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Checking Cordless Drill Charger

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  • 09-11-2020 4:43pm
    #1
    coL
    Registered Users Posts: 302 ✭✭


    I am trying to check the charger for my cordless drill with a multimeter. The problem I am having is that the charger only has two terminals, a negative and one other that I assume is a neutral/ground/temp. There doesn't seem to be a positive.

    Can anyone tell me how I can check the charger is working??


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    #2
    colm_mcm
    Registered Users Posts: 73,387 ✭✭✭✭colm_mcm


    Do you have a multimeter?

    Are there any indicator lamps on the charger?


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    #3
    coL
    Registered Users Posts: 302 ✭✭coL


    Yes I am using a multimeter. The charger has indicator lights but they don’t come on even tho going by the multimeter it is charging the battery at least partially. I am trying to find out if the problem is the battery or the charger.


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    #4
    SchrodingersCat
    Registered Users Posts: 746 ✭✭✭SchrodingersCat


    Normally there are at least three terminals: negative, positive, and temperature for some of the older/more basic chargers. What is the brand and model?


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    #5
    coL
    Registered Users Posts: 302 ✭✭coL


    SchrodingersCat wrote: »
    Normally there are at least three terminals: negative, positive, and temperature for some of the older/more basic chargers. What is the brand and model?

    That's what has me stumped, this charger only has two terminals. It's a Workzone 20v drill and is less than two years old.


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    #6
    SchrodingersCat
    Registered Users Posts: 746 ✭✭✭SchrodingersCat


    coL wrote: »
    That's what has me stumped, this charger only has two terminals. It's a Workzone 20v drill and is less than two years old.

    That is mad, I haven't seen that set-up before. :)

    Normally the thermistor that monitors the temperature inside the batteries has two legs. They would tie one leg to the negative or positive and expose the other leg on a terminal with the negative and the positive terminals. This gives the three terminals. The charger charges the battery through the positive and negative and monitors the voltage on the temperature terminal to determine how warm the batteries are getting to reduce and stop the charge current if needed.

    My guess (and I could be completly wrong, I would be interested to hear what others think), this battery has one leg of the thermistor connected to positive. The charger is charging the battery through the thermistor and the negative terminal. If the battery heats up, it increases the resistance of the thermistor which reduces the charge current. I dont think ive ever come across this type of wiring before. I couldn't imagine that it is a very fast way to charge a battery.

    Anyway, yes, my guess is that you should be reading a voltage across the two terminals on the charger regardless. It should be around 20-24v (assuming that it isn't sending our a small voltage to see if a battery is connected, and then when it does detect it, it increases the voltage). If you don't read any voltage, the thing is probably fit for the tip.

    Is that a barrel jack connector going into the charger? Can you remove that and see if you can measure a voltage on the barrel jack? Stick one lead inside it and the other to the outside of it. If you don't measure a voltage here, then the wall wart might be the culprit. Read the spec on it. See if you can find a replacement somewhere that has the same voltage and the same or more amps rating. If the barrel jack is a different size, you could splice on the one from the broken wall-wart.


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    #7
    coL
    Registered Users Posts: 302 ✭✭coL


    SchrodingersCat wrote: »
    Anyway, yes, my guess is that you should be reading a voltage across the two terminals on the charger regardless.

    I should shouldn't I. To confuse matters it is charging the battery when the battery is dead but doesn't charge it to full capacity. The fact its charging the battery makes it difficult to establish if its a bad cell in the battery or the charger but either way I should be reading something from the terminals shouldn't I??

    Unfortunately the prongs on my multimeter are too short to get inside the barrel jack so I can't check if that's the problem.

    Worx are offering to replace it under warranty but will only give me a brushed cordless drill as a replacement whereas this one is brushless. I would prefer a brushless one and it seems like a waste to throw it away if its only the charger that's the problem.


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    #8
    Merrion
    Registered Users Posts: 1,419 ✭✭✭Merrion


    I'd think that the + and - indicated on the battery are for when the battery is discharging so you'd want to flip the polarity on your meter terminals to get a reading from the charger?

    (i.e. the charger should have the opposite polarity to the battery in order to load it)


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    #9
    coL
    Registered Users Posts: 302 ✭✭coL


    Merrion wrote: »
    I'd think that the + and - indicated on the battery are for when the battery is discharging so you'd want to flip the polarity on your meter terminals to get a reading from the charger?

    (i.e. the charger should have the opposite polarity to the battery in order to load it)

    My understanding is that the polarity shouldn't matter when reading with a multimeter as if the polarity is wrong I will see a minus voltage?

    Either way I have tried every combination and I cannot get anything to register on the multimeter from the charger!!


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    #10
    Merrion
    Registered Users Posts: 1,419 ✭✭✭Merrion


    It is possible - my own meter has a diode in so would never display a negative voltage.

    Another possibility is that the meter has too low a resistance for the control circuitry in the charger to "think" it should be doing anything - do you have a decent size resistor you could put between the multimeter and one of the contacts?


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    #11
    John.G
    Registered Users Posts: 3,468 ✭✭✭John.G


    coL wrote: »
    My understanding is that the polarity shouldn't matter when reading with a multimeter as if the polarity is wrong I will see a minus voltage?

    Either way I have tried every combination and I cannot get anything to register on the multimeter from the charger!!

    Re the barrel jack, you can just tape a bit of wire to lengthen one of the probes to get inside the barrel jack?. Or you may be able to attach two strands of very fine wire with the battery & charger to get a reading.


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    #12
    SchrodingersCat
    Registered Users Posts: 746 ✭✭✭SchrodingersCat


    John.G wrote: »
    Re the barrel jack, you can just tape a bit of wire to lengthen one of the probes to get inside the barrel jack?. Or you may be able to attach two strands of very fine wire with the battery & charger to get a reading.

    Yes, I would suggest using wire to attempt to lengthen one of the probes too.


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    #13
    whizbang
    Registered Users Posts: 1,924 ✭✭✭whizbang


    can you post a pic of the charger power supply wall-wart ?

    It could be just a slow charger, with the battery protection inside the battery looking after the safety bit.


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    #14
    coL
    Registered Users Posts: 302 ✭✭coL


    I didn't get a chance to check the barrel jack but I did open up the battery and take a look inside it.

    What I saw were the +/- terminals and also a 'C+' terminal which I assume is a positive for charging. After a little googling it looks like there is a sensor of some description either in the charger unit or the battery that senses when it is connected before it delivers a charge. This is obviously why the charger is not registering on my multimeter.

    Curiously when I check the positive on the first battery in the series and the negative in the last battery of the series directly (i.e. before it goes through the circuit) I get a higher voltage than if I test against the the final +/- terminals that the battery uses to connect to the drill. Not sure why this would be only that it might indicate a problem with the controlling circuit, any ideas?

    I should also mention what the problem I am having is. The charger has red/green lights to indicate charging/charged. One battery was not charging at all and neither of the lights were coming on. The second battery started charging and the red light came on but went green indicating a full charge pretty quickly then drained pretty quick when in use. Eventually the second battery stopped lighting the lights on the charger too but seemed to get a bit of a charge anyway (enough to do a few minutes of work). This is why I thought it might be a problem with the charger but now I suspect it might be a problem with the circuit in the battery.


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    #15
    John.G
    Registered Users Posts: 3,468 ✭✭✭John.G


    I think that high voltage you are seeing is normal enough, I have a 18V charger and its unregulated (no load) voltage is around 30V I think (but can check it later) when the battery is fully charged the loaded charging voltage is around 21/22V.


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    #16
    coL
    Registered Users Posts: 302 ✭✭coL


    John.G wrote: »
    I think that high voltage you are seeing is normal enough, I have a 18V charger and its unregulated (no load) voltage is around 30V I think (but can check it later) when the battery is fully charged the loaded charging voltage is around 21/22V.

    I'm not saying the charger is reading high what I'm saying is that when I open the battery case up and measure direct from the cells I am getting a different (and higher) reading than if I measure from the final +/- terminals that are on the outside of the battery case and which the drill connects to.

    I cant understand why there would be a difference between measurements at these two locations.


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    #17
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,536 Mod ✭✭✭✭2011


    coL wrote: »
    The charger has red/green lights to indicate charging/charged. One battery was not charging at all and neither of the lights were coming on. The second battery started charging and the red light came on but went green indicating a full charge pretty quickly then drained pretty quick when in use. Eventually the second battery stopped lighting the lights on the charger too but seemed to get a bit of a charge anyway (enough to do a few minutes of work). This is why I thought it might be a problem with the charger but now I suspect it might be a problem with the circuit in the battery.

    I would expect the charger to work perfectly of to fail completely, one or the other. Your post suggests that the charger is working to some extent so I would conclude that the most likely issue is that the battery performance has declined substantially. This is quite common.

    How old are the batteries?
    How much use have they been subjected to?
    What make are they?


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    #18
    coL
    Registered Users Posts: 302 ✭✭coL


    2011 wrote: »
    I would expect the charger to work perfectly of to fail completely, one or the other. Your post suggests that the charger is working to some extent so I would conclude that the most likely issue is that the battery performance has declined substantially. This is quite common.

    How old are the batteries?
    How much use have they been subjected to?
    What make are they?

    At the start I was t sure if it was the batteries or the charger and thought it would be easier to test the charger than it has subsequently turned out to be. It does look now like the batteries are the problem. They are around 2 years old with light domestic/DIY use. They are Workzone.

    Any suggestions on what to do now? The drill unit is decent and brushless so it seems like a shame to bin it for something that should be repairable?


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    #19
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,536 Mod ✭✭✭✭2011


    coL wrote: »
    They are around 2 years old with light domestic/DIY use. They are Workzone.

    As this is a DIY product sold by Aldi I wouldn't expect it to last any longer than this. Many argue that the likes of Hilti and Makita are overpriced but the difference is they last for many years.
    Any suggestions on what to do now?

    Personally I would buy a better quality battery drill. That way you can buy spare batteries if required in addition to the batteries lasting far longer and outperforming the Workzone offering.

    I sometimes buy second hand power tools from hire shops at a reasonable rate.


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    #20
    coL
    Registered Users Posts: 302 ✭✭coL


    2011 wrote: »
    As this is a DIY product sold by Aldi I wouldn't expect it to last any longer than this. Many argue that the likes of Hilti and Makita are overpriced but the difference is they last for many years.



    Personally I would buy a better quality battery drill. That way you can buy spare batteries if required in addition to the batteries lasting far longer and outperforming the Workzone offering.

    I sometimes buy second hand power tools from hire shops at a reasonable rate.

    Unfortunately budget constraints didn't allow for the purchase of a better drill at the time.

    Is there not a risk that even a good brand of battery will deteriorate if not used for long periods?

    From what I hear about buying second hand power tools from hire shops the batteries are usually gone anyway so have to be replaced.


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