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HX-JH-004 4S 12V LiFePO4 balancer board test

A typical LFP or LiFePO4 cell has 3.2V nominal voltage which means that if you connect 4 LFP cells in series you’ll have a 12.8V battery pack. The charge end voltage for a 4S pack would be 4×3.65V= 14.6V but as you know battery packs need to be balanced to serve for a long time, especially if the cells have different internal resistance.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

HX-JH-004 is a balancer board for a 4S LFP battery pack which should not be confused with BMS – the latter also protects the battery pack from overcharging, overdischarging and going overcurrent. HX-JH-004 only does the balancing.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

Specifications of HX-JH-004 4S LFP balancer board
Dimensions (LWH): 26×20.5×2.4mm
Balancing current for each cell: 58mA
Balancing voltage for each cell: 3.60V (14.4V for the 4S LiFePO4 battery pack)

So when a cell’s voltage goes above 3.60V the balancer shoud start discharging until it reaches the 3.60V limit.

Let’s take a closer look at the components on the PCB.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

There are 4 channels with identical set of elements the biggest one of which is the 62Ω resistor (marked 620) which defines the 58mA balancing (discharging) current.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

Next comes a H&M Semi HM2302A (datasheet) n-channel power MOSFET in SOT-23-3L package with A2SHB marking, a Hycon HY2212-BB3A (datasheet) battery charge balance IC in SOT-23-6 package (marked AB3A M60J), an SMD capacitor and a 100Ω SMD resistor (marked 101).


Wiring the board to a 4S battery pack

For those who are going to build a pack for the first time here is the wiring scheme:
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

I’ve used 0.5mm copper wire for wiring.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

The PCB with soldered wires looked like this:
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

I used a holder for 4×18650-size cells and I intentionally used different cells with different internal resistance to complicate the job for the balancer.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews


Testing

The measurements showed that the balancing current was 58-59mA which is exactly what the specs tell. I’ve repeated the test 3 times. Between charging and balancing a 1-hour pause was left to have stable voltages of the cells.

Ch – number of channel of the balancer
Cell – number of cell
Before – cell voltage before balancing
After – cell voltage after balancing
Δ – the difference with 3.6V for a cell and the difference with 14.4V for the pack

ROUND 1
Ch
Cell
Before
After
Δ
1
1
3.768
3.600
0.000
2
2
3.625
3.596
0.004
3
3
3.725
3.595
0.005
4
4
3.707
3.584
0.016
Pack V after balancing: 14.375
0.025
.
ROUND 2
Ch
Cell
Before
After
Δ
1
1
3.697
3.600
0.000
2
2
3.685
3.595
0.005
3
3
3.663
3.596
0.004
4
4
3.683
3.583
0.017
Pack V after balancing: 14.374
0.026

In round 3 I’ve swapped the 1st and 4th cells to exclude the impact of a cell-channel combination.
ROUND 3
Ch
Cell
Before
After
Δ
1
4
3.691
3.598
0.002
2
2
3.692
3.599
0.001
3
3
3.678
3.595
0.005
4
1
3.694
3.587
0.013
Pack V after balancing: 14.379
0.021

In the first two rounds the cell on the first channel was discharged down to 3.600V which looks pretty nice. The next two channels were below 3.6V by 0.004-0.005V which is a miserable delta. Only the 4th channel was below 3.6V by 0.016-0.017V which is not as low as the other channels but still a good result.

The 3rd round showed that the results don’t rely on cell-channel combination because the first channel with the cell №4 again showed almost no difference with 3.6V and the 4th channel’s delta was again higher than 0.01V – 0.013V to be exact.


Upgrade

During balancing the 62Ω resistors heat up the board up to 60°C. To cool it down I took a couple of 9×9×5mm heatsinks and cut the ribs to 2.1mm
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

I attached them together by putting a sticky insulation tape on long sides. It’s very important to use insulation to avoid contact between the heatsink and resistors.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

Then I applied some thin layer of thermal conductive glue to resistors.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

And accurately put the heatsink on to the resistors and left to cure for several hours.
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

This upgrade helped to lower the temperature by 8-10°C.


Verdict

So, this balancer is not bad at all. The first 3 channels’ accuracy is between 0-0.005V and only the last channel showed 0.013-0.017V difference with 3.6V target voltage. The balancing current is 58-59mA which is also quite accurate. The high operating temperature is something I didn’t like and put an aluminium heatsink but even without that additional cooling the board will work fine. I took it for $1.5 which is not a too high price for such a performer.

Here is the video version of this review:
HX-JH-004 4S 12V LiFePO4 balancer board test review | Thunderheart Reviews

Check out my YouTube channel for batteries, chargers and other stuff reviews.

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