Mysterious battery fatality-- help!!

Laura P.
Laura P. Registered Users Posts: 4
in Off Grid Solar & Battery Systems #1
Hello,
I am new to solar systems and electronics, and I have recently (last month) installed a simple solar system on my truck with the help of a friend. I work outdoors and intend to use it sporadically to charge a laptop and some random field equipment.

Today I happened to notice that the load disconnect light on my charge controller was on, and when I went to check the battery with a volt meter, it read 8.3 V! Apparently, I starved my battery to death, but I cannot figure out why, and would like to fix the problem before I spend another $200 on a new battery.

I have a 14.5 V panel attached to my truck's roof rack, wired into a Morningstar sun saver 10-12V charge controller. I am using a sealed 12V Optima yellow-top battery. I have two DC outlets, one wired to the charge controller, and one wired directly to the battery. Each of the lines to the negative battery terminal has a fuse holder, 15V for the line from the battery to the charge controller, and 25V for the line going directly from battery to DC outlet. If I remember correctly, the battery read about 12.5V when I purchased it last month, and it has been charging all month with very minimal use. Nothing, not even an inverter, has been plugged into it for weeks. There has pretty much been full sun everyday since I set up the system. The charge light has been on everyday, and was in fact on along with the load disconnect light. I checked the wiring on the panel to make sure that the charge controller was not allowing a nighttime back flow.

This is a new world, and a steep learning curve, but I cannot think of anything obvious that is wrong with the system... Could I have wired it poorly? Is it possible there is a parasitic charge lurking somewhere? Maybe the battery was bad at the start? To my untrained eye, the system appears to be very tidy. Do any of you all have advice or ideas on where to start? I was hoping to leave for the field this weekend, but will have to get this fixed before I go. Any advice is most welcomed!!

Thank you!!
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Mysterious battery fatality-- help!!

    laura,
    welcome to the forum.
    it sounds like the lvd did not function properly for it is supposed to disconnect the load long before it would ever hit 8.3v. it's difficult for us to say precisely what may be going on there and particulars like the pv and battery specs as well as load specs are omitted from being reviewed by us to better evaluate the possibilities. we can't even say if it may have been wired wrongly without being there or having good pics of it.

    hopefully you can elaborate on this more and maybe one of us may hit the nail on the head.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Mysterious battery fatality-- help!!

    Welcome to the forum Laura, and I am sorry you are here under these conditions.
    Laura P. wrote: »
    Today I happened to notice that the load disconnect light on my charge controller was on, and when I went to check the battery with a volt meter, it read 8.3 V! Apparently, I starved my battery to death, but I cannot figure out why, and would like to fix the problem before I spend another $200 on a new battery.
    Get the battery on to a battery charger right away--You may be able to save it--Or if nothing else, use it to figure out what is wrong with your setup.
    I have a 14.5 V panel attached to my truck's roof rack, wired into a Morningstar sun saver 10-12V charge controller.
    Exactly what Brand/Model of solar panel do you have?

    Typically, there are "12 Volt" panels which have Vmp~17.6 volts (Voltage, maximum power). And there are some (typically older/smaller panels) which are Vmp~15 volts--The 15 volt panels are intended for use without a charge controller.

    Also, what is the wattage rating of the solar panel?
    I am using a sealed 12V Optima yellow-top battery. I have two DC outlets, one wired to the charge controller, and one wired directly to the battery. Each of the lines to the negative battery terminal has a fuse holder, 15V for the line from the battery to the charge controller, and 25V for the line going directly from battery to DC outlet.

    Are you talking about 15 Amp and 25 Amp fuses?

    Also, unless you are doing a positive ground system, the recommended location for fuses is in the positive wires, not the negative.

    If the fuses are OK (not blown or bad connections) it should not have mattered to your setup--but it should probably be fixed to avoid problems later trying to debug your setup.
    If I remember correctly, the battery read about 12.5V when I purchased it last month, and it has been charging all month with very minimal use.

    The battery at 12.5 volts is reasonably charged (assuming room temperature). ~12.7 to 12.8 (resting voltage) is fully charged.
    Nothing, not even an inverter, has been plugged into it for weeks. There has pretty much been full sun everyday since I set up the system. The charge light has been on everyday, and was in fact on along with the load disconnect light. I checked the wiring on the panel to make sure that the charge controller was not allowing a nighttime back flow.

    So, the problems may be:
    • Miss-wired
    • Poor connection
    • Solar Panel not functioning
    • Solar Panel may be flat or tilted up towards noon time sun--But there cannot be any shadows (vent stacks, wiring, antenna, etc.) on the panels from ~9am to 3pm minimum. Solar PV panels must be in full sun to work properly.
    • Charge Controller not functioning
    • Possibly too small of solar panel/array (low voltage, low power)
    I understand you have no loads plugged into the battery system?

    This is a new world, and a steep learning curve, but I cannot think of anything obvious that is wrong with the system... Could I have wired it poorly? Is it possible there is a parasitic charge lurking somewhere? Maybe the battery was bad at the start? To my untrained eye, the system appears to be very tidy. Do any of you all have advice or ideas on where to start? I was hoping to leave for the field this weekend, but will have to get this fixed before I go. Any advice is most welcomed!![/QUOTE]

    On your system, start with a volt meter:
    • Solar Panel/Array voltage at charge controller voltage? (Vbatt to 17-21 volts)
    • Solar Charge Controller voltage (should be ~Vbatt)?
    • Battery resting voltage (~12.0 volts 50% charge; ~12.7 volts full charge) [resting voltage is no charge/discharge current for several hours]
    • Battery Charging Voltage? 12.x-14.0 volts "Bulk Charging"; 14.1-14.5 volts Absorb set-point voltage (battery ~80-100% charged).
    Based on the above voltage readings, we can then (hopefully) point you to place to look at specifically.

    If you have a DC Current Clamp Meter (here is an inexpensive one that will do the job)--It is a very easy way to make quick measurements of current without having to cut wires/insert a DMM meter in the leads to see if current is flowing.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Mysterious battery fatality-- help!!

    Laura;

    Okay so you've got your V's and W's and A's mixed up. It happens. That's how we get alphabet soup. :p

    Probably you have a 14.5 or "15 Watt" panel. That's not going to do much for recharging an Optima. Maybe 1 Amp.

    Second, I notice you've got one DC outlet connected to the Low Voltage Disconnect on the Morningstar, but the other one connected directly to the battery. It is likely that loads drawing on this second connection brought the battery down, as the LVD has no way of shutting that off as Voltage drops. If this system isn't isolated from the vehicle's system all you'd have to do is leave a door ajar - the dome light will give you a dead battery by morning.

    BTW, as standard wiring practice fuses go on the positive wires, not the negative ones.

    Step One: put that battery on a charger and see if it will recover.
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  • Laura P.
    Laura P. Registered Users Posts: 4
    #5
    Re: Mysterious battery fatality-- help!!

    Wow, do I sound inept. Sorry-- this is a new lexicon for me.

    The panel is made by Sunpower. It is rated at 90W and 17.5V, however, it was a display model that I bought through a friend, and it really runs at only 14.5V, which I hear is plenty to trickle charge a battery with minimal, intermittent use.

    The battery is auxiliary-- it is in the back of my truck, not connected to anything but the two DC outlets, which I haven't used for several weeks. Also, the battery is brand spanking new, and regardless of how well the panel is working (all tests appear to be normal), it should not be so low.

    I've attached a crude diagram of my set up-- I hope it comes through the cyberpath to you. In essence, the panel on the roof is wired directly to the charge controller that is mounted onto a permanent, protected platform near my tailgate. The charge controller is then wired (#8 gauge) to the battery that lives in a snug wooden box towards the back of the truck's cab. I have an outdoor, rugged DC outlet mounted near the charge controller that is wired directly to it. I have a second line of #8 gauge wire coming directly from the battery to a heavy-duty metal DC outlet, mounted directly next to the one previously mentioned. The 15 and 25 AMP fuses are on the positive leads to the battery (sorry, I'm an idiot). All the wiring is running through accordion-style automotive wire housing, is color coded, and is secured to the underside of a wooden platform so that it doesn't get pinched or pulled in anyway. It would be a colossal pain, but I could unthread and recheck all the wiring to ensure I did it correctly. Would a switched wire drain the battery?

    And good point to the individual who pointed out that the charge controller should have saved my battery from starving. However, that implies that there has been a draw, which there shouldn't have been, since I haven't been using it at all.

    Very confused.

    Thanks for all your responses! If something else comes to mind, please let me know!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: Mysterious battery fatality-- help!!

    Okay, so no connections between systems. That's good.
    Possibly suspect panel, but if there have been no loads the battery should have stayed charged.

    That leads to the most likely suspect being wiring. As in somewhere the (+) and (-) are touching/crossed/shorted somehow because something has to be draining power from the battery.

    Do you have a multimeter? You'll need to look for continuity between the positive and negative wires - with the battery and solar panel disconnected. It is possible to hook the wires on to the charge controller wrong so the battery will actually drain through the panel at night.

    P.S.: This is perhaps one of those positive ground Sunpower panels. That could be the trouble.
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