Hello everyone. I bought a Ford Focus in 2019 (Mk4), ecoboost 1.0, 129CV I think. Everything works well, I like the car, the driving experience, and the engine response.

However, I have a battery issue almost since the beginning. The battery is drained after two-three weeks of no start. Unfortunately, I am becoming an expert on reviving the car. I saved a lot of money thanks to a portable jump starter…

The battery has been replaced at least once, twice if a I trust on a ford dealer that changed it for a new one when car was on guarantee.

I left the car to a couple of ford dealers, but for them everything is ok. After-sales service quality is very poor and shame, they go for the quick, easy, and cheap fix.

I am almost convinced I have a parasitic draw. After some hours the car stopped, a clamp meter measures around 300mA on the cable of the negative terminal. FordPass is disabled, and the car has no heated seats.

I need to take the car in a professional electrical engineer in order to analyse where the draw is, but meanwhile, I would like to prevent the battery drain when I go out for 2-3 weeks. I am thinking to disconnect the negative terminal, but someone told me this is not recommended as it might affect another internal battery for keeping the key code of the car and car settings.

It this true? Could anyone tell me if I can disconnect battery for 3-4 weeks without messing around?

Thanks in advance,

Antonio

4 hours ago, AntoineD said:

The battery is drained after two-three weeks of no start.

That would be normal for most owners, subject to the weather and temperatures and of course the State Of Charge when you parked it for 3 weeks.

A fully charged battery in excellent condition rated at 65Ah,  means the battery can provide 65Amps continuously for 1 full hour.

Time for some Maths:

A typical constant standby current drain on most cars these days is around 60mA

Parking up for 21 days = 504 hours

So that would mean a constant current draw on the battery of 0.06A x 504hours = 30.24Amps used.

If we assume that the battery was originally at a state of charge of 80% (which is the normal maximum) when parked that would mean the available capacity would be 52Ah

After the vehicle has been parked for 3 weeks and it has used 30.24Amps then that would leave only 21.76Amps (14.14%) remaining. The battery would be considered flat.