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I want to determine if it is possible to chain together smaller household batteries to produce the equivalent output of a 12V car battery (temporarily).

There is a practical reason for this bizarre query ;)

My car has an electric latch for the bonnet/hood. The issue is that the battery is flat and does not have enough power to pop the hood to get the battery out and recharge it (chicken and egg, I know!).

The manufacturer has provided a workaround, in that a spare car battery can be used with a set of jump leads to attach to a special fuse that will pop the hood. The problem is that I don't have a second battery.

Logically, the only thing that is needed is to send some power through this fuse for a short enough time to active the hood latch (negative on the door handle, positive on the fuse). My question is, can I achieve this with a combination of all the batteries I am surrounded by?

In theory, I should be able to take 8 AA (1.5V) batteries and chain them together to get the 12V the car hood latch circuitry is expecting. But I'm also aware life is never that simple and I that know little more about electricity than a child.

Hope this is enough for someone to inspire a DIY solution to this simple problem. Thanks in advance!

Peter

migrated from electronics.stackexchange.com May 21 '16 at 14:35

This question came from our site for electronics and electrical engineering professionals, students, and enthusiasts.

  • You can't call a friend who has a working car? (and some jumper cables) – Dave Tweed May 21 '16 at 14:35
  • If all else fails, an angle grinder can solve this. – Aaron Lavers May 23 '16 at 3:42
  • Can you try a 'memory saver' that connects a 9v to the cig lighter? – rpmerf May 23 '16 at 20:25
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Absolutely! In fact, you don't even need the amount of power which would come out of a standard battery to accomplish your needs. You just need enough power to get the hood to pop! Really, all you need is a 12vdc power source. A truly easy source of this would be to get one out of a battery backup system from a garage door opener. Another way to do it is to connect two 6vdc lantern batteries in series. You will need some amount of amperage to make this happen. I'm not sure if eight (8) 1.5vdc batteries would be enough, but it might be. Secondarily, you'll need to ensure you are hooking it up correctly, but running it through the fuse panel is not a bad idea. Another way to hook it up would be through the cigarette lighter port (or in-dash 12vdc power plug). It will get you directly into/onto the power without too much of a problem, plus the wiring would be enough to handle the amount of amperage needed to run the hood latch. Ensure you don't have any other power on when you do this (leave the key off and door shut). Having such a low amperage source of battery on the car may cause electrical issues with the computer or other sensitive electronic devices.

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You can do it, as long as it does not take huge amounts of current. Make sure you ground the batteries' ground to an UNPAINTED screw.

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It really depends how much power the "popper" needs to pop:

  • 8AAs might be enough,
  • 9 or 10 might work better (15V isn't going to damage anything)
  • or you might need fatter batteries, C or D

on the other hand it may be that your charger can be connected to the fuse and have enough power to work the latch.

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