I have a parasitic drain on my car battery. I have a fairly old Ford Fiesta brought from a second hand garage a year ago. It has a new battery. I went to one garage who did a diagnostic test and said it was the body control module and I would need to go to ford. Ford said they needed to do their own test ideally anyway they updated the software and told me to come back if any problems and that I would also need to buy a spare key. Since then I went away and I now seem to be jump starting it every day. Not sure what damage that would do? But I’m wondering about whether I should get a battery charger or paying more that the car was worth for a new body control module and spare car keys.

  • 1
    It could also be that the first garage didn't wanted to be bothered with your car, the BCM is fine and the drain is somewhere else.
    – Martin
    Sep 9, 2019 at 10:05
  • How big is the drain? How many amps?
    – Mark
    Sep 11, 2019 at 11:42

5 Answers 5


A cheap hack is to disconnect the battery every time you stop and leave the car, and reconnect it when you want to start the car and drive. Assuming the car keeps the battery charged while it's running, it's an easy solution.

If you want an easier way to disconnect the battery, you can get a switch.


Well, you can buy a charger for about 50 bucks that will deal with the symptom.

BUT you may find the bcm fails further and then you will need to replace it or the car... The charger will work on the next car...

Your choice.


A trickle charger is relatively inexpensive and can help you limp to the next stages of fixing the problem. But it will only help you launch from point A unless you pack it and take it with you, and it will suck to be without juice leaving from point B constantly.


First, if you are having to jump start your car every day, your current battery is toast (whether it is new or not). You may indeed have a parasitic drain that is the cause of your bad battery, but you still definitely have a bad battery. If it's been drained down more than a few times so much that it won't start the car, it's just never going to hold a charge anymore.

On the other hand, you may not have a parasitic drain at all, and it's just the poor state of the battery that makes it appear to drain down every day. But ultimately something caused the battery to drain. It could be a bad charging system, it could be a parasitic drain, or it could be the previous owner just left the lights on all the time (which will screw up a "new" battery just as easily as it will an old one).

If you get a charger, you are just putting a band-aid on the situation. You also need to definitely find out if the engine's charging system is fine or something is actually draining it when the engine is off. Further, running a bad battery for a length of time can cause wear on your charging system and ultimately you may have an alternator fail, which would then cause even a brand new battery to go bad. It's really a chicken and egg thing, and if you want to fix it you have to address all of the problems before any one thing can cause other parts of the system to fail, or you'll never make any progress.


a battery charger is good to have no matter what. I bought one of those jump boxes for $50 to have in case of emergency. Very smart move on my part.

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