Battery Protector Cut Out Device - Doesn't Work

I have always thought that they are set at 11.2 to protect the battery from deep discharge.
Safe starting would be around 12volts.
Regards Philip A

Hi Ozwasp

Very true, 11.2v is a flat battery.
IF you have a long run of undersized cable & loosing say 1v in that then it will protect the bat
I gather this is an elcheapo from Super cheap or Kmart

Ozwasp,

The low voltage cut out device is working if as you state it has cut out the voltage.

The problem you have is you are using the wrong type of battery. 11.2 volts is too low for a starting battery to provide enough grunt to start your vehicle.
Cut out devices are designed to protect a battery from being totally drained.
Actually 11.2 volts (1.89 volts per cell) equals about 10% remaining capacity and is still too low for long battery life.

11.6 volts (30% capacity) is as low as a deep cycle battery should be taken and then only occasionally.

Bill.

Hi
I had one inserted just before my fridge which is in the tailgate with power coming from the aux battery at the front of the vehicle. On 2 occasions I have flattened the battery due to excessive current drain and on both occasions the cut out device was useless. It was a $20 job. I found the fridge tries to start then waits a few seconds and tries again.

What we need is a device where we can set the cutoff voltage to meet our particular needs.

regards Kc

I have had a "Projecta" one in the circuit to my Engel for 10 years and it has worked well on the few occasions I have let the fridge run so long that the battery has been flattened.

IMHO the problem here is a misunderstanding about the intention of the device .

An older Engel does not have low voltage cutout and would keep trying to work even under the minimum needed for the compressor to work AFAIR 10.5 volts.
A few occasions of that would kill any battery .

So the intention of these devices is to protect the battery from total discharge not to allow starting.

Mine must be doing something right as my AGM has lasted over 5 years, although I am quite anal about usually not letting it get much under 12 volts.

Regards Philip A

Hello, we just picked up our new van and the dealer said that there is an anderson plug connection that goes in the car that not only charges the caravan batteries when driving, but can charge the car battery from the caravan batteries if the car battery is flat (ie work in reverse). Does anyone know of these and if they work?

Have a look at this LINK let me know if they are any good. Cheers.

It's impossible to design a Cutout that will stop at xx% remaining battery capacity that is -
- cheap
- works with a big range of batteries
- works with varying voltage drop in different cable-length/size.
- independant of battery temperature

The problem is that voltage drop varies with the current being drawn by the load, type and size of the battery and temperature.

The best you can hope for is a Cutout without adjustable voltage trip which you set for your particular situation, based on trial and error. I built my own based on the Oatley kit mentioned above.

EVERYONE keeps forgetting the voltage vs stae-of-charge tables are meaningless except when the battery has had no charge or discharge for several hours.

hi
i had one that was'nt cutting out until 10.5 volts that i bought and had in the shed for 3yrs before i actually got around to using it

so coud'nt take it back it was only a cheapy
think i got it at a show event somewhere so ditched it and bought one from supercheap and it's ok
there's cut-outs and there's cut-outs
it's buyer beware as usual
cheers

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