Low Voltage battery cut off???!!!

[dylanear]

I want a device I can put on/near my battery that will cut off the power from the battery when voltage drops too low, thus preventing a complete discharge.

I'd expect to see these available everywhere 12V batteries are sold, yet I can't find them anywhere at all.

The battery I bought last fall seems 100% dead and I'm not sure why. Perhaps the guy who wired my new brakes in left a short somewhere. Or I left a light on, but the only lights that might have been on are LED and I'd expect them to take over a week to drop that battery from over 12V to below the 8v at the low end of my meter's scale. It was around 12V one night, completely dead in the morning. 30 minutes charging from my car @14v and still reading under 8V. So I assume it's dead.

I assume some battery maker has a patent and won't let make anyone make any devices to do this because it would mean millions of less dead batteries, thus millions less battery sales every year???

Heck, every battery should have one of these built in from the factory!!! It couldn't cost more than a few bucks for such a protection circuit if made by the thousands/millions.

[Carol H]

Originally Posted by dylanear

30 minutes charging from my car @14v and still reading under 8V. So I assume it's dead.

Suspect it will take way longer than 30 min for the car to do much in the way of recharging a dead battery. You may want to put it on a charger overnight before declaring it dead or plugging into 110 for a night & let the converter take care of it.

When running on battery I have a cheap little plug in monitor that has a light that will come on as well as a little alarm if the battery gets to 40% discharge.

[cpaharley2008]

here is what you are looking for $70
LVD 12, 12V Low Voltage Disconnect
I may get me one of these myself

[Thomas G.]

Low voltage disconnect is a common feature in solar controllers, as well. Might be a cheaper route.

[RogerDat]

Originally Posted by Thomas G.

Low voltage disconnect is a common feature in solar controllers, as well. Might be a cheaper route.

I thought I saw that as a feature on a fairly high end controller, don't recall what brand or anything. Any recommendations down in the budget range?

[Thomas G.]

Originally Posted by RogerDat

I thought I saw that as a feature on a fairly high end controller, don't recall what brand or anything. Any recommendations down in the budget range?

Maybe this one? Amazon.com: HQRP Solar Power Controller 10Amp 150W with Digital LED Display plus HQRP UV Chain / UV Radiation Health Tester: Patio, Lawn & Garden

[RogerDat]

Originally Posted by Thomas G.

Maybe this one? Amazon.com: HQRP Solar Power Controller 10Amp 150W with Digital LED Display plus HQRP UV Chain / UV Radiation Health Tester: Patio, Lawn & Garden

Umm you mean the one I was just planning to order and reading about??? At the rate my mind is failing today I better hit map quest before pulling the car in the garage.

A cut off at 11.1 volts is essentially a 100% dead battery right? 12.1 makes more sense and that would be below 50 percent. Wonder if it is a typo?

[Darwin Maring]

My Silverado came with one from the factory - It don't work.

[Thomas G.]

Originally Posted by RogerDat

Umm you mean the one I was just planning to order and reading about??? At the rate my mind is failing today I better hit map quest before pulling the car in the garage.

A cut off at 11.1 volts is essentially a 100% dead battery right? 12.1 makes more sense and that would be below 50 percent. Wonder if it is a typo?

Dunno. Time to trot out the electronics experts. This Morningstar disconnects at 11.5 volts. I look to Morningstar to be a leader in engineering solar chargers, so maybe disconnect voltage is different than stabilized voltage in inferring state of charge?

Amazon.com: Morningstar SHS-10 Solar Controller 10 Amp 12 Volt 170 Watts: Electronics

[Dudley]

If you want cheap, these solar controllers have a built in cut off and are only $11. If you can solder, you can even add a second set of mosfets to double the amperage they can handle.
Solar Panel Charger Regulator Controller 10A/12V/24V Safe Protection CE Certify | eBay

[Byron Kinnaman]

It's not a good idea to leave a battery sitting without at least a trickle charger for long periods of time. Batteries will be discharged in about 3 to 4 months just sitting by themselves. If your trailer sits in a storage lot, remove the battery when not in use. Take it home and connect it to a Battery Minder or some other similar trickle charger. Make sure the charger has a desulfate mode.

[RogerDat]

I had a co-worker that used to nod off in his car at parties and such with the radio going, only to wake up with a dead battery. He whipped up some radio shack parts and made a low voltage cut off just for the acc. circut.

Was just a little plastic project box under his dash.

[Byron Kinnaman]

Originally Posted by Byron Kinnaman

It's not a good idea to leave a battery sitting without at least a trickle charger for long periods of time. Batteries will be discharged in about 3 to 4 months just sitting by themselves. If your trailer sits in a storage lot, remove the battery when not in use. Take it home and connect it to a Battery Minder or some other similar trickle charger. Make sure the charger has a desulfate mode.

I guess I didn't read thoroughly enough. I didn't see where the battery went dead in one night.
The first thing I would do is charge the battery with a battery charger, then take it to someplace that can do a load test. Many battery shops will charge and do a load test without a fee. Even if there is a small fee it's worth it to tell what shape the batteries in.
If this just happened and the battery has been in the trailer for several months and I couldn't find anything on, I would suspect the battery first.

I strongly suggest you track down the cause before attempting a fix. You might be fixing something doesn't need fixing.

[Byron Kinnaman]

One of the problems with low voltage cut circuits (switches) they draw power from the battery. Some of circuits I looked at will continue to draw current even after they've disconnected the battery from everything else.

It's always a good idea to know what caused the battery discharge.