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

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.

----- Original Message -----
From: "webpa"

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.

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.

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.

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.

he cells may use a slightly (or entirely) different chemistry and/or
physical
construction, even though they have the same voltage and current
ratings.

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.

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.

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.

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.

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.

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

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

RichK wrote:
----- Original Message -----
From: "webpa"

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.


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.


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.


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.


he cells may use a slightly (or entirely) different chemistry and/or

physical

construction, even though they have the same voltage and current
ratings.


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.


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.


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.


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.


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.


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


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

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