Active balancer, make it smart!?

[Capt Bill]

We may be talking past each other. Let me try it another way: Say your relay is turned off for one or more cells. Since the active balancer is measuring the voltage on each cell, how does it do that for the cells where the relay is off?

I would only use that 8 set relay ... with all 8 relays set up to close or open simultaneously. ... while thinking about how that inexpensive Heltec (or other brand) Active Balancers could malfunction (even with an off and on switch solder adjustment and switched off / from one story I heard ) ... when no one is there, and potentially harm your way more expensive battery cells.

 

[Blackmoses]

Will this relay work kn an active balance connected to 48v battery
link

 

[Capt Bill]

Will this relay work kn an active balance connected to 48v battery
link

I have tested two of those (for 24v) ...to get off/ on relay trip events "near" the high charge voltage of my 24v LifePO4 setup. I would want on my upcoming Heltec Active Balancer Test. I am sure the relay could provide an off / on switch @ upcoming Heltec Active Balancer Test; specifically at that soldered terminal that gets un-soldered from permanent ON ... to having wires for your switch. ... One thing I noticed it this unit get warm when connected for monitoring my battery bank voltage. ... Here's Another Option I saw on youtube that might be better for it's digital ability with (likely) less heat. https://www.amazon.com/gp/product/B01M1JEH7T/ref=ox_sc_act_title_1?smid=ATCVC199CHVK0&psc=1
I had to go to eBay for the 24v version. ... ;+)

 

[time2roll]

I would only use that 8 set relay ... with all 8 relays set up to close or open simultaneously. ... while thinking about how that inexpensive Heltec (or other brand) Active Balancers could malfunction (even with an off and on switch solder adjustment and switched off / from one story I heard ) ... when no one is there, and potentially harm your way more expensive battery cells.

I assume a malfunction will be self fusing.

 

[ocular]

The relay output on the Junctek Battery Monitor could also be used to trip at desired pack voltage to turn on active balancer. Not used one but appears to have reasonable reviews and available support.

 

[Hans Kroeger]

I have tested two of those (for 24v) ...to get off/ on relay trip events "near" the high charge voltage of my 24v LifePO4 setup. I would want on my upcoming Heltec Active Balancer Test. I am sure the relay could provide an off / on switch @ upcoming Heltec Active Balancer Test; specifically at that soldered terminal that gets un-soldered from permanent ON ... to having wires for your switch. ... One thing I noticed it this unit get warm when connected for monitoring my battery bank voltage. ...

No, the relay won't work, because the relay contacts must be floating (no connection to battary)

 

[BradCagle]

Max, thank you for the link to this video. I believe it answers all previous questions about the basic function of the balancer.

You found my video Glad it helps.

Here's another interesting thing, you can scratch the coating off the parallel bus traces and you can probe to get the average cell voltage, not sure how handy that is. But I think it would be interesting to add a +1 cell there. For example if you have a 4s, you could have a 4+1s, and not change your system voltage. Now of course you'd be limited in the amount current that can transfer to/from the 5th cell.

 

[Hans Kroeger]

The DVB01 may work....

 

[Vi s]

You found my video Glad it helps.

Here's another interesting thing, you can scratch the coating off the parallel bus traces and you can probe to get the average cell voltage, not sure how handy that is. But I think it would be interesting to add a +1 cell there. For example if you have a 4s, you could have a 4+1s, and not change your system voltage. Now of course you'd be limited in the amount current that can transfer to/from the 5th cell.

Yes many thanks for making and posting it! It was very well explained and illustrated.

BTW there is an interesting looking new model with a touch on-off button (supplier said so). It seems it works the same way as you explained in the video but costs a few dollars less.
There is no picture of the backside as well no review on YouTube or elsewhere yet.

Product description:
The average battery voltage is higher than 3.25V and the balance is turned on
1500uF solid capacitor.
The accuracy is around 0.005V.
The maximum equalizing current is about 5A, (the maximum current is 5A, not the continuous current!) The voltage difference determines the equalizing current.
This equalizer is different from inductive equalization, which is energy transfer between adjacent batteries, and this equalizer is the energy transfer of the entire group of batteries. Size 4.8cmX4.6cm

8.96US $ 10% OFF|4S 5A Lithium Battery Active Balance Board Capacitive batteries Energy transfer Balancer FOR BMS Li ion Lifepo4 4x 3.2V 3.7V | | - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

 

[ocular]

No, the relay won't work, because the relay contacts must be floating (no connection to battary)

I dont suggest that you directly use the relay logic board connections that connect to the external relay, but set it up as junctek shows for an external relay and use the dry contacts of the external relay to open/close the switch terminals of the heltec capacitor balancer or make/break the B+ balance wire of other active balancers that will self start from power off. By adjusting the OVP setting (and all other alarm settings to off) then the external relay can turn on/off balancer around 3.4V per cell. The output of the external relay is connected only to balancer. If the working voltage of the relay is the same as the battery pack voltage then maybe no separate external power supply is required as the battery pack remains connected all the time.

 

[BradCagle]

Yes many thanks for making and posting it! It was very well explained and illustrated.

BTW there is an interesting looking new model with a touch on-off button (supplier said so). It seems it works the same way as you explained in the video but costs a few dollars less.
There is no picture of the backside as well no review on YouTube or elsewhere yet.

Product description:
The average battery voltage is higher than 3.25V and the balance is turned on
1500uF solid capacitor.
The accuracy is around 0.005V.
The maximum equalizing current is about 5A, (the maximum current is 5A, not the continuous current!) The voltage difference determines the equalizing current.
This equalizer is different from inductive equalization, which is energy transfer between adjacent batteries, and this equalizer is the energy transfer of the entire group of batteries. Size 4.8cmX4.6cm

8.96US $ 10% OFF|4S 5A Lithium Battery Active Balance Board Capacitive batteries Energy transfer Balancer FOR BMS Li ion Lifepo4 4x 3.2V 3.7V | | - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

a.aliexpress.com

Interesting. I need to grab one, and test it.

BTW are you guys wanting to make the balancer only come on at a certain avg cell voltage?

 

[Vi s]

Interesting. I need to grab one, and test it.

BTW are you guys wanting to make the balancer only come on at a certain avg cell voltage?

Not only, on a certain avg cell voltage for those who have matched cells (or other reasons) and for those with unmatched cells (or other reasons) on single cell voltage. Yet so far there are only single cell voltage solutions (via an esp r pi) in concept available (no code available yet), for avg cell voltage there are already quite a few working ones.

 

[Vi s]

I would only use that 8 set relay ... with all 8 relays set up to close or open simultaneously. ... while thinking about how that inexpensive Heltec (or other brand) Active Balancers could malfunction (even with an off and on switch solder adjustment and switched off / from one story I heard ) ... when no one is there, and potentially harm your way more expensive battery cells.

Hi
I might have found something interesting for you. Remember a relay isn't a fuse, it's basically just a switch. So you might be safe during the time the balancer is disconnected (relay open) but if a malfunction occurs during balancing (relay closed), then your cells will be as unprotected as without the relays. Following example of a simple fuse solution offer some safety during balancing.




On that particular fuse board are also LEDs which tell you if there is a fuse blown or if a cell is below a 2.2volts.
Using only fuses should be pretty easy to assemble. For a 5a active balancer use maybe 10a fuses (something higher than 5a).

 

[Samcat]

Hi
I might have found something interesting for you. Remember a relay doesn't prevent a short or the like just an on-off functionality. So you might be safe when the balancer is disconnected but if a malfunction happens during ON, during balancing, then potential harm will still happen. Following simple good old fuse solution might ensure more safety.
View attachment 98639
View attachment 98640
View attachment 98641
View attachment 98642
On that board is also a led which tells you if there is a malfunction like a fuse blown or below certain voltage. You probably could also use just fuses which is pretty easy to assemble. For a 5a active balancer use maybe 10a fuses (something higher than 5a).

There is still unknown question if one of leads have burned fuse how it will react to balancing board. Will it fry board or throw errors or making things even more complicated. Why many Chinese balancers are not mentioning leads fuses is because they are not likely designed with this in design R&D . So i would advise anyone to benchtop test bms with this scenario and see how it will react if fuse blow on one lead by testing many different scenarios first lead ....one in the middle or one on the very end of leads setup.

 

[Vi s]

There is still unknown question if one of leads have burned fuse how it will react to balancing board. Will it fry board or throw errors or making things even more complicated. Why many Chinese balancers are not mentioning leads fuses is because they are not likely designed with this in design R&D . So i would advise anyone to benchtop test bms with this scenario and see how it will react if fuse blow on one lead.

If one fuse is blown it would mean the balancer has already shorted. what could be even more complicated? Rather let the short happen than...?

 

[Samcat]

If one fuse is blown it would mean the balancer has already shorted. what could be even more complicated? Rather let the short happen than...?

Sure...but if there is short still on the board not making enough current to blow other fuse it could lead to completely dead cell in the pack. One of biggest investments are battery pack and inverters so careful design and benchtop BMS testing are good choice to figure out everything and know all weaknesses before making wiring diagram and implementing safety hardware. I'm not judging just speaking out loud. I have already experience with REC BMS that made customer battery pack cell completely dead because of malfunction of bms board. But i will not say it was expensive BMS issue...while doing investigation i have found loose wire on the REC BMS that was overheating wire terminal for long time and eventually fried and made weak short to other lead and made one cell going down to 0.6 V . Most of the BMS from China are designed not for off grid battery setup and Ah ratings that many are running. It is possible to run but it does require babysitting more often than necessary.

 

[Hans Kroeger]

.......Here's Another Option I saw on youtube that might be better for it's digital ability with (likely) less heat. https://www.amazon.com/gp/product/B01M1JEH7T/ref=ox_sc_act_title_1?smid=ATCVC199CHVK0&psc=1
I had to go to eBay for the 24v version. ... ;+)

I bought the 12 V Version and tested it. The lower Voltage can be set to 11.0 ...11.9 V only, the upper Voltage level to 13.0...13.9 V only. The description says 0 ...99.9 V . Will send it back.....
Correction: I may have overlooked some adjustment steps, so I will tray again

New comment:
OK, In fact, you can set the voltage level as needed. However, the modul seemingly does not compare actual voltage and setpoints on the digital side of the module. The relay was turned on at 13.4 Volt (setpoint was 13.5 V) and it was turned off at 13,2 V (setpoint was 13.4 V).
This is not acceptable......

 

[Hans Kroeger]

If one fuse is blown it would mean the balancer has already shorted. what could be even more complicated? Rather let the short happen than...?

The Heltec balancer uses AWG 16 wires (?). Assume there is a short on the board or in one one of the components. I guess the current will be high enough to burn the short until it opens. If there is a fuse, I expect the fuse is blown before the short opens.
If there are shorted wires the fuse will blow immediately. If there is no fuse it becomes very difficult to predict what will happen.
I performed a test with shorted AWG 20 wires. The wires became very hot! The resistance of the wires doubled reducing the initial current. The wires started to glow. The wires were wound around a piece of wood (worst case) which started to smolder. The piece of wood became heavily damaged, there was lots of smoke but no fire. I stopped the test after a couple of minutes.
I think about repeating the test with AWG 16 wires......

 

[Hans Kroeger]

Hi
I might have found something interesting for you. Remember a relay doesn't prevent a short or the like just an on-off functionality. So you might be safe when the balancer is disconnected but if a malfunction happens during ON, during balancing, then potential harm will still happen. Following simple good old fuse solution might ensure more safety.
View attachment 98639
View attachment 98640
View attachment 98641
View attachment 98642
On that board is also a led which tells you if there is a malfunction like a fuse blown or below certain voltage. You probably could also use just fuses which is pretty easy to assemble. For a 5a active balancer use maybe 10a fuses (something higher than 5a).

Caution: the internal resistance of this fuse + circuit may be high enough to reduce the measured cell voltage too much.

 

[Samcat]

With BMS that has access to calibrate resistance for each lead and voltage calibration fuses are not a problem for as long it within BMS tolerance. This is why most BMS postings max Ah ratings not just to have any chance balancing big size Ah cells but also stay in the resistance tolerances. I'm still waiting for JK bms to try lifepo4 3.2 V cell 1000 Ah . Will see if this BMS can handle this monster cells.