Once again... Scooba 385 on LiIon

[petruchito]

Hello ppl, my scooba battery pack started to die recently, now i'm looking for alternatives.. As i've understood the downside of LiIon packs are overcharge limit of protection PCBs, that causes scooba to alert about battery faulty, and very high value of 4.3V, that causes rapid wear of the battery.

So i thought - maybe i can switch to 5-cell 18.4V battery with 5-cell pcb? It will not fall into overcharge protection mode, each cell will work from 2.8V to 3.6V that virtually should prolong its life to 2000 cycles or even more...

The only concern i see is longer high current stage when charging and probably 18V at the starting time of the run.

I consider 5x18560/3Ah cells and 5-cell pcb like this one:
http://www.ebay.com/itm/1-pcs-PCB-for-18V-5-Cells-Li-ion-Lipo-Battery-Pack-FR4-/150890151672?pt=LH_DefaultDomain_0&hash=item2321c0fef8

PS: i understand that i will loose something like 40% of the capacity, but it have to be enough for me, i usually used about half of the original battery, then charged to full while roomba did the work in the next room.

Thanks for comment and notices!

[vic7767]

I used to build 4800 mAH LI-ion Scooba batteries using 1200 mAH cell phone batteries (4Px4S) and if you use the external Scooba charging brick there will be no error conditions.

Space inside the Scooba battery case is very limited and it is difficult to find the proper cell phone battery packs to fit inside.

[petruchito]

Charging brick is not an option, too expensive for just a brick
Maybe i'll add balancing plugs and use Imax B6 balancer to charge the battery then...

How long have your liion-battery lasted?
And what protection PCB did you used?

[vic7767]

I used LI-ion cell phone batteries that each had its own PCB. The 4800 mAH battery lasted 4 years. I don't understand why an external charging accessory for the Scooba is more expensive than the purchase of a special charger, LI-ion batteries and a PCB control board for charging management.

BTW I have now switched back to using 4500 mAH NiMH cells to run my Scoobas. Here's a URL to perform that mod: http://www.robot-doc.com/23.html

[petruchito]

4 years seems pretty sweet... Probably it's the best solution just to set 4 cells of those:
http://www.ebay.com/itm/1PCS-UltraFire-18650-3-7V-Rechargeable-Li-ion-lithium-Battery-4000mAh-Torch-MP4-/110957124612?pt=US_Rechargeable_Batteries&hash=item19d58f5c04

$12 to renew battery LiIon is chaper than NiMh nowdays. I only doubt does is it really 4000mah battery...
Added after some reading: in reality they have only 2Ah at 1-2A discharge current.

I don't understand why an external charging accessory for the Scooba is more expensive than the purchase of a special charger

In this case scooba brick is special charger, and imax is universal, i can use to charge my car battery, charge all my NiMh AAs, and so on. And it's costs less - $46+shipping for brick on ebay, and $35+free shipping for imax.

[vic7767]

Those 18650 cells don't work well in series configurations. I've installed and tested that style LI-ion with PCBs with poor results.

[TechGuy]

I had used the 18650 Li-Ion cell with success. The question is that how good is the UltraFire 18650 battery?

The one that I used is the battery pack used in the old, brick-type, cellphone. Each battery pack has two 18650 in series. But it is only rated 1200mAH. I put 2 packs in series to get 14.4V. In order to get more energy, I put two sets in parallel to get 2400mAH.

You can put eight 18650s inside the Scooba battery case. Put UltraFire into 2Px4S configuration will give you 8,000mAH Scooba battery pack.

[petruchito]

It turned out to be just a NiMh depression - scooba sung dead song after 20min of cleaning, while battery had about 15.5V(bloody chinese mastek multimiter, but trustful enough for me).
Opened the battery, in empty state all cells couples showed 2.55V - there was no dead cells, perfectly balanced.
I have discharged the battery (just leaving it in scooba turned on) down to 7.8V(planned to go to 10.5V minimum, but missed the point occasionally), it took about 5 days, then slow-charged it in scooba.
Now my old battery runs for 1 hour and battery still have 14.7V and scooba didn't signaled empty battery yet.

So the rebuilding of one is postponed for me now

And also i've noticed only now - scooba manual says that tank should be removed or opened if charging in scooba, that might affect stock battery life too.

[Twobeers]

I currently am experimenting with Li-ion 26650 Uitrifire cells (@$5C) I purchased from DHgate.com out of China along with a Imax B6 charger ($28C) & free shipping to north america. They call the 26650 cells Li-ion but I think in reality that they are actually LiPo's (3.7v). The cells I purchased are 5000mah. The cells are too big to fit into the old scooba brick case. I was able to easily solder directly to the battery after lightly sanding the battery ends. At the moment I have simply soldered Deans connectors to the batteries & the Scooba. I use the Imax B6 to charge up the batteries. On my first couple of cleaning runs, the scooba ran for 70 minutes before the scooba said it needed to be recharged (red light). I simply soldered 4 of the 26650 cells together with bits and pieces of 18awg stranded wire to soldered the batteries in series and then used a hot glue gun to hold the batteries together in a 2x2 arrangment. Then simply put a couple of small strips of self adhesive velcro to hold the battery in place. I see now that they have 18650 batteries that are also 5000mah at the DHgate web site, I have ordered 30 of them for $96 (the others I will use to rebuild a couple of my Ryobi drill packs). BTW the thermistors in the scooba brick are approx. 5k ohms with the 2 of them in parallel. I bought a few 4.7k thermistors from a local electronics store to play with. The scooba charger will not charge these batteries while in the scooba with out some serious internal hacking. Charging with the Imax charger works out just fine for me. I am revisiting my post from a couple of days ago. The Imax B6 charger works great & is giving me pretty much the same results as my Triton & Ice chargers. HOWEVER, these batteries are crap. The 18650-5000mAh are only delivering 410mAh on average. The 16650-5000mAh batteries which BTW are labelled Uitrafire (that's an i not a L) are only giving me at best 2300mAh. I bought 25 of each. 4 of the 16650's are dead after 20 minutes of use. (open circuit) I have looked & looked but could not find any specs for these batteries whatsoever. But still I have averaged 90 minutes of run time with the 26650's.Its the Chineese new year right now, we'll see if DHgate honors their guarantee.

[Gordon]

"YIKES" because we have been led to believe the Scooba battery's temperature sensor to be composed of two thermistors in series! Your report of:

...BTW the thermistors in the scooba brick are approx. 5k ohms with the 2 of them in parallel. ...

caused me to scurry to my one specimen of a Scooba thermistor assembly and give it close scrutiny. Yep, the thermistors are parallel wired!

But, since the temp-sensors nominal ambient temperature resistance is ~5k ohms, we have two 10k ohm thermistors wired in parallel. And, that means iRobot has been building the // arrangement from Roomba stock.

That make soooooo much more sense than the company buying 2.5k ohm thermistors to then wire in series, for each Scooba battery assembly. Thanks for correcting our long standing misconception.
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I have one question about your Li-ion implementation. Does DHgate.com give you any data about the Protection IC that must be built into each Li-ion cell? The IC must be present since you had no problem using the Imax B6 for charging them.

[Twobeers]

I guess what they say about cheap chinese battery knock offs are true. They are truly crap as you can see on my edited post above. BTW, I am an electronics tech with over 37yrs experience so I am not shitting you. Here's the interesting thing with those cheap 26650's that died on me, I ran them in my scooba until the scooba quit (about 90min run time) I immediatly measured the voltage and read about 3.1v on each cell. The ones that died, died after sitting several minutes(more than 1hr) after use (still cool to the touch, no heat at all). It would seem if I charge them right away after use all is good. If they do have internal protection circuitry then somebody F'd up in production and stuck the wrong value of componets in them during the manufacturing process. When I say they died I mean 1 cell out of a 4 cell pack, O volts, nada, nothing, zip, dead as a door nail. I did some looking around and CMB boards can he had for less than $18 if you want to go that route. I have 2 scooba 380's and 2 roomba 572's. It seems that in Canada if something F's up during the warrantee period like they keep going in circles & you go thru all there steps over the phone to try to correct the problem and it doesn't work they say just keep it & we'll send you another one just keep the battery & tank. Bonus here! I purchased and additional tank with my first scooba. I will eventually change the scooba's charge jack to one like on the roomba & rewire it directly to the battery so that when I plug into the jack it disconnects the power to the Irobot and connects directly to the battery.

[Gordon]

... ...HOWEVER, these batteries are crap. The 18650-5000mAh are only delivering 410mAh on average. The 16650-5000mAh batteries which BTW are labelled Uitrafire (that's an i not a L) are only giving me at best 2300mAh. ... 4 of the 16650's are dead after 20 minutes of use. (open circuit)...

In the interim, awaiting your evaluation report I decided to check out the DHgate site, and after having done so I was very much not interested in buying anything from that source. Here are a couple observations:

a) Not battery / cell knowledgeable: Technical data is very limited or obscure. A buyer must take the hint that the 18650 Li-ion cells they sell are not intended for high discharge current application, simply because DHgate recommends service be limited to "electric torch / flashlight" use.
b) DHgate sells all sorts of other junk: By visiting the DHgate home page, one may see that battery sales is just a tiny part of its business, and
c) They no longer accept payment through Pay Pal: I presume that to be due to Pay Pal taking DHgate to task for ripping off too many buyers.

I left the DHgate pages as I decided to see what other vendors offer by searching for "18650 Rechargeable Lithium lon 3000mAh battery" -- considering Roomba application, not Scooba. Notice I excluded use of "UltraFire" in that search string. Of course there were numerous results, but the one I found very interesting was in an Amazon seller's pages. Below the sales pitch there was this very interesting review article under Comments by a dissatisfied buyer using the handle XYZZY:

...My only complaint is these batteries after being freshly charged cut out under a high load because of the protection circuit board which seems to be current limited to only around 2.5 Amps. For instance, when trying to drive a Ultrafire WF-502B or WF-501B flashlight with the 900 lumen Cree XML-T6 P60 LED drop-in on max power, it will only illuminate for a couple seconds and then cut off. Running it for a few minutes on medium power to partially drain the battery then allows it to run continuously on high power. The measured current draw on high power was 2.46 Amps. This suspicion was further confirmed when I cut open a cell and looked at the protection circuit card inside and found only one MOSFET driver IC, and two empty spots for additional MOSFET driver ICs. (Most other brands of 18650 batteries can sustain 5 to 7 Amps and contain two or three MOSFET drivers on the protection circuit card)...{and}...After having used these batteries for over a month now, and having gone through several charge/discharge cycles, I downgraded this review from three to one star. ... . What I found is the advertised capacity of 3000mAH for these Ultrafire 18650 batteries is a complete misrepresentation. The label on the battery says 3000mAH, however when I tested them I only observed 980mAH to 1070mAH discharge capacity for all four of the batteries I received. This discharge test was done using a Turnigy Accucell 8150 with a discharge rate of 600mAH, discharging the battery from 4.20VDC down to 3.00VDC. By comparison, I tested two inexpensive Tenergy 2600mAH 18650 batteries using the same setup and they came in at a reasonable 2460mAH and 2520mAH discharge capacity. ...

To read the entire comment see it at this address: http://www.amazon.com/UltraFire-3000mAh ... B004LHFU62

[Gordon]

... I will eventually change the scooba's charge jack to one like on the roomba & rewire it directly to the battery so that when I plug into the jack it disconnects the power to the Irobot and connects directly to the battery.

I think you will want to give that method of connection a bit more thought. I make that suggestion because Scooba's main_PCA will be subjected to higher than nominal voltage at the instant the first protective IC switches to open-circuit (in a 4S Li-ion pack) at high cell-voltage cut-off.

Also, if you plan on using Scooba's PSU for that charging operation, you will have to trick the PSU into outputting its high-rate current level of 1.8A. You might review this post, and contained links to see if anything helps your project: viewtopic.php?p=78666#p78666
Not every link therein will be of interest, since the thread's topic differs from your needs.

I simple way to avoid that "trickery" would be to use a Roomba PSU for charging the Scooba (Li-ion) battery (so what if its takes a bit longer); however, the over-voltage threat remains to be attended to.

[Twobeers]

I have no intention of using the scooba charger for charging the lithium battery pack. I simply want to use a simple to use plug (ie similar to the jack on the roomba) that has a built in switch. I plug my adapter from my Triton, Ice or Imax charger into the jack and it automatically cuts out the devices power feed by disconnecting one side of the battery and connects directly to the battery. Somebody mentioned a search of Li-on batteries excluding Ultrafire. The batteries i bought were advertised as Ultrafire. The batteries I recieved are labelled Uitrafire & are useless. At this moment I am playing the email tag game with this supplier, they have requested I send them photo's........I am now thinking now more along the line of posting a couple of video's on YouTube that I can take with a couple of security DVR's that I have. That way I would be able to take video's of the charge & discharge process & greatly speed up the playback. Who wants to watch a video of a battery taking 1 hr to charge & discharge, when I could display the whole process in less than 2 minutes. I can send them a link to the vid.
I did try the tricking the Scooba charger to output its full power output but the Scooba's internal charging circuitry balked at it. I have tried both 5 cell & 4 cells. There was not much differencce in run time. However with 5 cells the Scooba runs the pack to low for my liking, with 4 cells the Scooba quits running at just the right time. But you can't leave the Lion pack connected due to the fact that even when switched off the Scooba still draws power from the battery. Back again to my switched jack idea. Instead of plugging & unplugging batteries I can simply plug in a plug into the jack to disconnect the battery.