Hi all,We have a 19' TT that we take out a handful of times a year. (Would love to go much more often, employer does not agree. :( ) The longest we've been out for in one trip was six days.The only electricity we use is some LED lights (2 watts each), the water pump (50 watts when running?), and our phone charger (5 watts). According to an online calculator I found (http://midsummerenergy.com/solar_panel_information/solar_panel_calculator.html), based on estimates of how long we use each "load", our total amp-hours a day come to a whopping 3! (37.5 watt-hours.) As for our battery, it's an AGM battery that's listed as having 68 amp hours. Q1: does the fact I use 3 amp hours a day mean I could effectively go about 20 days on my 68 amp-hour battery? (I never would, I'm just verifying that I understand the meaning of these numbers.) Should I even worry about trying to charge the battery on the short trips I take, given how little power I use? If the answer to Q1 is Yes, then on to Q2...Q2: the trailer came with a 5 watt panel attached to the roof and they wired in an on/off switch. In direct sun it puts out 19 volts. Can I leave this panel on without fear of overcharging my battery? I've read a few places that have implied a small enough panel doesn't require a charge controller. Is that true? And if so, what would be considered "small enough"? Should I just install a controller to be safe?Thanks! Hope all of that made sense. James

Prolonged less than fully charged condition can be a battery killer. About one week is all I would permit. Battery damage from prolonged discharge is much like radiation poisoning -The more intense (discharge) the faster it damagesThe longer the exposure (to undercharge) the more it damages the batteryYour example is a textbook case to choose a solar panel to maintain a more fully charged battery. A fifty-watt panel would be enough for your present load, unless you use your accessories as described day and night.

JHFox wrote:Hi all,We have a 19' TT that we take out a handful of times a year. (Would love to go much more often, employer does not agree. :( ) The longest we've been out for in one trip was six days.The only electricity we use is some LED lights (2 watts each), the water pump (50 watts when running?), and our phone charger (5 watts). According to an online calculator I found (http://midsummerenergy.com/solar_panel_information/solar_panel_calculator.html), based on estimates of how long we use each "load", our total amp-hours a day come to a whopping 3! (37.5 watt-hours.) As for our battery, it's an AGM battery that's listed as having 68 amp hours. Q1: does the fact I use 3 amp hours a day mean I could effectively go about 20 days on my 68 amp-hour battery? (I never would, I'm just verifying that I understand the meaning of these numbers.) Should I even worry about trying to charge the battery on the short trips I take, given how little power I use? If the answer to Q1 is Yes, then on to Q2...Q2: the trailer came with a 5 watt panel attached to the roof and they wired in an on/off switch. In direct sun it puts out 19 volts. Can I leave this panel on without fear of overcharging my battery? I've read a few places that have implied a small enough panel doesn't require a charge controller. Is that true? And if so, what would be considered "small enough"? Should I just install a controller to be safe?Thanks! Hope all of that made sense. JamesYou normally would not go below 50% on the battery (but you can get away with going lower to say 30% if required at times)Don't you have a fridge? On propane, it will use about 15AH a day from battery right there. (the burner uses 12v --half an amp when on, which is about 2/3 of 24 hrs)No need to pretend you are in a tent on a survival course. You have a TT. You are allowed to have an inverter (say a 300w) attached to the battery so you can plug 120v things into it, like a tv/dvd. Watch a movie on rainy evenings.Easy to get two batts instead of just the one, and enjoy your TT more.You could benefit right now from a bigger solar panel with a controller for it, to make up some of those AH you were not counting. IMO no point in getting anything less than a 100w panel.

JHFox wrote:..5 watt panel attached to the roof .. Can I leave this panel on without fear of overcharging my battery? You can leave that panel on without fear of charging your battery.

Q1 No because you use more energy than you think.Q2 a 5 watt panel is safe to use without a charge controllerWater pump is a negligible item. Mine would use 7 amp-hours to drain the entire fresh water tank.In your shoes, I'd redo the energy audit and then plan a solar system upgrade.

Thanks folks!I had no clue the propane fridge used DC power! :o It's an old system ('77) and the burner runs all the time. I clearly need to redo the energy audit, and I'll probably just go with a more-than-adequate panel (probably 100W) and a charge controller. Was just thinking I could save some $ and use the panel I have, but obviously I have a lot to learn. Much obliged!

Battery/solar questions | Good Sam Community

JHFox
Explorer
Jun 09, 2015
Yup, light it manually and it stays lit constantly. Controls are physical knobs that just change the size of the flame. No fan or any other moving parts.
jrnymn7
Explorer
Jun 09, 2015
plus lp/co2 monitor draw, perhaps?

your fridge may not draw 12v for controls? do you have to light it manually?
JHFox
Explorer
Jun 09, 2015
Thanks folks!

I had no clue the propane fridge used DC power! :o It's an old system ('77) and the burner runs all the time. I clearly need to redo the energy audit, and I'll probably just go with a more-than-adequate panel (probably 100W) and a charge controller. Was just thinking I could save some $ and use the panel I have, but obviously I have a lot to learn.

Much obliged!
pianotuna
Nomad III
Jun 09, 2015
Q1 No because you use more energy than you think.
Q2 a 5 watt panel is safe to use without a charge controller

Water pump is a negligible item. Mine would use 7 amp-hours to drain the entire fresh water tank.

In your shoes, I'd redo the energy audit and then plan a solar system upgrade.
2oldman
Explorer II
Jun 09, 2015
JHFox wrote:
..5 watt panel attached to the roof .. Can I leave this panel on without fear of overcharging my battery?
You can leave that panel on without fear of charging your battery.
BFL13
Explorer II
Jun 09, 2015
JHFox wrote:
Hi all,

We have a 19' TT that we take out a handful of times a year. (Would love to go much more often, employer does not agree. :( ) The longest we've been out for in one trip was six days.

The only electricity we use is some LED lights (2 watts each), the water pump (50 watts when running?), and our phone charger (5 watts). According to an online calculator I found (http://midsummerenergy.com/solar_panel_information/solar_panel_calculator.html), based on estimates of how long we use each "load", our total amp-hours a day come to a whopping 3! (37.5 watt-hours.) As for our battery, it's an AGM battery that's listed as having 68 amp hours.

Q1: does the fact I use 3 amp hours a day mean I could effectively go about 20 days on my 68 amp-hour battery? (I never would, I'm just verifying that I understand the meaning of these numbers.) Should I even worry about trying to charge the battery on the short trips I take, given how little power I use?

If the answer to Q1 is Yes, then on to Q2...

Q2: the trailer came with a 5 watt panel attached to the roof and they wired in an on/off switch. In direct sun it puts out 19 volts. Can I leave this panel on without fear of overcharging my battery? I've read a few places that have implied a small enough panel doesn't require a charge controller. Is that true? And if so, what would be considered "small enough"? Should I just install a controller to be safe?

Thanks! Hope all of that made sense.

James

You normally would not go below 50% on the battery (but you can get away with going lower to say 30% if required at times)

Don't you have a fridge? On propane, it will use about 15AH a day from battery right there. (the burner uses 12v --half an amp when on, which is about 2/3 of 24 hrs)

No need to pretend you are in a tent on a survival course. You have a TT. You are allowed to have an inverter (say a 300w) attached to the battery so you can plug 120v things into it, like a tv/dvd. Watch a movie on rainy evenings.

Easy to get two batts instead of just the one, and enjoy your TT more.

You could benefit right now from a bigger solar panel with a controller for it, to make up some of those AH you were not counting. IMO no point in getting anything less than a 100w panel.
MEXICOWANDERER
Explorer
Jun 09, 2015
Prolonged less than fully charged condition can be a battery killer. About one week is all I would permit. Battery damage from prolonged discharge is much like radiation poisoning -

The more intense (discharge) the faster it damages

The longer the exposure (to undercharge) the more it damages the battery

Your example is a textbook case to choose a solar panel to maintain a more fully charged battery. A fifty-watt panel would be enough for your present load, unless you use your accessories as described day and night.

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