W panels flat on the roof, they produced less than peak charging capability, thus, more panels would be needed to charge the batteries faster, and to a higher level. I'm thinking another 3 panels ought to do it, and I also have one 120W portable panel I use as well, as I can point this at the sun and angle it for better charging ability.

BFL13

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Posted: 11/28/20 12:34pm Link  |  Quote  |  Print  |  Notify Moderator

An Li does not charge "faster" unless the Li will accept the charger's max amps, but the ordinary battery bank of the same AH size won't. Solar is generally a low amp business, with all day to recharge.

So any so-called "faster charging with Li" is not going to be realized with solar recharging. You would need a much higher amp recharge scenario to get any of that. A pair of flooded batts at 200AH at 50% can accept 60 amps no sweat. 60 amps means a lot of solar and would probably be at 60 only around lunchtime anyway.

There can be good reasons to have Li, but the "faster charging" claim needs to be very scenario specific.


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2oldman

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Posted: 11/28/20 12:46pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

There can be good reasons to have Li, but the "faster charging" claim needs to be very scenario specific.
Correct. I'm charging at 34 amps at 50v right now. Equivalent of 120. Gives my Hondas a good workout.

4x4ord

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Posted: 11/28/20 01:05pm Link  |  Quote  |  Print  |  Notify Moderator

I’m pretty new at this solar thing but I’d recommend starting with a 40 amp MPPT charger and 400 watts of solar with two golf cart batteries. If you need more you could add two more golf cart batteries and if that isn’t enough you could add another 400 watts of solar. If you need more than that you might want to run a generator.


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2oldman

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Posted: 11/28/20 01:17pm Link  |  Quote  |  Print  |  Notify Moderator

I hope the OP is getting some help from all this.

Itinerant1

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Posted: 11/28/20 01:19pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

An Li does not charge "faster" unless the Li will accept the charger's max amps, but the ordinary battery bank of the same AH size won't. Solar is generally a low amp business, with all day to recharge.

So any so-called "faster charging with Li" is not going to be realized with solar recharging. You would need a much higher amp recharge scenario to get any of that. A pair of flooded batts at 200AH at 50% can accept 60 amps no sweat. 60 amps means a lot of solar and would probably be at 60 only around lunchtime anyway.

There can be good reasons to have Li, but the "faster charging" claim needs to be very scenario specific.


If there is just one scenario that fits the bill of lfp being able to "faster charging " then it charges faster. I won't bother with my scenarios that would fill the batteries "faster" but then I'll take what ever charge the panels will produce but as fulltime boondocker living off of lfp & solar and being able to charge to 14.1v absorb instead of 14.6 or more that lead needs make a difference or accepting everything I can throw at it to 98-99% SOC where your lead slows way down much earlier in its SOC trying to absorb the charge. Isn't that faster?

One more thing I thought about is if I had to use the generator and solar to charge for fast charging which I have done once the batteries were being charged at 175a, that makes for a fast charge off grid.


12v 500ah (5,120Wh usable) , 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts) 2s4p. Panels mounted flat on the roof. Magnum PT100 controller, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365

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