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Charging 12V mini-pack from car battery

I need to run a 12V low-power electronic device from a small rechargeable battery pack.

Could such a pack be recharged or maintained at full charge by leaving it plugged into a car's 'cigar lighter' socket more or less continuously, whether or not the engine is running?

If not, what additional components would be required to avoid run-down, overheating, exhaustion etc?

Alternatively, is there a cheap commercial device for trickle-charging a little 12V pack from a big 12V DC source?

What type of batteries would be most suitable?

Lionel

Reply to
lion_elk
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To plug into a car system with no other circuitry, use a 12V gel cell (sealed lead-acid). They'll happily coexist with your car system. I think you can even get 2V gelcells in approx. D size - just a sec...

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Yeah, but it isn't worth the bother, if you have room for one of the boxy ones. :-)

Good Luck! Rich

Reply to
Rich Grise

Thanks - I'll chase this up.

Lionel

Reply to
Lion_Elk

A typical 12 pack wont charge unless the engine is running, unless you boost the voltage with a dc-dc converter. alternativly if you can get away with spliting the pack into 2 x 6 volt ones .. you realy need something to limit the current for a smal pack and it depends what type it is how big etc, eg resistor, current controled regulator, at the very least a fuse !

I tend to use AA size NimH @ 2AH as theyr quite versatile and easy to get. depends how much capacity you need, and how much you want to pay.

Colin =^.^=

Reply to
colin

Colin - thanks.

There'd be no problem limiting the charge period to when engine is running - if I add a diode to prevent discharge could that dispense with the DC-DC convertor?

I reckon the AAs you suggest would suit my purpose - what rating fuse and/or regulator would I need?

Lionel

Reply to
Lion_Elk

Hi,

I would use a small 12 volt gel-cell. Connect it to your cars accessory line via a shotkey diode. This will charge the gel-cell to nearly full charge when the car is running.

Luhan Monat (luhanxmonat-at-yahoo^dot^com)

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"Reality: what a concept!"

Reply to
Luhan

If you add a diode to prevent discharge, you'll drop voltage across the diode and the Batt won't charge fully.

car +12 -->|---+-------Device Gnd | Batt | Gnd

Just take the +12 from a wire that is +12 only when the ignition switch is on.

This all presumes that the battery you are using is the same technology as vehicle battery.

Ed

Reply to
ehsjr

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