In-line manual rebalancing

[markcouz]

Originally Posted by s/v Jedi

That’s interesting, they even have versions with display on smartphone apps as well as 8s and 16s versions.

I wonder how they do it, must be relatively simple as there doesn’t seem to be any settings for cell voltage. If I find out, I may include that in my bms design.

It doesn't require voltage setting, so long as the connected cells are within the range of operation they will be balanced by taking energy from highest cell and feeding into the lowest cell until all balanced.

Note that it is not the resister type which will simply burn off energy from higher cells to match lowest cell, those are common and not great in my opinion.

[s/v Jedi]

Originally Posted by markcouz

It doesn't require voltage setting, so long as the connected cells are within the range of operation they will be balanced by taking energy from highest cell and feeding into the lowest cell until all balanced.

Note that it is not the resister type which will simply burn off energy from higher cells to match lowest cell, those are common and not great in my opinion.

Yes, I’m wondering how they do it. There are many active balancers but I believe those require a setting for cell voltage. I need to dive into it. If you ever open the housing, make photos!

[tanglewood]

Originally Posted by GoneDiving

How did you confirm this? I assume just checked for continuity between -12VDC and AC Ground while turned on?

Well, first the specs say it's isolated, so that was a good start. I then checked continuity between the neg and ground, but with the unit off. Then I connected to a cell in the middle of the bank, but with the current limit set real low, and while squinting . No sparks, so the spec sheet was right.

[GoneDiving]

Originally Posted by tanglewood

Well, first the specs say it's isolated, so that was a good start. I then checked continuity between the neg and ground, but with the unit off. Then I connected to a cell in the middle of the bank, but with the current limit set real low, and while squinting . No sparks, so the spec sheet was right.

Whose got time to read manuals? I do have some safety squints though. 😁

Thanks

[T1 Terry]

Originally Posted by markcouz

I have attached the Chinglish (oh-oh!) User guide - the HA-02 can be used with 2.4v/3.6v/6v/9v/12v cells - or effectively any cell between 2.4V and 12V nominal.

The point is that they switch on and start balancing continuously once the terminal voltage is above 2.4V, which with LiFePO4 should be all the time as you would certainly not like to see your cells below 2.5V (or below 3V in my own system).

I previously used them with a 48V 500Ah lead acid bank made up of 24x 2.4V cells on a home PV system, they worked so well that they effectively hid how rubbish the batteries were because they were always in balance.

Needless to say my experience with the 500Ah lead acid bank cured me of lead acid use for ever (except for start battery where they are the right choice).

We often use these for the 24v battery packs, 2 cells in series for each leg of the balancer. It can result in one cell high and one cell low in each series pair, but when combined with a charge cut when any cell exceeds 3.6v, the differential is never very much.
We cut the terminal off and link the positive from string 1 to the negative of string 2, repeat this until you have a single negative at one end of the string and a single positive at the other end. We found this to be very important when the battery bank was large and made up of a lot of parallel/series groups that were back to back, 2 x 12v batteries back to back in series. If the connecting wires get mixed up so the voltage step between each wire is not as it should be, the smoke comes out of the box and it actually starts dragging the battery out of balance and eventually completely drains cells destroying them .... a very expensive lesson requiring a 5,500km round trip to fix and a rather expensive set of replacement cells .....

T1 Terry

[T1 Terry]

The balancer uses inductor coils and a switching system to first charge each coil from the corresponding cell, then linking the coils together so they equalise their voltage, then connect them back to the cell. If the cell voltage is higher than the coil voltage, some current passes into the coil, if the cell voltage is lower than the coil voltage, the coil discharges into the cell, then the process repeats.
No value in removing the backing plate, the whole thing is resin encapsulated so nothing there to see.
One day I'll soak the dead unit to dissolve the resin material to see just what gear is in there, but they are so cheap you just wouldn't bother.


I was going to post a photo of an off grid 48v system that utilises 5 of these units, but I can't figure out how to post a photo on here

T1 Terry
EDIT: Didn't scroll down far enough