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Battery question

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jazdz007

New Member
Hi all,

I have a question about battery power conversion

I have a 12V car battery that I am pulling 6V off using a car cigarette lighter outlet and a 6V plug in converter. I am powering a small circuit board that requires 6V. The question is, do I need to put any kind of voltage/charge regulator in between the battery and the cigarette lighter or can I simply hook the battery to the cigarette lighter to the 6V converter. The circuit board is really expensive and I don't want to ruin it.

Please email me an answer asap at:

[email protected]

Thanks

JDJ
 

stevez

Active Member
If the 6 volt convertor is rated for the load you intend to impose on it AND you have appropriate overcurrent protection for the wiring (and possibly the equipment) then it would appear that nothing else is needed.

A few questions that might be relevant:

1. A restatement of the above, the obvious, but I thought it best to restate it.

2. Can the convertor handle and suppress voltage spikes that are common to autos?? Will it pass those spikes on thru to your expensive circuit board? Maybe extra protection for this is required.

3. If the voltage regulator fails on the auto the system voltage can go extremely high. I've been told that auto systems designers allow for as much as 60 volts. This could occur if battery was removed and regulator failed to 100% output - at least on some autos. If that happens - will your convertor pass that on, possibly ruining your expensive circuit board??

4. Is the wiring adequate for the current source?? If connecting directly to the battery make sure you have a fuse or fusible link or similar to prevent a fire. If connected to cirgarette lighter - can the wiring handle the max current of the lighter socket?

There are some convertors that are modest in cost and that will do the job for general purpose use. What you have may or may not be suitable and I've shared a few of the things I'd consider if I were powering something relatively valuable.

FYI, except in special cases we reply to the forum, allowing others to share, add or even correct errors or misunderstandings.
 

jazdz007

New Member
It is not in an automobile. I just have a 12V car battery that I am using to remotely power the circuit board. Right now, the circuit board runs on a DC adapter that is 5V 1.0A. I would like to attach a standard cigarette lighter to the car battery terminals, and then just buy a standard 6V adapter to plug into the cigaretter lighter and run the 6V to the circuit board (I am told that the board will handle 6V just fine). So long as the 6V adapter only puts out 1A I should be fine, correct. I just want to make sure that as the battery dies and reaches the minimum operating voltage for the circuit board, it won't do anything that will damage the board. I'm not sure I need a fuse inbetween the battery and the cigarette lighter, as very little can go wrong to short this simple circuit out. However, eventually, I will add a solar cell to recharge the battery, in which case, then I will add a charge regulator to the design. About charge regulators, how do I pick on for the job?

http://www.etaengineering.com/regulators/pbr.shtml

I obviously want a 12V one, but is the amperage based on how many amps the photocell puts out?

Thnx again.

JDJ
 

JimB

Super Moderator
Most Helpful Member
Just a few quick comments.

Put in a fuse, at the battery terminals. Burning insulation and red hot wire is a sickening sight. Even in a "simple" circuit things can go VERY WRONG!

"cigarette lighter sockets" - YUK!
I realise that you are probably buying the converter already built into a cigarette lighter plug, but these things are horrible.

JimB
 

jtleo11

New Member
sorry, newbie to the board, but wouldn't a 7805 work ok with this project. also a 12 volt solar panal with a rectifier in series with the positive end of the solar panap to battery positive will keep the battery fresh. P.S. add a 1 amp fuse between output of 7805 and circuit board to protect it.
 
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Hero999

Banned
This thread is nearly two years old; somehow I think it's a bit too late.

Yes, an LM7805 would be perfect and there wouldn't be a need for a fuse since it's short circuit protected.

If transient protection is required then I'd use a 30V zenner in parallel with the circuit with a 2R2 resistor in series with it to limit the current surges.
 
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