ADEM III ECM — No CAN Signal & Power Supply Issue

[Giola]

View attachment 15277
I’m working on a Caterpillar ADEM III ECM that currently has no signal on the CAN bus (CAN_H and CAN_L). I suspect the problem is in the power supply section, specifically the UC3843B PWM controller, which may not be switching correctly. This IC controls the regulated 5 V rail that powers the AN82527 CAN controller and other logic.


Right now, the AN82527 does not seem to power up fully — so TX0/RX0 have no activity and the CAN lines stay inactive.

I’m looking for:

• Ideas to properly diagnose this issue.
• Possible common faults in ADEM III ECMs that usually cause no CAN signal or problems in the power supply stage.
• Any advice on how to check the switching circuit and ensure stable Vcc for the CAN controller.

Any suggestions or troubleshooting tips would be very helpful.
Thanks in advance!

 

[TugboatEng]

Common faults? Cat designs their controllers with a service life of 25 years. There is memory battery that is the life limiting component. I have repaired a few controllers by replacing this battery but not specifically a Cat controller

 

[Giola]

Thanks for your comment — it really helped me to look into the battery idea. I checked my Caterpillar controller and I found it does have a memory battery: it’s a Rayovac FB 2325 H2 module mounted on the PCB.


Do you have any idea where I could find a replacement for this specific battery pack, or if there’s an equivalent I could use?
Any tips on where you sourced yours when you repaired other controllers would be really appreciated.


Thanks a lot for your advice!

 

[3DDave]

The product is discontinued by Rayovac. This is the datasheet for the module: https://www.master-instruments.com.au/files/data_sheets/FB2325H2-B.pdf

From the product number it appears to be a package of 2 lithium primary coin cells that are each 23mm diameter, 2.5 millimeters thick in a sturdy case that supports through-hole pins. Given the application, that size mainly sets the amount of lifetime current that will be available. Each cell has a separate connection to two pins. Presumably one could get a pair of coin cells with leads and solder them in, but it won't have the industrial packaging protection.

There are a few suppliers of new (but) old stock, items that were available before the maker stopped producing them. One site lists them for about $170 with a 2 year guarantee.

Per https://www.rayovacindustrial.com/wp-content/uploads/2021/09/2325ReplacementOptions.pdf they were discontinued in 2010, so 15 years ago. The cells typically have a shelf-life of about 10 years. From the sheet:

Contact Rayovac OEM Engineering for a compatible replacement part and devicedesign assistance by email oem@rayovac.com or phone 608-275-4492

Edit - reading is hard this early in the day. On that sheet it says FB2032H2 is the replacement. Still worth making the call.

 

[IRstuff]

The individual coin cells are apparently available on Amazon

 

[Giola]

"Hi everyone, I’m finding it difficult to replace this backup battery module at the moment. Could I safely test the operation of the circuit by injecting 3 volts directly to simulate the battery? Any advice would be appreciated!"

 

[3DDave]

Look for the ones that have welded tabs added to give something to solder to without cooking the cells, such as https://www.digikey.com/en/products/detail/panasonic-energy/BR-2325-HCN/45791?gQT=2

 

[TugboatEng]

The controller I have been having battery failures on uses a battery with welded tabs. The tab configuration has been discontinued. I have found a replacement battery with wire leads and have been using that and attaching it to the circuit board with hot melt glue.

Make sure you get one that is rechargeable!!!

 

[3DDave]

Is there a part number for the one with wire leads or, better, a datasheet? Most all lithium cells that have a wired attachment have welded tabs as the cells do not well tolerate the temperature and duration required to solder copper wire to them. The leads are soldered to the tabs. This is typical in rechargeable battery packs.

Rechargeable lithium cells run at 4V which might be a bit too much for circuits that are designed for 3V primary cells.

 

[Giola]

"Hi everyone, I’m planning to power the board with 3 volts on the backup battery pads at the top, and 12 volts on the main power input below to supply the main circuits. If you have any advice or recommendations before I do this, I would really appreciate it. Thank you!"

 

[TugboatEng]

There are 3 volt rechargeable cells. I don't know specifically that OP needs one but they need to pay very close attention to the chemistry of the original battery.

https://www.mouser.com/pdfDocs/3562_fileversion.pdf

 

[3DDave]

From Mouser the highest capacity 3-3.3V is 100mAh.

Example https://energy.panasonic.com/eu/business/products/coin-rechargeable/models/VL3032 (which is 30mm diameter vs. 23 original size.)

How is this recharged when soldered to a board that is not intended to recharge the cell?

 

[TugboatEng]

Yes, you can inject 3 volts to test the board after removing the battery. Have you probed the terminals? According to the discharge curve anything below 2.5 volts indicates a dead battery .

I haven't had time to follow the links until now. I see that it is a Li-Carbon Fluoride battery and is a non-rechargeable chemistry.

It won't look the same but this one may be the correct replacement.

https://www.mouser.com/ProductDetail/Panasonic-Battery/BR-2325-HBN?qs=hgpIN6ks1e6McEjadVsCgw%3D%3D

It has the H configuration which is 2 solder pins for through hole mounting.

Since it's non-rechargeable it doesn't matter what chemistry you go with electrically but this application likely requires a high ambient temperature tolerance.

 

[3DDave]

As I noted above, Rayovac specified a drop-in replacement.

Injecting 3 volts needs 2 independent isolated power supplies, one for each cell connection unless it is known that the circuit uses the cells in parallel.

For someone looking to do board-level repair and diagnosis, the beginner level questions suggest that finding a reliable repair service is the best option.

 

[Giola]

Hi everyone,


I’m still working on this Caterpillar unit, but the issue remains the same. The current draw stays steady at around 0.500 A, which is the expected idle consumption, but I still don’t get any signal on the CAN lines.


If anyone has ideas on what could be blocking CAN communication despite the normal current draw, I’d really appreciate your suggestions.


Thanks in advance!

 

[TugboatEng]

Your wires are in the wrong positions. The battery connects here:

 

[Giola]

Your wires are in the wrong positions. The battery connects here:

View attachment 15382

IF YOU CONNECT IT THAT WAY SEE MY LAST MESSAGE AND I THINK IT MUST BE THE UC3843 ON THE BOARD THAT SENDS 5 VOLTS AND THE OTHER COMPONENTS OF THE BOARD.

 

[3DDave]

If you lost the memory battery, you lost the programming the battery was to maintain. Simply restoring the battery won't fix that. Like replacing the battery in a watch won't set the correct time or restore previously stored alarms, you need the programmer for the board to restore the missing data.

It is also not clear that you know if any data is going into the chip. You need a logic analyzer and a functional schematic as well as a CANbus transceiver attached to the output. Unless you have a known-good unit to compare to, at best you can look for mechanical faults, such as fractured solder joints, failed capacitors, or corrosion under the chips.

Also, I think your wiring to the battery connections is doing nothing. As mentioned, if that board uses the cells in series, that requires 6V, but since you didn't trace the board, applying 6V in that way could just blow the related ICs off the board. Trace what is powered by the cells and determine which ICs are being battery backed.

 

[3DDave]

Your wires are in the wrong positions. The battery connects here:

View attachment 15382

What part of the package makes those contacts?

 

[Giola]

Hi everyone,


I’ve already injected the required voltage into the battery circuit, but the current draw didn’t change, so I believe that wasn’t the root cause. I’m now going to keep troubleshooting the PWM controllers, especially the UC3843BVD, since I think the issue might be there. This IC plays a key role in powering the board as it supplies voltage to many other components.


Any advice or ideas would be greatly appreciated!