Question on Parasitic Draw

[rayfloyd170]

What is the safest value for parasitic draw in order not to drain my battery and render my car inoperable?


1.) I installed ultrasonic mouse/rodent repellant which says 40mA working and 5 mA on standby. It has ON/OFF switch and i tried switching it ON during night time. (i got no choice, an expensive hydraulic motor mount already was damaged and replaced, water hose for wiper fluid also had to be replaced because of rats/mouse)
2.) OBD 2 Bluetooth 4.0 - which says 3mA on standby
3.) generic keyless entry - with 5 actuators including the back compartment (i don't know the rating)

I am not sure if what i am doing is safe, i don't want to get stuck one day esp early in the morning while on the way to work.

Can someone please mention to me the safest parasitic current draw?

I normally drive my car everyday and parked it on average of 12-16hours at night.

Thanks in advance.

[mannycheckers]

You probably want to keep it below 100 mA or 0.1A. For most batteries, the capacity is 50Ah fully charged. 50Ah/0.1A = 500 hours or about 20 days.

In other words, if you have a fully charged battery, it will take 20 days of non-use to fully drain the battery with a 100mA parasitic draw.

This draw also degrades battery lifetime. Car batteries are designed to be "topped up" most of the time so it can adequately power the starter. Keep your parasitic draw as low as possible or look into installing a deep cycle battery. Deep cycle batteries are designed to be drained fully because it doesn't need to crank an engine.

*Edit* in your case you are probably fine.

[rayfloyd170]

Originally Posted by mannycheckers

You probably want to keep it below 100 mA or 0.1A. For most batteries, the capacity is 50Ah fully charged. 50Ah/0.1A = 500 hours or about 20 days.

In other words, if you have a fully charged battery, it will take 20 days of non-use to fully drain the battery with a 100mA parasitic draw.

This draw also degrades battery lifetime. Car batteries are designed to be "topped up" most of the time so it can adequately power the starter. Keep your parasitic draw as low as possible or look into installing a deep cycle battery. Deep cycle batteries are designed to be drained fully because it doesn't need to crank an engine.

*Edit* in your case you are probably fine.

Thanks a lot for your reply, good info where i can compare to my battery spec. Mine has only 45Ah.

I actually measured my parasitic draw yesterday and it showed 0.12-0.15A (120-150mA) with both OBD and ultrasonic repellant installed & the Add-on permanent keyless entry, by removing the OBD it showed 0.02-0.04A (20-40mA) only. But i know the OBD will shutdown only after 30 mins (standby when there is no activity) and will just consume 3mA as per the manual.

I think i am fine with my set-up. It will draw much at first 30min due to OBD and after that it will be drawing ~40mA current only. On top of that i am driving my car daily so it wont be an issue.