Connect with us

12v Powerbox for Camping/fishing

Discussion in 'General Electronics Discussion' started by Carlrizzo, Apr 13, 2014.

Scroll to continue with content
  1. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    I want to build a portable power supply to take when I go fishing.
    This will be to power mobile charger, USB for my ecig, portable DVD, led light etc.

    I would like to be able to switch the unit on and off, recharge via mains and solar and also feature a battery volt and amp meter. Also wondered if it would be an idea to fit a fan with a temp sensor to keep cool?

    Basic electronics knowledge so would appreciate some guidance on what I need and how to fit together.
    Thanks all
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,443
    2,628
    Nov 17, 2011
    Welcome to our forum.

    Your request is a bit on th ebroad side of the spectrum, lacking details like:
    • What capacity (in Ah or mAh) do you need?
    • Have you decided on a battery chemistry (lead acid, NiMh, LiIon...)?
    • Do you already have a charger or do you want the charger to be part of the box (Probably not unless you want to carry it around)?
    • What power requirements do the loads have (Volts, Amperes)?
    A quick and dirty solution could be build from only a 12V car (or bike) battery and a few cigarette lighter receptacle.
    You can charge the battery via one of the lighter receptacles from from a standard car battery charger.
    You can get 5V (USB) using one of those small adapters for operating USB powered devices in a car - just plug it into one of the receptacles (or integrate it into the box, leading only the USB receptacle to the outside).
    You can get any other voltage by adding a suitable regulator to the box plus the necessary receptacles.
    Turn the box on or off with a master switch that interrupts the 12V power from the battery.
    You probably don't need a fan and temp sensor, as car batteries are designed to operate at comparatively high temperatures (think summer, under the car's hood).
    You could integrated any components (e.g. radio, CD player, speakers etc.) that are designed for cars and operate them directly off the 12V battery (behind the master switch, off course).

    Regards,
    Harald
     
  3. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    Thanks Harald, the max period I am away is a week so was thinking about 14a, won't be using the mobile a lot but will be wanting to charge the DVD, I have seen the 12v adapters for a car that increase the sockets to 3 and include a USB, was thinking could that just be wired in permanently.

    Would appreciate some advice on battery type, was looking at mobility scooter batteries.

    I can buy one all built but they are a low ah and seem costly for what is pretty simple
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    You could also try Googling rechargeable power pack. There are many kinds available.
     
  5. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    I would like to build my own as the amps seem low on the ones you can buy
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Fair enough.

    You're going to be carrying this in a backpack, right? So you want to minimise weight? Have a look at http://en.wikipedia.org/wiki/Rechargeable_battery#Table_of_rechargeable_battery_types. I don't know how up-to-date it is, but it should give you a good idea of which technology to go for.

    You'll probably want a separate charger; I'd suggest buying a commercial one. Do you want to be able to recharge your power pack from your car battery? That seems like a valuable feature...

    Apart from that, Harald's suggestions sound good to me. You can get digital voltmeters and ammeters on eBay, as well as switching power supply modules to generate the 5V supplies you need. I'd suggest using a battery voltage between 12V and 24V or so.

    Edit: I kind of doubt that recharging via solar will be feasible. You need quite a large surface area to get any decent amount of energy, and solar panels are bulky and can be expensive. I could be wrong though. Check out some specifications. Beware of no-name Chinese products - the specifications can be too good to be true, literally.
     
  7. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    Thanks all, couple of other questions, do I need to fuse each adapter I fit or just a fuse at the master on of switch, I am going to have 3 12v sockets and 2 USB?

    Also what would be the best way to show the battery charge level?
    Thanks
     
  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    I recommend fusing each outlet separately. For this application, PTC resettable fuses are a good idea. See http://www.digikey.com/product-search/en/circuit-protection/ptc-resettable-fuses/656272?stock=1 and for some typical components, http://www.digikey.com/product-detail/en/0ZRC0025FF1E/507-1332-ND/1560187 http://www.digikey.com/product-detail/en/0ZRC0050FF1E/507-1336-ND/1560191 http://www.digikey.com/product-detail/en/RUEF090/RUEF090-ND/1045799 http://www.digikey.com/product-detail/en/RUEF250/RUEF250-ND/1045776

    You can connect an LED and series resistor across these devices, and the LED will light up when the PTC fuse opens, so you can tell that there's a problem.

    Incredibly, a US patent has been granted on this new application of a very old and well-established idea! See http://www.google.com/patents/US20050062579 And I thought that patents had to be non-obvious!

    That's a bit tricky if the charger is external to the unit and cannot monitor the current being drawn from the battery as it discharges. There are smart ICs for use in battery packs that try to track the battery energy, but of course you would need a way to read the device and display the result. I have no experience with these devices but you could Google for battery pack energy monitor IC, or something like that. That is probably the best option.

    Otherwise the charger could just charge the battery using standard end-of-charge detection (rate of temperature rise etc) and discharge it "blind", with no way of knowing for sure when it will run out. If you use a removable battery pack, you could carry a spare.

    Or someone else may have a better idea.
     
  9. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    Thanks for that, probably going to get a pair of 14ah 12v mobility scooter batteries, I will be charging the phone, powering and led strip light and running a portable DVD so this would seem to give me enough power for a week?

    I did look at using a 12v lipo that was on fleabay but the review wasn't great, weight isn't a huge factor, just want something powerful and not too expensive.

    You would recommend that fuse option rather than a standard inline blade?
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Here are some calculations.

    Battery capacity: 14 Ah @ 12V = 168 Wh. Treat this as a maximum; a typical figure might be 140~150 Wh.

    Mobile phone charger 1A @5V = 5W ÷ 0.7 for 70% converter efficiency = 7.2W * 4 hours to recharge (sounds about right) = 29 Wh.

    I don't know how much power your electronic cigarette, portable DVD player and LED light use, but you can do the calculations in the same way.
    Your call. Make sure the batteries are really well sealed. You don't want sulphuric acid leaking into your backpack!
    Yes. You don't need to take spare fuses!
     
  11. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    Thanks Kris, last thing I promise!
    Would like to include a digital ammeter and voltmeter. Voltmeter to keep an eye on the battery and an ammeter to check on the drain from any connected devices. As this will be wired in parallel is this possible?
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Yes.

    Many people buy digital meter modules cheap from eBay. I don't recommend it, but here's a current meter that might be suitable: http://www.ebay.com/itm/Yellow-LED-...107?pt=LH_DefaultDomain_0&hash=item5663ccd2a3

    This one monitors the current in the negative lead of the battery. That should be OK. It can be powered from the battery. You might want a switch to save battery power when you're not interested in the meter reading.

    Digital voltmeters are available too. Just make sure the measurement range fits, and the power supply range fits too. Most of them are only three digits, and if you're measuring a range of around 10~15V, the first digit is effectively wasted and you'll only get one digit below the decimal point, which might not tell you enough. So you could consider getting a four-digit module.

    If you would rather not try your luck with eBay, there are companies that sell these modules. I would start by searching for digital voltmeter modules and digital ammeter modules on digikey.com and mouser.com, or Google.
     
  13. Carlrizzo

    Carlrizzo

    9
    0
    Apr 13, 2014
    Kris thanks for all your help
     
  14. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    You're welcome :) Good luck! Please let us know how it goes.
     
  15. morphingstar

    morphingstar

    56
    1
    Mar 1, 2012
    I used an analogue VU level device, with a 8 vdc zener diode and a resistor in series. The 3 color scale can be used as good / critical / warning, depending how you calculate (Ohm's law required) and calibrate the circuit. I use 12 to 14(15) as good, below 12 as warning, above 15 as critical. Whatever you fancy. The zener eliminates useless range. The device needs no separate power to operate.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-