Battery loses significant power shortly after dark

System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
I recently bought an new travel trailer and the dealer transfered my solar panel and controller to the new trailer. Since then I have noticed that shortly after dark the battery level drops from excellent to good with no lighting or anything of significance drawing a charge. One night I disconnected the charger from the batteries and the batteries seemed to stay charged better. Could there be a simple connection issue I could resolve to correct this problem. I also notice that the trailers battery indicator doesn't agree with the charge controller indicator, the trailer indicator showing considerably more charge.

I have a 75watt panel a Specialty Concepts Mark 15 controller and a single Kentics HC 2000 glass mat battery.

Thanks
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Comments

  • Sheldon
    Sheldon Solar Expert Posts: 51 ✭✭✭✭
    #2
    Re: Battery loses significant power shortly after dark

    A wild guess: since your controller disconnected left your batteries in a good state, vs connected after dark, did your dealer perhaps ew-connect your panel without using the blocking diode?
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Battery loses significant power shortly after dark

    Not to be too dumb but how would I verify and correct that?

    Thanks
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #4
    Re: Battery loses significant power shortly after dark

    Where you are reading that level drop from? If you are using one of those generic good-fair-bad type meters without an actual voltage reading, it may not mean much.
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Battery loses significant power shortly after dark

    I'm only looking at the readings on the controller and on the campers battery level indicator. I'm on the road and don't have a real meter with me.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,641 admin
    #6
    Re: Battery loses significant power shortly after dark

    You will need a good DVM/DMM (digital volt/multi meter) to confirm.

    Also, you can read about the care and feeding of lead battery banks here:

    www.batteryfaq.org
    Deep Cycle Battery FAQ

    If you have a battery charge controller (even an inexpensive one), you should not need a blocking diode anywhere. For systems with a solar panel connected to a battery -- the solar panels do bleed back current at night and a blocking diode prevents the self discharge.

    I should also add that most people terribly overestimate the amount of power that a solar panel can provide and underestimate the amount of power their loads consume.

    Depending on where you are at and the weather--you may get 2-3 hours of full sun equivalent per day. The charger + battery controller + inverter (if you are using one) are roughly 50% - 60% efficient for the typical system.
    • 75 watts * 2 hours of sun * 0.50 = 75 Watt*Hours of charge in winter
    75 Watt*Hours, say you use power for 4 hours an evening (computer, lights, etc.) works out to:
    • 75 WH * 1/4 hours * 1/12 volt battery = 1.6 amps average load
    • 1.6 amps * 12 volts = 19 watt average load
    This leads to "deficit charging" or constantly running the storage battery mostly discharged/deep discharging. Wears out the battery fairly quickly (a few hundred charging cycles) and ages them quicker to (sulfates hardening).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: Battery loses significant power shortly after dark

    I think Bill has it about right. I would suspect the led on the controllers are pretty arbitrary. I have used the same controller before, and if memory serves the leds go to yellow with any load at all, battery voltage ~12.5 or so.

    I also think that the campers battery level meter is probably very inaccurate. I would fully charge the battery with shore/genny power sooner than later to prevent any further damage,and then watch it for a few days while you travel and see how it reacts.

    Tony
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #8
    Re: Battery loses significant power shortly after dark

    That model of charge controller is pretty ancient - first designed in the late 70's with some changes in the late 80's. Relay based on-off controller, so there could be some significant voltage drops when the panel is shut off.
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