Low voltage disconnect

System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
I am looking for a low voltage battery disconnect, so I can shut the juice off at 12 volts. The little inverters don't shut off until 10.5 or 11 volts, which damages batteries, of course.

I have found the Newmar unit http://www.lowvoltagebatterydisconnects.com/ but it is about $149, doesn't cut off until 10.4 volts, and needs an adjustable regulated power supply (which I don't have) to adjust the screwdriver pots to another voltage.

Is http://www.mccampingsupplies.com/home/index.php?main_page=product_info&products_id=8173 any good? Looks like it might do the job.

Any other suggestions welcome.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Low voltage disconnect

    it does look like it might work, but what bothers me is that it draws 5w to operate it. that seems like a high draw for what it is and what will disconnect this from the battery when it drags the voltage down too far?
    our sponsor has one http://store.solar-electric.com/volconswit.html
    it's cheaper, but i don't know what the idle power draw from the device is.

    anybody have one that could chime in with that info?
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #3
    Re: Low voltage disconnect

    the problem with what you suggest is if there is any kind of surge the battery voltage can dip down to 11 volts or so if you set it for 12 volts to cut out any kind of largish surge will turn the inverter off. excuse the typing i just got home from solarfest in vermont
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  • SolarJohn
    SolarJohn Solar Expert Posts: 202 ✭✭
    #4
    Re: Low voltage disconnect
    halfcrazy wrote: »
    the problem with what you suggest is if there is any kind of surge the battery voltage can dip down to 11 volts or so if you set it for 12 volts to cut out any kind of largish surge will turn the inverter off. excuse the typing i just got home from solarfest in vermont

    I use a Morningstar Relay Driver. It has programmable setpoints for high voltage threshold (which you would use for reconnect) and low voltage threshold (for disconnect). It also has programmable delays. Programming a delay would prevent temporary voltage dips (like when a compressor kicks on), from causing the inverter to shut down too soon. This feature is well worth the cost of the device. It is programmable using any PC or laptop. I've explained my application in more detail on my blog: http://solarjohn.blogspot.com

    John
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