Cellog 8S display goes blank

[mrbill]

Hi Folks:

I just bought a couple of Cellog 8S battery monitors (firmware version 2.0.8) from HobbyKing, and I'm having trouble with both of them.

After being hooked up to the battery I get the start-up chime, then the intro screens, then a voltage screen. As I cycle through the voltage screens, the screen often goes blank, and no key press, whether held for an instant or for more than 3 seconds brings back the display. I can see the backlight is still lit, but no data displays. The screen is blank. Occasionally the screen display will reappear on its own, or I can get it to reappear by pulling the JST-XH connector out slightly. But the display disappears again after I cycle through the voltage screens.

I have not had display trouble when the Cellog is connected to the USB bus only. But when connected to a battery whether or not it is also to the USB, the display is flakey.

Both Cellogs exhibit this behavior, but one exhibits it worse than the other, being almost unusable, while the other display reappears several minutes later on its own and is stable enough to make the unit usable. Also, the displays of both units are more stable after the Cellog has been "on" and warmed-up for several minutes.

I suspect I got a couple of defective units, but before I start the return process, I want to check with others who have used these for advice in case I missed something in the user manual. Is this normal behavior, is there a workaround, or should I send them back?

Thanks.

 

[heathyoung]

Yeah I have two that do the same thing annoyingly.

They do still alarm if over or under though - I have them set up as a BMS for bulk charging.

 

[Ykick]

Save yourself a bunch of time and go into system setting, scroll to start.... Once there you can turn off - start music, logo screen, Inf screen which will then allow it to start-up almost instantly.

As far as your screen going blank - I've had that happen over the years and often traced to a shoddy balance wire and/or JST assembly. However, one unit did that and never came back up.

 

[wb9k]

Some of mine do the same thing as well. I've assumed the problem was in the display circuitry as the unit appears to otherwise continue to work normally. I haven't got around to troubleshooting though. It sure is annoying, whatever the case.

 

[mrbill]

Thanks for your replies.

Since this problem does not appear to be unique to the units I received, I'll assume that going through the returns hassle is likely to leave me with replacements that exhibit the same problem, that there is a firmware bug, or a design or assembly error in common with the batch from which our units came.

The unit appears to function otherwise when the display goes blank. The display will go blank and return at random moments even when connected to the battery for many hours. I have not been able to observe a repeatable pattern in spite of what I wrote earlier--e.g. I was not able to repeat my manual re-lighting of the display by pulling on the JST connector.

If anyone discovers a cause or a fix, please post it. Also, if anyone is not having trouble with their Cellog display, could you please report your firmware version?

Thanks.

 

[dnmun]

i cannot recall exactly but if you go into the initialization screen you may find there is place where it asked how long you want the screen to display, and that is separate from the backlight time.

you might find your answer there.

maybe someone else who recently initialized their cellog can comment. been a long time for me.

 

[mrbill]

Hi dnmun:

Yes, I know about the "power saver" settings. I've set the backlight to dim after 5 minutes, but not for the unit to go to sleep.

The display-blanking problem appears to be random. Sometimes the display will blank for several minutes, then return for a few seconds or even blink once or twice before blanking again. Sometimes it will blank for a few minutes, then return for a few minutes, then blank again. There is no pattern.

Whether it blanks or not does seem to occur when I'm in its proximity, either touching or grasping the outer plastic case or pressing the buttons. Perhaps it is a sensitivity to static, or maybe I just notice its misbehavior while I'm observing it.

Still an annoying mystery.

 

[electrodacus]

Those celllog 8s are quite bad. I have two of them BVM-8S. I made a video on how to reduce the power consumption by about 2.5x but is still bad.
It also using power just from the first two cells so it will unbalance the cells substantially.
It was using 31mA before modification that is huge. I reduced the back light current from more than 15mA to 5mA and reduce the microcontroller to 4Mhz so now is using 12.5mA still a huge amount and will create unbalance even in my 100Ah cells.
As an example my Solar BMS the one I designed uses 25mW so only 1mA from a 25V battery not only this is 30x less than the BVM-8S but it using this from all cells so it will not create imbalance. The Solar BMS is by far more complex and smarter also is not just a simple monitor is a full featured BMS capable of 40A charging and 80A discharging.
I do not think there is any device as low power as the one I designed and that is because people care only about cost optimization and not power optimization.
I can leave my BMS working for 3 months and will only use 10% of a small 8cell 20Ah battery with no imbalance to any cell.
The BVM-8S same as celllog 8s will drain the same 20Ah battery (first two cells) in less than 25days if fully charged initially and will probably damage them permanently. Even when left for a few hours will severely unbalance the pack by discharging the first two cells only.

 

[dnmun]

ok, i thought it would just go to that state after regular and fixed period of time.

i have had mine glitch too. so put me down for the same symptom, on three different ones. i just unplug and replug. i still wanna do the depletion mode pmos linear voltage regulator that Otmar came up with on richard's thread on the cellog hack. i found those cheap little SOT223 packages and never ordered the legal minimum. was thinking i would get some with the next order to mouser but it never came.