Solar trickle charger help

[Raven52]

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.

[rbpru]

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]

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]

Wow, that is impressive. The most I have seen with my 200 watts MPPT is 14 amps.

[pianotuna]

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]

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]

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]

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]

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]

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]

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.

[Boon_Docker]

TomG2 wrote:
"Nothing" wrong with answering unasked questions, but why not address his real concerns first?

Good point!

[TomG2]

"Nothing" wrong with answering unasked questions, but why not address his real concerns first?

[Boon_Docker]

He spends 60% of the time at an un-serviced lot, so what is wrong with suggesting a good solar system to cut back on generator run time. :R

[TomG2]

About a thousand watts (minimum) some would say.

The OP asked, "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."

You guys are really something, suggesting hundreds and hundreds of watts to maintain batteries in storage between camping trips. Maybe I missed where he said he was going to dispose of his generator?

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