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

SkiSmuggs
Explorer
Jun 11, 2015
2oldman wrote:
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.

LMAO!
westend
Explorer
Jun 10, 2015
red31 wrote:
neanderthal grade trailers/campers do exist.
Yeah, I've got one. My Neanderthal has a 32" flat screen, a 120V fridge, NAD stereo receiver, Blue-ray disc player, battery monitors, and all that other stuff.
I have no parasitic loads and no furnace fan. The only thing I haven't brought out of the cave era is air conditioning and that is on the horizon.

Now that I think about it, I wonder how cave paintings would fit in with the decor? :B
JHFox
Explorer
Jun 10, 2015
Hehe, neanderthal quite possibly. No CO2 sensor, no fire alarm, no charger/converter, not even an inverter. Less to go wrong I suppose? But to reiterate, we just take short little trips, charge our phones with the one DC outlet, and watch movies on an iPad that runs for five days while in airplane mode (turning it completely off between movies.) We hope to be full timing it one day though (in the distant future :( ).

Regardless, I had no clue leaving the battery below full charge was so detrimental, so I'm going to take everyone's advice and get a 50 or 100w panel and a 10 amp charge controller, keep the battery topped off from now on!

Thanks!
JiminDenver
Explorer II
Jun 10, 2015
Until I got the solar system up and running, I was envious of a older trailer like that. With no parasitic loads, a gravity furnace and LED lighting, boondocking is a lot easier than with a modern trailer.
red31
Explorer
Jun 10, 2015
neanderthal grade trailers/campers do exist.
JiminDenver
Explorer II
Jun 10, 2015
I think there is a good chance a 1977 trailer has none of those things connected to the house battery.
fitznj
Explorer
Jun 10, 2015
Use an Ammeter to determine you actual usage (I think you are underestimating you usage - fridge/CO2/fire-alarm, inverter.....)

One of the biggest killers of lead acid batteries is to discharge them more than 50%. I'm careful to keep my batteries as close to 100% charged as possible and have the solar panel connected all the time (with a controller).
Seems to extend the life of the batteries considerably.

You may want to consider a second battery and keep the solar panel switched on all the time.

Gerry
MrWizard
Moderator
Jun 10, 2015
the old ones use NO battery power for working, NO control use
a thermocouple keeps the gas valve open
it does use a little for the light bulb when you open the door
BFL13
Explorer II
Jun 09, 2015
JHFox wrote:
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.

Those old kind of fridges may not use 12v so much when on gas, I don't know. (I was thinking of a more modern type) You need an ammeter on a battery wire to get the actual draw when things are on and off.
jrnymn7
Explorer
Jun 09, 2015
As Mex pointed out, it's best not to allow the battery to remain in a discharged state for very long. In you situation, 3ah/day for 6 days is very minimal. Even a 50w panel would likely do the trick, late spring to early fall. But you may very well find a 100w panel for less than the cost of a 50w panel, and a small 10a pwm controller might cost you about 15 bucks? And a 100w panel is still quite manageable, for many folks, if going with a portable set-up.