Contec RS01 battery life

[gnluna]

Are any Contec RS01 users experiencing poor battery life?

I got my RS01* near the beginning of the year, and I was able to record at least two nights on a full charge. Now after a fresh charge, it will not record a full 9 hours.

The size 403040 LiPo battery is labelled 430mAh, which seems consistent with the capacity of similar cells advertised online. At room temperature on my desk, I observed the device shut off while recording when the voltage at the battery connector reached 3.28V. Later, I observed the device begin charging in constant-current (CC) mode at ~230mA, then ramp down below 30mA as the voltage went from 4.16 to 4.20V in ~constant-voltage (CV) mode. I think the cutoff voltage and these charging parameters are reasonable for this battery.

I think the issue is a matter of battery health, rather than some increased power demand. The CC portion of the charge lasts around two minutes, while the following CV portion is roughly an hour. In total, the device seems to draw only roughly 100 mAh before the green light comes on.

The speed of this battery deterioration is the mystery. My suspicion is that some unnoticed corner-case may badly mistreat the battery, such as:
A) Draining the battery too low. At around 3.28V, the device may actually crash, which may plausibly result in a continued sizeable current drain lasting until next charge, boot, insufficient voltage, or intervention by a battery protection circuit. If so, it would be advisable not to run the device longer than it has charge for, and to boot/charge the device soon if it ever shuts off unintentionally.
B) A (possibly sporadic) charging fault may occur, such as an excessive CC rate, CV level or failure to terminate CV. I have only measured the last two charges of my weak battery, and the cheap USB power meter I used does not have the resolution to detect under 30mA. If anyone else has a RS01 and a USB power meter, please monitor the behavior and report back!

* I started an earlier thread about malware discovered on my device. It's possible that the device was not new, but I don't think any strong conclusions could be drawn. Even if the device was not brand new, the battery deterioration in 3 months doesn't seem reasonable.

[Philipp]

I received the Pulox SAS-500 last week (same as Contec RS01). This night, the battery was empty after 7.5h (fully charged before).

[gnluna]

Welcome Philipp,

You have my condolences.

1) Did you end the prior recording, or did it end because it ran out of power?
2) How many total hours were recorded on the prior charge?
3) What is the largest total number of hours the device has recorded on a single charge?

I replaced the battery in my RS01 and have not experienced rapid capacity loss again. Based on a USB power analyzer that measures delivered charge, it appears my new battery is slowly losing capacity. However, that is expected behavior for a LiPo battery, so I'm not particularly concerned. I have considered lowering the charge rate in hopes of slowing the capacity decline and/or internal resistance rise. If I'm not mistaken, the charge controller is U1 (LTH7R by Shen Zhen Fine Made Electronics Group), and it's output current is programmed with resistor R7 (4kΩ, SMD) by the formula I=1000/R7.

I have not done any more investigation of hypothesis B from my prior post, but I have some new thoughts about hypothesis A. I noticed that my RS01 would still boot up with an "empty" battery but then promptly go through a shutdown. Thus, it seems that some software is responsible for the "empty" battery shutdown. If there is no fail-safe shutdown method, it seems plausible that a fault could result in the battery getting over-discharged and damaged. It also seems plausible that the shutdown sequence itself could induce faults if the shutdown sequence needs power exceeding the capability of it's nearly-empty old battery with high internal resistance. Thus, an old but usable RS01 battery might quickly deteriorate if it reaches the "empty" battery threshold. I continue to support the suggestions I proposed with hypothesis A in the first post.

I replaced the original 403040 size battery with a 502248 size and I like the fit a little better. I believe the battery connector on my RS01 is a 2-pin JST ZH (1.5mm pitch) connector, but I'm a bit unsure of these details. I was able to buy a battery on ebay with the correct connector already installed. Unfortunately, that particular ebay listing is gone. I may have had to exchange the terminals in the connector body because the replacement battery polarity was wrong. Such a task is easy with a little tape to prevent shorts, a sharp tool, and good eyes!