AGM overcharging?

Bunkie314
Bunkie314 Registered Users Posts: 11
I have 3 concord lifeline 4D batteries in a trailer with an inverter system. I only use the setup in the summer and its in mothballs for winter. There are two 136 watt thin film solar panels on the rooftop connected to a xantrax C40 controller charging the batteries. Should I just let it go for the winter or disconnect it and check OCV from time to time this winter? I don't want to overcharge. Seems to be a lot of different opinions.

Thanks.

Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: AGM overcharging?

    12V system? sounds like it. Panel specs? Any parasitic loads? Some fridges and water heaters have these even though in the Off position. Lots of radio/stereos too. Clocks?

    Once fully charged you can drop the Absorb and Float settings to reduce gassing off thus minimizing the need for watering. Not familiar with the C40 settings.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Bunkie314
    Bunkie314 Registered Users Posts: 11
    Re: AGM overcharging?

    Everything is disconnected via a switch. The only things left are a midnite battery SOC panel and the charge controller. And yes its a 12 volt system unfortunately. I wished I would have gone 24 volts now. Panels are 44 OCV and somewhere in the 4 amp range. Vmp is in the 33 volt area, hence my previous statement. The controller runs the voltage up every day for an hour then drops to float is the reason I am asking for input. Yes, it is temperature compensated and I can set voltage.

    I don't want to overcharge this winter and in the spring have 375 lbs of recycle battery material.......
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: AGM overcharging?

    You are running 33 Vmp panels through a PWM controller to a 12 Volt system. This is a waste of panel power to begin with. What's more, the C40 is not a good choice for long term storage charging because of its operation in Absorb. As such this combination will regularly try to push the Voltage up, and AGM's do not like high Voltage.

    Disconnect it and check the batteries once a month. Next year see about getting a better MPPT type charge controller so you can make use of all the panels' power.
  • Bunkie314
    Bunkie314 Registered Users Posts: 11
    Re: AGM overcharging?

    Yes, not optional.

    A classic is in my future. Just not right now.

    Thanks for the input!
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: AGM overcharging?
    Bunkie314 wrote: »
    A classic is in my future. Just not right now.

    Classics are wonderful, but a bit oversized for your system. There are other very good, smaller controllers, such as the Rogue. Do you know about Midnite's kid controller?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Bunkie314
    Bunkie314 Registered Users Posts: 11
    Re: AGM overcharging?

    I have 8 more of the thin film solar panels (10 total) I will install after I get a classic. I've thought about the kid, and made inquires, and it would give me a the chance to split up panels to different jobs and locations. Wait and see what the reviews and issues are, if any. The solar is just a supplement, tinkering toy for me to keep the batteries at full charge rather then running a gen set for 6 to 8 hrs at a time to fully charge things up. But even at $4/hr it would be cheaper to just run then gen or give a $20 to a fellow neighbor to plug in.
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: AGM overcharging?

    I will second Caraboocoot, disconnect the batteries and check once a month. Best to pull the negative battery lead unless you absolutely know that there are no small loads. I have a smaller version single 185W high voltage panel feeding a 150AH Lifeline through a Morningstar MPPT controller. My cut off switch cuts everything but the Vectron battery monitor.