Scorched Discovery SE! Almost a fire!

PWP · Joined: 22 Jan 2006 Posts: 13

I put my Discovery out to pasture when I received the 560 last fall.

2 days ago, I decided to dock it upstairs & schedule it to run.

I charged the yellow APS battery with the 2 hr charger connected directly to Roomba, then ran it till battery died - about 1hr+.

I then reconnected the charger directly to the Roomba. About 4 hrs later, I noticed an odd smell and traced it to the Roomba which was emitting s very harsh burning smell!

I immediately unplugged the charger & the power light still pulsed. I took out the battery - it smelled ok, the scorched smell was from inside the Roomba. When I reinstalled the battery, the power light began pulsing red.

So now it's all disconnected. Luckily, I was around - a fire could have started!!!!!

What happened? Is it DOA???

RoombaHolic · Joined: 01 Feb 2008 Posts: 97 Location: Mountain Center, CA

PWP wrote:
What happened? Is it DOA???
Not really . . . but it probably is now!!!!! (Sorry, couldn't help myself!) :wink:

vic7767 · Joined: 14 Jan 2006 Posts: 3288 Location: Louisiana

Actually you can save most of your Roomba. All you need is a new PCB.

PWP · Joined: 22 Jan 2006 Posts: 13

[quote="vic7767"]Actually you can save most of your Roomba. All you need is a new PCB.[/quote]

Save?? Not bury at sea?

Scary part is.... could it have caught on fire?

What's a PCB?

Where is a PCB?

How much $$ for PCB??

RoombaHolic · Joined: 01 Feb 2008 Posts: 97 Location: Mountain Center, CA

PWP wrote:
What's a PCB?

Where is a PCB?

How much $$ for PCB??
PCB = Printed Circuit Board which can be obtained from http://www.roombaexchange.com.

Gordon · Posted: June 5, 2008, 9:44 pm Post subject:

PWP should not obtain a PCB-assembly from Chris directly; he should do it indirectly by sending the SE to Chris so that Chris can install it and check out the robot.

PWP should also toss out that old battery (which I presume had not been maintained since last Fall !) and buy a new battery.

fancyfreewv · Posted: June 6, 2008, 10:01 am Post subject:

Gordon, what would the technical reasons be for the failure?

I am concerned about the "almost" fire description given here. If the battery can short out in such a way after a few months of non-use that it takes the PCB or components with it, would this be "normal?"

:shock:

Gordon · Posted: June 6, 2008, 11:34 am Post subject:

fancyfreewv wrote: Gordon, what would the technical reasons be for the failure? Nancy, I cannot know for certain what PWP's equipment did. More data are needed, e.g., the particular states of charge on each cell in that battery, and what component(s) failed.

I therefore have to make assumptions based on the operating data presented. PWP told us the SE & its battery had been parked since he got a new 5XX Roomba last Fall. When he decided to return tbe SE to service, he was able to re-charge its battery (which I found surprising) and provide a one-hour run for the 'bot.

I am assuming that the weakest cell in the battery (of 12 cells) took a nose-dive, and discharged itself (to zero-volts) before any others fell even to V = 12V/11OKcells = 1.1V/OKcell. Roomba was then able to operate for a short while after that point, and as it did, current necessarily continued through that null-voltage cell in the same direction as before, however, that means the cell was then being charged (by the others) in reverse-polarity. But, that reverse-charging would not have continued for long, (since its voltage would have subtracted from the sum of the others, and cause an early call for re-charging) nor would it have been efficient.

Later, when that battery was subjected to re-charging, charging current travels through the battery in reverse (reverse, compared to when its powering Roomba). Eleven (assumed) cells would be getting reasonable charge, but (as I have read, yet have had no hands-on experience in testing) the weak cell has been ruined and can't be expected to reciprocally flip its charge back to the correct polarity. While I could use some expert help regarding the fate of a rev-polarity cell, I'm fairly certain that I have read statements which say the cell is irrecoverable.

With that cell out of commission (maybe it can be looked upon as *shorted*), an abnormal (high) load would have been placed on the charging-controller components (located on the main-elex PWB); and, thinking mainly about MOSFETs U2 & U4. Those FETs have failed in thousands of Discos. Quote: I am concerned about the "almost" fire description given here. PWP falls into the "alarmist" class, and that is understandable since he apparently has no familiarity with heat-failure characteristics of electrical/electronic components.

Roomba's PCB (printed circuit board) substrate material is fiberglass/resin, with the "resin" being epoxy (I think). I also think that material is fire-resistant. Here is a photo of an area on the main-elex PWB which suffered a component failure (not one of the FETs, but a TVS (transient voltage suppressor):

The item which blew up and charred the PCB and various neighbor items looked just like nearby TVS parts, black boxes with "30" | "CA" markings. The PCB was burned through the board's thickness about half depth! But, no flame was sustained. At top of frame, two charred connector bodies are shown. They simply pulled off their pins while trying to de-mate their cable-plugs! This extensive damage would have emitted quite some wierd odor!!

When U2 or U4 fail, you may not be able to discern that by looking at them. That suggests PWP's failed, smelly parts must be something else that got over-loaded. Quote: If the battery can short out in such a way after a few months of non-use that it takes the PCB or components with it, would this be "normal?" I think it tends to be a normal failure mode for the Discoverys, after all, someone just said: "Those FETs have failed in thousands of Discos."! :-)

I should probably say that the "thousands" count is my personal opinion, based on viewing the tip-of-the-iceberg that we see here at RoombaReview.

fancyfreewv · Posted: June 6, 2008, 11:58 am Post subject:

Thanks Gordon. One can only hope this might be one of the parts they DID improve on the 5xx series.

Re: smelly parts and electrical burning smell in particular. Coming from a computer technical support and hardware background, that smell is never a good thing and to most people would be something that would alarm them. If you don't understand what is smelling, smoking or burning, you would very likely be quite nervous.

Now another question. Why, if one of the batteries in the array can fail and cause (if you are correct) such a current flow, do they not move to a different solid state type of battery? Expense? Or is it easier to just tell people to keep it charged all the time and make the materials fireproof so no flame results and thus it passes the OSHA requirements?

fancyfreewv · Posted: June 6, 2008, 12:37 pm Post subject:

TO PWP:

Are you sure you used the correct charger? You state you have a 560 and a Disco. You plugged directly into the Roomba? Why no Home Base which would be more normal operation?

Did you by any chance use the 560 charger on the Disco?

PWP · Joined: 22 Jan 2006 Posts: 13

[quote="fancyfreewv"]TO PWP:

Are you sure you used the correct charger? You state you have a 560 and a Disco. You plugged directly into the Roomba? Why no Home Base which would be more normal operation?

Did you by any chance use the 560 charger on the Disco?[/quote]

I used the correct charger & skipped the homebase just to eliminate a problem.

Here are photos of the area & the scorched plastic cover:

Gordon · Posted: June 6, 2008, 1:11 pm Post subject:

PWP: Your problem area matches the fault in my posted image. The TVS associated with the rear charging jack got over-driven --possibly by a power-line surge, or area electrical activity.

Nancy: I'll talk to your new Qs in a few hours. I have just been tasked to run an errand.

Gordon · Posted: June 6, 2008, 5:33 pm Post subject:

fancyfreewv wrote: ...Now another question. Why, if one of the batteries in the array can fail and cause (if you are correct) ... PWP has given evidence that the smoked parts may not have been due to a faulty battery. He should not toss that battery out just yet! Quote: ...such a current flow, do they not move to a different solid state type of battery? iRbt has only the two nickel technologies from which to select re-chargeable cells. The lithium field has got to be too expensive for OEMs that can't pass on their higher cost. I'm also guessing that the gel-cell lead-acid battery has objectionable features too. Quote: Expense? Cost is the main driver at iRbt. It is apparent to me that iRbt does anything it needs to, in order to hold selling prices of floor-cleaning bundles to what it thinks the market will bear.

To remain solvent, the Company simply must hold manufacturing costs low enough that customers, in agreeing to pay stated retail prices, are, in fact, paying for more of each item in the bundle than just the number of units bundled in the box. For example, s/he pays for 2.37 robots, 1.45 Home-Bases, 1.87 PSUs, 1.1 Remote-Control devices, and 2.1 VWUs. The additional paid-for items can then be used to satisfy warranty returns, at no cost to the Company.

Without doing that sort of cost-control, the Company would operate in the red. Quote: Or is it easier to just tell people to keep it charged all the time and make the materials fireproof so no flame results and thus it passes the OSHA requirements? Yes, it is easier to say that. iRbt is very careful to not complicate their robots' operating instructions. If the Company desired to prepare accurate and up-to-date Owner's Manuals, think how easily that could be done at its website. User-feedback could be accepted to help re-write recently added sections that are not being well understood by general users. It would be a great process! Yet, the Company seems not to be interested in that sort of owner aid.

Re: the fire-resistant PCB, I think the Company is essentially forced into using that material to well support manufacturing a complex PCB having four layers of copper which uses hundreds of plated through vias to interconnect foil traces between layers. I would not be surprised to learn that a less costly substrate-material, say glass/phenolic, would not well support that type of construction. It looks to me like iRbt does a great job in board fabrication!

PWP · Joined: 22 Jan 2006 Posts: 13

[quote]Without doing that sort of cost-control, the Company would operate in the red.[/quote]

First - I'm a she, not a he....

Now I have to decide what to do with this useless robot.

I have another discovery SE with dead battery & a dirt dog with a dead battery.

Do I invest in batteries for these 2 units ($100+est) & wait till they die a horrid death, or use the $100 toward another 500 model which seems to have less problems than previous models?

I've had all the units since the first model & frankly, I am getting tired of problems & troubleshooting.

It used to be fun to do the diagnostics, take it apart, shim parts, clean the guts up, etc, etc, etc but now it's really a pain. Having dead chargers and osmo tricks is time consuming. Doing 72 hr cycles to see if a battery comes back to the living is also a pain.

I just want to turn it on & have it do what I paid so dearly for ....!

I do not understand why IRobot rechargeable circuitry is so faulty... rechargeable batteries & chargers have been on the market for a long time...

So wise robot boardies - are the 500 models batteries & charging circuits better equipped for a untroubled life, or am I going to have fried parts with this model also? My 560 is 9 months old - born in the first batch.

Thanks!

fancyfreewv · Posted: June 7, 2008, 1:51 pm Post subject: Re: How about users cost control?

PWP wrote: I do not understand why IRobot rechargeable circuitry is so faulty... rechargeable batteries & chargers have been on the market for a long time... So wise robot boardies - are the 500 models batteries & charging circuits better equipped for a untroubled life, or am I going to have fried parts with this model also? My 560 is 9 months old - born in the first batch. Thanks!

Mine are first batch too even now that they are replacements for the two I originally bought. These are now going on 9 months in use daily.

As to your question about chargers and batteries. I am on this board almost every day and have not seen any postings about this. Maybe I'm just not aware of them but I think your situation sounds fairly rare.

Since you seem to be a long term and knowledgeable user of robots, I would suggest that either you, a spouse or electrician take a long look at your circuitry in the house. Checking things like breakers, overloading by using extension cords or power strips etc. Something is causing all this grief you are describing. Do you have electrical issues with any other appliance you use in the house?

Have you consistantly used the same circuit area in your home to put the HB or transformers? If this has only happened to your 4xxx series, are you using the same transformer and possibly this has gone bad? Did it happen with direct plug in only or also on the HB? Do you have lots of power surges or outages due to weather? I think some detective work is needed. My background is not in batteries or electrical engineering like some here but in computer electronics and I know from experience that power fluctuations can cause havoc with computerized circuitry.

Keep us advised as to what happens as all of us have a vested interest in troubleshooting problems with the robots.

Gordon · Posted: June 7, 2008, 4:35 pm Post subject: Re: How about users cost control?

PWP wrote: ...First - I'm a she, not a he.... Sorry about not seeing that in the PWP moniker! :-) Quote: Now I have to decide what to do with this useless robot. Yes, it tends to now be in the "parts-bot" class. I expect it might need more than just a PWB/PCB replacement; it may also require replacing a couple wire harnesses if the two plugs which straddle the fire-zone have gotten fused to their jack-bodies. You might consider posting this parts-bot in the Buy/Sell/Trade Forum. Quote: I have another discovery SE with dead battery & a dirt dog with a dead battery. Do I invest in batteries for these 2 units ... Until you decide, you could plan on running the battery that was being used in the SE that just blew a TVS device. I can't see how that battery promoted the failure of the TVS, so there should be no threat to charging it in either of those other 4XXX bots. If it works, just shift the battery back and forth between them (assuming you have no real need to run both at once). Quote: I've had all the units since the first model & frankly, I am getting tired of problems & troubleshooting. ...I just want to turn it on & have it do what I paid so dearly for ....! Amen! And that's the way it should be! I empathize. Quote: I do not understand why IRobot rechargeable circuitry is so faulty... rechargeable batteries & chargers have been on the market for a long time... Nor do I! I have a variety of battery-powered hand tools and their chargers, and they are essentially faultless. Why can't iRbt get it right? The Company has been struggling with charging control since their first minimal attempt on the 3XXX Pro models. The 4XXXs have suffered PSU failures, HomeBase failures, and main_elex controller failures all because the Company decided to save a few cents by using under rated components. Batteries (cells within) for the 2XXX & 3XXX Roombas suffered early failures due to lack of cells-matching. Early runs of Scoobas killed their batteries by applying too high trickle-charging current (2X to 3X too high!). And now, earlier this week, we have seen a possible battery-life threat for 5XX batteries. It is premature to be alarmed, because we have only a sample size of one; but, from charging data which vic7767 obtained from his 535's SCI data-stream (more info) we notice that high-rate charging cut off due to the controller recognizing a high-temperature (battery-temperature) limit had been exceeded. Cells' temperature climbed to a peak of 65ºC, even after power was cut!! Way too high, and an odd temperature increase!

I think vic7767 plans to obtain more 5XX charging data to see if the data repeats in the same 535, and/or if it is systemic.

fancyfreewv · Posted: June 7, 2008, 4:47 pm Post subject:

Sorry didn't know this was so prolific in the earlier series. However, I think we need to think about the fact that we who frequent this board tend to see more than our share of "problems" with these things.

There are hundreds of thousands of them out there and I can't see IRobot staying in business if the problems we hear about were extrapolated to include that many failures. Maybe one failure is too many.

Like the side brush failures that happen to some often but happen to others never, external sources and environment has to be considered IMHO to explain some of this stuff.

PWP · Joined: 22 Jan 2006 Posts: 13

Gordon -

I was thinking the exact thing about all my other devices that have rechargable batteries - no problems (well, there was a recall on the 18v DeW@@t cordless drill battery & recharger because of over voltage) but other than that one instance, no problems like IR has.

fancyfreewv -
To the question of household current - the chargers & home bases have been plugged into various circuits over the years without a problem. A electrical power surge took out one IR fast charger, so now I use a power surge strip - just in case.

I was looking up purchase dates (I buy all roombas directly through IR) and see that this particular one was a remanufactured exchange I received in 8/06 after my first Discovery SE died. Maybe that is a clue to the failure....!

Well, my 560 just did a great job while I was out this am, so my faith in IR is still strong. I just wish that doing all the iRobot Advisory Panel surveys would count for something - all they ask is marketing questions - very little focus on durability!

Thanks to everyone for posting & helping out!!
PWP