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Some basic help on electrics please. Ref using a power pack to run a dashcam.

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Submariner1, Jan 14, 2018.

  1. Submariner1

    Submariner1 Senior Member

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    Very embarrassed to ask, but I need some education.

    Electric Logic:
    My understanding is a device will only pull the current (Amps) needed to operate it. i.e. say you plug in a tyre pressure pump and it says its rated at 3 Amps. Just because the cigar lighter socket is rated, and I guess fused at 15A. Your tyre pump would only draw 3A. Maximum.
    Q1. Is the above correct?

    If hopefully yes,
    Q2. does the same apply to “USB chargers”?


    Requirement:
    My dashcam says one must use the supplied Cigar Plug lead, that plug thing converts the 12V cigar socket (rated at max 15A) into 5V and 1A (sadly on a moulded cable terminating in a USB Micro B male, which you insert into the dashcam.

    I need to find an External Battery Pack to power the dash cam in “Parking mode”. I.e. once the ign. Powers down.
    Ideally I would like a power pack, that had a 12V 2A female cigar socket output.
    But I cant find one with a LiFePO4 battery in it (safer than Lithium Ion batteries).

    I have however found a near perfect substitute, other than it only has two USB type A output sockets rated at 3.1A each. But No female 12V cigar socket. :(

    My thoughts are:-
    Get a Cigar plug charger with a 5V 1A output, and buy a USB type A to USB type Micro B. To run the dashcam when I am driving. I.e. powered by the car socket ... no issues there.

    I could then pull the USB type A end out of the cigar plug charger , and insert it into one of the battery pack’s USB Type A output sockets (rated at max 3.1A).

    My concern is ... unlike most simple electric circuits, where the dashcam would only draw up to 1A, because that is what it is rated at; would the battery-pack “charger”, (because essentially that is what it is .. a charger) force out 3.1A and essentially send too many amps into the dashcam and either burn it out, or blow an internal fuse in the dash-cam?
    Or
    Would the dash-cam just take 1A?


    My fear is based on the minimal experience of Apple chargers. Namely the iPhone 6 plus came with a 5V 1A charger, and the iPad Air came with a 5V 2.1A charger.
    If you accidentally charge the iPhone with the iPad Air’s charger ... it takes about half the time!
    Ergo I assume its sending 2.1A into the phone not the prescibed 1A.
    And the Apple salesman, did say it was not a clever thing to do .. as it would shorten the iPhone’s battery’s life expectancy.

    My other concern is when one reads that it has “intelligent circuitry to maximise the charge” and names a few devices like an iphone or samsung. What happens when it doesnt know what the device is ?
    Does it force the maximum current out?

    A quick education in basic electrics would be much appreciated.

    As I would hate to fry my new dash-cam LOL

    Proposed external battery / charger
    Tqka 20000 mAh portable charger £19 at Amazon
    Tqka 20000mAh Portable Charger, 3.1A Dual USB Output Smart Charge External Battery, Ultra High Capacity Power Bank with LED Digital Display for iPhone, iPad, Samsung and More - Black https://www.amazon.co.uk/dp/B073QQPKVY/ref=cm_sw_r_cp_tai_HZRwAb6Y5PVGF

    Of course the official option is to buy a Cellinc Neo for £200! And thats only rated at 6000mA!
    ... not good value.
     
  2. umblecumbuz

    umblecumbuz Senior Member

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    Charging a battery (your iphone and ipad for example) is a little different from assessing the rating - stated amperage - of a known appliance.

    As an example, you can charge a Tesla at home from your domestic socket and it will take all night, but you can also charge it in minutes from the Tesla Supercharger network (find one first!). That's what you did with your phone and tablet.

    If an appliance states that a certain amperage is required to run it, that's what it will draw, no matter what the available amperage at the power source. Plug an appliance into a power source - dashcam into car battery for instance - and the same source is used whether the dashcam is operating or is on standby (higher or lower amp draw).

    That's my understanding as a total layman. I now stand ready to be instructed further.
     
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  3. LostKiwi

    LostKiwi Senior Member

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    An electric device will only draw the current it needs. So a 1A device in a 15A socket will only draw 1A. The socket rating is the maximum the socket can safely supply.

    If you look at your mains wiring you have 13A sockets. Your iPhone doesn't draw 13A to charge it does it (if it did it would get very very hot - 13A is less than a kettle takes)?
     
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  4. Frontstep

    Frontstep Senior Member

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  5. Paul Goff

    Paul Goff Senior Member

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    The critical things when supplying any electrical device or appliance is that the SUPPLY VOLTAGE must meet the specification required by the device.
    AND the supply must be CAPABLE of supplying a CURRENT greater than or equal to, the maximum current that MIGHT be required by the device in the course of it's normal operation.

    The voltage stated is what it WILL provide, the current stated is the maximum it CAN provide.

    All that information should be clearly marked on both the power supply and the device. Except for wall outlet sockets! It can be assumed in this case, that the supply will meet the appliance specification of anything that has been fitted with a suitable plug by the manufacturer.

    Battery charging is more complex, Lead Acid batteries have very different requirements for controlled charging compared with Lithium, Ni Cad & NiMh batteries. However, quality devices which contain any of the above, or similar, carry out their own control of charging and therefore the niceties need not concern us, provided that the device is connected to a supply which meets the required specification.

    The vital difference between the two battery groups is that Lead Acids need the charging VOLTAGE to be strictly controlled.
    Whereas the others need the CURRENT to be LIMITED, to what extent varies widely between the types.

    To what extent the current limiting needed when charging a smartphone is carried out by the charger, as opposed to within the device itself, I don't know! However I really would not worry about any loss of battery service life caused by halving charge time by dint of using a 2A charger instead of a 1A one, providing charge time isn't much below 1 hour, it will be fine.
     
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  6. ajlsl600

    ajlsl600 Senior Member

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    despite the nextbase instructions i wired my dashcam direct to the lighter socket via a , i cant remember which,a 1 or 2 amp fuse. and into the circuit board of the fag lighter adaptor, which i removed from the nextbase lighter adaptor lead and encased in something like platicraft resin. nextbase wanted me to give another 20 plus for the hardwire kit my dashcam is working just fine, car running cam on car off cam off.
     
  7. OP
    Submariner1

    Submariner1 Senior Member

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    Thanks everyone.
    So it works like I think it should. I just thought I would check, when I saw the phrase “ intelligent charging to maximize the charge” that they were not managing to boost the amps out.
     
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  8. OP
    Submariner1

    Submariner1 Senior Member

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    I discounted these ( see my post on Battery ) becaus they fundamentally drsin the battery and then cut off. Not so good for a low mileage car circa 2,500 miles per annum.

    I prefered these, as the dashcam is powered from a LiFePo4 battery bank when the ign. Power is cut.
    https://www.ebay.co.uk/i/2923945537...3D710-134428-41853-0%26rvr_id%3D1414579299235

    But I didn't like the £200 price tag for only 6000mA. :):)
     
  9. Frontstep

    Frontstep Senior Member

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    Don't they have a battery protection circuit to prevent flattening the battery ?
     
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  10. OP
    Submariner1

    Submariner1 Senior Member

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    You can buy them as a £48 extra.
    But not so clever as, my battery voltage varies so much.
    E.g. after 3 days of non use, it might read 12.1 Volts momentarily after opening the doors, which recovers to 12.4V. When they are shut again. Likewise in daily use or after a top up charge with the CTEK; then the corresponding figures are 12.4v after opening a door, wing mirrors opening etc. And then recovers to 12.6V or 12.7V.
    There is no documentation to see if it auto resets, i.e. will it come back on when the voltage rises?
    So if you set it to 12.3v as a cut off in general use ( i.e. if it sees < 12.3V it cuts off ). Then this means it will drain the battery quite a lot before its active.
    Hence my investigation into a back up (LiFePo4 powered) solution. So in Parking mode it only runs off this back up and not the cars battery. So far it looks like it would cost about £50, so for me being a low mileage user, thats a better route.
    Note my CL was a later model, only having a single battery.
     

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