LSN50v2: When the battery runs out, the Lora_ST module never works again.

[Walter Hofstaedtler]

If the ER26500 runs out and the LSN50v2 remains connected to the empty ER26500 for several days, the ST processor on the Lora_ST module will no longer start when a new battery is connected. Approximately 12mA of current is constantly drawn from the new battery. However, there is no serial communication, the green LED does not light up, and the reset button does not function. 

Is there an explanation for this, and how can this problem be fixed?

Walter

[Mengting]

Hi, Walter,

Thank you for providing the detailed description of the issue you are experiencing with your LSN50v2. We understand the frustration when a device doesn't function as expected, and we will do our best to help you diagnose and resolve this problem.

To assist us better in troubleshooting, could you please provide some additional information?

1. Battery Configuration: Could you confirm the exact battery pack you are using as a replacement? Specifically, are you using the standard ER26500 + SPC1520 Battery Pack (which includes a supercapacitor), or just a standalone ER26500 battery?

• This is a critical detail. The supercapacitor in the SPC1520 pack is designed to provide stable power and protect the circuit during voltage fluctuations, especially in scenarios like a complete battery drain. Using a battery without this supercapacitor could potentially lead to circuit issues.

2. Based on the symptoms you described (constant 12mA draw, no communication, unresponsive reset button), our analysis points to a possible voltage backflow issue caused by capacitive energy storage. Here's our theory:

When the battery is fully depleted and remains connected for an extended period, the internal capacitors on the board might discharge their residual charge through the circuit in reverse.This abnormal voltage spike could potentially latch up or damage the Power Management Unit (PMU) or reset circuit on the ST processor, preventing it from booting correctly while still drawing a small amount of current.

3. Please try the following steps to attempt a recovery:

• Switch Check: First, please check the small switch on the LSN50v2 motherboard and ensure it is in the FLASH position (not ISP).
• Full Power Cycle Reset:

Disconnect the new battery completely.

Press and hold the RESET button for about 10-15 seconds. This will help drain any residual charge stored in the capacitors.

Release the button and reconnect the battery. This might allow the processor to reboot normally.

• Disconnect Sensors:

If the issue persists, please disconnect any connected sensors from the mainboard and then try powering the LSN50v2 on again. This will help determine if a peripheral sensor is causing a short or drawing excessive current.

4. If the above steps do not resolve the problem, it would be very helpful if you could share:

• The detailed parameters/photos of the replacement battery pack you are using.
• Clear photos showing the current wiring and the switch settings on your LSN50v2 motherboard.

This information will allow us to provide more targeted advice. We look forward to your reply and are committed to helping you find a solution.

Best Regards
Ting
Technical Support Engineer

 

Dragino Technology Co., Limited

Room 202, Block B, BCT Incubation Bases (BaoChengTai),  No.8 CaiYunRoad

LongCheng Street, LongGang District ; Shenzhen 518101,China

Direct: +86 755 86610829 |Fax: +86 755 86647123

------------------------------------------------------------------

发件人：Walter Hofstaedtler <hofsta...@gmail.com>

发送时间：2025年9月9日(周二) 09:13

收件人："Dragino-user"<dragin...@googlegroups.com>

主　题：LSN50v2: When the battery runs out, the Lora_ST module never works again.

If the ER26500 runs out and the LSN50v2 remains connected to the empty ER26500 for several days, the ST processor on the Lora_ST module will no longer start when a new battery is connected. Approximately 12mA of current is constantly drawn from the new battery. However, there is no serial communication, the green LED does not light up, and the reset button does not function. 

Is there an explanation for this, and how can this problem be fixed?

Walter

--
You received this message because you are subscribed to the Google Groups "Dragino-user" group.
To unsubscribe from this group and stop receiving emails from it, send an email to dragino-user...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/dragino-user/d27a0db9-6204-4592-91fb-d6407f3715fan%40googlegroups.com.