Charging while gone

System
System Posts: 2,511 admin
Hi everyone, new to the forum and have a couple of questions.
I have a travel trailer in Arizona and have a 3 year old 90w solar panel, I would like to hook it up with the intention of keeping 12v batteries charged while I'm gone, 6 months a year. I'm reading information and it's making my head spin as everything is in technees and I don't understand it.
I keep my trailer plugged in while I'm gone but usually come back to dead or very weak batteries. What I ideally would like is most probably some type of regulator that will keep the battery or batteries charged while I'm gone. I will leave Az. this year with no batteries but wish to get 1 12v or 2 6v batteries when I reurn later this year.
Is there a charger that will keep my battery charged without total loss of acid/water and as a backup to use while boondocking.
Any help is greatly appreciated.

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Charging while gone

    Welcome easywind,

    With your 90 watt panel,,, a good (simple) charge controller, proper fusing and you should be all set. http://store.solar-electric.com/mochco.html

    I leave one set of batteries on a single 60 watt panel with a simple charge controller for up to 11 months, and they are fully charged, even though temps drop to -40 for much of the time.

    My one concern would be making sure that the batteries have water. If you are in a hot climate, consider water miser caps, or a sealed AGM battery.

    I suggest you read the following: http://www.batteryfaq.org/
    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    Feel free to ask more questions as they arise,,

    Tony
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Charging while gone

    Look for a charger that has multiple stages--including a "float" stage... That is where it keeps the voltage around 13.5 volts or so... Just enough to keep the battery from self discharging.

    And, if the controller includes equalization--make sure that you can turn it off (or just equalize manually). Too high of charging voltage/current will boil the batteries dry in that much time.

    Ideally, overall you also want to get a charge controller that has a remote battery temperature sensor too... Batteries are very sensitive to charging voltage and that voltage changes with temperature. May not help keep water in the batteries--but when you are out using the trailer, the batteries will be better charged (overall) with a RBTS.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Charging while gone

    that's interesting that you have a 90w pv on your trailer and haven't been using it for 3 years. anyway, you are most of the way there assuming you have the pv mounted and wired in properly with fuses. this would just connect to a charge controller (pwm type of about 6amps or more would do fine) and i recommend one that has a lower float voltage setting as bb mentioned as something like the pwm sunsaver series will maintain the absorb voltage (over 14v) and just keep folding back on the current. from that charge controller it should be properly wired and fused with the fuse nearer the battery. remember that running long wire runs will cause wire resistances to increase mandating a larger wire to be used and that wire should be no smaller than #12.
  • System2
    System2 Posts: 6,290 admin
    Re: Charging while gone

    Everyone, thanks for your replies. Tony the links were awesome and answered most all my questions. I have decided to go with a AMG battery and have written a couple of stores to request the best charger for my needs. Although this year is now gone for RVing. I'd like to pre wire everything so I can just buy a battery, hook up the pv and controller and be on my way.
    The other question I have is what size wire should I run between the battery and charger? The solar panel wires are # 12 and the run between the battery and charger is about 6 feet.
    Thanks all for you time and patience with this newbie.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Charging while gone

    EW,

    I'm glad the links were helpful.

    As always,,, size the wire for the amperage of the charger. http://www.faqs.org/faqs/electrical-wiring/part1/section-20.html

    Also as always,,, bigger is generally better,, less line loss. The caveat being that larger wire is harder to work with.

    As for chargers,, consider looking at the Xantrex TC series of chargers,,, full 4 stage charging with good temperature monitoring. http://www.xantrex.com/web/id/3/type.asp

    Tony
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Charging while gone
    easywind wrote: »
    I have decided to go with a AMG battery and have written a couple of stores to request the best charger for my needs.

    Be sure you configure your charge controller to the proper settings for your brand of AGM battery (they are sealed, so if you make a mistake and they boil, you cannot add water). Espically check the float voltage, and disable Equalisation.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    Re: Charging while gone
    easywind wrote: »
    I keep my trailer plugged in while I'm gone but usually come back to dead or very weak batteries.

    Just to point out why the battery maybe dead, the on board charger is more than likely a single or dual stage charger. They can over charge the battery. So when you do get the solar worked out. Do not plug in the trailer during long term storage.