I'm pretty sure that yes, you need some modifications to make work lithium batteries in roomba in the best way, otherwise or you'll ruin the roomba or make the batteries to last for only six months.

4s. 4x18650.

See @andrewsb5879 1 year later!!! Cc CV charger already built in just solder extended 1.7mOhm (need to avoid error 5 and pull down woltage) resistance to 207 resistor in main bird and it will work well I check it.

Ran pretty good long term, cycled 7 or 8 thousand cells. I never had a problem. But I also never had 96 fully depleted cells on the board at a time, since I would charge 96 cells of various soc and as they were fully charged I would pull them and put them on the opus chargers for discharge capacity testing, then once I got the capacity I would throw them back on the board to charge them back up... I could only discharge 28 cells at a time so really I was swapping all the time. So probably never really experienced a peak current draw. Now it just collects dust on my wall as a reminder of the pain and suffering I endured making 2 - 10kwh packs... Tens of thousands of spot welds lol.

You need a charger capable of producing the correct voltage. I use an icharger x8 for my 7s banks, it's best that any charger you get be capable of setting the final voltage, for example 4.1v/cell (28.7v) instead of 4.2 (29.4). I also charge using a solar charger controller when not home, once again capable of adjusting final voltage...

@@havinfun4014 thank you for explaining but how can I get the i charger?

Still running strong, no issues at all.

It run ok with Lithium, but it has problem with charger system. So the importance thing here is how to mod the charging. Ni-MH charging with 14.4V, Lithium have to charge with 16.8V.

Best answer I have found until now. Thanks

@@vuquan3163 This is the Ni-MH battery charge sequence and end conditions for old Roombas 500 & 600 extracted from Roomba 500 Service Manual: 1) Charge circuit (FET) check: if it fails, the charge is interrupted 2) Pre-charge cooling {0mA} Until the battery temperature is below 50°C, or an END OF CHARGE condition is met 3) Charge: runs until an END OF CHARGE condition is met in one of the following modes: - NORMAL {1250mA} if the battery voltage is higher than 10.8V (AMBER LED FLASHING) - RECOVERY {300mA} if the battery voltage is less than 10.8V. (FAST AMBER LED) 4) Post-charge cooling {0mA}: Until the temperature drops below 35°C, or 2 hours pass. (STEADY GREEN LED) 5) STANDBY CHARGE {50mA} - Runs indefinitely, stops if temperature exceeds 42°C, and re-enables when it drops below 40°C (STEADY GREEN LED) END OF CHARGE. Charging ends if one of these conditions is met on the battery: a) If the voltage drops more than 30 mV from the maximum voltage. b) If the temperature increases more than 0.5 ° C per minute. c) If the measured load is more than 2 times the nominal. d) If the time in NORMAL mode exceeds 9 hours e) If the time in RECOVERY mode exceeds 16 hours f) If the battery temperature exceeds 60 ° C for 1 minute. g) If the Battery Voltage exceeds 21.6 V for 1 minute. h) If the battery has been discharged less than 150 mAh since the last full charge. According to g) voltage value is not a limitation for LIthium, a), b) and f) conditions works well for Ni-MH, and do not so much for Lithium , but the main problem for Lithium is 5) due to nomal maximum use of Roomba is 1-2 hours /day, and the rest of the time is overloaded in the dock. By means of my new 671 Roomba connected to my phone with a serial cable (Cable USB UART TTL Serial Port1) and using app ('Serial terminal USB') I saw lithium battery charge is a more simple procces than Ni-MH, and and the fact that new firmware can detect the type of battery and apply a different charge sequence, and tricke charge or not depending of is a Ni-H or Lithium battery. This was tested with the original iRobot X-life and Lithium 1800, I don't know if works with third parties batteries. Obviously use a Ni-MH in a Lithium Roomba only has the sense of taking advantage of an old battery But I didn't find any practical solution to charge a Lithium battery in an old Roomba avoiding degradation: Neither extract and charge the battery externally (charger or other Lithium Roomba), nor be aware of removing the roomba from the dock after charging. For all this, and due to in Spain a second hand 671, 675 or 676 (same model, different year with 1800 mAh Lithium) can be easily purchased for 80 euros (this price really means Roomba is one the most failed gift...), and especially considering the great advantage of the lithium battery, does not degrade because a seller had not used it in the last year (in Ni-MH this is total battery destruction), I have prefered use the modules of my old 531/650 for spare parts, and replace by these new 600's. About a Roomba Lithium battery 'well treated', my first 671 bought new in october 2018, after 1804 services and 1162 hours (I can see it in app historial) the authonomy is 65 minutes, versus 100-110 min of my 3 second hand Roombas 671/676 purchased in 2021 (iRobot specification is 90 min.). But the most important of this info is I saw the great part of this 671 capacity loss was when in 2109 -because of my lack of information-, I tested and used some weeks this lithium 671 battery I my old 650. Regards.

@@andreiandries3594 In case you are interested, I have added additional information. Regards

1amp per hour. so a 2500mah cell will take around 2.5 hours

My Nastima battery DIED after a short run of about ~6months. But I did not remove it off the charger as I was supposed to. So maybe would last longer if I just did the charge and then unplugged as soon as I see it full.

I got same issue. Is there any solution?

Bad contact between Roomba and battery

@@fatihsaygin2355 it's somehow reconciled, and now it's charging