PR2 battery cell replacement.

[Roxana Leontie]

Hi all,

I want to replace one of the PR2 cells in the battery system as it is overheating. I managed to get one from clearpath, but they can not offer assistance to determine exactly what cell it is. 

The dashboard error is for 3.2 cell. I was wondering if anyone has experience with this and can help me determine which one it is. My intuition is that it is probably the bottom rack on the left of the PR2, second from the top.

Thank you,

Roxana 

[Sam Pfeiffer]

Hello,

I'm not familiar (yet, as I'll need to do the same soon) with the batteries of PR2. But I'd aim to do some trick to identify the battery.

If you can discharge the new cell, and charge all the cells currently in PR2 just charging the robot, you could exchange your new cell with the one you think it is and then check the diagnostics of the robot to check which battery is now the one with less battery... And with this guessing game you could find it out.

Alternatively you could do it the other way around of course, let the robot discharge and add the cell having full charge.

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[Roxana Leontie]

Hi Sam,

Thank you for reading my post. I thought about that option, but I am saving it as a last resource. There is also the possibility that it is a different rack, and it would take a few guesses to do this. Maybe the batteries are labeled inside, but just taking the panels and the pr2 skirt I was not able to see any labels. 

[Matthieu Herrb]

Hi,

The battery serial number is available next to the battery connector
(brown on black), not on the white sticker, it corresponds to the one
in the software battery information (serial number = hardware_id)

Here we determined the correspondance once and added stickers to the
battery slots to avoid having to do it everytime.

I thought we also made a picture with the correspondance, but I can't
find it right now, sorry.

--
Matthieu Herrb

[Roxana Leontie]

Thank you all. All this advice it is very helpful. Once I get the battery cell and replaced it I let you all know the approach I took, or what is the easiest.   I also got a private reply that has very helpful information:

Hi,

I'm not sure whether your charger has the same configuration as ours (100V in Japan) but in our case, I determined the failing battery as follows:

0. Turn off the robot and unplug the power cable for safety

1. Each battery module (1 module has 4 batteries) has a serial comm device connected to the serial-usb located in the inside most of the left (the side of C2) battery modules. Please check the location.

2. Prepare RS-232C - USB device (e.g. http://a.co/5lFud0B ) and connect one of the serial cables to the device and the usb to your laptop.

3. Install `Fullbats' program ( provided here: https://ocean-server.com/software-and-guides/ ) and `Teraterm' on Windows (I know this is the hardest procedure...)

4. Launch `Teraterm' and `Fullbats'

5. In the Teraterm, connect to the usb serial port (You will see some characters on terminal window, though they are not yet human-readable)

6. In the Teraterm, set the baud rate to 19600 and hit the 'space' bar so the banner comes up on the terminal (you will see the menu) and then press 'x' so the data output is HEX mode.

7. Close Teraterm

8. In the Fullbats, press `Connect' button and you will see all the information on the battery modules. (I attached a screenshot)

9. Please take a note of the serial No. of the replacing battery

Here you can determine that the failing battery is at least one of the four batteries.

Please remove each battery from the module and you will find the serial No. printed at the root of the cable.

I hope it will help you.

P.S.

BTW, I'm interested in how is the usage of the batteries of your PR2.

About the battery you plan to replace, how much is the value of `Cycles` and `Full Charge Capacity`?

We currently have another trouble that the `Full Charge Capacity` decreases less than half of the designed capacity (=6600mAh) even if the cycle count of the battery is less than 40.

However, in the official document from the battery supplier, we can find the article about reliability:

Given normal storage & usage, user can expect the battery to deliver 80% or more of it's initial capacity after 300

charge/discharge cycles

http://www.inspired-energy.com/pdfs/datasheets/NL2024A22-spec.pdf

I'd like to determine what is the cause...

Best regards,

-- Yuki Furuta

University of Tokyo

[Roxana Leontie]

Here is my update. I used the instructions I got from Yuki Furuta, and I was able to indicate the battery module and then the cell that is not working on that battery module. The critical part is having an RS-232C - USB cable and access to a windows computer. 

Attached is a screenshot of the fullbats software feedback that helped me identify the battery cell that had the issue. Once I identified the module I had to disconnect the battery cell from the battery controller (it connects with a 6 pin connector wire) and that would cause it to disappear from the software. I did that until the one I wanted to replace was not on the screen.