No, they are not about to blow up. Please recycle them though!
search “ultrafire” and “explosion” in YouTube 
BOOM !!!
Carry16 is right, exaggerating only a little bit.
Ultrafire batteries are known to be recycled batteries , rewrapped and sold as new. If an ultra fire gets to a very low capacity, like yours, with 300 mAhs, they may be very old, or may have been abused, and are considered AT HIGHER RISK of vent and flame. I would NEVER keep a battery like that in my house. They could very well be about to blow up. Get rid of them now.
If I charge a battery and click display to show me the mAhs after it is finished, is that accurate, or is it only accurate after certain modes?
It will show how many mAh you have charged into the battery, that is not the same as the battery capacity.
With LiIon the charge and discharge are about the same, but with NiMH it is very common to charge 10 to 30% extra into the battery (This charger is in the low end with extra charge).
So with a 18650 or 26650, or 14500 I can use the reading after a charge and be pretty accurate, but with nimh I should use the discharge?
Does discharge stress either type of battery?
As long as you start from an empty battery, yes.
It does apply some wear to the battery, especially if you discharge to a very low value (The charger will not do that).
Thanks HJK.
I thought that it was already settled that the charge figures for a Li-Ion were not accurate with this charger unless the 12v PSU was replaced? At least not in all configurations. In other words, not something end users should rely on in the stock configuration.
I don’t mind charging one at a time since I only rotate between 2 18650s usually, is any particular slot the best for a single.
When you say one, how about one 18650 and 3AAs at the same time, and again which slot for the 18650?
For a single the slot only matters if you want a 2A charge rate (I generally do want a 2A charge rate when I can get it :laughing:. The outside slots facilitate a 2-Amp charge rate. My understanding is that you can charge NiMH/Li-Ion in any slot you want. Unless HKJ says otherwise though, if I wanted accurate charge figures with the stock PSU I’d do a single, meaning nothing else in any slot but the one I’m measuring.
Concerning the feedback with V2.0 BT-C3100, we are going to release a new version in August: V2.1
The changing contents are:
- voltage refresh update rate is changed to 30s, instead of 60s.
- charging NCR18650B or NCR18650PF type Panasonic battery mAH data is optimized by controlling charging current level( regulate li-ion charging voltage from 5.0v to 4.65v, and its peak charging current needed will be less now), and mAH data will be correct, with our supplied power adapter used( still need to meet minimum output current to be over 3A@12v). This problem has been improved with v2.0 in the later shipments to Gear Best in June already.
- temperature sensing for controller board now not only turns on/off cooling fan(v2.0), but also accurate controller board temperature monitored so that over heating condition will be sensed as well. This is better safety feature when fan is not running and overheating on controller board will trigger over heat charging/discharging protection to be kicked in. We don’t recommend any operation of this charger without fan operation with v2.0 charger, especially during discharging time with li-ion batteries.
- improved accuracy of charging and discharging current measurement to be within +/- 3% accuracy now, while v2.0 version has 5% current regulation accuracy. This is realized through hardware change. Improved battery voltage accuracy via hardware design change.
- when reversed polarity batteries installed on charger, with v2.0 charger, there can have high pulse charging current existed due to pre-charging feature activated( charger detects reversed battery as 0v voltage, and treated the battery as complete flat ones, so pre-charging on flat batteries are activated and this can cause high pulse current). With v2.1 design, this pre-charging pulse is cancelled to avoid high pulse current during the time of reverse battery polarity being connected on charger.
- Battery self discharge and charger related leakage will lead to batteries voltage keep dropping after fully charged. Auto recharging procedure will activate when battery voltage dropped beyond 4.12v.
7.Improved charging termination for ni-mh batteries. Much less heat generated during last charging phase period. - For 4.35 and 3.7 batteries, charging CV stage starts at 4.26 and 2.8v respectively. This is helpful in reducing the charging time needed for fully charged
With the above changes done, we think this charger needs no more firmware update anymore.
Since the controller on board is One Programmable Only type, so we can’t support on line firmware grade option. And I am really sorry for this.
The XStar charger used pure DC current charging design , while our BT-C3100 uses averaged PWM CC charging algorithm. There are still debates going on with the two different charging method for nimh batteries. Some researches say that PWM type averaged CC is better for nimh or nicd batteries. However during our own research, we do find pure DC CC charging has one obvious advantage: There is no extreme high power pulse built during charging phase, while our BT-C3100 suffered this problem. This high current exists mainly when completely empty batteries are charged. When battery voltage is over 3.6v, the current is not that high at all. The panasonic li-ion battery stores much more energy at the voltage range of 2.8v ~3.7v ( about 1000mah), while samsung li-ion battery stores only 100mah at this voltage range. So extrem high current charging time needed for panasonic batteries are much longer and its charging current is much higher. We cornered around this problem by controlling the DC/DC bulk converter output voltage from 5v to 4.65v. This brings the benefits of having less high current needed, and thus have the charging capacity data improved.
As HKJ mentioned, this problem can be improved by shifting the phase of 4 charging channels, and split the high current evenly. But the controller resources is not allowing us to do so. We are working on a pure DC current charging circuit now, and I hope we can have a new model out sometime in 2015.
HKJ: Can I send our improved V2.1 for your further testing?
The updates look like a significant improvement.
Sadly I cannot do a full review in the near future, I have about 15 chargers in queue.
I might be able to squeeze a "update review" in between the other chargers. This will include some charges/discharges and oscilloscope checks.
Thanks, HKJ. You are so kind.
Yes please.
15 other chargers to review, now THIS is something I look forward to.
There are a few duplicates in the pile, just with different brand labels on (I believe), but they will all get the full treatment.
It also looks like it is very popular to support both NiMH and LiIon in the same charger.
but maybe the OPUS is the most relevant to the crowd? :)
it has been the most discussed, most read, and 700pcs bought charger on this forum lately, or is my impression wrong?
That is exactly the reason I will do a mini test of it, where I check the improvements, but does not test all functions.