Subject:
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Re: Overcharged NiCd Batteries?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 9 Apr 2002 22:18:59 GMT
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Viewed:
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7397 times
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I'm sorry, I didn't explain myself well enough. I meant to say that I used
the 500mA 12V power supply (block AC to DC transformer) by connecting it to
the handyboard. From the specifications, the handyboard is supposed to be
able to charge 800mAh NiCds with approximately 50mA with a 500mA supply.
Since I have 1000mAh, I was wondering if a 1000mA power supply would be
better. This would make the charge current about 100mA, right? I have read
that there were problems with 1000mA power blocks, and that is why i'm asking.
Jeremy
In lugnet.robotics.handyboard, Benton Jackson writes:
> Jeremy,
>
> You hooked it straight to a 12V power supply? That's kind of a brutal way to
> charge NiCad's. Who knows what that's going to do. If it's regulated at
> 500mA, then it should take just a little over two hours to charge a 1000mAh
> pack, which is a bit on the fast side. NiCad batteries can be left on a
> trickle charge for an indefinite period, although I think doing that is hard
> on them in the long run- but we're talking years. "Trickle charge" is
> typically 1/10 of the capacity of the cell, which is 100 mA for a 1000 mAh
> cell, and it should take a bit over 10 to 12 hours to charge at that rate.
> If you left it at 500mAh for 12 hours, they are probably cooked. The way
> they get destroyed is they overheat and "vent"- they have a valve that lets
> the electrolyte out before they explode.
>
> NiCad cells have a "nominal" voltage of 1.2 volts, which is 9.6 volts for 8
> cells. They can give up to 1.4 volts for a short burst with a fresh charge,
> whch would explain your 11 volts. Even vented cells can show a voltage with
> fresh charge, they just won't have any capacity.
>
> You might be able to tell if the cells have vented visually. Is there a
> white powder around the positive contact of any of the cells? Then they are
> surely toast. If there isn't, that doesn't mean they are OK- it doesn't show
> right away on all cells.
>
> -Benton
>
> P.S. I fly electric powered R/C planes, which teaches a lot about NiCads
> very quickly.
>
> In lugnet.robotics.handyboard, Jeremy Overesch writes:
> > Overcharged NiCd Batteries?
> >
> > Hello,
> >
> > I recently built a handyboard and bought a set of 8 1000mAh NiCd batteries
> > for it. I charged the batteries using the handyboard and a 12V 500mA DC
> > adapter from radio shack. I only charged the batteries for approximately 12
> > hours, and they seem to work fine. However, when I measure the voltage of
> > the batteries, it's higher than 9.6 volts, when they dont work any more. I
> > then tried a charger that charges at 150mA and left it on for approximately
> > 16 hours. The charger had not turned off yet when I stopped charging. The
> > batteries measured over 11 volts with no load. After draining the batteries
> > once again, I measured the voltage when I had the handyboard turned on. It
> > measured 7.8V. When I turn it off and unplug the batteries, the voltage
> > slowly rises to 9.4V. Is this normal or should I get new batteries? I was
> > also wondering if the 500mA power adapter is adequate for the 1000mAh batteries.
> >
> > Thank you for your time,
> >
> > Jeremy Overesch
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Message has 1 Reply:
 | | Re: Overcharged NiCd Batteries?
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| Aha, I know nothing about Handyboards, only about NiCads. I don't see why you need a larger power supply to charge slightly larger cells. Your handyboard is probably only drawing about 75 to 100 mAh to charge at 50 mAh, so a bigger power supply (...) (23 years ago, 10-Apr-02, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Re: Overcharged NiCd Batteries?
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| Jeremy, You hooked it straight to a 12V power supply? That's kind of a brutal way to charge NiCad's. Who knows what that's going to do. If it's regulated at 500mA, then it should take just a little over two hours to charge a 1000mAh pack, which is a (...) (23 years ago, 9-Apr-02, to lugnet.robotics.handyboard)
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