Vintage RC truck charger help

Discussion in 'General Electronics Chat' started by programmer6502, Jul 8, 2014.

  1. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    Hi,

    I have a vintage RC truck that lost it's charger in a move a long time ago. I've looked for the charger online but the truck is a little rare and there's no information about it (It's about 30 years old!). The charger was a wall wart but I have no idea what the voltage requirements were. So that being said, what can I safely use to replace it? The only information I have is that it takes four C cells and four AA cells. So that would be about 12v total? Now the golden question is, what amperage would I need to safely charge them?

    Thanks guys!
     
  2. wayneh

    Expert

    Sep 9, 2010
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    The C cells are likely separated from the AA cells and need to be charged separately, although 4 of each could be charged in parallel with the other 4 in a constant-voltage charger. After 30 yrs the batteries are likely shot.

    Is it impractical to simply remove the batteries for charging? Would it be hard to open up the truck to view the original wiring?
     
  3. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    Yes, I could remove the batteries and charge them separately but that would likely get old overtime :p (It actually doesn't have batteries in it but I know that's what it takes.) And answer to your question, since the truck is antique (RC wise), I wouldn't like to take it apart as it might loose some value.

    I don't know if this is any help but both the AA's and C's are in the same compartment and were charged by the the same circuit (inside the truck) using one wall wart.
     
  4. Austin Clark

    Member

    Dec 28, 2011
    409
    44
    The 4 C cells and 4 AA cells are likely charged in parallel. That is, each battery type is in series, but charged together in parallel.
    What doesn't make sense to me is why they didn't just use the 4 C cells on their own. Why use two separate types of batteries? Odd.
     
  5. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    I wonder the same thing!

    So do you guys think I could try using a 12v 1 amp wall wart? Then the truck could just draw the amperage it needs like a light bulb? The original wall wart just had a single voltage going in. Not dual or anything.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,127
    3,048
    No! I think the two types are in parallel so you need a 6V charger meant for the battery chemistry you are using. You should be able to probe with a meter and confirm this.
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,446
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    Having two sets of batteries is not uncommon. The four C cells are to power the motors while the four AA cells are for the receiver. Presumably the original batteries were NiCd.

    Is there a jack on the RC truck where you plug in the charger?

    If the batteries have been removed from the truck, simply go and buy rechargeable NiMH batteries along with a universal charger that charges both C and AA sizes.

    Or you can choose NiCd batteries.
     
  8. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    Yes, there is a jack on the truck for the charger. Okay yeah, I've been considering that. But it would be really nice just to use the built in charger.
     
  9. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    Gotcha. How would I use a meter to confirm this?
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    If you are going to use rechargeable NiCd batteries, I would get a charger that outputs 7.5VDC 350mA (or 500mA) maximum.

    Then I would charge the batteries at 1/10 capacity rate for 16 hours.
    For example, if the C cells are rated at 3500mAh, I would charge them at 350mA for 16 hours.

    How do you do this? I would put an ammeter and a 1W resistor in series with the charger output. Select a resistor value (try 22 ohms for starters) that gives you the desired current (e.g. 350mA) on the ammeter. Once you have found the right resistor value you can permanently wire the resistor in series with the charger output.
     
  11. programmer6502

    Thread Starter Member

    Feb 1, 2014
    126
    6
    Okay, sounds good. Thanks guys! :)
     
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