A few months ago, we traded our truck camper for an 18 ft travel trailer. Our plan is to spend 60% of our summer vacation time on our un serviced country property & 40% of the remaining time on the road. We charge our 12 volt battery with a Honda 2000 generator but the phantom loads can completely drain our battery if we are away for a few days. A solar trickle charger has been suggested to us but we have no idea what size of charger would be strong enough to keep the battery charge healthy. Would really appreciate some help with this.

If you plan to stay off-grid for at least 60% of the time, a 100W panel would be a minimum, IMO. The panels that are less than 100W have an inordinate spike in price and 100W will offer some charging while you are using your trailer. Home Depot had 100W panels on sale awhile back. They also sell the Grape brand charge controllers which are regarded well.

Get a real solar system and don’t fool around with a trickle solar charger. $145 complete except for wire. Other companies are similar. https://www.windynation.com/Polycrystalline-Solar-Kits/100-Watt-12-Volt-Solar-Panel-and-Charge-Controller-Battery-Charger-RV-Boat-Off-Grid/-/366?p=YzE9NDY=

That depends, how much does he sun shine and is the site shaded or full sun all day?

There's a ton of info on this all over the internet. If it were me I'd get a couple of batteries and solar panels capable of charging them in a reasonable amount of time. A trickle charger wont do that. I also would not mount the panels on the roof. But, that's just me. I have spent too much time over the years repairing RV roof leaks. I refuse to do anything to compromise my roof.

With moderate amounts of sunshine, my 30 watt portable solar system keeps well ahead of phantom or parasitic loads on a couple of deep cycle batteries in storage. It would not be enough to keep up with lights, furnace, and other usage related to operating my travel trailer. That is why you have a generator.

Solar trickle charger help | Good Sam Community

25 Replies

rbpru
Explorer II
Nov 22, 2017
I agree with Boone Docker, the best battery disconnect is a wrench on the battery cable. :)

Straight forward and effective.

I do find the solar discussion informative.
D_E_Bishop
Explorer
Nov 22, 2017
It seems that the big question is how much paracitic draw you have. With my Bounder I had it down to the radio memory and my 15 watt Battery Tender could KEEP TWO FULLY CHARGED GC BATTERIES TOPPED OFF. Would it do moe?, NOT.

I too would suggest a full battery disconnect switch and a Deltran 15 Watt Solar Battery Minder..

The best disconnect is a wrench that fits the battery terminals.
Boon_Docker
Explorer III
Nov 22, 2017
Wow, that is impressive. The most I have seen with my 200 watts MPPT is 14 amps.
pianotuna
Nomad III
Nov 18, 2017
Hi Boon Dooker,

150 watts X .98 MPPT =~ 147 / 12.6 volts =~ 11.6 amps when using an Mppt controller. When panels were $5.50 per watt this made great sense.

I do harvest up to 21 amps from 256 watts of solar wired in series/parallel for 33 volts input to a Blue Sky 3024 controller. That is with a flat fixed installation.

The harvest would be lower with PWM. With panels as low as $0.24 cents per watt, adding more panels is today's solution.

Boon Docker wrote:
I don't think you are going to get 12.5 amps from a 150 watts of solar, seeing as the average amperage for a 100 watt panel is around 6 amps. To get 12.5 amps you would need 200 watts of solar. Plus you have to take into consideration that the sun is not always shining at 100%
Boon_Docker
Explorer III
Nov 18, 2017
TomG2 wrote:
full_mosey wrote:

What is the OP's parasitic draw during storage?

HTH;
John

Nothing that could not be handled with a ten dollar battery disconnect. Or hundreds of watts of solar which is not what he asked about. The subject of this thread is , "Solar TRICKLE Charger Help". Not, "How much solar do you guys have?

Yeah come on guys, stay on track here now. :B
TomG2
Explorer
Nov 18, 2017
full_mosey wrote:

What is the OP's parasitic draw during storage?

HTH;
John

Nothing that could not be handled with a ten dollar battery disconnect. Or hundreds of watts of solar which is not what he asked about. The subject of this thread is , "Solar TRICKLE Charger Help". Not, "How much solar do you guys have?
Boon_Docker
Explorer III
Nov 18, 2017
I don't think you are going to get 12.5 amps from a 150 watts of solar, seeing as the average amperage for a 100 watt panel is around 6 amps. To get 12.5 amps you would need 200 watts of solar. Plus you have to take into consideration that the sun is not always shining at 100%
pianotuna
Nomad III
Nov 17, 2017
Hi Boon Docker,

There is little point in having more than 150 watts of panels per 100 amp-hours. The acceptance rate, for a flooded lead acid jar, at 85% state of charge, is around 12.5 amps per 100 amp-hours (or about 150 watts).

60 watts is enough to allow for equalization.

For my detailed thoughts on solar, surf here:

https://freecampsites.net/adding-solar/

Boon Docker wrote:
scrubjaysnest wrote:
pianotuna wrote:
Raven52,

Start with an energy audit. From that, size the battery bank. From that allow 60 watts per 100 amp-hours of storage.

What he said but I prefer 120 to 140 watts per 100 aH of battery

X2
A minimum of 100 watts of solar per 100 AH of battery, the more watts the better.
full_mosey
Explorer
Nov 17, 2017
TomG2 wrote:

My little 30 watt system keeps my batteries topped off for months at a time.

Good for you!

What is the OP's parasitic draw during storage?

HTH;
John
MURPHY55347
Explorer
Nov 17, 2017
I purchased a Battery Minder 15W solar panel and controller for our motorhome. Layed the panel on the dash, just because it was the easiest to do, and ran the cable to the battery. The controller is a smart charger that has a float mode so as not to cook the batteries. Only hooked it up a week ago and it has been cloudy here ever since but I am confident that it will work. I am charging 3 batteries - 2 coach and 1 starter.