Low voltage disconnect

[GerryS]

Someone left a light on inside our TD....unfortunately, the battery discharged to < 10 volts.....it took a charge, and has been running my 12volt refer for 24 hours now...I hope it lives (the battery that is)

The refrigerator will turn off in low voltage conditions...but the TV and lights keep on sucking juice until they battery is empty. Is there a device with an adjustable "low end" that will disconnect the battery if it gets to X volts? And stay disconnected until a charge is applied to the battery?

I hate to think such a simple oversight could cost my a couple hundred bucks for a new AGM deep cycle battery upgrade, when just 48 hours ago my old flooded battery was just fine

[jeff0520]

Yes, and Freightliner trucks had them standard on their Century Class tractors. If you can find a big truck junkyard, and find a wrecked Century, it will be located in the wiring compartment in the wall, behind the passenger seat, just to the rear of the passenger door The access door has a latch mechanism that requires a standard screwdriver to unlatch. There is a big plastic screw head in a recessed hole. Just turn it 90 degrees counterclockwise, and the door will open. The low voltage disconnect will be attached to the back of the compartment door. Hope that helps

[Shadow Catcher]

You should have a master 12V off switch for safety if nothing else and it makes it easy to turn it all off.


Ours is the red key.

[GerryS]

I've got the master disconnect as well....if looking for automatic, so we can disconnect he battery when it's dead....lights will suck the voltage below 10.5V. That's a quick way to kill a battery. Dummy proof!


I'll look for the truck disconnect...thanks.

[bdosborn]

This might do the trick:

Cole Hersee LV Disconnect



Bruce

[jeff0520]

This might do the trick:

Cole Hersee LV Disconnect



Bruce

This picture looks very similar to the disconnect installed in Freightliner Century Class tractors. That's the critter you are looking for.

[GerryS]

Too bad amazon doesn't have em

Any idea where to get these?

[eamarquardt]

You can get em on EBay: http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

Or you could buy a solar controller with a low voltage disconnect built in and a mechanical or solid state relay to increase the amperage capacity and kill a couple of birds with a couple of stones for about the same money.

http://www.ebay.com/itm/Morningstar-Sol ... 5adf8fbae9

http://www.ebay.com/sch/i.html?_sacat=0 ... =100&rt=nc

http://www.ebay.com/itm/2-Pack-Car-Truc ... 4ab1cb72ca

Although the solid state relays seem to intended for AC current AC (at a single instant in time) is actually DC so I don't see why an AC relay (with the proper control voltage) wouldn't switch DC. Especially if the relay were "oversized". However, there are different things going on when switching AC and DC. Perhaps someone might know for sure if it would work.

Different ways to address the issue.

Hope this helps.

Cheers,

Gus

[eamarquardt]

You can get em on EBay: http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

Or you could buy a solar controller with a low voltage disconnect built in and a mechanical or solid state relay to increase the amperage capacity and kill a couple of birds with a couple of stones for about the same money.

http://www.ebay.com/itm/Morningstar-Sol ... 5adf8fbae9

http://www.ebay.com/sch/i.html?_sacat=0 ... =100&rt=nc

http://www.ebay.com/itm/2-Pack-Car-Truc ... 4ab1cb72ca

Although the solid state relays seem to intended for AC current AC (at a single instant in time) is actually DC so I don't see why an AC relay (with the proper control voltage) wouldn't switch DC. Especially if the relay were "oversized". However, there are different things going on when switching AC and DC. Perhaps someone might know for sure if it would work.

Different ways to address the issue.

Hope this helps.

Cheers,

Gus

[TPMcGinty]

I did a search for RV Low Voltage Disconnects. How about one of these?

http://stores.rogue-engr.com/-strse-36/1950-dsh-222,-LVD,-Low-Voltage/Detail.bok

[Bogo]

Although the solid state relays seem to intended for AC current AC (at a single instant in time) is actually DC so I don't see why an AC relay (with the proper control voltage) wouldn't switch DC. Especially if the relay were "oversized". However, there are different things going on when switching AC and DC. Perhaps someone might know for sure if it would work.

AC and DC are very different beasts. First off if the solid state relay is zero voltage cross style, it will only turn on and off when the voltage is at zero. DC power won't ever have that happen unless the battery is dead. Random turn on and off AC solid state relays may or may not work to control DC loads. Note, the relay will likely be rated for both AC and DC if it can handle both.

[bdosborn]

I did a search for RV Low Voltage Disconnects. How about one of these?

http://stores.rogue-engr.com/-strse-36/1950-dsh-222,-LVD,-Low-Voltage/Detail.bok

That's perfect for what the OP was looking for.
Bruce

[bdosborn]

So this thread got me to thinking that I'd wanted a LV disconnect for awhile. I just pulled the trigger on this:

Intellitec Battery Guard

and this:

100A Battery Disconnect

30 amps was a little small for what I need or I would have gone with the Rogue model. I'll post more after I get everything.

Bruce

[bdosborn]

I got the Battery Guard installed; installation was pretty straight forward. Just stick the mechanically held relay in line with the wire from the battery to the main fuse block, then wire the control module to the relay. I don't have the reconnect switch wired in yet, I'm waiting on a momentary switch to get here from Amazon. The battery is disconnected when I push the test switch (and I lose all my stereo presets - doh!, didn't think that one through.) so I guess it works. I have it wired with an override switch so you can set the relay to stay connected all the time. I also wired it so I can easily disconnect the relay and connect the battery straight to the fuse block if the module craps out and disconnects inappropriately. I haven't tried it camping yet but I'm going out tomorrow so we'll see how it works.



The only tough part was the termination of the wiring at the module itself. It has some kind of weird delphi plug that was not supplied with the module. I looked all over the net for the plug and couldn't find it so I just soldered wire straight on the terminals. Hopefully none of the wires come off over time.

Here's the manual for info on how it works:

Battery Guard Manual

Bruce

[bdosborn]

Hey Gus,

You probably noticed that there's a Sunsaver 10 with LV disconnect sitting right next to the Intellitec module. So why didn't I use that to control the relay? The intellitec relay is mechanically held and draws zero current except when it being switched on or off. That means you need a 12V pulse to turn it on and a 12V pulse to turn it off, which the Battery Guard monitor module supplies. The Sunsaver only has 12V continuously on or off so it can't control the relay. The Battery Guard monitoring module only draws a couple of milliamps of current, which is why I went with this system as it has the lowest continuous current draw that I could find.

Bruce