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low voltage cutoff

Posted: Wed Apr 21, 2010 8:26 pm
by sprungupcruiser
Hey lads, bit of an auto sparky noob. Tried searching and it didn't turn up much. I've got an Evakool fridge/freezer and it has a low voltage cutoff at about 10.4v. I run it off a aux. deep cycle agm battery and don't really need the cutoff (or do I?). So my potentially silly question is there anyway to remove or alter the low voltage cut off? Or will this damge the fridge if it gets to low or any other sort of negatives involved with it?
cheers
Rob

Posted: Wed Apr 21, 2010 8:47 pm
by DamTriton
The cutoff is there to save the battery from being irretrievable damaged by being over discharged.

If it works, don't fix it.
If someone installed it, they didn't do it by accident.

Posted: Wed Apr 21, 2010 9:10 pm
by sprungupcruiser
yeah fair point, I thought the deep cycle batteries could get discharged lower than your regular lead acid batteries without damaging the battery, or is that not true. If it could be modified to cut off lower then that would be good as I've only got a 60ah aux. battery. Obviously a bigger battery is a better option but it also means spending more money.
cheers

Posted: Wed Apr 21, 2010 9:29 pm
by DamTriton
sprungupcruiser wrote:yeah fair point, I thought the deep cycle batteries could get discharged lower than your regular lead acid batteries without damaging the battery, or is that not true. If it could be modified to cut off lower then that would be good as I've only got a 60ah aux. battery. Obviously a bigger battery is a better option but it also means spending more money.
cheers
Not necessarily that much deeper (50% DoD normal batteries vs 70-80% DoD on some specific AGM Deep cycle), but more often without damage. They have thicker plates but fewer of them than a starting battery, and are therefore only able to deliver lower currents, but for longer periods of time without the mechanical issues of heat affecting the plates themselves.

A bigger, more appropriate battery now while in the planning stage may be a better option than being stuck out in the middle of nowhere with a dud battery at some stage in the future. Cheaper long term insurance against future problems.

Removing safeguards to compensate for planning inadequacies is asking for Mr Murphy's involvement............

Posted: Thu Apr 22, 2010 5:55 am
by sprungupcruiser
Good info, cheers for that, bigger battery it is then.

Posted: Thu Apr 22, 2010 7:51 am
by drivesafe
Hi sprungupcruiser, the cut-out voltage in the fridge is actually as low as the manufacturer of the fridge wants you to take the fridge and they don’t give a damn about the battery.

Any lower and the compressor motor starts to run hot.

But, at 10.5 volts, you are running the battery too low and if you really want to improve everything, use a much bigger battery and install a low voltage cut-out device that will cut out no lower than 11.5 for an AGM and 11.75 for a flooded wet cell battery.

Posted: Thu Apr 22, 2010 4:26 pm
by sprungupcruiser
oh ok.... my fridge is a evakool 55L model and it only lasts about 18-24 hours after a full charge(checked with the multi meter) before it cuts out. Does that sound about right or is there a problem elsewhere i.e. the fridge or the wiring?