Does one exist or can it a small circuit be made to stop a lead acid battery discharging lower than a set voltage ?

 

I saw something like that somewhere, maybe ebay? It's conceivable that a 1S lithium-ion protection board could be modified by adding a voltage divider, or maybe it would just be a useful source of mounted MOSFETs that could be switched by an Arduino.

 

There are "Starting-Batteries", and there are "Deep-Cycle-Batteries".
Starting-Batteries will NOT withstand very much discharging if not immediately being re-Charged.

If You leave any type of Lead-Acid-Battery discharged for more than maybe ~10-hours,
you will do permanent incremental damage, and shorten it's Life-Expectancy.

Lead-Acid-Batteries should, ideally, be kept permanently connected to a "Maintenance-Charger".
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You could look at some Solar charge controllers if you just want an off the shelf device.

 

I think I've got it wrong,, its not lead acid,,,,it says on the battery

Valve regulated rechargeable battery

It's like those golf cart batteries but smaller, 12v,, ,,,,, 1.3Ah



EDIT,,,,,vyes it does say,,,, sealed lead acid ?

 

The problem with an overly-simple low-voltage cutoff is what happens during a brief but high load, like starting an engine. In normal low-load usage you would absolutely want to cutoff service if the battery has dropped to, say, 11V. But that drop is not unusual during the few seconds of cranking an engine. I suppose you could design a cutoff that uses some kind of timing algorithm that would allow brief drops but would cut out if it sees more than X seconds below the target voltage.

I'm pretty sure there are off-the-shelf devices meant to prevent discharging a battery beyond the point where it can no longer start the engine. It's a common issue in boats and RVs, where you want to use electricity for prolonged periods with the engine off.

 

This is a tiny 1.3Ah, it wont be starting any engines, Im going to use it to power a handheld oscilloscope, I gave up with the 18650's so I want something to cut the power when its down to say 11 or 11.5v