Charger TrustFire TR-007





The TrustFire brand covers many different flashlights, batteries and chargers, but usual the quality is a bit low. Here I am testing a simple charger LiIon charger that can charge two batteries simultaneously with high or low current, it does also have a usb output.



I got the charger in an enevelope.



The box lists many of the battery sizes that the charger support, but forget to add reservations (It cannot charge two large batteries simultaneously, due to space).



The box contains the charger, a power supply, the manual and a warranty chart.



The charger has a 12 volt 1 ampere input and uses an external 12V DC mains supply.



There is 3 leds on the charger, one for each channel, that shows red while charging and green at other times.
In the center is a green led, that is one when usb output is active.



The switch has 3 settings:
H: High charge current (Max. 650mA).
L: Low charge current (Max. 500mA).
O: USB output activated, it disconnects the battery used for usb power from the charging circuit and connects it to the usb output circuit.



The usb output.



The charge slots can handle from 51mm to 71.9mm long cells, including flat top cells. The slider has a plastic foot, this makes the slider very smooth.







The charger can handle 70 mm long batteries, inclusive flat top cells.



Measurements

• When not connected to power it will discharges with up to 0.4mA, when usb is on the usb slot will discharge with 5mA.
• When power is connected with a full battery, the charger will charge with 0.2mA.
• Below 0.5 volt the charger does not detect a battery and does not charge.
• Above 0.5 volt the charger uses full charge current.
• It will not restart charging, if the voltage drops.
• It will restart charging on reinsertion of the battery or power cycling.
• The channels on the charger are independent, i.e. there are small differences between them.

This charge curve looks very special. First it charges with a steady falling current, then it switches to pulsing and some time before the battery is full, it turns the green led on and reduces the current.
This is not CC/CV and reporting the battery full nearly two hours before the charge current is turned off is cheating.
The charger time is about 10 hours.



The other channel works the same way, but with slight different values.



A larger cell takes longer to charge.



But the 2600mAh cell takes about the same time as 3100mA, due to different charge voltage.



Two cells are charged at the same speed as one cell. The temperatue does not raise much (Maximum is 34°C), probably because the charger is using low power levels.



It can also handle my old IMR cell.



There is not much difference between low and high setting. On low the initial charger current is limited, but the total charger time is about the same.


M1: 42,8°C, M2: 41,8°C, HS1: 51,2°C

There are some parts within the charger that generates heat. With the thermal camera I do also record higher battery temperatures.
This image is from very early in the charge cycle, later on the charger is cooler.



The charger uses a soft startup when power is turned on.



Constant current charge look fairly constant.



But when the current is reduced, the current is pulsing.



USB output

• USB output does not turn off when battery is empty.
• USB output does not turn off when overloaded, output voltage will just decrease.
• USB output is coded as USB charger (DCP).
• When usb output is unloaded it will drain about 5mA from the battery (That is about 25 days with a 3100mAh battery).

The load sweep is not very impressive, the usb output can only deliver 0.25A, before the voltage drops.



Even at 0.25A, it cannot hold a stable voltage, when the battery is discharged. It is also missing a low voltage disconnect for the battery. The discharge stops at 2.5 volt when the AmpMax over discharge disables the battery.



Even at this low load, there is noise (72mV).


Testing with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems.



Conclusion

I am not very impressed with this type of charge curve, it is slow and the first termination current is way to high and also at a low voltage. The second termination some time later is much better. The charger does not do anything bad to the batteries, but it is slow and if you uses the charge finished indication, the battery is not full yet.
There is no reason for the two current settings on the charger, the practical difference is to low.
The usb output is not very good, they output power is way to low and it must only be used with protected batteries.



Notes

Here is an explanation on how I did the above charge curves: How do I test a charger