Gamekeeper
New Member
- Joined
- Nov 1, 2021
- Messages
- 25
My first solar project of some complexity, is upgrading the solar system on a brand new Winnebago 2108TB, travel trailer.
It arrived with a 27 series lead acid dual purpose battery, a flexible 100 W solar panel, and a Go-power PWM charge controller.
The immediately observed problem, is that my use of it is primarily in the fall and winter, within the great lakes region. That means, endless cloudy days. And low panel output.
So, the battery dies quickly, and is slow to recharge.
Usually, when I am solving a thorny problem, I reverse engineer back from where I want to end up.
I list the symptoms, and make a list of possible solutions..
Then I optimize.
In this case, my problem is baseload usage in the trailer when it is cold, damp, and rainy or cloudy.
The symptoms manifest as inability to keep the furnace operating.
Also, while I have not fully tested them, it would seem the tank heaters would quickly follow the furnace when the battery state of charge declines.
in the great lakes, in an off grid situation, this could go on for months.
That is unacceptable to me.
The brain trust here, I believe, is fully capable of helping me to optimize my situation.
My first thoughts were to address the battery state of charge problem.
Normally, I encounter it at the end of the day, when I am returning to the trailer.
before anyone says well, just shut everything off when you leave in the morning, I should remind everyone that my wife will probably be sitting in the trailer, and also, that it is my full intention to be using it in below freezing circumstances. That’s why I bought it.
In order of practicality, it would seem, setting my truck up to charge the batteries as needed would be the simplest immediate solution, and relatively economical. After all, the truck is always there when I am.
I have a 2500w generator, and I hate listening to it.
After the DC to DC charging problem is addressed, it would seem expanding the solar panels on the roof would be next.
There is room on the roof for approximately 800 W of rigid solar panel.
I took advantage of Black Friday, and ordered 10, 100w , HQST solar panels at $75 each.
They are of a size where eight of them can be easily affixed atop the trailer.
Now, I need to select the equipment to combine the automotive, and solar, charging sources.
I have been looking at the Renogy combined 50 amp DC to DC with MPPT charge controller unit.
On DC to DC charging side, it appears to be an adequate choice.
In my mind, I can return to the trailer after a day of hunting, look at the state of charge, and then plug the truck into an Anderson connector, and let the truck run for a period of time to bring the batteries up to a higher state of charge. I must confess, I haven’t done the math to determine how long I would have to run the truck connected to the trailer batteries, to keep the systems running until the next day.
My desire, is to take advantage of travel days to top off the batteries, but realistically and primarily, rely on the solar array to keep the batteries fed. Using the truck in lieu of a generator to top off the batteries during bad weather seems just good business.
On the PV side, I have room for eight panels, and it would seem a tidy installation would be 4 in series, with two strings in parallel, down to the charge controller.
I would like to explore the calculations for this relatively small system, and it’s unfortunate operating environment, in this thread.
The 100 W panels I have, show 21.6 V open circuit voltage, and 6.5 A when short circuited.
Let’s explore this.
It arrived with a 27 series lead acid dual purpose battery, a flexible 100 W solar panel, and a Go-power PWM charge controller.
The immediately observed problem, is that my use of it is primarily in the fall and winter, within the great lakes region. That means, endless cloudy days. And low panel output.
So, the battery dies quickly, and is slow to recharge.
Usually, when I am solving a thorny problem, I reverse engineer back from where I want to end up.
I list the symptoms, and make a list of possible solutions..
Then I optimize.
In this case, my problem is baseload usage in the trailer when it is cold, damp, and rainy or cloudy.
The symptoms manifest as inability to keep the furnace operating.
Also, while I have not fully tested them, it would seem the tank heaters would quickly follow the furnace when the battery state of charge declines.
in the great lakes, in an off grid situation, this could go on for months.
That is unacceptable to me.
The brain trust here, I believe, is fully capable of helping me to optimize my situation.
My first thoughts were to address the battery state of charge problem.
Normally, I encounter it at the end of the day, when I am returning to the trailer.
before anyone says well, just shut everything off when you leave in the morning, I should remind everyone that my wife will probably be sitting in the trailer, and also, that it is my full intention to be using it in below freezing circumstances. That’s why I bought it.
In order of practicality, it would seem, setting my truck up to charge the batteries as needed would be the simplest immediate solution, and relatively economical. After all, the truck is always there when I am.
I have a 2500w generator, and I hate listening to it.
After the DC to DC charging problem is addressed, it would seem expanding the solar panels on the roof would be next.
There is room on the roof for approximately 800 W of rigid solar panel.
I took advantage of Black Friday, and ordered 10, 100w , HQST solar panels at $75 each.
They are of a size where eight of them can be easily affixed atop the trailer.
Now, I need to select the equipment to combine the automotive, and solar, charging sources.
I have been looking at the Renogy combined 50 amp DC to DC with MPPT charge controller unit.
On DC to DC charging side, it appears to be an adequate choice.
In my mind, I can return to the trailer after a day of hunting, look at the state of charge, and then plug the truck into an Anderson connector, and let the truck run for a period of time to bring the batteries up to a higher state of charge. I must confess, I haven’t done the math to determine how long I would have to run the truck connected to the trailer batteries, to keep the systems running until the next day.
My desire, is to take advantage of travel days to top off the batteries, but realistically and primarily, rely on the solar array to keep the batteries fed. Using the truck in lieu of a generator to top off the batteries during bad weather seems just good business.
On the PV side, I have room for eight panels, and it would seem a tidy installation would be 4 in series, with two strings in parallel, down to the charge controller.
I would like to explore the calculations for this relatively small system, and it’s unfortunate operating environment, in this thread.
The 100 W panels I have, show 21.6 V open circuit voltage, and 6.5 A when short circuited.
Let’s explore this.