Rebuilding a Roomba Battery for Less

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Re: Rebuilding a Roomba Battery for Less

Postby a1robotrepair » August 28th, 2016, 8:31 pm

Robocleaner,
Those are Samsung ICR18650-32A in that pack.
http://gamma.spb.ru/media/pdf/liion-lipolymer-lifepo4-akkumulyatory/ICR18650-32A.pdf
ICR batteries still have the largest capacity per volume. They will heat while being used. They should
never be discharged above 2C or charged above 1C. You should let the battery pack cool before charging.
3 parallel, 10 series, or 30 batteries is what the pack needs to reach 9.6Ah @ 36V nominal.

With no balance or individual cell protection noticeable, you may want to look into building your own pack.
I don't want that thing between my legs. It is highly unlikely it will fail catastrophically, but there's always that chance.
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Re: Rebuilding a Roomba Battery for Less

Postby robocleaner » August 29th, 2016, 3:34 am

a1robotrepair wrote:With no balance or individual cell protection noticeable, you may want to look into building your own pack.

I might’ve considered doing that. But given the phenomenal growth in popularity and thus development of both e-bikes and the cells to power them... both e-bike and cells are cutting edge when you order, and obsolete by time they’re delivered (witness the new Panasonic NCR18650B, PF, and the seriously whacky GA reds). I’ll be keeping this bike a year, then sell it on for something newer and (hopefully) safer.

But keeping this discussion in context, I find it seriously worrying that this poor battery-building practice is even allowed - be that for a Roomba, e-bike, or anything else. Surely there should be some minimum safety standards imposed in the form of regulation?
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Re: Rebuilding a Roomba Battery for Less

Postby a1robotrepair » August 29th, 2016, 6:10 am

But keeping this discussion in context, I find it seriously worrying that this poor battery-building practice is even allowed - be that for a Roomba, e-bike, or anything else. Surely there should be some minimum safety standards imposed in the form of regulation.

One only need look into the favorable trade practices given to the makers country by politicians for received donations. As for regulations, they are there but unaffordable to check every product, everyone needs to be their own regulator, Caveat emptor.

NCR batteries are the best for high capacity and safety. They should still have individual cell protection for safety and balance for longevity. <- trying to stay in context, if possible, build your packs with NCR batteries.
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Re: Rebuilding a Roomba Battery for Less

Postby useRoo400 » September 13th, 2016, 12:53 pm

The R4 lithium ion batt from Lithium Power Inc, purchased 14 months ago and used ~weekly for 10 months, suddenly failed: looks to Roomba 400 as if it's charged (green light), but no voltage @ output terminals.

Voltage at the output pins is 0.08 v. measured off the machine. Opening up the unit, all appeared good. Voltage of each of the 4 cell packs was 3.9 v. and voltage at the end tabs, measuring all batt's series voltage, was 15.5 v. Nothing appeared amiss on the circuit board.

Trying again in the Roomba to charge, power light gives red flashes at normal rate for a minute or two, then green comes on steadily. But it's still dead when trying to run.

Lithium Power customer service suggested putting 17 v. to the terminals to 'wake it up' on the chance the R4 had entered sleep mode. Putting 17 then 18 v. to the terminals, for a few seconds, then for a few minutes, showed no current flow at any point, nor did it have any effect: no voltage at terminals when removed. He stated they do not sell replacement circuit boards for this batt. [does anyone else?, or know how to repair?]

I don't have skill or equipment to diagnose/repair the circuit board, so will probably try to remove the board entirely, and wire cell end terminals (15.5 series output) to the batt output terminals directly. Also, wire connectors to the separate cells to hook up to my balance charger -- to do off the machine. Question: do the individual 3.9 v cells have built in protective device to make it safe to charge from the Roomba in normal way? If not, then would it still be safe to remove at end of use, and just use the balance charger for all charging?
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Re: Rebuilding a Roomba Battery for Less

Postby a1robotrepair » September 13th, 2016, 1:28 pm

One of the protective circuits or charge/discharge switching devices have failed.
The cells are not individually protected without the circuit board.
Don't charge in Roomba.
Don't know what charger you have but each cell should have over voltage, under voltage, over current, short circuit and thermal protection before charging or discharging.
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Re: Rebuilding a Roomba Battery for Less

Postby useRoo400 » September 13th, 2016, 5:28 pm

Thanx for that informed advice A1RR. It looks like I can buy replacement 4 cell charge/discharge protection boards (with goal of charging it in in the Roomba) pretty cheaply (<$15):

20A rating: (w/ heat sink presumably, 10A without one)
https://www.amazon.com/XINY-lithium-bat ... B01J9X3PI2
15A rating (ditto -- would I need heat sink in Roomba ?)
https://www.amazon.com/SMAKN®-Lithium-Battery-Charger-Protection/dp/B018JVE2FA

neither of the above have any indication of thermal protection, an obvious safety advantage in case of a failure, but in normal charging the R4 w/ the Roomba 400, heat has never been a limiting factor. I'm guessing the thermistor in the R4 would continue to do its job as far as feedback to the Roomba charger.
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Re: Rebuilding a Roomba Battery for Less

Postby a1robotrepair » September 13th, 2016, 5:56 pm

They do not have thermal protection.
Your Roomba uses the thermistor circuit to terminate rapid charging.
The aftermarket li battery packs use that circuit to terminate rapid and trickle charging.
The board you buy should be rated for the batteries installed, Boston Power duo cell 4400mAh Swing if they haven't changed.
Look up their data sheet and verify the board is compatible.
Design a circuit to mimic the the thermistors in a standard pack or charge the pack after it has cooled externally using a rated 14.4 V INR Battery pack charger.
Most of the information is in this post, except the mimic circuit.
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Re: rebuilding li-ion R4 for Roomba 400

Postby useRoo400 » September 19th, 2016, 11:11 am

Wiring new protection circuit board

I didn't know how to do all the things a1 suggested and was unclear what "this post" in last sentence referred to. I did buy and install one of the aforementioned protection boards w/ 15 A working capacity. I paid $12.50 and got fast shipment from KY (https://www.amazon.com/gp/product/B00JJIZYSC). Same YH11047A can be bought for $6 if you get shipped from China.

I removed the R4's thermistor, checked that its response curve is identical to one from an old NiMH pack (it is), and put it between output negative terminal and the sensor terminal (wide strip on the side) -- same location as in NiMH packs. I did not add a heat sink. All the original R4 cells tested good, and were left the same. Photos show it wired in place.

Charging in the Roomba 400 seems fine. When charged in 15 min. segments (6 hrs rest between segments) the Roomba case gets slightly warm to touch, the batt stays room temp. When green light indicates full charge, the output terminals show 16.55 V without load. Run time is slightly better than with the original protection/balancing circuit.

This circuit appears somewhat less complex than the original; whatever protection and balancing it's doing is probably less sophisticated. I'll run it for a few cycles of use / recharge, then open case and load test each cell to get a better idea if it's charging evenly. With the careful recharging method I use, in the Roomba, in short periods on timer so as never to overheat the batt or charging parts, I think this simple solution may be adequate, tho admittedly not as safe as the original circuit. [also I never leave batts in the Roomba once they fully charge.]
Attachments
R4rebuildB.jpg
R4rebuildA.jpg
Last edited by useRoo400 on September 19th, 2016, 2:36 pm, edited 1 time in total.
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Re: Rebuilding a Roomba Battery for Less

Postby a1robotrepair » September 19th, 2016, 11:57 am

I want your old bad board.
Attachments
image.png
The Swing 4400 specs.
image.png
The proper way to charge.
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Re: Rebuilding a Roomba Battery for Less

Postby aBlackCat » December 13th, 2016, 1:54 pm

I tried to rebuild my battery, but it didn't last long. Maybe cheap cells. I just bought a new one at irobotbatterycanada.com and they had free shipping and free side brushes package included with it. I won't bother trying to rebuild again.
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Re: Rebuilding a Roomba Battery for Less

Postby SE_machine » January 10th, 2017, 10:30 am

After 5 long years, my NiMH battery finally gave out. The Roomba could only back off the dock before it died.

I started looking at lithium ion packs, but after seeing this thread, I should be able to dissect a hoverboard battery and re-use the good cells to get both my 570 and 410 running again for only $30 (two BMS boards). A hoverboard battery is 10s2p, and each pair of cells is roughly 4.5 Ah.

I took the NiMH battery out to test it with my RC charger and found this along with very high internal resistance (can only pull .1 amps out for any decent length of time):
Attachments
image.jpeg
Hmm, got a little warm.
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- Roomba 570 with bin mod (viewtopic.php?f=1&t=19321)
- Roomba 530
- Roomba 410 (burgundy)
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