Auto Battery Load Disconnect

Just wondering if anyone has any experience with one of these? https://www.amazon.com/Digital-Batt.../B07929Y5SZ/ref=psdc_2236627011_t2_B07R8C9JW9

On paper it sounds like a pretty cool and inexpensive gadget that could save your battery from over discharge damage (like mine has).
It has user adjustable voltage disconnect and reconnect, so for instance if you have your fridge running off the battery and your solar panel out charging the battery, and it clouds over while your gone, you could have it set to cut the battery's load off when the battery voltage reached 12.2 volts (approx 50% capacity), then if the sun returns and the panel starts charging again you could have it set to reconnect the battery to your load when it reaches 12.8 V charge. Either one of those parameters are adjustable to whatever you'd like based on the type of battery you are using, and its likes and dislikes.
Sounds cool, but maybe someone else has been there, done that, so wanted to check if there is any experiences or considerations?
Thanks!

 

I have a similar device on the main battery in my tow.
https://www.amazon.com/dp/B0030A10V0/ref=cm_sw_r_cp_apa_glt_fabc_M7BSFYR78JSGK0BA9KXE
It disconnects the battery from everything if the voltage is too low, preserving enough to restart the engine. It has saved us several times, especially when the fridge was running from the car's battery, though I don't do that any longer.

The device you found is limited to a 20 Amp load, the one I have can pass more than 300 Amps. 20 Amps is adequate for the fridge and the automatic reconnect feature is useful.

 

Thanks rotus8!
Our Camp-Inn is a 2007 which has the smaller 33ah battery, and no room for up-sizing. The main issue I've run into is trying to run the Dometic fridge without an elec. hookup using just the solar panel. The panel keeps up fine as long as it's in the sun, but unless you are keeping an eye on it, that can change in a hurry. Consequently our battery has gone down below 12V on several occasions, and lost a lot of it's capacity. Before replacing it, I wanted to see about trying to do something to prevent that from happening to a new one. I know it's kind of pushing that size battery to the limit, but the fridge will actually hold it's temp pretty well un-powered overnight when the panel isn't making any juice, as long as it's full (just found that out during a couple days at the Oshkosh airshow this past week...went from 33 to 37), so if if we can get the load removed before the battery level drops too far to do any damage, I think the fridge would be fine until sun-up, and then so would the battery. This gadget is only made for 20 amps, but that should be plenty for the fridge load, so might just be worth a try to make the battery last a little longer.

 

My 7 year old Dometic has a built in cutoff with three low voltage settings. I do have other devices where this might be useful.

 

Thanks for your reply rmbrowder!
I checked out the info in the Dometic operating manual and from what I found, it sounds like the cutoff voltage even when set on high will cut off the current to the fridge at a voltage(11.8V) that corresponds with what is considered a very deep discharge, well below 50% of capacity (actually at about 30%).
From what I've been reading it sounds like 50% is the maximum depth of discharge (DOD) a deep cycle battery should be taken down to before damage to it's charge capacity will begin to occur. The Lithium Iron Phosphate batteries can safely be taken down that low and lower, but it doesn't sound like any of the lead acid batteries should.
I found the following DOD chart, followed by the info from the Dometic owners manual describing the battery monitor function and setting:


CF 18, CF 25, CF 35, CF 40, CF 50Operation

In “HIGH” mode, the battery monitor responds faster than at the levels “LOW” and
“MED” (see the following table).
Selecting the battery monitor mode (CF 25, CF 35, CF 40, CF 50)
➤Switch on the cooler.
➤Press the “SET” button (fig. 4 4, page 4) three times.
➤Use the “UP +” (fig. 4 6, page 4) and “DOWN –” (fig. 4 7, page 4) buttons to
select the battery monitor mode.
✓The selected mode then appears in the display for a few seconds. The display
flashes several times before it returns to the current temperature.
I
NOTICE! Danger of damage!
When switched off by the battery monitor, the battery will no longer be
fully charged. Avoid continuous starting and shutting off of the vehicles
engine when using the cooler in an automotive environment. Allow the
vehicle to recharge the battery before powering the cooler on.


Battery monitor mode CF 18C CF 25, CF 35, CF 40, CF 50
LOW HIGH LOW MED HIGH
Switch-off voltage at 12V 10.4 V 11.5 V 10.1 V 11.4 V 11.8 V
Restart voltage at 12V V11.5 V12.5 V 11.1 V 12.2 V 12.6 V
Switch-off voltage at 24V 22.1 V24.0V 21.5 V 24.1 V 24.6 V
Restart voltage at 24 V23.6 V25.4 V 23.0V 25.3V 26.2 V
NOTE
When the cooler is supplied by the starter battery, select the battery
monitor mode “HIGH”. If the cooler is connected to a supply battery,
the battery monitor mode “LOW” will suffice.
If you wish to operate the cooler from the AC power supply, set the
battery monitor to the “LOW” position.

 

We have just started using our 560 with solar for the Dometic. It kept up fine with 12V in galley while on the road and with a 100W panel when stopped and
and set to “Lo”. Getting ready to head out for a much longer trip with mostly non/shore power stops. We have kept the Dometic running in the galley so far but are wondering about using it in freezer mode in the TV while traveling to reduce buying ice (and going easier on CI batt when traveling) and then setting it to 37 w/ solar on our 2 day camping spots. Anybody have advice / experience on traveling in freezer mode?

 

Are you charging the trailer battery from the tow vehicle? If so, you should be fine. A fully charged battery is the norm for us upon arrival. The fully charged trailer battery will last a couple of days if you aren't running a lot of lights, televisions, laptops, etc.

The Dometic is pretty friendly. Ideally, you should keep it in the shade and with the vents open --- it breathes better that way.

Make sure you don't do what I did --- "lo" <> energy use (more/less cooling) it just controls where the Dometic will turn itself off to save the battery....probably more important when running from a car cigarette lighter.

 

Thx- Yes, the trailer battery is charged via the TV when traveling, then solar when camping. From what I have read…setting the Dometic on “hi” is the safest bet when running it off the TV going down the road.

 

I think you're new here Welcome! How long have you had your trailer?

That is correct. The lo/med/high will turn the fridge off if voltages drop below a threshold. High is 11.8 volts. 11.4 for medium. Low is at 10.1 volts. That is very low. If you are driving, your alternator will keep the voltages at 13.3 or higher the whole time, charging both the car and trailer battery...so none of this should be a problem.

When this setting really matters is at night, when stopped and not plugged into shore power. That is when you will be discharging the battery.

For me, Medium is my safe setting. 11.8 volts is right the 40-50% mark, which is where theoretically damage to the battery begins. Going lower will not immediately hurt your battery, but it will reduce its overall life span but I've dead-flat discharged mine twice so far this summer. Take that as another camper-confessional topic

Just a thought...

Do you know if you have a battery isolator installed? The CTEK option incorporates one into its design, I do not know about the battery monitor. What this will do is to turn off the juice between your tow vehicle and the trailer when the tow vehicle isn't running. My F150 had one built in as part of the towing package.

If you do not have one, make sure you unplug the trailer from the tow vehicle if you park it for any time. The imbalance between the two batteries (vehicle and trailer) can result in a dead battery at the most inconvenient time. No one has time for that

 

We got our 560 late Oct of last year. No CTEK but we do religiously unplug TV from TD when stopping for the day. We also discussed our planned Dom. use with Craig and Cary of CI. My distillation of all of these very helpful sources of info is that we can run it in freezer mode in TV with no problem (hi batt setting would be good) when the car is running. Our Outback shuts off power to 12V outlets when ignition is off but for a short break stuff will stay cold. When camping without shore power we can run in freezer mode in Galley / side table using our 100W solar (lo batt setting). We’ll have a regular cooler which we’ll supply with ice in the form of frozen plastic water bottles from the Dom freezer. Best laid plans etc., but we are giving this a shot.

 

Welcome Bob.

We've got a '12 outback as well --- very common tow vehicle. Love it. Except for the fact is odometer is getting a little high. It Sounds like you've got a handle on this.

October of last year? We were probably being built next to each other, I took delivery in mid-November. Seems like forever ago

Did you opt for the roof-mounted solar or are you using a folding panel? I had the CTEK put into mine, so I'm prewired for solar. I do have a small 50 watt panel, but it doesnt' do much. One of these days, I'll get up to necedah and have the roof panels added. I ran out of money when I was optioning mine out. Plus, I wanted to see how they performed after a couple years.

We stay mostly at state parks --- down here in Indiana, there's no way you can camp without air conditioning. So we've got power easily available to us. In fact, its hard to find a spot that doesnt' have power. Soon, I'd like to get down to Arizona in the winter. We've planned it a couple times, but the best way to make God laugh is to tell him your plans.

Are you planning on going to CICO? Hope to meet you there. Look for an ultra 560 LOL...I have no idea how I'm going to navigate the bathrooms after a shot or "two" of "apple pie"

 

To the OP --- its funny, I was just looking at this exact same part yesterday The one rotus8 posted looks a bit heavier duty.

I'm a bit afraid of fire, we ALMOST lost our Fleetwood Bounder to a gas leak and a spark. Nothing, and I mean NOTHING will get your blood pumping faster than seeing black smoke pour out of the fridge vent....

It all ended well...but it was definitely touch and go there for a few minutes.

 

We went with a

We went with the 100w Renogy suitcase because 1) we had already checked too many accessory boxes, and 2)maybe we don’t really want to have to park it in the sun when camping in order to get solar from the top. We’ll be camping during the CICO dates. Maybe next year. I’m also thinking about the SW this winter but I’m a little iffy about hitting winter road salt (we’re in nw WI) between here and there - maybe just be ready and head out when the weather is clear into the snow free zone?

 

I agree that the one rotus8 has looks a bit heavier duty, however it appears that it's main goal is to protect the TV battery from over discharge by the TD load, and is not adjustable for the disconnect, and the reconnect voltages of the load on the TD battery, like the one I purchased. I did a little surgery on my battery compartment to make room, and replaced my 33ah TD battery a couple weeks ago with a Victron 100ah AGM deep cycle battery. I haven't had a chance to test the auto disconnect device yet since the replacement, but hope to next week on a short trip to a campground where we won't have an electric hookup. Hopefully it will prove itself to be the answer to over discharge of the TD battery.

 

Sounds like our through processes were pretty close....I am glad I added the CTEK for future proofing if anything. There's probably a thread on it...or should be. I hate hijacking good threads, but find I"m good at it. My worry about winter roads si the same. I need to put another couple coats on mine, but we settled on Collinite 885 wax -- about 3 coats before we left the nest. I'm happy with it.

The nice part too, is it actually smells good when applying...its pure carnuba.

 

If you are trying to protect the car, a battery isolator is a much simpler solution. You need one per tow vehicle. Typically these are relays that switch off with the accessory switch....very simple.

Another option that you could use is a similar heavy-duty relay, but it switches off when voltage drops below a set voltage - You an search for "Voltage Sensitive Relay" or VSR and find several options.

I think the "priority start" is more for those who leave a car parked for long times. I have heard of people traveling internationally for weeks, leaving their cars in airport parking lots coming back to dead batteries....I think this device is designed to prevent that, not for towing...

 

I think we’ve used 5 tow vehicles in 30+ years. Just a note that not all TVs keep the charge power hot to the trailer when the key is off. Many do, but this is worth checking; your TV may already be protecting its battery!

 

My experience is limited, Ive only towed with 3 vehicles. F150 with factory harness, Jeep Liberty with factory harness Both had isolators on the tow vehicle. The 3'rd is my subaru...it has an aftermarket harness, and does not have an isolator --- so you need one on the trailer. I suspect there is a pattern there. .

The easiest way to check if your vehicle has one is one of these cheap testers. Turn off the key, plug it in, and if the 12 volt line lights up, you need an isolator. The cheapest way is to probe with a test light or a volt meter -- assuming you have one

For $10 you can't go wrong, just throw it in the tongue box and its there if you have a lighting problem on the road, although it is a "single tasker" that takes up space. On a rainy day -- I'll give up a few square inches.

 

Yes, that is what I did when I wired the VW for the trailer hookup. The relay is powered by a lead in the under the hood fuse block that is only hot when the key is on...., no dead TV battery, unless I would leave the key in the ignition and turned on.

 

Thx dustin! I just realized I need to do this as well.