I’m using an AstroAl AM33D.
I replaced the alternator and battery about 3 years ago. My battery now sits consistently at 12.2 volts. When running the battery reads 13.9 volts without load and 14 volts under load (radio, fan, lights). After the engine is shut down the battery will uptick in voltage but will eventually settle back down to 12.2 volts.
When I check for a parasitic draw I get 0.56 amps.
The alternator is clearly charging the battery so it would appear that I have a failing battery.
My understanding is that with my meter set at 10 amps I shouldn’t see anything when I do the parasitic draw test. I don’t think .56 amps is a significant draw but, unless that draw is somehow related to an open hood, I’d have thought it would be enough to cause the battery to drop below 12.2 volts after not having been driven for a couple days.
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DIYer advice: 0.56 amps is a significant draw.
Small car batteries have a capacity of around 40 amp hours.
https://homebatterybank.com/how-many-amps-is-a-car-battery/
40/0.56=71. So it would take around 71 hours (3 days) for that draw to make a fully-charged battery totally flat. And less time than that for the battery to be too flat to start the car.
I’ve read that an acceptable draw should normally be less than 50 miliamps, which is 0.05 amps. So yours is 11 times as big.
BUT, it may be that you took that 0.56 amps reading without waiting long enough for everything to go to sleep.
since you have a multimeter run these six tests…
https://i.imgur.com/SnzhDh0.jpg
you did not mention year make model… obd2 cars have circuits that turn off after shutting down the car, getting out and closing and locking the door…
hooking the battery back up can activate these circuits so you could have a false parasitic draw reading.
obd2 cars… i lately with my multimeter have opened the hood, run the engine for a minute… shut down… got out… locked the doors, looked at the time… in 7 minutes… i set the meter to 20 volts DC and start probing both ends of every fuse in the underhood fuse block…
the fuse is a narrow spot in the circuit… so any electrons flowing thru a circuit… not stationary will show a slight voltage drop …
if you get 0.00 rerun the test at 2 volt DC scale… see if you find any fuses with tiny fractions of volt… note the fuse location… your owners manual will hopefully tell you what the fuse operates… access to wiring diagrams can tell you more…
you can then check the individual circuits…
this second step of the voltage drop test also takes just a few minutes…
to do a proper voltage drop test requires 2 short battery cables… a battery master disconnect switch… a set of volt meter test leads with banana plugs on one end and ring terminals to go on each disconnect switch post… you can disconnect the negative cable… hook the switch cables between it… by the way… this is a great use for dead battery jump start box cables and clamps…
do the set up as above. with slight variations. meter disconected… switch ON… run engine for a minute… shut off… take keys… get out… close and lock door… look at time… in 7 minutes. plug in the meter to the AMP ports… turn off master switch… get an accurate parasitic draw reading… you still don’t know which circuit is causing issues which is why i do the voltage drop across the fuses …
