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Battery charger - cordless drill Ryobi

Discussion in 'Electronic Repair' started by RichK, Sep 9, 2005.

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  1. RichK

    RichK Guest

    Hi,

    More of a puzzler, than repair.

    Item in question is Ryobi cordless drill 7.2V. Bought it with one battery
    and charger. Added another 7.2 V battery from home depot. All's fine some
    far. When I charge the battery, the charger gets somewhat warm, but seems
    normal.

    Later I found batteries on sale at HD and bought two more. These are
    physically the same and came with short adapter cable for the old charger,
    which had bigger plug. These batteries have a differnet p/n but according
    to Ryobi have the same capacity in mAh and clearly the same voltage. When I
    charge these NEW batteries, the charger gets much hotter.

    Called Ryobi and confirmed all numbers, both batteries are 1300mAh. The
    charger recommended with these new batteries has a different p/n and also
    has lower current rating (200ma vs 400ma original).

    Why would batteries of the same capacity and design, overheat the charger,
    while others do not. TS at Ryobi is not very helpfull. If anything a
    higher cap charger should be less likely to overheat, and it's behaving
    "backwards".

    Rich
     
  2. webpa

    webpa Guest

    Why do you think the charger is "overheating"? In a practical sense,
    if the charger isn't melting or smoking, then it is probably working as
    designed.

    Why do you think the new batteries are of the same "...design"? If they
    were, then they wouldn't draw any more current from the charger (thus
    making it run hotter) than the old batteries. Seems possible the new
    battereis are, in fact, not of the same internal design. The cells may
    use a slightly (or entirely) different chemistry and/or physical
    construction, even though they have the same voltage and current
    ratings. Over the past few years, battery technology has changed very
    substantially, and many of the improvements have been aimed at
    permitting faster charging. Another fact is that no two manufacturing
    facilities make "NiCad" or "Ni-Mh" or "Lithium" cells exactly the same
    way...even when building to the same specs. Finally: If the new
    batteries require an "adaptor cord" to attach them to the old charger,
    that is a pretty substantial hint that SOMETHING is rather different.

    Bottom line: If the new batteries charge and then power the drill, use
    them until they fail to do so.
     
  3. RichK

    RichK Guest

    ----- Original Message -----
    With the older batteries, the temp of the charger is at a level that I can
    touch and hold my hand on it during the charge cycle of several hours.

    Same charger and new batteries - after 20 min I cannot hold my hand on it.
    I disconnect it and let it cool. Then plug in again.
    Perhaps this is the question - if they are. Both have the same voltage, mAh
    rating. If Ryobi tech support was better, they would explain the diff.
    There cleary is some diff, as evidenced by the heating of the charger.
    This is why I'm asking the question. Did not think that slight difference
    in chem or construction would make that much diff. NiCad batteries have
    been made for ages and used the same chargers.
    Only one of these 4 batteries clealry says NiCad on it. All others are
    missing that info, although they are meant for the same drill.
    The adapter is a short piece of wire that changes the plug - no electronics
    involved. It is sold with these new batteries to all usage with existing
    chargers.

    The mystery is that these apparently "very similar" batteries have such a
    different characteristics, when it comes to charging.
    In a way they do, but I have been babysitting the charging process, being
    afraid to just leave it on for a long time - fearing a meltdown of the
    charger.

    Would be much nicer if Ryobi provied good info on their products, so I would
    not have to bother folks here :) Of course you do not find out these
    things until after you buy it and a bit later try and observe.

    Rich
     
  4. Ken Weitzel

    Ken Weitzel Guest

    Hi...

    Have no idea at all, but thinking out loud....

    Wonder if the charger wasn't made to charge either regular
    or "quick charge" cells. If so, is it possible that
    there's a current limiting resistor inside the battery
    packs? (in your case, a different value in each of yours)

    Take care.

    Ken
     
  5. Ross Herbert

    Ross Herbert Guest

    Ryobi (Japan) sold their brand name to Hong Kong based Techtronic
    Industries in late 1999. Since then Ryobi branded power tools have
    been made in China and they are not a patch on the original Japanese
    made tools, especially when compared to the old Ryobi Tradeline series
    (blue green casing) which were really robust.

    I bought a Chinese Ryobi 14.4V drill a couple of years ago and it came
    with 2 battery packs, all for around AUD100. After a week of use I
    discovered the batteries would not hold a charge and the charger also
    ran pretty hot. Opening the battery packs (screws only securing)
    revealed the NiCd's were of Chinese origin and the battery charger
    design was woeful. It was such a heap of junk and I ended up
    complaining about it so much that Ryobi swapped it for one of their
    new 12V Professional series drills. This was more in keeping with the
    old Japanese Tradeline series and the Ni-Cd's were Panasonic brand
    made in Japan and they would hold a charge quite ok. The charger was
    still a piece of junk and I managed to modify (hacked and plastic
    welded) and old DeWalt charger to accept the Ryobi battery packs and
    it now works well.
     
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