24 Eneloop AA batteries Roomba 581 modification

[glnc222]

AA cell background info
Interesting data on AA rechargeable battery brands in comparison review, revealing issues, lot of details, tests, charging methods, trade-off between capacity and cycle longevity.
http://thewirecutter.com/reviews/best-r ... batteries/

[fergambo]

Hi to all, and thanks for this fantastic post full of information

After bad experiences with all batteries I've tried for my Roomba 560, some time ago I could find this post and I've tried to make a similar battery, besides of I'm a lover of Eneloop Batteries (and my old Romba too)
As my main requirement is the possibility of easy refreshing / replacing any individual eneloop, I've used battery boxes to avoid any soldering, so I can only use 12 AA batteries.

My first test has been with normal (1900 mAh) eneloops, in order to change to pro (2500 mAh) if the experiment was acceptable.

I've put the 12 eneloops in 2x6 AA box and the thermistor (measured 10 ohm to 26 ºC, so is OK according to Service Manual) inside the box of my last Li battery, I've done a final charge (eneloops was installed charged previously), and the battery length was 45 min (so 60 min for 2500 mAh Eneloop Pro)

After charging my second test, was very similar, 43 min.

But in my third Test I've only obtained 15 min after a very short time of charging. When Roomba stopped in low battery, almost suddenly changed from green to red, and after testing battery was over 14 v, and any individual AA was over 1 v, but really pack is really hot.

For muy fourth test, the charge time was short too, si I forced a pair of additional charges ereseting Roomba, but the cleaning time was the same, 14 min.

I know charging is stopped by cells temperature, I'm not sure if during cleaning temperature stops too, the only I'm sure the voltage is correct. All this could even have some relation with the failure of my last bought batteries, start well die before one year.

My Roomba base output is fail (2v output) so I always charge Roomba directly by connecting the PSU directly into the charging jack on the side of the Roomba.

Sorry if it's not convenient to post here after two years, but it's the only thread of eneloop battery for roomba I've found

Thanks and regards

[glnc222]

Experiments were made with AA cells for Neato Botvac batteries used by one owner, maybe not too different from Roomba batteries. Testing equipment constructed showed this size cell cannot support the current drain levels of the robots without severely shortening the battery life. The Neato puts about a 3 amp load on the pack, which may be divided into less per cell depending on parallel construction. There seems to be a reason, though, why larger size cells are used in robots with their power requirements. The AA cells can appear misleading in initially running the bot but wearing out quickly.
http://www.robotreviews.com/chat/viewto ... 20&t=17994

Besides testing the cells in a robot, a continuous battery cycling tester was constructed to measure the cycle life of the cells under loads similar to the robot -- run inside a cook pot in case of any damage unattended 24/7. It was surprising to find such short life. In normal load use for that size cell I would expect much longer life. The higher load applied would seem to make the difference. There are different load specs for AA cells, some mentioned as higher load oriented. The Eneloop technology, now adopted by other brands as well, offers the advantage of long shelf life, less self-discharge in storage which was a disadvantage of NiMh cells compared to lithium in the past.

Of course, enough parallel series could reduce the load on AA cells to whatever is needed, but the number of cells and space requirements -- and cost -- could make it impractical for the robot.

[fergambo]

Oh ... actually some of my Eneloop had already rigid and deteriored the extrenal plastic cover due to the heat ... fortunately functionally they seem to be well

So the only way is any maintenance of Roomba battery, such as removing the cover of each of the 24 poles and wiring each cell to a smart charger using the 'refresh' function...

Thanks for the answer!

[glnc222]

A new NiMh battery is listed at $29 and a lithium ion replacement (for the NiMh charger, with adapter electronics) at $65. The lithium will have longer life and priced accordingly; not clear if cheaper in the end. Also depends on how long the robot will be used. Retail markups on battery cells make it more expensive to make DIY batteries. It would be interesting to make a much longer lasting LiFePo4 battery, but probably won't fit in the Roomba at least with the necessary capacity. It was possible in the Botvac with its particular battery compartment shape. A newer higher capacity LiFePo4 cell was used. Thread http://www.robotreviews.com/chat/viewto ... 20&t=19149
Analysis required to tell. The Botvac only used 12v, so an additional cell in series would be needed for 14.4v Roomba, 5 series LiFePo4 compared to 4 series regular lithium, 12 series NiMh.

[fergambo]

From I bought my Roomba 560 in 2009 I've used five batteries in these 9 years. From the life of my first iRobot almost 3 years, the life I've got for next ones has been shorter and shorter (another iRobot NiMH battery, two no iRobot NiMH and the last Lithium)

Every battery I've bought more care I've taken (complete discharge cycles, charge only after complete discharge, a minimun of weekly uses of Rooma, never long periods stopped in base ...) and shorter live I've got!

This last Lithium battery looked very good, 4 h of cleanning at the beginnig, but after only six months, one our. After reading a lot of posts, as I've never upadted firmware, probably my 560 charge system is not prepared for Lithium.

The life of last non iRobot batteries was much shorter than previous iRobot ones, I don't know if there's a particular quality reason, or may be any disfunction in my charging ssytem.

[glnc222]

The robot supplied with NIMh batteries uses lithium replacements by means of an adapter which simulates NIMh behavior for the charger. NiMh pack charging is controlled by temperature, with a thermistor in the pack, where the temperature rises when the battery is full (NiMh then continues to conduct just dissipating as heat). Lithium batteries do not get hot and charging is terminated at a maximum voltage (lower then the NiMh maximum; over voltage damages and requires protection shut off circuitry); an adapter modifies the thermistor signal to simulate a temperature rise for the NiMh charger.
It is possible that replacement batteries used over time where not best quality. The Asian sources for brandless batteries can be dubious. Capacities have been known to be exagerated.

[fergambo]

Thanks for the info, about the adapter to simulate NiMH, the Lithium I bought indicated something like that I din't understand, and as I see Amazon user reviews are good, I'll try to check my charge system cause something must be wrong (clean the main board as seen in other post)

Probably the 3500 mAh Lithium battery from iRobot does not include the adapter, cause is not sold for the 500 series, only for 600 or higher. By the way, the price from local irobot web here is a 'bargain', 119 € and the reviews are 1,6/5,0

Some Asian capacities are exagerated, but it's more depressing the NiMH battery from iRobot is a 'black box', no any technical info, mAh... only explains: 'XLife = Extended Life' = double of cycles, Fantastic... an authentic 'one equations with two variables'

[glnc222]

There may have been after-market 3rd party suppliers of 500 series lithium replacement batteries with adapter electronics, I never looked. I think Tenergy is a reputable battery brand and lists 500 series
http://www.all-battery.com/roomba-34057 ... X4QAvD_BwE
That is a U.S. dealer in all sorts of batteries and chargers, and I suppose you need UK or Europe. I thinkTenergy is Asian and might ship direct from there.
You could also ask this dealer or Tenergy whether the battery replaces NiMh originals.
Google Roomba 500 lithium batteries.

[Brett]

... cause is not sold for the 500 series, only for 600 or higher ...

Ignore that. The battery design/requirements for the 5xx and 6xx machines are the same.

(-8

[fergambo]

I think Tenergy is Asian and might ship direct from there.

Ufff, any package to the European Union directly from Asia is a 'lottery' in terms of customs control, fees and taxes ... the option in local Amazon does not seem bad, ANewPow 4400mAh Lithium.

Ignore that. The battery design/requirements for the 5xx and 6xx machines are the same

Interesting!

Again thanks to all for the info

[glnc222]

AnewPow is the European branch of Taiwanese LithiumPower Inc/ Boston Power Inc. Their products are thoroughly engineered, with even a "sleep mode" in the adapter electronics for long term storage. Their Neato Botvac 12v battery however, is not such a good idea for the 12v system, which does not divide well into lithium cell voltages, unless lower cell voltage LiFePo4 is used, which they did not. So they put a lot of excess capacity in it to use just a top part of the discharge curve. The higher voltage XV model (and lithium equipped newer Botvac's) two-pack system works better. They took a long time to offer the Botvac battery. They are supposed to have main business in medical device batteries. Roomba is on the same voltage as Neato XV.
Their NiMh replacement business is somewhat temporary in that newer robots all use OEM lithium batteries. Market for the older models has to be more limited over time.

Tenergy can probably be found at European battery dealers. Lot of individual cell business.

[fergambo]

Finally I have been quite conservative, and I've got an iRobot XLife battery 3000 mAh, not only after the bad results with non iRobot batteries, but I've found a good Amazon offer for it.

After this I've made a serial USB cable according to Kelad's guide and I've beeing checking the charge and trying to see the parameter than make to finish it.

At this moment I've only seen the final charge values (2850, 2660 and 2780 mAh) beacuse in both with Putty and Realterm I can't acess to all data up in the window, so it seems to be necessary what I didn't: wait the charge ends in front of the monitor...

Is there any way to to get a file ??

[mfortuna]

Teraterm has logging capability and you can also increase the size of the text buffer if you don't do logging.

[fergambo]

Teraterm is perfect, creates a text file as receives the roomba information
Many thanks!