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Expected Current Draw When Car Is Asleep - Ford Fiesta 2014


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Hi all, 

I have checked my battery for parasitic drain and it is drawing 0.10-0.11A (fluctuates between this range). 

This is after I leave vehicle for 30 mins or so. 

I've pulled most of the fuses except for the big bulky ones but none of them seem to make it drop any lower than 0.1A.

The radio seems to turn on briefly (says "Traction Control On") when I put F24 (Sync, Bluetooth) back in after I remove it (rises to about 1.5A and then returns back to 0.10-0.11A). Not sure if this is expected? 

So my question is what is the expected current draw and is 0.11A acceptable?

Vehicle is Ford Fiesta 2014 1.0L EcoBoost. 

Thanks! 

David 

 

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To be honest, a current drain of only 100mA is fantastic ! You don't have a problem.

What is the concern you have ?

Just for your information as an example see the following:-

A Telematics (Black Box) draws about 50 to 100mA when at rest. So if a vehicle was parked up and not used for a couple of weeks then yes it would drain the battery.

If you take a typical car battery and say it has a capacity of 56AH then that means (in theory) that the battery could supply 56 Amp continuously for 1 hour before being flat. Or to look at it the other way around the battery could supply 1 Amp continuously for 56 hours.

Just to keep the maths easy if your Black Box was using 100mA (= 0.1 Amp) then it would take 560 hours to run the battery flat.

Of course in real life once the battery voltage falls much below 11 Volt then you risk your car not wanting to start. Depending on how good a battery you have and how well it was charged when you parked the car will alter how long it is before your battery is too weak to start the engine.

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56 minutes ago, unofix said:

To be honest, a current drain of only 100mA is fantastic ! You don't have a problem.

What is the concern you have ?

Just for your information as an example see the following:-

A Telematics (Black Box) draws about 50 to 100mA when at rest. So if a vehicle was parked up and not used for a couple of weeks then yes it would drain the battery.

If you take a typical car battery and say it has a capacity of 56AH then that means (in theory) that the battery could supply 56 Amp continuously for 1 hour before being flat. Or to look at it the other way around the battery could supply 1 Amp continuously for 56 hours.

Just to keep the maths easy if your Black Box was using 100mA (= 0.1 Amp) then it would take 560 hours to run the battery flat.

Of course in real life once the battery voltage falls much below 11 Volt then you risk your car not wanting to start. Depending on how good a battery you have and how well it was charged when you parked the car will alter how long it is before your battery is too weak to start the engine.

Thanks for the reply. Ok was just wanting to check as I have been having trouble with my car starting after not driving it much recently. I thought it was something to do with my audio unit staying on even in sleep mode but pulling those fuses doesn't seem to affect it. 

My battery is 65Ah so essentially should last for 650hours (~27 days) with a 100mA drain. Recently its been dying after a week or so (maybe even less) but maybe that's due to the cold weather? 

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1 hour ago, david795 said:

Thanks for the reply. Ok was just wanting to check as I have been having trouble with my car starting after not driving it much recently. I thought it was something to do with my audio unit staying on even in sleep mode but pulling those fuses doesn't seem to affect it. 

My battery is 65Ah so essentially should last for 650hours (~27 days) with a 100mA drain. Recently its been dying after a week or so (maybe even less) but maybe that's due to the cold weather? 

how old is the battery? also have you checked that the battery is actually fine?

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Hi David, I can understand that your car might not want to start after 2 or 3 weeks. The battery will need to have at least 65% of its capacity left in order to have enough power to start the engine. So if we assume that due to the age of the battery and how well it was charged when you parked up, plus the cold weather recently then your 65Ah battery may be a lot less than you think - say perhaps only 90% which is about 58.5Ah.

Then if we say the battery needs to be 65% of that to have a fair chance of starting the car than would mean you would need 38Ah left. So if we take the 58Ah we started with and subtract the 38Ah that we need to start the engine then that means you afford to use 20Ah on standby which is about 8 days. Forgive me if I've got the maths wrong, but I'm sure you can get the idea that after just over a week of doing nothing your car might not have enough left in the battery to start.

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