Solar Battery Charging

Something like this 200 watt kit from Renogy would work. https://www.renogy-store.com/200-W-solar-panel-full-RV-kit-p/off-rv-2rng100d.htm
Add a battery monitor like a TriMetric TM2025RV, Victron BMV600S or Xantrex LinkPro and you would be set.

In my simple thinking I run into the characteristics of what you are getting...

The 200WATT RENOGY solar panel kit identified here is two 100WATT panels and is probably rated as 18VDC output @ 5.5AMPS from each panel to get its 100WATT panel rating. You will double the amps output using two of these.

For you to re-charge a battery that has been discharged down to a 50% charge state you will need the provided solar controller to give you something in the 14.4VDC range. A single 100WATT solar panel will probably end up being 14.4VDC@4-5 AMPs that is physically going to your battery terminals coming from a 100WATT solar panel when it is in the high sun period of the day. With 5AMPS output you are only getting 72WATTS of usable DC power from your 100WATT panel. You will have to decide that is this enough power power to keep your deep cycle batteries charged up for the one day/night run off the batteries.

Lets look at how your system recharges batteries for you. My simple thinking is a normal smart mode charging unit will recharge your two batteries back to their 90% charge state in a three hour period. Your smart mode converter/charger will produce 14.4VDC to get this charge state going. The bad news is the two batteries will demand around 40AMPS of charge current for a short time period to get to the 90% charge state in the three hour period. This 40 AMPS of charge current has to come from the smart mode converter/charger. After about 20 minutes or so the two batteries will drop down to demanding 5-6 AMPS until they get to their 90% charge state.

Using your new two 100WATT SOLAR Panels you will only get 14.4VDC@ 10AMPS to get this 90% charge state going. When the two batteries demand the 40AMPS charge current only 10AMPS will be available. Your two batteries will charge OK with the 10AMPS charging current but it will not get to the 90% battery charge state in a short three hour period. It will take "MUCH" longer and most likely you will run out of available SUNLIGHT during the one day SUN WINDOW which is probably around 6-8HOURS long for high SUN. This will be your short comings using the smaller solar panels in my opinion.

I too am just trying to plan out a solar install and not finding my situation is as black and white as alot folks seem to pass along. My saving grace is I have been running my battery system camping off the power power grid for the past five years or more so I know what to expect from my batteries.

I only have enough room on my off-road POPUP for three solar panels and am thinking two 100, 120, or 130WATT panels on one end and hopefully I can afford maybe a 220WATT panel on the rear end of my roof. I suspect I will only get 14.4VDC@25AMPS (or around 360WATTS) from the solar controller for these three panels to recharge my battery bank with. This is a long way from the stated 460WATTS worth of solar panels... The big question for me is this going to be enough charge to re-charge my three 255AH battery bank back up to the 90% charge state during the high SUN time period of 6-8Hours. Probably going to be close haha... My daily battery consumption is consistently 300WATTS when camping off the power grid.

My other problem is I only have a short window to know for sure I will get to the required 90% charge state on my three batteries. I have to know by 4:30 each day if this is going to happen so that I can go to PLAN B and recharge for three hours using my 2KW Generator for three hours if it doesn't happen. Not having a 90% battery charge state each evening to start my run off the batteries is NOT an option for me. My trailer will get dark on me around 10PM at night and I can't run my generator until 8AM the next morning due to generator run time restrictions here on East side of the US. These generator run time restrictions are relaxed alot in the western part of the US especially if you are camping in non developed (Dispersed) campsites. We don't have many of those here on the east side of the US.

Just passing all of this along to add to your thinking process of what you might need to be successful charging your batteries with your solar panels.
If your battery consumption is low the two 100WATT RENOGY Solar Panel Kit may work just fine for you. The price sure is right on that kit..

Will require some planing Be sure to check out MELLO MIKE'S TC setup with his solar panels.

Roy Ken

It might be good to also look at Jack Mayer's information to get up to speed. http://www.jackdanmayer.com/rv_electrical_and_solar.htm

Other sites with good info:
http://www.amsolar.com/home/amr/cpage_9/rv_solar_education.html
http://cuernoverdesolar.wordpress.com/
http://mellomikeswolfcreekcamper.blogspot.com/2012/02/solar-power-101.html
http://cheaprvlivingblog.com/2012/07/installing-a-solar-power-system/
http://www.rv-boondocking-the-good-life.com/rvsolarpowerinstallation.html
http://www.macandchris.com/RVSolar.htm
http://wheelingit.wordpress.com/category/solar-power-2/

wallguy wrote:
...how many amps do I need....

Approximately 150% of the amps you use daily. The extra is for the heavy use days or for the bad weather days.

More information is needed for pertinent advice: What type, size, and AH rating are your batteries? And, how much do you discharge them in one day?

Downloadable spreadsheet calculator for solar

I recommend about 200 watts.


PWM system:
2x 140w $288
20a controller $77

MPPT system:
24v 235w panel $155
MPPT controller $230
Some are using an "Eco-Worthy" MPPT controller at about half the price.

These range from large & complex to small and simple:
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