Review last updated: June 9th, 2010
ReviewThanks to David Gray over at ProgressiveRC for sending me an CellLog 8S to use, review and show off.
Every now and then you come across a cool little device that fills a niche you never knew you needed filled. The CellLog made by Junsi is one of these devices. In basic terms the CellLog is a voltage monitor for lithium batteries. Like many other similar devices, it connects to the balance plug and displays the cell voltages of the pack. But this is where the CellLog leaves the ordinary. It doesn't just stop at showing you the cell voltages but expands on this idea with 4 different methods of showing you the pack and individual voltages. Next up are the 8 alarm types it supports for using tit is various applications. Then there is the logging feature, where the CellLog can log the voltages for up to 36 hours and then later you can connect the supplied USB cable to your computer and download them to view using LogView. With the USB port also comes the ability to update the firmware. Yes sir, this is a little more than a simple voltage monitor.
As a note, I am reviewing the logging capable 8S version of the CellLog but there is also a non-logging version called the 8M.
Like many modern devices, you are immediately amazed by the small size of the CellLog 8S.
The CellLog is extremely light but feels well built. The outside is an almost rubbery plastic that feels good to the touch. There are three buttons on the front, the battery connection on the left side and 2 ports on the right side, the USB port and the alarm port.
Playing with the CellLog 8S
When you connect a battery to the CellLog 8S, you are greeted by a short musical tone and then it shows you 2 screens of info before taking you to the voltage screen used last. You can then cycle through the screens or hold the "Menu" button to access the other features. See the user's manual to understand how to step through the many screens. The boot up time is not super fast, so quick pack checks can get annoying.
The 4 voltage screens.
Connecting the CellLog 8S to a computer
When you connect the CellLog 8S to a computer with the supplied USB cable, it will power on. You can then connect/disconnect packs to it and it will function as normal.
Note on the driver: The CellLog uses the same USB VCP chip as the iChargers, the "CP210x USB to UART Bridge VCP". You can download the VCP driver here.
The CellLog is designed for many uses but most will only use it to view lipo pack/cell voltages by simply plugging in a lipo balance connector. Of course that is fine because it does this very well but it also can be used as a volt meter by using the included alligator clips. It will measure any voltage from 4V-43V as a stand alone meter or if it is powered with USB, it will measure down to 1V. This allows the CellLog to be used for all kinds of things including checking the voltage on your car battery, 9V smoke alarm battery, AA flashlight batteries, 3V watch battery and pretty much any other DC source the average hobbyist can find.
The CellLog supports 8 alarms including low/high pack voltage, low/high cell voltage, safety timer and more. These alarms allow the CellLog to be used for many purposes from warning that the battery is low in flight to being wired into a lipo discharger to be used to monitor and halt discharges. The CellLog gives the option of NO or NC for the alarm output and ships with a wired connector for the output port. The CellLog really is designed for the tinkerer.
I have not played with the alarm features other than browse through the options on the CellLog. If I get a chance to do anything interesting with it, I will update the review.
The 8S version supports logging for both the pack and cell voltages. The 8S can either log while attached to an aircraft in flight and then transferred to a computer later, or it can be connected to a computer and give you real-time logging.
I did some very simple logging, both recording on the CellLog and real-time while connected to a computer. I started by setting the log interval to .5sec and then I enabled LogFile1 as the log file. Then you can go back to the voltage screens and start/stop the logging by holding the "Hold" button for 3sec. I did his for a short while while I checked the voltages on several packs I had. I then stopped logging and connected it to my computer. I ran LogView and selected "Open port / Recording". I told the CellLog to transmit LogFile1 and it popped up on LogView. I then went back to the voltage screen and started logging once again. LogView immediately began to get data and display it. Cool!
Testing the CellLog's accuracy
I happen to have access to a high quality Fluke 45 bench-top meter and I used this meter to check the accuracy of the CellLog 8S. I do not own an 8s lipo, so I used the iCharger balance board and (3) 3s lipos to act as an 8s pack (a 9s pack really but the CellLog can only see the first 8 cells). I then measured each voltage with the meter and compared that to the displayed voltage on the CellLog screen.
I can not speak for all CellLogs but the one I own is amazingly accurate. The largest difference was only 3 thousandths of a volt. In fact the CellLog is likely much more accurate than 99% of the meters owned by hobbyists. This goes to show that not only is the CellLog a quality device but it was indeed calibrated at the factory, and well calibrated at that.
Note on results: Some may look at these results and think that since none of the voltages lined up perfectly, that the CellLog is not very accurate. Let me let tell you a small fact, most cheap volt meters that hobbyists own would be lucky to be within .01V, if not more like .03V. These results are 10 times as accurate than most meters can provide.
The CellLog 8S is great little device that everyone should have in their charging kit. It is both very useful and very accurate for not a lot of money. The 8S version has logging capabilities that some will find very useful.
Specs - Features - Photos
Here is a link to the user's manual for more info. The CellLog manual is one of the more detailed manuals I have come across.