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Thread: Kids Ride on Remote Car

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    Default Kids Ride on Remote Car

    The grankids have a 12volt ride on remote car and the charger has failed. I had tested it before it failed and it read 19 volts output

    I have an old HP charger from a laptop I think says 19.5 volt 9.23 amp output, could I use that ? ( see pics for both chargers)



    thanks Thomo



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    The original power pack indicates it is 12V output not 19V. Either way, I would not be using the 19.5V power pack on an item that requires 12V. Some devices may tolerate the difference, others will start smoking.

    The increased amperage output shouldn’t be a problem, the device (if built correctly) should only draw the amps it needs.

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    Well spotted, Peter. Any 12v D.C. supply that delivers 1 Amp at minimum should be enough, the only thing then is to ensure you have the correct polarity at the plug. i.e. +ve in the middle.
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    Bad news to let the smoke out its damn hard to collect and put back in
    . Please treat people as you would like to be treated yourself.

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    There are two reasons why you measured 19V.
    Either it was already faulty when you measured it or it is an unregulated transformer power supply. The latter is fairly thick and heavy. From the picture I can not determine it.

    Transformers are very rarely used these days but if this is an old item and a transformer is used you might not get the battery to fully charge with a modern switch mode 12V supply.
    That would be the case if the car used a 12V SLA or NiCad/NiMh battery as they need over 14V to fully charge.

    As a rule of thumb a 12W transformer would weigh about 400-500g and a modern switched mode supply roughly 100-200g.
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    Quote Originally Posted by Uncle Fester View Post
    There are two reasons why you measured 19V.
    Either it was already faulty when you measured it or it is an unregulated transformer power supply. The latter is fairly thick and heavy. From the picture I can not determine it.

    Transformers are very rarely used these days but if this is an old item and a transformer is used you might not get the battery to fully charge with a modern switch mode 12V supply.
    That would be the case if the car used a 12V SLA or NiCad/NiMh battery as they need over 14V to fully charge.

    As a rule of thumb a 12W transformer would weigh about 400-500g and a modern switched mode supply roughly 100-200g.
    Yea I beleive it is an unregulated power supply, and the battery is a standard 12 volt SLA 12Amp hour.

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    Quote Originally Posted by RedXT View Post
    Yea I beleive it is an unregulated power supply, and the battery is a standard 12 volt SLA 12Amp hour.

    Not easy to find these days, all the way from Italy and last one !


    I have exactly the same one, probably over 25 years old that I still use for experiments where I want a simple solution for the voltage to drop under variable load.

    Alternatively you could use the HP 19.5V charger with a ballast resistor about 7.5Ω in series to the car's charge port.
    To create this resistor you could use two 10W 15Ω parallel to each other:

    The resistors will get a bit hot when the battery is in bulk charge, so allow sufficient airflow.

    You need to check that the voltage on the SLA doesn't exceed 14.5V when it is fully charged and not kept too long near that voltage either.
    Last edited by Uncle Fester; 17-10-19 at 11:36 AM.
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    Actually with that 19.5V supply you just need to put a simple voltage regulator cct to drop the voltage to something useful. Back in the early days I actually built an analogue supply for my desktop computer when the PSU failed. The only issue that I had with that was the stray emf that made the screen go funny when I sat it on top. There was no Hard drive to worry about, I only had twin 360K floppies back then.
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    Quote Originally Posted by lsemmens View Post
    Actually with that 19.5V supply you just need to put a simple voltage regulator cct to drop the voltage to something useful. Back in the early days I actually built an analogue supply for my desktop computer when the PSU failed. The only issue that I had with that was the stray emf that made the screen go funny when I sat it on top. There was no Hard drive to worry about, I only had twin 360K floppies back then.
    Would something like this be OK


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    Quote Originally Posted by Uncle Fester View Post
    There are two reasons why you measured 19V.
    Either it was already faulty when you measured it or it is an unregulated transformer power supply. The latter is fairly thick and heavy. From the picture I can not determine it.

    Transformers are very rarely used these days but if this is an old item and a transformer is used you might not get the battery to fully charge with a modern switch mode 12V supply.
    That would be the case if the car used a 12V SLA or NiCad/NiMh battery as they need over 14V to fully charge.

    As a rule of thumb a 12W transformer would weigh about 400-500g and a modern switched mode supply roughly 100-200g.
    Yea the old charger weighs about 400g and I have tried a newer one and as u said it doesnt get the battery up to the required 13.2v

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    Quote Originally Posted by RedXT View Post
    Would something like this be OK

    No

    You don't want a constant voltage. You want something that regulates/limits current and maybe has a voltage limit, although the charge circuit in the car should do that but you never know.

    So you need something that allows you to adjust both.
    You need to be able to set the current to 1A and the voltage limit at around 14V.
    This is just a simple example, there are fancier ones that also have a display but you need two adjuster pots, one for current and one for voltage:


    Being a 12Ah SLA it may be possible to charge faster at a higher current than 1A but for some reason they used a 1A supply, so I would stick to that.
    Last edited by Uncle Fester; 18-10-19 at 10:12 AM.
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    Quote Originally Posted by RedXT View Post
    Would something like this be OK

    No idea with that one I built it from scratch using a dick smith kit IIRC.
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    The old one worked great and my initial search didnt find the exact charger, I have since found one on fleabay so I will try that first

    Thanks everyone for youre input

    Cheers Thomo

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