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Old 28-03-2016, 12:18   #1
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Automatic electrical shutoff based on V sense

I am on a mooring, have solar, and want to leave my refrig running, or at least running on warmest setting. I am leaving the boat for a week to 2 at a time.

I am looking for a device that would sense battery voltage, and if it goes below a certain level, would automatically shut off either the entire electrical circuit or at least the refridge.

Figuring this device must exist , I just must be searching on the right terms.
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Old 28-03-2016, 12:24   #2
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Re: Automatic electrical shutoff based on V sense

Might want to check the specs on the fridge, many do not run at a voltage that although it's not good on a battery, it isn't sure death either.
I think mine has a low voltage cut off at 11VDC.
I would think it not too hard to get enough Solar that low batteries would be a problem on a 38' Lagoon?
I'm thinking enough Solar to cover your daily budget wold be WAY more than needed on the mooring, with just the fridge and an automatic anchor light?
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Old 28-03-2016, 12:26   #3
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Re: Automatic electrical shutoff based on V sense

I don't know anything about this one, but if you search for low voltage battery disconnect, you will get many hits
Amazon.com: Low Voltage Battery Disconnect (EC-LVD2) By Energy Core Products: Automotive
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Old 28-03-2016, 13:19   #4
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Re: Automatic electrical shutoff based on V sense

Thanks. More worried about un accounted situation. For instance, for some reason solar panel breaker trips, nothing coming in to battery for 2 weeks but fridge is still running. This device would prevent battery from draining all the way. I did more of a search (thanks to you). The item you showed seems to cut out at 12V, that is a bit low.

But there is a blue seas programmable item, maybe overkill http://www.amazon.com/Blue-Sea-Syste...5VWAW9VWF5PVCG

Also, from littelfuse FlexMod Low Voltage Disconnects Series - FlexMod Electronic Modules from Battery Management - Littelfuse
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Old 28-03-2016, 13:29   #5
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Re: Automatic electrical shutoff based on V sense

Actually it cuts out at 10.5 to 12V.
You want the cut out above 12V?

Seeing as how there isn't much difference in price, I 'd go towards the Blue-Sea myself.
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Old 28-03-2016, 14:29   #6
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Re: Automatic electrical shutoff based on V sense

I have Plasmatronics solar regulators which have a load terminal which can be set for cut off and restart battery voltages. Check yours, it may have a similar arrangement.
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Old 29-03-2016, 13:48   #7
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Re: Automatic electrical shutoff based on V sense

Quote:
Originally Posted by jbinbi View Post
I am on a mooring, have solar, and want to leave my refrig running, or at least running on warmest setting. I am leaving the boat for a week to 2 at a time.

I am looking for a device that would sense battery voltage, and if it goes below a certain level, would automatically shut off either the entire electrical circuit or at least the refridge.

Figuring this device must exist , I just must be searching on the right terms.
What type of reefer? Compressor of absorption.
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Old 29-03-2016, 15:44   #8
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Re: Automatic electrical shutoff based on V sense

There are battery monitors specifically for boats that can provide a signal that can go to a relay/solenoid which trips a battery switch or to switches that have built in relays that can open the battery circuit. The beauty of the battery monitors is that you can set the voltage to what you want. The signal can also be used to trip an alarm but you might not want to have an alarm drain the last of the battery if you are not there.
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Old 29-03-2016, 15:56   #9
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Re: Automatic electrical shutoff based on V sense

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Originally Posted by exMaggieDrum View Post
There are battery monitors specifically for boats that can provide a signal that can go to a relay/solenoid which trips a battery switch or to switches that have built in relays that can open the battery circuit. The beauty of the battery monitors is that you can set the voltage to what you want. The signal can also be used to trip an alarm but you might not want to have an alarm drain the last of the battery if you are not there.
Excellent. Can you point me to some products like this?
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Old 29-03-2016, 16:00   #10
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Re: Automatic electrical shutoff based on V sense

I would question whether you are concerned about something that is in fact a nothing. I have 190 watts of solar on my boat, fridge runs 24/7 year round, on a mooring in Sydney Australia and the battery is always above 12.5 volts, according to the victron monitor, in the morning on those days that I am onboard.
If your battery bank and solar are up to the task all should be good.
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Old 29-03-2016, 16:39   #11
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Re: Automatic electrical shutoff based on V sense

Quote:
Originally Posted by jbinbi View Post
I am on a mooring, have solar, and want to leave my refrig running, or at least running on warmest setting. I am leaving the boat for a week to 2 at a time.

I am looking for a device that would sense battery voltage, and if it goes below a certain level, would automatically shut off either the entire electrical circuit or at least the refridge.

Figuring this device must exist , I just must be searching on the right terms.
The Blue Sea m-LVD is one of my favorites, robust, simple and can handle decent in-rush currents for fridge compressors.. Cut off voltage is adjustable from 11.3V to 12.1V. I would suggest leaving it at 12.1V seeing as your bank should not go below that anyway. The reconnect voltage is 13.0V. It also will accommodate up to 10 minutes of under-voltage to avoid nuisance cuts for such items as a windlass or short term inverter use.
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Old 30-03-2016, 09:14   #12
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Re: Automatic electrical shutoff based on V sense

There are a few ways to set up circuits to do what you want, but Maine Sail's recommendation is a good choice and not as expensive as putting in a battery monitor. A battery monitor is good in its own right for good battery use and maintenance but not absolutely required. They are much more expensive and would require a lot more wiring.

I would suggest that you only interrupt the reefer circuit rather than your whole panel or bilge pumps. You should turn off all non-essential circuits when leaving the boat of course. The BS m-LVD is rated for 65A continuous and 115A intermittent which is more than adequate for many entire boat panel usage, but not all. It is certainly adequate for most reefer circuits.

Normally you would have a circuit breaker/switch for the reefer on the panel or elsewhere to completely turn off the reefer. You would wire the m-LVD between that CB/switch and the reefer on the positive circuit. You would probably not want to interrupt the power to the whole panel and certainly not to bilge pumps (which you may have a manual override switch for to keep on/off). Maine Sail's recommendation to set low voltage setting on the switch to 12.1v is a good one.

The switch will take some minor current to operate so it will gradually take power out of the batteries. This would not normally be enough to worry about but could be if you left the boat for a very long time with no charge supply to the batteries.
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Old 30-03-2016, 10:01   #13
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Re: Automatic electrical shutoff based on V sense

Quote:
Originally Posted by exMaggieDrum View Post
I would suggest that you only interrupt the reefer circuit rather than your whole panel or bilge pumps. You should turn off all non-essential circuits when leaving the boat of course. The BS m-LVD is rated for 65A continuous and 115A intermittent which is more than adequate for many entire boat panel usage, but not all. It is certainly adequate for most reefer circuits.

Normally you would have a circuit breaker/switch for the reefer on the panel or elsewhere to completely turn off the reefer. You would wire the m-LVD between that CB/switch and the reefer on the positive circuit. You would probably not want to interrupt the power to the whole panel and certainly not to bilge pumps (which you may have a manual override switch for to keep on/off). Maine Sail's recommendation to set low voltage setting on the switch to 12.1v is a good one.

The switch will take some minor current to operate so it will gradually take power out of the batteries. This would not normally be enough to worry about but could be if you left the boat for a very long time with no charge supply to the batteries.
That is exactly what I was thinking of doing. I only wanted to turn off refrig. And like you say, it is wired into panel with a breaker, so my thought was to interrupt wire between breaker and refrig, i have lots of room next to refrig, so was going to put the panel in there. I think quiescent is 14 open-95 closed ma, so maybe will use 2A a day when on, (but solar would be ok), when it cuts out, goes down to 14ma or .3A a day.
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Old 30-03-2016, 10:33   #14
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Re: Automatic electrical shutoff based on V sense

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Originally Posted by jbinbi View Post
That is exactly what I was thinking of doing. I only wanted to turn off refrig. And like you say, it is wired into panel with a breaker, so my thought was to interrupt wire between breaker and refrig, i have lots of room next to refrig, so was going to put the panel in there. I think quiescent is 14 open-95 closed ma, so maybe will use 2A a day when on, (but solar would be ok), when it cuts out, goes down to 14ma or .3A a day.
I cannot understand cutting off the reefer if the battery goes low, unless the only thing in there is beer. Foul food is no fun. If it is a concern clean out the reefer and turn it off prior to going ashore and save the batteries for bilge pumps.
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Old 30-03-2016, 11:24   #15
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Re: Automatic electrical shutoff based on V sense

ebay and Amazon are among the places you should find ads for "Battery Brain" and similar battery low-voltage cutoff devices. Some have remote control fobs to turn them back on, others have to be turned back on with a physical switch. Different brands and models (including a "marine" one) that all basically isolate the battery once voltage drops too low.
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