SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

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SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby leoo2001 » March 16th, 2017, 8:15 am

I need specialists advice if it’s possible to make a custom battery with following sub-c 5000mh pack which is currently sold around 35 eur for 10pcs. What I really want to achieve is more running time as my Botvac 85 don’t get to clean the house in just one run.

https://www.amazon.de/Kraftmax-SUB-C-Ak ... FX6JFPWP1B

Or maybe recommend another proved battery for the task . Thank you.
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby JEfromCanada » March 16th, 2017, 12:03 pm

As I understand it, the max run time is limited by software, not the battery capacity. A higher capacity battery will supposedly extend the life by not draining it as much with each cleaning cycle.

Over time, the higher battery capacity should allow the Neato to perform at peak efficiency (i.e. maintaining maximum run time) rather than having the run time reduced as the battery ages.
Current robots:
Roomba Discovery 4210 (R.I.P. - Freecycled)
Roomba 560 (retired)
Neato XV-11 SW version 3.1.17844, LDS version 2.6.15295, with Pet Brush and Vic's filter (sold)
Neato Botvac 80 SW version 1.1.97, LDS version 2.6.15295, Board SW version 22753
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby glnc222 » March 16th, 2017, 12:56 pm

Extensive detailed information on the cell is required to know whether it would work well. Sub-C size cells I tested did not support the high drain rate of the robot (compared to larger 18650 sizes used in the XV models). The effect is to wear out the battery very quickly. It will run a few times.
High drain rates also can come with lower capacity. The cells Neato used may not be available retail.
Brandless cells also have over-stated capacities.
The only proven DIY Botvac battery reported was made of LiFePo4 lithium chemistry, the longest lasting type of battery superior to any NiMh, but maybe more expensive (though fewer cells are needed). http://www.robotreviews.com/chat/viewtopic.php?f=20&t=19149
These cells will not fit the higher voltage used in the XV models, requiring too many cells. Major brand LiFePo4 batteries are usually limited to 1100mah, but some newer ones were found in this project with higher capacity.
[edit] Correction: with the 1700mah cells used it might be possible to make an XV battery; my attempt used 1100mah cells which would require too many. The original XV battery was only 3200mah.
Last edited by glnc222 on March 18th, 2017, 5:05 am, edited 2 times in total.
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby leoo2001 » March 16th, 2017, 1:07 pm

Thanks for the quick reply. Maybe I will try with some batteries used in the electronic cigarettes (high quick drain up to 60-90w) like LG HE4 or Samsung 25. Have read the forum but no input for those yet.
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby glnc222 » March 16th, 2017, 1:15 pm

AA size EBL cells were tested in another project and found to wear out quickly. See Mods & Repairs list main forum page for links. The LiFePo4 project uses 18650 sizes similar to the XV, which fit the Botvac with fewer cells. That battery might last the lifetime of the robot, several times any other type -- costing less over the long term.
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby leoo2001 » March 16th, 2017, 2:26 pm

Well then LiFePo4 will be.
http://budgetlightforum.com/node/46146
I found those on a bargain and they had some positive reviews on the net, but still not decided to buy them because they are stated as protected and I don't know how this will affect the high drain and they are little bit larger than regular 18650
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby glnc222 » March 16th, 2017, 3:00 pm

Protection end caps increase length and generally don't fit the robots. Protection PCB boards were used. Also the specific brand of the LiFePo4 project is advised. Major suppliers A123 etc. known in the industry, for cars and solar power etc., electric bikes.

Check details of balancer boards in the project as only certain ones can activate the thermistors with enough heat, and whether protection is used. There is a wide range of battery characteristics supplied in different cells for different applications, and only certain ones match robot requirements. DIY batteries are experimental, no guarantees. Much more has been done on XV models with software settings for lithium charging (not for LiFePo4, different voltages).

LIFePo4 is inherently safe like NiMh and protection is for the battery damage only, no fire hazard like lithium ion. Soldering is possible with a high power iron or gun used quickly not to damage the battery, no fire hazard. If interested, the Lithium Ion Revisited thread shows possible circuits for simulating thermistor control signals instead of actual heat transfer from balancing boards. 74665 voltage comparator. XV lithium ion replacements for NiMh have proprietary circuit boards of this kind, with microcontrollers, very thorough. LithiumPower/AnewPow also supplies a Botvac battery.

[edit] Carefull assembling packs not to short out a battery with stray wiring; use tape on all loose wires etc. during assembly. Cells support high currents, dangerous sparks and heating, like car batteries.
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Re: SUB-C Baterry - 5000mAh / 1,2V / NIMH for Botvac 85

Postby glnc222 » March 16th, 2017, 11:03 pm

Correction: looking at the fit shown in the LiFePo4 project referenced, there appears to be plenty of room for the extra 3mm of protection caps on the cells mentioned above (18650 = 18mm x 65mm). The vendor gives current specifications which appear to be adequate.
I am not sure about soldering to the protection cap though, which could have a thermally triggered fuse -- too small for usual circuitry (some descriptions on the web). Commercial packs use spot welding (cheapest unit $125) -- not sure that can be used either. Those cells are made for flashlights and such where PCB's are absent. Also I think those cannot be reset, not sure -- not the same as a semiconductor mosfet switch transistor on circuit boards. The original project also used chinese cells, another company there.
Never can tell until it is tried, without professional involvement in the industry.

The balancer boards were not used as supplied, but enhanced with additional parallel resistors for heating current. All a bit Rube Goldbert but worked.
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