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TNrob's avatar
TNrob
Explorer
May 20, 2016

Solar and inverter.

Last year when I brought my battery in to winter in the garage, I hooked it to the charger and it would not take a charge. I took it back to camping world who installed it new as we took delivery on the TT last may. The exchanged it for free with no questions asked. I'm guessing I killed it by using factory charger and not keeping it adequately watered. I would plug it in once a month and let it "top off" overnight. I'm learning that is a poor way to manage things.

So, I got a new battery, and decided that two are better than one. I bought anther exide group 24 80 Ah to pair with it. Found a Rigid tool box at home depot to install them in. Used 2 gauge wire to hook them up, 4 blue sea bulkhead terminals (two pairs of output-one for the old house wires, one for the inverter run.) I put a disconnect on the house line and a blue sea 50 amp breaker on the inverter line. I installed a 500 watt inverter in the front closet near the batteries and ran AC through cabinets to anew surface mount outlet to run TV, small fan, whatever. Not for boondocking, but just in case power goes out at campground. A tiny bit of backup "just in case."

In order to care for the new batteries I kept the switched out from both the TT charger and the inverter. I was using my "smart" charger every week or two to run them back to full charge until it switched over to float. Then someone gave me a solar panel.

I bought a Battery Tender solar charge controller, hooked it up with the panel to the batteries, and put the charger in the cabinet. COOL! No more dragging extension cord. Then the wind caught the unmounted panel, threw it to the ground, and shattered it and my job well done spirit to pieces.

Finally got a new panel in last week. 45 watts and just what the Tender can handle. This panel is a perfect fit to set upon the propane tank cover wedged against the front of the camper with a wind proof fit that is very snug (and at a nice 30 degree angle facing just a bit east of due south). So far, given a week of use, it is going to green every day by the time I get home, and operating at a nice 13.13 volts. Pulses about 25-30 miliamps every 5 or 10 seconds while holding voltage steady. I'm very pleased to have this little solar system in place and on quick connect plug for easy pack up. It should last for years, cost not another dime to run, and provide trouble free maintenance charging that won't cook my battery juices away too quickly.

Total cost on the box and inverter system was about $250-$275. Total cost on the solar was about $125. Install was very easy on the solar and moderate pain in the _ on the inverter.
  • Chandalen's avatar
    Chandalen
    Explorer
    May 20, 2016
    Make sure the inverter is a Pure Sine inverter. It will always say it on the inverter.
  • ewarnerusa's avatar
    ewarnerusa
    Nomad
    May 20, 2016
    If your camper is a newer model, it probably has a "smart" charging converter already and you could theoretically leave it plugged in continuously and it will drop to float once the batteries are full and not boil them out. Leaving the trailer unplugged without a battery disconnect engaged means the trailer's parasitic draws (propane detector, stereo, various control boards on 12V appliances) drain the batteries over the course of a couple days. This is what killed your old battery. The disconnect will shut off those parasitic draws.

    If 500 watt inverter is its continuous rating, it probably has a 1000 watt surge rating. 1000 watt surge may briefly pull in the neighborhood of 100 amps which would pop your 50A breaker. If you don't ever pull that much, then no problem. I'm just pointing out that your 50A breaker may bottleneck your inverter's potential performance.

    You don't mention if you used more of your 2 gauge wire to supply power to your inverter, but I would suggest doing that.

    Congratulations on getting a small solar setup. 45 watts should be able to maintain those batteries while in storage, provided that they were fully charged first and you engage your disconnect. You'll need more solar wattage if you want to use the sun to bring discharged batteries back up to full.

    Beware the path you're on, you now have an inverter wired up and solar input connections. Soon you might be surfing solarblvd.com and other such sites for upgrading your off-grid potential!
  • Golden_HVAC's avatar
    Golden_HVAC
    Explorer
    May 21, 2016
    Hi,

    I found that my motorhome draws 0.8 amps per hour while not plugged in and the solar is off. This works out to about 35 AH daily when I include the refrigerator (1.2amps when the gas valve is on). This is about what one of my 120 watt solar panels will produce in a average day, considering they are not all 100% pure sunshine.

    You can buy a 140 watt solar panel for about $250 at this place. SunElec.com but check on shipping costs as well.

    You can search for a 20 amp PWM controller at this website for about $20. AliExpress.com

    I would not worry about the pure sine wave inverter, sure it is "Better" but also 4 times as much money as a 300 watt MSW inverter. Back in 1996 when I bought my Trace 1500 watt inverter/charger, it cost $750 for modified sine wave. A pure sine wave at the time was around $2,250.

    Now you can get a 1,800 watt brand name sine wave for a little less than $1,000, and a 500 watt Coleman modified sine wave inverter for $30.

    I can deal with the MSW power. Just do not run a laser printer on MSW or a motor. You can run a small fan (nothing that is high torque, and check the motor for overheating after a few minutes). I charge my drill battery, run a laptop, and DVD, TV, satellite system, ect from either my 300 watt inverter, or rarely the 1500 watt inverter (it consumes much more power to get the job done).

    Have fun camping!

    Fred.
  • Chandalen's avatar
    Chandalen
    Explorer
    May 21, 2016
    Not worrying about a Pure Sine inverter is insane.

    No idea what prices you are using but a simple search on Amazon finds a 2k PSW for ~$200. I use MicroSolar, ya it may be a generic but is perfect sine wave (as checked on O-scope) and rock stable voltages.

    A standard inverter (MSW) is good for:
    Non sensitive electronics, like power tools.
    Blowing up everything else.

    Thats pretty much the end of the list. Oh wait, if there is a built in USB plug its ok to charge phones on.

    What a Pure Sine Inverter is good for:
    Everything.

    Plug in a laptop to a MSW inverter and feel how hot the brick gets. Mac's have been known to blow up instantly, or just not work at all.

    MSW inverters use MORE power to accomplish the same task. What would take 200w on an MSW would take ~160w on a PSW (these are estimates, as it depends on device used)

    This video explains a lot : https://www.youtube.com/watch?v=wimTJw_Gpgk

    Lastly, if blowing things up seems unlikely to you, then save the $ and get an MSW. My 2k PSW was about $50 more than a like MSW. That Macbook power brick is $80.

    Lastly... there is a negligible standby power drain difference between a 300w PSW inverter and a 2000w PSW inverter, maybe 0.5a.

    Also the closer you are to the inverters max power rating, the less efficient it becomes. This is worse in a MSW as the 'wave' gets more corrupted. You are better off having a larger inverter to run a smaller load than a smaller inverter and maxing it out.

    Lastly, Voltage on an MSW cycles from 80-140 volts typically as the wave is corrupted, and the 0 point is variable. The Hz cycles as much as 5 Hz as well. A PSW is consistent and has a pure wave. The 0 point is stable.
  • TNrob's avatar
    TNrob
    Explorer
    May 23, 2016
    We had a cookout last night and had the battery switched on in the camper. There was at least one LED light burning from about 4:30 until about 11:00 and I left the battery connected overnight. Was drawing 0.08 amps just running the various detectors when I checked it this morning. I left it connected and monitored the charger to see when it switched over to float. It just so happened that I was checking the charge current when it suddenly went from about 2.3 amps to 0; it was fully charged at 10:10 this morning with full sun. That means I should be able to keep the battery switched on so that there is always DC inside for lights while it's parked in the driveway, and the charger can keep up even on cloudy days. I'm going to try it for a while and keep an eye on it.

    If it's keeping up and staying fully charged every day, would I still have to bring the batteries inside for an East Tennessee winter?
  • ewarnerusa's avatar
    ewarnerusa
    Nomad
    May 23, 2016
    If you can point your panels so they are perpendicular to the sun during winter noon, then you can probably leave them hooked up in place. But also keep in mind you get way fewer hours of light during winter.
    The majority of my parasitic draws are off of a single circuit, so I can pull that fuse and virtually eliminate them. That is fridge, propane detector, stereo, and antennae booster. See if yours is the same.
  • time2roll's avatar
    time2roll
    Nomad
    May 23, 2016
    TNrob wrote:
    If it's keeping up and staying fully charged every day, would I still have to bring the batteries inside for an East Tennessee winter?
    As long as the battery is fully charged it will be fine to at least -40.
    Snow on the panels could allow discharge so use the disconnect.
  • westend's avatar
    westend
    Explorer
    May 23, 2016
    You may wish to use the onboard charger/converter a few times a year to push some higher voltage into the batteries (higher than 13.10 V mentioned). The higher voltage will stir the electrolyte and desulphate the plates. After a bout of higher voltage, it is a good time to check electrolyte levels and add water, if necessary.
    FWIW, my batteries sit out year round in MN, getting charged daily by solar. No problems so far.
  • TNrob's avatar
    TNrob
    Explorer
    May 23, 2016
    I have a "7-statge" electronic charger that I can use after each trip, and we're trying to do a spring, summer, and fall trip each year. It nominally charges at 14.8 volts and I've seen 15.0 when it's cold. Haven't used in real summer heat yet to see how it backs off for elevated temperatures. It supposedly does a de-sulfation cycle at the beginning of every charge, and will do a recondition phase if the built in battery test indicates one. It has a sellectable auto,10,20,40 amp beginning charge rate. I had been using 20, but excide says it can be up to 10 times the 20 hour rate which is 40 given my 160 AH combination.

    The battery tender claims to do a brief high voltage equalize charge at the end of every daily cycle around 5-15 minutes. It bulk charges at 3 amps (or whatever the panel allows) and gains voltage to 14.4 before starting to taper the amps during saturation. When fully charged the controller does a brief equalization before switching to float. To the extent I've been able to monitor it that seems to all be true.

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