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Old 24-09-2013, 04:52   #1
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Advice on a Low Voltage Disconnect

I am wondering if anyone has some advice on a low voltage disconnect switch. My goals are I have a set of Rolls batteries and I would like for them to not to discharge to 10.5 before loads get shut off. I have one 12v freezer that I want to make sure doesn't drain the system. Currently I have a victron Battery Monitor and I have been using that with a SS relay to accomplish this, but the SS has failed and so I am trying to find a bit more robust solution. Does anyone know of a good LVD with adjustable voltage settings? Thanks
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Old 24-09-2013, 05:19   #2
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Re: Advice on a Low Voltage Disconnect

Good idea.

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Powerwerx Compact Low Voltage Disconnect (LVD) Battery Guard [LVD-35] - $89.99
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Old 24-09-2013, 06:37   #3
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Yes, I have a couple in different applications. Battery Brain brand. They make a few different versions. Some for start batts that cut out at 12V and some for house banks that cut out at about 10.5.
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Old 24-09-2013, 10:08   #4
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Re: Advice on a Low Voltage Disconnect

I haven't kept up with solid state switches but assuming they drop 0.4 Vdc and you're pulling 4 amps to your refrigerator that means the switch is turning 1.6 watts into heat. Notice the solid state switches look like big heat sinks. It'll be winter soon so the extra heat might be a plus. :-)

If you're really hurting for energy you may want to look at the equivalent in relay technology. That's the way I'd go unless it turns out they have a reliability problem with contact pitting.

Anyone with some experience with these technologies out there?
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Old 24-09-2013, 10:58   #5
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Re: Advice on a Low Voltage Disconnect

Another solution is a Victron Cyrix. Since it is a relay, there is no voltage drop. Cost about $70.
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Old 24-09-2013, 13:13   #6
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Battery Brain I think uses a relay, not certain, but you can hear the click when it switches and there is no visible heat sink.
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Old 30-09-2013, 12:09   #7
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Re: Advice on a Low Voltage Disconnect

Robertson and Caine (leopard cats) use a low voltage signal to trip a shunt trip breaker. Very reliable and no current draw but not easy to find and won't automatically come back on when the voltage is back (it would need to be reset)
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Old 09-10-2013, 06:14   #8
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Re: Advice on a Low Voltage Disconnect

Thanks for everyone's thought's after thinking about what each person said and then trying to come up with a cheap solution. I finally decided to use a three phase contactor, the coil can be replaced with a 12v version and they seem to be very robust and will last a long time. I was able to connect this contactor, to a relay to my victron BMV. The BMV tells the relay when the voltage low hits and the contactor cuts the current and will automatically turn it back on when the voltage hits the low voltage clear set point. Thanks again for everyones thoughts
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