I have had this robotic floor sweeper for a half dozen years. The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Now the robot fails after a few minutes with a red light showing that
indicates insufficient power. The service info says to remove the battery
and to press a particular button to "reset the battery". Of course, this
procedure doesn't reset the battery, but resets whatever sensing circuit
checks the battery. I tried that. Still fails. The NiMh replacement is
labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me.

I sent an email to the robot company asking for their take on the problem.
Their response was that buying a new NiCad from them would solve the
problem.

I am a skeptic. I think that customer service just has a checklist that is
simple-minded and covers only what the average consumer can do.

Along with the email response was a phone number if there was still a
problem. I called and essentially got the same answer. I said that my
concern is that a new battery will not solve the problem. I think that the
voltage sensing circuit has failed. I asked if there wasn't someone who
understood the inner workings of this box who could shed light on what is
happening. I was put on hold and then was told that there was nobody else to
talk to.

What was offered was a discount on the replacement and that if it did not
solve the problem the replacement could be returned for a refund. I bit at
that offer and we will see what happens.

I am open to thoughts that there is a reason that the replacement battery is
at fault. If the fault is in the robot, it is doomed to the recycle bin.
There is not likely to be anything that I can do without a service procedure
for guidance. I also suspect there will be a control board with
non-standard components that are unobtainable.

Charlie

On 2014-02-21, Charlie wrote:
I have had this robotic floor sweeper for a half dozen years. The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Now the robot fails after a few minutes with a red light showing that
indicates insufficient power. The service info says to remove the battery
and to press a particular button to "reset the battery". Of course, this
procedure doesn't reset the battery, but resets whatever sensing circuit
checks the battery. I tried that. Still fails. The NiMh replacement is
labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me.

It means nothing that the battery shows 14V into a multimeter's
multi-million-ohm impedance.

That is not an indicator of its capacity, nor of its ability to supply current.

How about this test: can that battery light a 12V bulb rated for several
watts? And for how long?

I am open to thoughts that there is a reason that the replacement battery is
at fault.

One reason would be that the replacement battery is no longer new; you've had
it in there for several years already. These things don't last forever.

Batteries are actually complicated and fascinating. There is a lot
of info on the "Battery University" website, if you're interested:

http://batteryuniversity.com/

Read this:

http://batteryuniversity.com/learn/a...ased_batteries

Especially, find the table of Advantages/Limitations of NiMh batteries.
Among the limitatons of NiMh:

- "Limited service life; deep discharge reduces service life"
- "Requires complex charge algorithm"

Regarding the last one, what are the odds a device designed for NiCd batteries
does *not* implement the "complex charge algorithm" required for NiMh?

Contrast that with NiCd:

- "Fast and simple charging even after prolonged storage"
- "High number of charge/discharge cycles; provides over 1,000
charge/discharge cycles with proper maintenance."

If the fault is in the robot, it is doomed to the recycle bin.

You do realize that "I intend to throw it away if it actually needs repair" is
hardly in the right spirit for an electronics repair newsgroup.

In article , Charlie wrote:

I have had this robotic floor sweeper for a half dozen years. The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Now the robot fails after a few minutes with a red light showing that
indicates insufficient power. The service info says to remove the battery
and to press a particular button to "reset the battery". Of course, this
procedure doesn't reset the battery, but resets whatever sensing circuit
checks the battery. I tried that. Still fails. The NiMh replacement is
labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me.

Are you measuring the voltage "open-circuit", or with a current load
similar to what the Roomba actually draws while it's operating?

You may find that the battery voltage "sags" badly when it's under
load. If so, it's probably dying and will need to be replaced.

Try temporarily connecting a power resistor or other load across the
battery terminals... something like a car tail-light bulb would be
good... pull a half-amp or so out of the battery, and see what sort of
voltage is delivered under those circumstances.

My understanding is that NiMH batteries are more easily damaged by
over-charging than NiCd... even low-level "trickle charging" of a NiMH
can cook it when it's full.

It's somewhat tricker to detect "full charge" in a NiMH than a NiCd.
With a NiCd, the terminal voltage rises as you charge it, then peaks,
and then begins to drop (this happens at full charge, when the current
into the battery ceases to pump up the electrochemistry and just heats
up the battery). NiMH cells don't show such a substantial drop in
terminal voltage at full-charge... the terminal voltage stops rising
("zero delta V") but doesn't start falling ("negative delta V").

What this means, is that many devices which were built with "NiCd"
charging circuits, will tend to over-charge NiMH batteries and
appreciably shorten their lives.

On Friday, February 21, 2014 11:31:28 AM UTC-6, Charlie wrote:
I have had this robotic floor sweeper for a half dozen years. The original NiCad battery died and I replaced it with an aftermarket NiMh replacement that worked fine for several years. Now the robot fails after a few minutes with a red light showing that indicates insufficient power. The service info says to remove the battery and to press a particular button to "reset the battery". Of course, this procedure doesn't reset the battery, but resets whatever sensing circuit checks the battery. I tried that. Still fails. The NiMh replacement is labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me. I sent an email to the robot company asking for their take on the problem. Their response was that buying a new NiCad from them would solve the problem. I am a skeptic. I think that customer service just has a checklist that is simple-minded and covers only what the average consumer can do. Along with the email response was a phone number if there was still a problem. I called and essentially got the same answer. I said that my concern is that a new battery will not solve the problem. I think that the voltage sensing circuit has failed. I asked if there wasn't someone who understood the inner workings of this box who could shed light on what is happening. I was put on hold and then was told that there was nobody else to talk to. What was offered was a discount on the replacement and that if it did not solve the problem the replacement could be returned for a refund.. I bit at that offer and we will see what happens. I am open to thoughts that there is a reason that the replacement battery is at fault. If the fault is in the robot, it is doomed to the recycle bin. There is not likely to be anything that I can do without a service procedure for guidance. I also suspect there will be a control board with non-standard components that are unobtainable. Charlie

We don't even know that the battery is being fukky or partially recharged, at all or maybe incorrectly since NiCad and NMh batteries are somewhat different as other poster have noted.

Charlie wrote:
I have had this robotic floor sweeper for a half dozen years. The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Now the robot fails after a few minutes with a red light showing that
indicates insufficient power. The service info says to remove the battery
and to press a particular button to "reset the battery". Of course, this

have you lubed the motor and geartrain at all? roombas get all dirty and
nasty inside and can grind to a halt.

A hard running powertrain could drain a questionable to start with battery
or cause a low voltage problem.

On Fri, 21 Feb 2014 12:31:28 -0500, "Charlie"
wrote:

I have had this robotic floor sweeper for a half dozen years.

What's the exact model number? I've fixed a few of these and found
that each has its own idiosyncrasies.

The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Perhaps it would be helpful if you converted "several" into a number.
How many years did the NiMH battery last? More specifically,
approximately how many charge cycles? A really good NiMH battery will
last for about 1000 cycles if everything is done perfectly, or about
50 charge cycles if you do everything wrong. Much depends on the
detection of the EOC (end of charge) point in the charge controller.
If it's a dozen years old and was originally designed for a NiCd, it
is unlikely that the EOC algorithm is suitable for an NiMH battery.
You can easily overcharge the battery, with will kill an NiMH battery
rather quickly.

The NiMh replacement is
labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me.

Test it under a load outside of the sweeper. Try to approximate the
operating current of the Roomba with a resistor. For more accurate
results, borrow a discharge tester such as a West Mtn Radio CBA:
http://www.westmountainradio.com/cba.php

I sent an email to the robot company asking for their take on the problem.
Their response was that buying a new NiCad from them would solve the
problem.

You can get a NiCd replacement cheaper on eBay or Amazon. If you're
not sure if the charger will work properly with an NiMH battery, then
perhaps reverting to a NiCd might not be such a bad idea.

I am a skeptic.

I am a cynic.

I think that customer service just has a checklist that is
simple-minded and covers only what the average consumer can do.

In my experience, that covers at least 90% of the questions. Answers
like "is it plugged in?" are all too common. In the distant past, I
spent some time on a support phone pool creating a database of boiler
plate answers. I wasn't too happy with the software or my answers,
but it was a start and worked tolerably well.

Along with the email response was a phone number if there was still a
problem. I called and essentially got the same answer. I said that my
concern is that a new battery will not solve the problem. I think that the
voltage sensing circuit has failed.

The only way you're going to know if the voltage sensing or whatever
circuit has failed is to either buy or borrow a known working battery.
Troubleshooting by replacment is an old and quite effective method of
fixing things.

I asked if there wasn't someone who
understood the inner workings of this box who could shed light on what is
happening. I was put on hold and then was told that there was nobody else to
talk to.

I used to design marine radios. The dealers knew the engineers by
name and usually bypassed the normal support channels. They would
spread the broken radio onto the table, and then have me walk them
through the troubleshooting and repair. That saved them the cost of
hiring a qualified technician. That might explain why there was
nobody available with a clue.

What was offered was a discount on the replacement and that if it did not
solve the problem the replacement could be returned for a refund. I bit at
that offer and we will see what happens.

I suspect a replacement battery would have been cheaper and faster.

I am open to thoughts that there is a reason that the replacement battery is
at fault.

You may have killed the NiMH with a charger made for a NiCd. Or, you
overcharged it with a charger that didn't have a suitable EOC circuit.

If the fault is in the robot, it is doomed to the recycle bin.

http://www.ifixit.com/Manifesto

There is not likely to be anything that I can do without a service procedure
for guidance. I also suspect there will be a control board with
non-standard components that are unobtainable.

About half of my repairs are mechanical, not electrical. A sweeper
full of hair, dirt, and crud will bog the motor, causing the battery
to drain or die rather quickly. Add those that like to fix things
with far too much oil, which soon turns to tar. It's amazing how many
things can be fixed by simply cleaning out the crud.

Good luck.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Charlie"


I sent an email to the robot company asking for their take on the
problem. Their response was that buying a new NiCad from them would solve
the problem.

** They are probably right.

But NiCds are getting scarce these days and you might find replacement packs
for appliances are rather old and hence not in top condition when you get
them.

I bought some sub C cells for my Bosch screwdriver the other day and found
that Sanyo no longer sell NiCd cells under their own name - but badged "
Panasonic " instead. The fine print says made by Sanyo and they look exactly
like the N-1700SCR cells I was after so it was all OK.

IME buying loose cells from a wholesaler is a lot safer than some dodgy
after market or even OEM pack that could be ten years old.



.... Phil

In article ,
Cydrome Leader wrote:

have you lubed the motor and geartrain at all? roombas get all dirty and
nasty inside and can grind to a halt.

A hard running powertrain could drain a questionable to start with battery
or cause a low voltage problem.

I recall reading this somewhere else, it involved removing the brush/rollers
and literally chiselling out a couple of bearings made out of compressed,
burnt (by friction) hair. Followed by some hacking to prevent it happening
again, because -- it did keep picking up and storing more burnt hair!

It caused a "motor overload" situation, but that would have knock on effects
for the battery getting overloaded too.
--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

--- news://freenews.netfront.net/ - complaints: ---

"Charlie" wrote in message
...
I have had this robotic floor sweeper for a half dozen years. The original
NiCad battery died and I replaced it with an aftermarket NiMh replacement
that worked fine for several years.

Now the robot fails after a few minutes with a red light showing that
indicates insufficient power. The service info says to remove the battery
and to press a particular button to "reset the battery". Of course, this
procedure doesn't reset the battery, but resets whatever sensing circuit
checks the battery. I tried that. Still fails. The NiMh replacement is
labeled 14.4 volts. My cheap VOM show about 14-15 volts. Seems good to me.

I no longer have the facilities to hang a load on the battery.

For all those who suggested cleaning out crud etc., this unit has reasonable
sensors that tell you it needs cleaning. The biggest problem is hair that
wraps around places. There are no consumer available places for lubrication.

For all those who remarked about the different charger requirements, I have
found that the replacement coming from the mfgr is now a NiMH. I'll have to
wait and see if they include specific charging requirements.

Charlie

On 22/02/2014 5:40 PM, Phil Allison wrote:
"Charlie"


I sent an email to the robot company asking for their take on the
problem. Their response was that buying a new NiCad from them would solve
the problem.

** They are probably right.

But NiCds are getting scarce these days and you might find replacement packs
for appliances are rather old and hence not in top condition when you get
them.

I bought some sub C cells for my Bosch screwdriver the other day and found
that Sanyo no longer sell NiCd cells under their own name - but badged "
Panasonic " instead. The fine print says made by Sanyo and they look exactly
like the N-1700SCR cells I was after so it was all OK.

IME buying loose cells from a wholesaler is a lot safer than some dodgy
after market or even OEM pack that could be ten years old.


**Agreed. FWIW: My Bosch screwdriver (GSR 12VES-2 blue series) had a
battery which was on it's last legs, when the chuck decided to fail.
Coincidentally, Aldi had a special on an 18 Volt, lithium screwdriver
for $149.00. Experience told me to hold out for a week or so. I did just
that. I snagged one for $60.00. It includes two batteries and a charger.
It's quite a nice screwdriver (two speed gearbox, 1,300RPM and 30%
lighter than the Bosch), for less than Bunnings charges for a single
lithium battery. Emboldened, I noticed that Aldi had an 18 Volt impact
driver for $149.00. I waited two weeks and snagged it for $49.00. It
also includes two lithium batteries. 1.5 A/H. 180Nm of torque. Nothing
much stops it. Best of all the batteries fit my screwdriver (they even
have a 'fuel gauge'). 3 year warranty to boot.

Gotta be happy with that.


--
Trevor Wilson www.rageaudio.com.au