Category: gadgets


Several people over the years have found my blog posting on why not to use Lithium battery packs in Roombas.  Some people have taken the information at face value, others have argued with me in the comments and tried to claim my views on the subject are not valid.

Some of the folks over at Tenergy also noticed my article and decided to send me a battery to prove to me they have resolved the issues I was citing.  Here is a link to the battery in question:

In the interest of full disclosure, in consideration for the battery, they only asked for my honest review along with a link back to the product to allow people to find it.


At this point in time, I have been using the battery lightly for about a month.  I use my roombas somewhat sporadically.  This may actually shorten their life due to lack of cycles and a poor factory charger circuit.  So far, this pack seems to be holding up just fine.  One thing I should point out that is different about this pack from the other lithium packs I used in the past…  When the other packs ran low, the Roomba light would start to glow orange and then suddenly the roomba would die in place.  In other words, it never had enough charge left to bring itself back to the base.  The batteries low volt protection cutout would kick in and save the cells from damage.

This pack appears to work like a typical NiMH pack.  The light eventually goes red like it should and the robot stops moving but the power remains on.

As far as runtime, I’m using the pack on hard surfaces.  I haven’t paid close attention but it seems to go for a couple of hours.  One day I will time it and update the review, for now though, I wanted to post my initial thoughts.

Similarly, I will obviously need to reserve my judgement on longevity until the pack starts to noticeably deteriorate.  That could be months or could take over a year.

So far, if I had to pick one complaint about the pack, I would say that one of the retainer clips is unable to snap into place.  This is a pretty minor issue that I could probably fix with some sandpaper or a knife but I shouldn’t have to.  I’ve cleaned the area under the battery and pushed on it pretty hard but it just won’t snap in there for some reason.


For now, I will say that the price is currently $68.99.  This is marked down from the typical $90.  The Tenergy packs for the 400 are $25 on Amazon.  So what do you get for 3x the price?  I’m not sure yet.  Only time will really tell there.  The pack is certainly lighter than a NiMH pack so it’s putting a little less wear on the robot.  It seems to last similarly to some of the best NiMH packs I’ve had.  It’s not exactly an all-day battery pack however.  In the coming months, I’ll try to monitor the health of this pack a bit more closely and possibly more scientifically.

My first lithium pack for the Roomba was $150.  When it prematurely cooked, I was not pleased.  At $69, if I got a year out of this one, I probably wouldn’t complain too much but then again, if it only lasts a year, why pay any premium on it at all?  Let’s hope that I’m able to favorably speak of this pack for years to come as “the best Roomba battery I’ve ever had”.

I was waiting on the sidelines for the Sprint Evo to be released.  At the time, I had a Windows Mobile 6.5 phone…  the Palm Treo 800w.  What a turd that was.  I really can’t believe that old Windows Mobile platform lasted as long as it did.  The concept of trying to scale down a desktop OS to a pocket size was just plain silly.  This is why I looked forward to the HTC Supersonic handset.  At that time I didn’t know it would be called the Sprint Evo.

Usually in the past, Sprint had not gotten the latest and greatest handsets.  I always considered their selection to be somewhat second rate stuff.  This was another reason I looked forward to this handset so much originally.  It made a lot of promises.  Things of note were a large beautiful screen, 4G and the Android operating system.  Those very things are some of the reasons I’ve become disenchanted with this handset.

The screen – This has a huge, beautiful screen.  There is no doubt that the thing is gorgeous, however, this is not without it’s downsides.  The obvious downside is that the shear size of it makes the phone extremely large.  I didn’t mind at first because it was a lot thinner than my Palm Treo with the extended battery but really it doesn’t need to be quite as large as it is in my opinion.  Taking the screen down 1/2 and inch in size would make the phone a far more manageable size.  Also while I’m talking about the screen, the digitizer on this phone sucks.  Sure it works fine but it is getting a fog/film on it that cannot be wiped off.  A couple people have mentioned that I should use a screen protector but I have to call BS on that.  Why?  I gave my son my (already used) iPod 2G roughly 6 months ago.  He’s 3 years old.  If anyone could abuse a device with drool, sticky fingers and an occasional drop, it’s him.  Even considering all the abuse, when I wipe his screen off on my shirt sleeve even, it looks almost brand new barring a couple of tiny nicks.  Nicks I can deal with…  fog I cannot.

The 4G – This has always been fairly useless to me for the whole time I owned the phone for several reasons.  Most notably, it barely worked for months after I got the phone.  Even now, the coverage is spotty here in the Seattle area.  Aside from the lousy coverage, Sprint forces you to pay $10/mo extra for having a 4G handset whether you use it or not.  To add insult to injury, it’s not an always on thing.  It’s  a whole separate radio like bluetooth or wifi.  Turning it on drains the battery at an alarming rate.  If I turn it on and forget that I did, the battery will be dead by noon in some cases.

Android – Sorry, I don’t get it guys.  And it’s NOT that I don’t GET it.  I’m a Linux guy.  I first started using Linux in ’95 or so.  I just don’t like this incarnation of it.  Part of my gripes could be with the Touch UI provided by HTC but I really just don’t like the way the icons are organized and the navigation of the interface.  Nothing seems polished or finished to me.  The other pisser is that not Sprint or HTC will have any interest in upgrading the operating system to a newer revision when they stop selling the phone(should be soon now).  They would rather I buy a new phone.  That pisses me off when “evil” Apple has made the latest and greatest versions of iOS 4 work even on an ancient Touch 2G which they haven’t sold for at least 2 years.

Bugs – The bugs are unbearable.  I don’t remember much in the way of bugs when I first got the handset but over the past(less than a) year, all hell has broken lose with the gremlins.  One of the worst ones is where the phone rings and the screen will not respond to my touch.  I try to answer the phone with all my might and the sliding bar on the screen won’t budge.  Not much could possibly piss me off more than having someone call who I cannot call back due to corporate policies trying to ring me and my phone won’t allow me to answer the call.  That can waste a day or a week trying to get that person to call me again.  Quite frankly, my time is more valuable than that.  The next bug on my hate list that has started to pop up is that when I end a call, my phone will decide to call somebody else on my recent called list.  That’s really obnoxious trying to explain to someone that “no, I didn’t pocket dial you and I wasn’t trying to call you”.

Skype – So there is Skype on the Android now…. So what?  It’s absolutely, 100% useless as hell.  Why is this?  Well Sprint decided that Skype shouldn’t work on 3g or 4g.  It has to be used on wifi only.  I can’t even call Skype-only contacts on there.  This is total BS.  When I pick up my wife’s iPhone and try Skype on there it works perfectly.  I have an unilimted plan with Sprint.  In fact many/most of the plans Sprint sells are unlimited to my knowledge so what’s the deal with Skype not working?

Pocket dial/Pocket hang up – It’s too easy to grab your phone out of your pocket and pick up or hang up the phone on someone before you can even see who it is.  This is pretty annoying.  Not to sound like a fanboi but sorry, Apple has thought this feature through WAY better.  It is very unlikely that this would happen with an iPhone.

Sprint’s junkware – Dear Sprint, please let me delete the crap you put on my handset that ruins my user experience and gets in my way.  This would include blockbuster, Nascar, Sprint Zone, Sprint TV and most of all Sprint Football Live.  I’m a nerd, I hate Football and Nascar so why the hell would I want to look at those things on my phone?!?

Several months after I bought this handset, I purchased an old, used, outdated iPod Touch 2G.  Ever since then, I have carried around an iPod Touch(now a 4G) along with my Evo handset.  The reason for this is that the Evo handset simply doesn’t do everything I want or need it to and I find pretty much everything about the way iOS works to be far superior to the functionality of Android or at least Android on this phone.  When I look at my iPod Touch, (even the old 2G), the newness and appeal still has not worn off for me.  I hate to be an Apple fanboi or bigot but when my user experience is this bad on an Android device and that good on an ancient iOS device, I can’t really argue with the facts.

The real bummer is that I was forced to sign a 2 year contract to get this phone.  In the past, I had gotten 1 year contracts because I’ve always know well enough that mobile devices change quickly and 2 years has generally been too long of a time period to hold onto such a device.  My initial inkling was right.  I got the phone in May and not even a year later I’m ready to throw it off a cliff.

People have told me that I should root the phone to make it work the way I’d like.  Screw that though.  I don’t have time to mess around with a device that I rely so heavily on.  Are there things I like about the phone?  Sure!  Quite a few actually but there is only one thing I can think of that this phone does that my iPod Touch won’t….  make calls.

Let me rant about Apple a little here.  I’ll preface with saying that I love many of their products but I’m irritated sometimes by their ultra/over secrecy…  I ordered my iPod touch 4th Generation the hour that it was announced.  I was waiting for it to be released and it was a planned purchase opposed to an uncontrollable lust for any shiny object Steve holds up in his hand.  As punishment for my early adoption, I had to wait months for a decent case to come out.  Like hell would Apple actually share even their measurements to any third party accessory manufactures and god forbid they actually release their own protective case to tarnish their beautiful objects…

Now that I’m done ranting, let me talk about the Speck PixelSkin.  First I will say that I don’t really trust it nearly as much as my Tech21 iBand that my son inherited with my old iPod Touch 2g.  I have full confidence to THROW the iPod at the ground in that case and have it survive unscathed.  I don’t have quiet the same confidence in the PixelSkin but I think it would withstand an accidental drop just fine.  There are plenty of other things I like about the Pixel vs. the iBand though.  Most notably, the power button is much easier to press in the Pixel.  The volume buttons perhaps are not aligned as well as I would like but I wouldn’t even ding this case half a star for that.  Overall, the case fits very snugly and has a fairly high ridge that should do a reasonable job protecting the screen from the table top and other devices in my pocket.  The case does SLIGHTLY encroach on the home button.  That is really the worst thing I can say about it.  Other than that, it looks great, feels great in my hand and appeals to my love of 8-bit things for some reason


Lasers are cool

My friend James likes to play with fire and burn stuff.  It’s a bonus for him when he can use previously unobtainable technology to do so.  Recently he has been buying Casio XJ-A140 projectors for the purpose of parting out the 445nm Nichia laser diodes(24 of them!).  He has sold some of these on eBay to others who don’t want to tear into an $800 projector but recently he hooked one up to an LM317 regulator to see what it can do.  What you see in the pictures is the result of roughly 1.2 watts of output.  The visible blue light is totally dangerous and even the reflections could cause permanent eye damage but I’m SURE he locked away his kitties and wore protective goggles(yeah right).

Usually when I modify something, I try not to ruin the aesthetics. It has to perform and look better(or the same) than before I start the project, otherwise I don’t want to do it. I think this mod has achieved that. With some help from a friend, I managed to design and build a surface mount serial level converter board that fits inside the Zipit Z2 behind the screen. It pops out of the Zipit in the form of a 3.5mm headphone jack that is stuffed up in one of the only spots it would possibly fit. From there, I built a short cable that turns the 3.5mm plug into a DB-9 for plugging into any standard serial hardware.

The mod is powered entirely from the Zipit it and will have an unnoticeable effect on battery life. The chip I used is the Maxim 3221 CAE 16 pin SOIC variant which also has some built in power saving functionality. This was the smallest chip that I could find that would do the job. The size of the capacitors on the board are not entirely critical but their function is. They help the IC boost the voltage up to the proper level for communicating with RS-232 devices. Without the caps, chances are that the converter will work for some devices and not for others because it will fail to fall within the RS-232 spec. I used .1uF surface mount caps in a 603 package. They are pretty tiny but certainly not unmanageable. There are plenty of tutorials out there on soldering surface mount components if you happen to be nervous about this.  Here is the schematic.

Before we can put the board in, we need to crack the case so I put together this Zipit disassembly guide.  After it was apart, I could see the space that I had behind the screen.  It’s a surprising amount really.  They could have made this thing a little thinner if they wanted to.

Here is a good view of the area behind the LCD

Test fitting the 3.5mm jack

As I was I saying, the 3.5mm jack is stuffed in the only spot I could find for it.  It’s where the LCD cable comes down from the upper half of the Zipit.  I happened to salvage this headphone jack from a Sansa Shaker which is a great MP3 player for a baby.  I had an extra one that was broken so I took the two headphone jacks out of it and gave one to my friend.  rkdavis found a 3.5mm jack on Digikey that looks pretty similar to what I used.  The space is very tight so the size of the jack is critical.

The wires routed and board mounted

As you can see, that board fits perfectly in that empty square.  I used a few dabs of hot glue to hold everything together and route the wires where I wanted them to go.  I took care to mark the wires with Sharpie pen notches so I knew which wire went where.  The wires I used are Kynar 30 AWG wire wrap wire.

Using helping hands to solder the 3.5mm jack

After the wires were all routed, I stuck the LCD housing back together.  I pulled all 7 wires through the same spot where the LCD wiring comes into the lower half of the unit.  I used some Helping Hands to hold the headphone jack and solder tiny wires to it.

3.5mm jack hot glued in place

I used copious amounts of hot glue to make sure that headphone jack didn’t move.  I also drilled the hole extra tight and crammed the jack into it so I don’t expect any movement at all.  After this step, the hard part is done and there are only 4 wires left to hassle with.

Mainboard locations for hooking up the serial converter

I stuck the keyboard back together and put the motherboard back into the zipit it.  Then it was fairly easy to solder the last four leads to these locations and put the bottom half of the case back together.  Now that it’s done, it’s time to plug it into a serial port.

The completed mod including the dongle

I’m using Hyper Terminal in Windows XP under VM Ware Fusion.  The port settings are 115,200, 8 bits, 1 stop bit, no parity and NO flow control(very important).  Here is what pops up when I first boot the Zipit.

This is what pops up when you first boot the Zipit

If anyone wants to replicate what I’ve done, here is the PCB layout for Kicad.  Feel free to comment if you need more assistance.

Now for that USB host mod

If you are interested in buying your own Zipit to hack and you like the information on my site, please buy your Zipit using this link and support my site. You won’t find them anywhere cheaper than that anyways.

Zipit Z2 disassembly guide

The Zipit Z2 is the perfect little hacking platform.  Searching around on the web, I couldn’t find a decent group of pictures showing how to disassemble the Zipit so I decided to post my own little guide.  Obviously use this guide at your own risk…

First we slide a plastic card to separate the dark gray plastic piece behind the screen from Zipit  Using a plastic card will avoid scratching the case.  In this case, I used a Borders key chain membership card I found on the sidewalk.  This will expose three screws behind the screen and the ribbon connector for the screen that I would suggest not messing with.  Remove those three screws.  The top two are slightly shorter than the bottom one.

Now you will need to use a slotted screwdriver to pop the plastic snap loose that is shown in the picture.  Don’t force it too hard but it IS fairly tight so you’ll have to use a bit more force than you’d normally expect.  Now that you have that nice gap, wedge your plastic card in place and slide it down the lcd housing.  There should be four plastic snaps that you will be able to work lose.  Notice the little magnet towards the top of the picture?  That’s what makes the Zipit stay closed nicely.

After I get this far with it, I like to flip it over and crack the bottom case.  The battery needs to come out if you haven’t already done so.  There are three screws under it.  Go ahead and pop those out.  After you’ve done that, it’s time to start prying with your plastic card.  I like to start at the back near the hinges since I seem to be able to wedge my card in there the best and get the case to flex the furthest.  I’ve tried it from the SD slot as well but it’s hard to get enough leverage that we since you don’t have the screen to hold onto from that side.  There are four of those snap tabs that are holding the bottom case together.

After you have the bottom separated, go back to the top.  There is a small piece of plastic that is in the hinge section.  You can now pop that off from underneath if you need to or whatever other angle.  After it’s off, you’ll need to pry upward as shown in the picture.  After it’s popped loose, you need to slide the whole back/upper half of the LCD housing towards the side you are prying from.  There is a small lip on the back half that is keeping it in place.  Similar to the lip near where the screwdriver is prying in the picture.  That’s it!  There is one extra piece that rkdavis insists is necessary but I’ve been using mine fine without it for a month now so you can make the final call.

Mozzwald graciously loaned me his picture of the mystery plastic piece installed in place:

If you are interested in buying your own Zipit to hack and you like the information on my site, please buy your Zipit using this link and support my site. You won’t find them anywhere cheaper than that anyways.

As much as I love my new HTC EVO 4G, so far I’ve been very disappointed with the so called 4G performance.  I am going to run a series of tests randomly, right now, and post my results here so you will see what I mean.

Testing 3G – I used the app on the from the Android Marketplace.  I’ve seen this number as high as 1.5Mbps but today I am getting 831kbps down and 295kbps up.

Testing 4G(local) -Speed testing while on 4G resulted in 2272kbps down and 370kbps up.  Better?  Yeah, sure, way better.  Worth $10/mo to me?  No way.  It doesn’t make the phone any more usable to me as it sits.  It’s also nowhere near the bandwidth that was promised.

Testing 4G(shared on hotspot) – Running on my iPod touch connected to my home wifi yields me a 4835kbps downstream and a 610kbps upstream.  No, I don’t have the fastest internet out there but it’s NEVER gone down in 6 years and I have a static IP.  Anyhow, this final statistic is the punchline of my whole blog posting…  When I connect my iPod to the EVO in 4G hotspot mode, I get a whopping 168kbps downstream and a 248kbps upstream.  I’ve repeated this test over and over again at different times of the day.  This is actually the fastest speed I’ve gotten out of the mobile hotspot.  Generally it has been under 100kbps.  I tested this before and after 2.1-update1 was pushed out to me and the results were the same.

One last note here is that it is NOT possible to run a mobile hotspot on 3G.  I find this extremely annoying since you can’t get 4G service everywhere.  Presumably the coverage won’t be as good even when Sprint does fix the speed problems.  This one poor decision on from Sprint means that this device currently cannot replace my Verizon Mifi.  I am patiently hoping that the 4G improves dramatically and will report back when I actually obtain some acceptable speeds.

I always carry my iPod Touch with me so I can listen to podcasts.  With the Touch, I also have the Apple Earphones with Remote and Mic with me.  These are not the most durable headphones and perhaps aren’t the best sound quality but they are definitely the best match to the iPod Touch because they allow me to control the iPod while it’s in my pocket.  I can stop/play, adjust the volume, etc right from the little 3-button mic/remote.

Since I always have them with me, I decided to see if they would work on my new EVO.  Do they work?  Sure, sort of.  There is a thread on Android Forums that goes into detail about specific functions of the headphones working or not.  But my findings are that the mic and headphones DO in fact work.  The middle button for start/play/hangup also seems to work.  The plus and minus button do not seem to work for me.  Lastly, I found that the volume is way too quiet for me to use these headphones as a headset in the car on the freeway.  I listen to my iPod in the same situation all the time with no trouble but when plugging them into my EVO, I couldn’t hear the other caller well at all.

Update 7/13/2010: My previous iPod headphones find kicked the bucket and I opened up a new pair.  I can now hear the other caller perfectly.  They work just fine for this application so I can wholeheartedly recommend them.  If you carry both devices in your pocket, the iPod headphones are a no brainer.

Don’t get me wrong, I love my new phone but here are a few of the things I DON’T love about it that I’ve found in the last few days.  In no particular order, here is my list of nitpicks:

My iPod Touch browser seems quicker – With a 1GHz Snapdragon, I was expecting big things.  It’s not bad at all but it doesn’t blow away my 2G iPod Touch.  That being said, the screen on the EVO DOES blow away the one on the touch.  I’d expect this much though because it’s a newer device.

My iPod keyboard seems smarterThe problem is that the Android keyboard thinks it’s smarter.  It tries to do more auto correction and completion than the iPod does.  There may be a way to tweak some of this behavior but I haven’t looked that deep yet.

4G coverage sucks at least it is in my area yet I’m still charged $10/mo extra for it.  This was NOT disclosed to me at the time I reserved the phone.  I only found out shortly before I activated the phone.  Furthermore, it doesn’t seem to reconnect to 4G very consistantly.  What I mean is that when I first connec to 4G, it will sometimes connect but even in an area where the signal is strong, once the 4G drops, I’ve yet to see it reconnect on it’s own.

I was under the impression that the mobile hotspot would be a free featureStupid me.  Why would I possibly expect them to give away a feature that they can charge for?

4G was supposed to work simultaneously with voice – It was my understanding that I would be able to surf the web or run a mobile hotspot simultaneously with a voice call.

You have to have 4G on to use the mobile hotspot – This really kind of sucks since the 4G service is currently so spotty around here.  I thought my wife would FINALLY be able to replace her ancient flip phone and her Verizon Mifi with this one device.  Not today…

Speedtest fail When I ran the mobile hotspot and did a speedtest from my iPod Touch, I got 16Kbps down and 892kbps up.  BOTH of these scores are absolutely pitiful but the 16kbps is worse than the lousy T-mobile GPRS aircard I got stuck in a contract with for a year.  I though THAT was bad but at least it was dependable and had good coverage.

Sense UI lacks refinement – The HTC Sense UI is very good and has features that put the IOS to shame BUT it’s not quite as polished.  One example is when I try to thumb between homescreens sometimes I will “catch” on a widget accidentally.  This would never happen on IOS.  I think Android/Sense UI are far more powerful than IOS but IOS is far more intuitive and user friendly right out of the box.  Argue if you like but which device would YOUR grandmother or a 4 year old have an easier time learning?

Non-existent standards – This phone features a micro HDMI port. Have you ever seen a micro HDMI cable or adapter?  Nah, me either…

No skype – I was really surprised that Skype hasn’t been released for this platform yet.  It’s disappointing since I use it for international calls to Canada.  I thought it would also be ideal because of the true multitasking too.  Hopefully when it finally arrives it can be used as a home screen widget.

Market Place woes – The market place is great because they allow anything but also horrible for the same reason.  There is a ton of garbage in there including unfinished apps, beta(abandoned) apps and fart apps.  I found one today called “Do not buy this app”.  Can’t they clean this crap out?  Would it really be that hard?

I firmly think that all of these problems I’ve mentioned are quite fixable and will probably be worked out in the first few months.  The exception being the Market Place.  I think it’s the wild wild west when it comes to vetting out good apps.  They have opened the flood gates to compete with Apple’s claim of 100,000 apps but they’ve ended up with 75% junk apps that would never have made it into iTunes in the first place.  That being said, I like that fact that Metasploit on Android without rooting is on the horizon and there are a stack of NES/SNES emulators available.  The fact that iTunes blocks applications like that is fairly irritating.  I also like the fact that I never have to plug the phone into my computer to load music, docs, calender/email sync, etc.  That being said, both the iPod Touch and HTC EVO 4G will be SHARING spacing in my pocket for the foreseeable future.

I have a huge arsenal of Roombas.  I think the count is up to 3 400 series Roombas, 1 500 series Roomba, 1 Dirt Dog and 2 Scoobas.  I love having lots of these robots to clean and vacuum my house and houses that I sell too.  As a result, I’ve gone through a LOT of batteries.  What I’ve started to do is write dates on the battery of when I purchase them.  If there is anything else special or substantial(such as used or li-ion) about the battery, I’ll write that on it too.

Looking to gain more run time and a longer cell life, I’ve tried out several Lithium Ion battery packs.  If you’ve shopped for these, you’ll know that they are substantially more expensive than the plain NiMH batteries.  I’m here to tell you that they are NOT worth the extra money.  If I could buy a Lithium Ion pack for a 400 series Discovery for the same price as a NiMH, I might do that but otherwise I would advise against it.  There are specifics for each robot as to why they are not well suited for use with a Lithium Ion pack.  I will detail that below but the long and short of it is that the Roomba charging circuits are NOT designed to optimally charge a Lithium Ion pack.  Most of the time the cells are being charged to 4.3v or maybe even higher.  If you drop the peak charging voltage down to 4.2v, you gain substantially more charge/discharge cycles.  I would say 4.2v versus 4.3v would result in a 100% increase in charge/discharge cycles.

The other problem is protection circuitry.  Most(all?) of the Lithium Ion packs commercially available for the Roombas and Scooba do not have separate balancing/charging circuit boards.  They all rely on “protected” cells.  The protected cells have a circuit built in to protect them from catastrophic over charging and/or over discharging.  These protection circuits are set at the absolute upper and lower limits of the cell’s operational ranges.  They are set to protect against explosion and cell instability, not for cell longevity.  Here are more specific problems present in each of the iRobot platforms:

500 series –  The charging circuit is very touchy and is expecting specific characteristics.  If those aren’t met, you will likely get an “error 5” on the screen.  Much more likely than you would with a NiMH pack.  The internal charger also will consistently charge this pack over-voltage.  It’s supposed to be 22.5v on the input side but mine puts out 22.97v even in circuit.  I’m taking a wild guess that mine is not the only one that has this problem.  By the time you trace the voltage to the battery pack, it calculates out to over 4.3v per cell which is too high.

400 series – The 400 series is probably the best candidate for a lithium-ion battery pack but still not necessarily a good one.  Most vendors who sell these lithium-ion packs are relying on an internal cell protection circuit and the Roomba’s over discharge circuit to shut the pack down.  Neither of these circuits are actually designed for that purpose.  The Roomba’s circuitry is adjusted to optimally discharge NiMH packs and the internal cell protection is worst yet.  That is ONLY a last resort and should never be relied on to repetitively be used for that purpose.  If the cells somehow become out of balance, this can start happening a lot.  The symptom is that the Roomba won’t park or go to a red light, it will simply die in the middle of the floor and become entirely lifeless.  The power button won’t do anything until you charge it enough to be recognized.  Another problem with the 400 series is that the Li-Ion pack makes the Roomba much lighter and it seems to have a harder time making contact on the dock without the added weight holding it down.

Scooba – This one is one of the worse of all.  Personally I have a BAD habit of not taking the battery out right away when the Scooba dies.  While I was fixing a Scooba for a friend one time, I was probing around trying to diagnose a problem and found that even when the Scooba is TOTALLY off, it’s still drawing quite a bit of power.  I tested the output leg on the 78XX series regulator and found voltage there and a few other places.  The logic was all still hot and drawing power as well.  The power switch on the Scooba is essentially soft power.  This is probably the case with the Roomba too although I haven’t tested it.  The difference being the Scooba isn’t designed to dock.  Not only that, I’ve always charged the battery out of the unit in the Scooba Charging Base.  This is an extra step that I sometimes don’t have time for.  As a result, I’ll sometimes forget about it entirely and the battery will sit in the Scooba and over discharge.  Doing this a few times will surely fry a lithium ion pack and will eventually fry a NiMH even.

The bottom line is that you are far better off sticking with NiMH battery packs for the Roomba, Scooba and Dirt Dog.  I have used the Tenergy Scooba Battery with success in the past although one of my friends has had VERY mixed results with the Tenergy rechargeable AA’s.  For the Roomba, they have OEM Roomba batteries at the Renton, WA Frys for $40 which is a steal for a local store in my opinion since the list price is $69.99 or they have them on Amazon even cheaper at this link: iRobot 4905 Battery.  For the 500 series, I have had success with this Aftermarket 500 series APS Battery sold by Allergy by Gone.  If iRobot products were designed specifically for Li-Ion chemistry, I have no doubt that Li-Ion packs would perform fantastically and we would all benefit from longer run times and cell life but since they are not, I don’t think it’s a great idea to run these types of battery packs in your robots.

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