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Thread: Fully 100% automatic battery charger

  1. #1
    FLAC
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    Fully 100% automatic battery charger

    I'm looking for a fully automatic battery charger. Usually in the battery charger world, fully automatic just means it switches amps/volts automatically to suit the battery's charge state. That still requires a user interaction to start the charge process, however. I need a charger that I can just mount in the car and when you plug it in it starts, no questions asked.

    These are extremely common in boats but boat models are extremely expensive. I'm looking to get 15+ amps at a sub 100 price. Anyone know where I can find one of these?
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  2. #2
    FLAC
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    Guess not... Looks like I'll do one of two things: get a solar charge controller and have a desktop atx supply pretend to be a solar panel, or hack up my black and decker charger to get controlled by a fusion brain.
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  3. #3
    FLAC
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    this is the one i have- http://www.amazon.com/Schumacher-SS-...709713&sr=8-11

    had it for a year now. a couple things. first, its rugged as hell. i mounted mine to the back of the truck bed, so it gets rained/snowed on all the time.

    it doesnt need user interaction, just plug it in and it will start charging. however, it needs about 2 minutes without any major load on the battery... or any varying load. so if i have just my computer on (3amps) it still detects the battery normally and starts charging. however, if i have the stereo on (10a+ with varying load) the battery charger goes into default mode and i think it just trickles the battery until you unplug the charger.

    whats cool is that it DOES work as a power supply. just plug it in, wait for the bulk charge mode to engage (after a couple minutes) and then turn on your stereo or whatever you want. it will push up to 20a at 14v, so you can play music and leave your headlights on indefinitely and your battery will not discharge.

    the price is a little high i think, but free shipping makes it worth it. you might find it elsewhere. and its also large. look at the specs for size, basically its about the size of a basketball. its also heavy. weighs like 15 pounds. like i said though, this type of transformer/ecu charger should virtually never break.

  4. #4
    Raw Wave
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    Have you searched for circuits? There are various add-ons to add "smarts" to dump chargers.
    And there's always the CTEKs (LOL! Since I get 8 years from my batteries, it's cheaper buying new batteries!)

    Using a solar charger is a good idea - they are cheap for the Amps. (I got my ~15A/30A solar reg (kit) for ~$20 & 8A/2A 12V/6V AC charger for $30 - I've seen less for over $80 respectively).
    But you'd have to retune the ATX for over 14V...

  5. #5
    FLAC
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    trader007: Yeah that looks like a bad*** charger. Problem is I have no room to put the thing in my volvo S60 and yes it is on the pricey side, but nowhere near some of the other chargers I've seen!

    oldspark: CTEK does have quite a few cheap chargers, but it looks like none of them come in the amperage range I need. They have a 7 amp model which I could settle for, but it's 150 bucks. Other brands make chargers at that amperage cheaper.
    The input voltage on a solar regulator expects an input of over 14 volts?
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  6. #6
    Variable Bitrate
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    Quote Originally Posted by PaulF View Post
    The input voltage on a solar regulator expects an input of over 14 volts?
    You can't charge a 12 volt lead acid battery fully unless you can get at least 14.4V to the terminals. Proper topping charge voltage for a lead acid battery is 2.4V/cell.

    There may also be some cheap RV chargers out there.
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  7. #7
    FLAC
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    Quote Originally Posted by CraziFuzzy View Post
    You can't charge a 12 volt lead acid battery fully unless you can get at least 14.4V to the terminals. Proper topping charge voltage for a lead acid battery is 2.4V/cell.
    Oh I know that.... I just figured the regulator actually regulated and would be able to take the 12 volts and convert up/down. Guess it only goes down....
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  8. #8
    Raw Wave
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    No - regulators are usually linear step downs. You are thinking of dc-dc converters (like some MPPTs etc).

    But if considering a solar charger, some simple PWM voltage regulator should be fine - ie, drop 14-20V (whatever) to the typical 14.4V & 13.8V for battery charging.
    If you want to add charging profiles (boost, pulsing, etc), that's a different story. (So is dropping from 14.4V to 13.8V, but that's merely current sensing - maybe with temp as a backup.)

    If you can get any PWM charger, you should be able to modify it for higher current - swap its output (transistor or FET) for an appropriate MOSFET (>60A being common & cheap - from $2 upwards). And using a FET is much simpler than a transistor - no bias currents etc - just a suitable minimum on voltage (eg, 5V or more above GND or below the +ve supply rail).

    12V Solar regulators usually expect 22V or more input (21V being a common OC output voltage for many 12V panels).

  9. #9
    Constant Bitrate vull's Avatar
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    i need one too :s
    then i could bring the sound system into the house in the winter and still enjoy tha baassss?

  10. #10
    FLAC
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    Well, looking at the Optima website, the suggested charge rate is 10 amps.
    During lunch today I stopped by Advance Auto Parts to pick up some spade terminals and I happened to see this guy: http://shop.advanceautoparts.com/web...ci_sku=9200002

    10 amps. Automatic. Fairly small. $40. Perfect.
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