Hi, Everyone! ^^ I am really excited to post about this charger. :bigsmile:
You may be thinking, "What makes this charger so special to invoke such feeling?" Well, I would say this is a next generation multi-chemistry charger; a dreamcharger, if you will.
Finally, a truly multi-chemistry charger, combining essential features we expect from intelligent Ni-MH/Ni-CD chargers with Li-ion charging capability.
Not only can it charge several cells at once of different size and type at current the user decides, it also provides useful data on charging, has discharge and refresh capability and the ability to measure internal resistance of cells.
The BT-C3100 was supplied by OPUS Instrument Co. Ltd for review. A special thank you to kreisl for helping with it. ^^
The name Opus may not be familiar. Opus designed and manufactured the AccuPower IQ-328.
In addition to the charger unit, a 4 page (2 sheet) manual and 3A 12V adaptor was included. The adaptor is rated 100-240V and has built-in Euro plug connector, so some users will need an additional adaptor to suit their locale (fortunately I already one). For those in the UK do check the plug is rated 3A minimum and fused accordingly, as the power supply does not have a user-replaceable fuse.
Charger and PSU:
Label on PSU:
On the underside of charger there are vents, four soft feet and information about the product, including CE mark.
At back of charger a 25mm micro-fan and power input socket:
The first thing I noticed on unpacking was its dark blue livery. Casing feels like ABS and feels strong. In fact it has already survived a golf umbrella falling on it! :oops: Charger is quite light, weighing 8oz, just over 200g.
Four bays with spring sliders. Note the additional concave cutaways to bays 1 and 4, for charging 26650 cells.
The slider "feet" have two small raised bumps in addition to a single larger bump. These little bumps fit into the slightly recessed negative terminal on smaller cells with thick wrapping, such as my Ultrafire 10440s.
Each bay slider at minimum 32mm. For smaller cells such as 1/2 AAA size (10280) spacers or neodymium magnets can be used.
Slider under spring tension at maximum 73mm.
Side profile with cell inserted:
Top view with cells inserted:
With back removed:
Most notable is the 3-way slider near the edge of the PCB (top in the above picture) for an undocumented adjustable termination voltage set to 4.2V position, with option for 3.7 and 4.35V termination. More on this later. The two pin fan connection is also accessible.
On the inside of the lower casing is black tape sealing the vents. My guess is these cutaways were unnecessary:
With PCB removed, four thermal sensors are visible, attached to the upper housing near the positive terminals:
Side shots:
Plugging it in, white LEDs illuminate a familiar display. You may recognise it from the IQ-328. To be honest, I found this screen a little difficult to read at first. It takes a little getting used to (only a little!).
At power up, the display briefly shows all whilst it initializes. With backlight active, all display legends remain clear to read.
Features and Operation
There are four slots/bays, each providing up to 1A of charge or discharge. With cells placed in slot 1 and 4 only, charging current option of 1.5 and 2A become available:
Slot | Charging current | ||||||
1 | 200 | 300 | 500 | 700 | 1000 | 1500 | 2000 |
2 | 200 | 300 | 500 | 700 | 1000 | ||
3 | 200 | 300 | 500 | 700 | 1000 | ||
4 | 200 | 300 | 500 | 700 | 1000 | 1500 | 2000 |
Each bay is completely independent allowing for great flexibility.
The BT-C3100 has five modes of operation:
BT-C3100 Modes of Operation | ||
Mode | Display | Description |
Charge Mode | Charge | Charge to maximum capacity (for Li-ion, termination voltage of 4.2V can be changed by undocumented slider on PCB) |
Discharge Mode | Discharge | Discharge cell to preset voltage (0.9V for Ni-MH and Ni-CD, 2.8V for Li-ion) |
Refresh Mode | Discharge Refresh | Refresh capacity of old cells (3 complete charge-discharge cycles) |
Test Mode | Charge Test | Check present capacity, determined by discharge (charge-discharge-charge) |
Quick Test Mode | Quick Test | Display internal resistance of cell under load, in milliohms |
Below the display are four buttons to program the charger. Pressing the Mode button cycles through the modes in the above order.
Pressing the Display button cycles through the information displayed:
Legend | Description |
mA | Charging/discharging current |
V | Charging/discharging/termination voltage to two decimal places |
mAh | Capacity in milliampere-hours |
h | Operation time in hours and minutes, updated every minute |
Lastly, pressing the Slot button selects the slot to alter its mode, in this order: 1, 2, 3, 4, all, exit. The corresponding LCD legends begins to flash like a cursor. After ten seconds of no further input, this flashing ceases and the selected mode begins operation.
In use, I find it's a very logical, straightforward system. It takes some use to become familiar with but once familiar it is very easy to use. There are no hidden menus or special button combinations to remember.
Charging
With no cell inserted the display reads "null". Inserting a cell into a bay, the BT-C3100 detects chemistry and the LCD flashes in Charge mode. The user can then choose the charging current by pressing the Current button. The default charge current is 500mA.
If the charger detects a full cell, it will display "Full". Pressing Display button will show the termination voltage.
To test this, I inserted freshly charged Sanyo eneloops and the charger would enter charge mode. With a multimeter connected to measure current, one could observe the cells being charged at 500mA for an additional <15 minutes before entering trickle charge.
The manual states trickle charge is "about 10mA". In my testing the BT-C3100 the trickle charge varied a little but never exceeded 40mA.
Full Li-ion cells were always detected as "Full" with no charge current applied. Occasionally the charger will detect a Li-ion cell that is near 2.8V as "Full"; more often cells were only just under 4.2V. It is a quirk and fortunately it is possible to override this by pressing the Mode button to cycle through the modes as one might to choose a different mode, and select Charge.
Is it possible to charge an already full Li-ion cell? I tried this with some unprotected Sanyo 18650 cells in each bay just to be sure:
Charging "Full" Li-ion cells (4.20V) | |||
Slot | Time to termination (mins) | Termination voltage (V) | Additional charge (mAh) |
1 | 2 | ||
2 | instant detection | - | - |
3 | instant detection | - | - |
4 | 7 | 4.21 | 11 |
I would not worry about Li-ion cells being accidentally overcharged by this charger.
One criticism of this charger is not being able to tell whether the charge cycle is complete at a glance. For someone who keeps the charger close by it is perhaps less of an issue, although some might find the fan noise a little annoying (more on this later).
The LED backlight automatically turns off after ten seconds, and only turns on when power is connected, a cell inserted or a button pressed. There are no flashing lights to cause distraction.
Discharging
One of the nice features in this charger is the discharge mode. For Li-ion cells, it is possible to track degradation in capacity by performing periodical discharge tests.
It is also useful for Ni-MH cells. Discharging at 1A I was able to see my Contour Energy AAA cells could not keep up with 3rd gen Sanyo Eneloop AAA. I was also able to restore some capacity to some very old Philips cells that other intelligent chargers refused to charge.
Test Mode
This mode combines charge and discharge cycles to check the capacity of a cell. The manual doesn't specify exact behaviour, however.
After inserting a cell and selecting charge current the charger enters charge mode until the cell is full. During this stage the display will read "-- --" mAh. It then enters discharge mode, discharging at the same current until the capacity is ascertained. It then enters charge cycle again to restore capacity, without updating the total discharged capacity.
So, if you do not mind leaving the charger running, you can pop cells in for a capacity test and come back to them fully charged.
Quick Test - Measuring internal resistance
The manual goes into some detail about this, so much so that I almost want to copy and paste the whole section. There are also several articles on internal resistance at Battery University.
The manual stresses that measurements will vary from slot to slot and with contact resistance. With repeated testing I observed that some bays are consistently lower than others in their resistance figures, so I would recommend noting the slot used when recording figures, and performing several tests and taking the average. Cleaning contacts of cell and charger with isopropyl alcohol can also help.
Averages of repeated internal resistance measurements |
||||||||
# | 18650A slot 1 |
18650B slot 1 |
18650A slot 2 |
18650B slot 2 |
18650A slot 3 |
18650B slot 3 |
18650A slot 4 |
18650B slot 4 |
1 | 11 | 80 | 94 | 88 | 100 | 86 | 41 | 39 |
2 | 84 | 78 | 91 | 83 | 92 | 89 | 44 | 43 |
3 | 83 | 77 | 89 | 83 | 91 | 85 | 43 | 41 |
4 | 84 | 86 | 86 | 89 | 93 | 83 | 41 | 40 |
5 | 86 | 77 | 89 | 82 | 92 | 97 | 49 | 40 |
6 | 491 | 87 | 95 | 82 | 92 | 88 | 44 | 40 |
7 | 86 | 78 | 93 | 85 | 93 | 87 | 43 | 41 |
8 | 89 | 79 | 99 | 86 | 94 | 97 | 41 | 42 |
9 | 86 | 85 | 105 | 83 | 97 | 95 | 42 | 40 |
10 | 86 | 80 | 87 | 88 | 107 | 87 | 43 | 41 |
Average mΩ | 118.6 | 80.7 | 92.8 | 84.9 | 95.1 | 89.4 | 43.1 | 40.7 |
In my sample, slot 4 produced the lowest internal resistance measurements, followed by slot 3, followed by slot 1 and 2 (no order).
Internal fan and thermal performance
Another thing that sets this charger apart from others is the inclusion of a small 25x25x8mm fan at the back of the charger. This fan runs at 12V and turns on automatically when temperature inside the charger exceeds 40°C, and turns off again when temperature is below 40°C.
In all my testing the cells never got hot. Even repeated charging and discharging AA eneloops at 1A, the cells only got warm.
There is also additional overheating protection with a sensor under each slot near the positive contact. If these reach over 60°C the charger will halt operations on all four slots until temperature cools to 40°C.
The only downside to this micro-fan is the additional noise, but I would rather have the cooling and peace of mind than a quiet charger that cooks my cells! Really, it is as if the designer was reading BLF last year and taking notes. :surprise:
I made two short videos to accompany this review. The first demonstrates charging operation:
http://www.youtube.com/embed/_dIejehfAkc
In the second I test the 60°C thermal protection:
http://www.youtube.com/embed/A6wqY4dFMTE
Technical data
Operating Voltage | 12V DC | |
Power Adapter | Input: | 100~240V AC, 50/60Hz |
Output: | 12V DC, 3.0A | |
Charging Current Range | 200,300,500,700,1000,1500,2000 mA | |
Discharging Current Range | 200,300,500,700,1000 mA | |
Max. Charging Capacity | 20000 mAh | |
Operating Temperature | 0 to 40°C | |
Voltage Deviation | <0.04V | |
Current Deviation | <5% |
Where do I get one?
Currently this charger is not available to buy in the Western market. ;_; At time of writing there are few relevant links for "BT-C3100":
It will certainly be interesting to see how much this charger will sell for, and if other manufacturers will take note. Will it replace a multimeter and hobby charger? No, nor does it strive to. What it does do is combine useful features in a very useable package. I have been using it almost every day since it arrived!
(fixed big pictures, sorry! >.<)
Noteable reviews
By HKJ:
http://lygte-info.dk/review/Review%20Charger%20Opus%20BT-C3100%20UK.html
By UPz:
http://www.forolinternas.com/viewtopic.php?f=6&t=8246
By mjlorton:
By Mountain Prophet:
http://www.mountainprophet.de/2014/03/15/preview-akkulader-opus-bt-c3100/