Thread: Question for those auto electrically minded

Originally Posted by Graeme

How are you determining that the battery was fully charged, how old is the battery and does the fridge cut-out regularly?

I had been charging right up with CTEK chargers and then testing voltage and also running under load and testing around 20 minutes later. The aux battery is an optima blue top and barely 18 months old and not actually used that much.
I am trying to determine if it is the main battery draining it via the dual battery system, parasitic drain or just the fridge draining it.
Had the batteries fully charged and a 27 litre engel drained it in less than 8 hours below the cut out level. I used to get 4-5 days with an 80 litre running.
I may need to get a battery tester, possible the optima has failed I suppose.
Easy to do with a battery with caps and a hydrometer, but not as easy with the sealed battery. At least the AC Delco start battery has an indicator window.
I have found maybe with incorrect readings several drains, wether they are enough to cause the rapid drain not sure.
HF radio has some amperage turned off.
Voltmeter has some even turned off.
Fridge has some turned off but plugged in. Unplugged has none.
Elec brakes have some drain.
GPO has drain when usb plug put into it, rmoved no drain.
The other 6 odd have no power drain at all using same meter.
I would have thought there would be zero power drain on the fridge if plugged in and turned off.
HF maybe a small amount of power to keep memory.
Elec brake should be none, voltmeter should be none.
Cheers
Craig

Any device whose off switch is not an old-style mechanical switch will consume power whilst "off" because it has to have at least the power circuits active to know when the device is switched back on. The percentage of consumption varies with each device depending on how much of the circut the electronics shuts down, with older(earlier design) devices being worse than more recent ones. Even a USB power socket powers a voltage regulator chip regardless of whether or not a load is connected.

I agree that the battery should be given a proper load test once fully charged as a priority. I had a dual purpose calcium battery that got discharged too low a couple of times and it never regained full capacity even though its voltage indicated it was fully charged. Its still starting a small pump engine more than 5 years later but had become useless for running a car fridge.