Green New Energy Active Balancers-do they do anything?

Getting into the nuts and bolts of wind and solar power components, installation and performance issues, ask technical questions, answers and tips

Green New Energy Active Balancers-do they do anything?

Postby NealinPerth » Sat Apr 22, 2017 5:47 pm

Seeking comments from members using the Green New Energy Active balancers.

IMG_1106.JPG

I purchased the 4s version to balance a 12volt 200Ah pack of Winstons. The specs from the manufacturer claim that the cells will be kept within 10mV after using the balancer.

I’ve performed several charging cycles with the balancers connected and so far they seem to be doing nothing other than produce an audible high frequency tone.
The individual cell voltages continue to diverge when approaching the cells upper voltage knee and are never brought within 10 mV.

IMG_1110.JPG
IMG_1110.JPG (98.26 KiB) Viewed 3411 times

The second pic shows the cell delta volts of 26mV, towards the end of absorption (pack volts 13.88V),
when the charge current has tailed off to about 8amps.
I’ve also charged with a bench top power supply at 14.4V until the current tapers to 2 amps and the cell delta volts reached 70 mV with the balancers connected.

Am I missing something? Has anyone using these things observed cell delta volts less than 10 mV with cell volts around 3.5-3.6v with the balance modules operating?

Neal
NealinPerth
Solar Supporter
Solar Supporter
 
Posts: 7
Joined: Fri Apr 21, 2017 11:19 am

Re: Green New Energy Active Balancers-do they do anything?

Postby Gordon-Loomberah » Sun Apr 23, 2017 12:15 pm

What charge controller do you use, and what charging set points and times do you have?

I think 10mV is just wishing thinking, perhaps from the marketing dept. I have a set of these on my 16 X 400AH LiFePO4 cells, and have seen some huge divergence near the end of charge at low net charging current of <5A, well within their supposed 6A continuous rating. I'll dig up a graph to demonstrate later.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5762
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Green New Energy Active Balancers-do they do anything?

Postby NealinPerth » Sun Apr 23, 2017 7:10 pm

I'm using a 40 amp mains charger. Bulk charge to 14 volts. When the charge current tapers to 8 amps it switches to 13.5 "float" voltage. The bank was at about 50% when I started the test with all loads removed and the whole process took about 2.5 hours before switching to float.

The bench power supply I used for the earlier test at 14.4 volts is also 40 amp. Time taken for the charge current to reduce to 2 amps was also about 2 hours because the bank was at a higher state of charge. The cell delta volts of 70mV I saw at the end of the test is probably quite acceptable balance for cells at 3.6volts.

My expectation was that I would see the balancers gradually drawing the cell voltages together during the charge process until they were all within about 10 mV of each other at 3.6 volts. In fact the opposite happened and the cell voltages diverged which made no sense to me.

Interesting that you are seeing a divergence at end of charging also.
NealinPerth
Solar Supporter
Solar Supporter
 
Posts: 7
Joined: Fri Apr 21, 2017 11:19 am

Re: Green New Energy Active Balancers-do they do anything?

Postby Gordon-Loomberah » Sun Apr 23, 2017 9:54 pm

This is a graph showing the 2 8 cell half voltages of my battery. 15 X 400AH CALB + 1 Winston 400AH which replaced a low capacity CALB last year. I installed the CALBs in late 2012.

20170229voltages.gif
click on graph to de-fuzz it


The 2 halves don't diverge like this ATM, since I did a long absorb stage a few weeks ago the 2 halves have become more equal, but there is still quite a bit of cell to cell variation. I noticed one cell was at 3.6V the other day, while the lowest one was under 3.4V, although the 2 halves were within 30mV. I'm still using the balancers as sold by EVPower to absorb a bit of current if any cells go too high.

The reseller's claim that they are working correctly when making the high pitched noise is clearly not true.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5762
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Green New Energy Active Balancers-do they do anything?

Postby Warpspeed » Sun Apr 23, 2017 11:33 pm

My expectation was that I would see the balancers gradually drawing the cell voltages together during the charge process until they were all within about 10 mV of each other at 3.6 volts. In fact the opposite happened and the cell voltages diverged which made no sense to me.

Your expectations are a bit unreasonable.
Do you really expect instant <10mV results in only a single charge cycle ?

Cell balancers do not transfer tens of amps between cells, probably more like tens of milliamps, and its going to take a very long time to transfer enough charge to make a difference, especially with higher capacity cells.

And another thing to think about. Suppose you have one 200 Ah cell, and one 180 Ah cell connected in series. Can perfect balance be achieved ? Obviously not. The weaker cell will charge and discharge more quickly to higher and lower voltages than the stronger cell. The voltages can only be the same at one point.

These cell balancers are small and very limited in power. The idea is you fit one, and over weeks, months, and years it gradually nibbles away at the problem. Its not a case of clipping it on and coming back in an hour to see all the cell voltages absolutely identical. Be patient, and assuming all your cells are in perfect condition things will very slowly improve.

If your cells are in less than healthy condition, you will never get them to balance and track each other over the entire range.
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 435
Joined: Fri Jan 03, 2014 3:18 pm

Re: Green New Energy Active Balancers-do they do anything?

Postby Gordon-Loomberah » Mon Apr 24, 2017 9:05 am

Warpspeed wrote:Cell balancers do not transfer tens of amps between cells, probably more like tens of milliamps,


The balancers in question are claimed to be able to transfer 6A continuously, and 10A peak. Clearly they don't though.

We don't know how old Neal's cells are, but the online blurb does say the balancers work best with new cells, and as you mention, you will never get perfect balance with cells of differing capacity.

However, that doesn't explain the divergence at the top of charging when net current is well under the claimed current transfer ability of the balancers. A high cell's voltage should not continue to increase when the net current flow into that cell is negative, ie it should be discharging, making the voltage fall, if the specs are to be believed.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5762
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Green New Energy Active Balancers-do they do anything?

Postby Warpspeed » Mon Apr 24, 2017 9:36 am

I am experimenting with my own home brew balancer right now.
And one thing that has suddenly become quite obvious is that, you cannot use the same cell connection wires simultaneously for both voltage sensing and charge redistribution and achieve any kind of voltage measurement accuracy.

Voltage drops along the wiring make a nonsense of getting an accurate balance if high rates of charge or discharge are involved along the same actual wires.

A great many commercial top end balancers, and the high voltage EV battery management systems use tiny surface mount resistors to dissipate power. The Nissan Leaf vehicle BMS uses 450 ohm resistors (probably about 8mA and 28 milliwatts) to balance 60 Amp hour cells.
That sounds incredibly low, but its probably working 24 hours per day, and it must obviously work.

But it sure isn't going to do anything you can actually see working over a few hours or even a few days.
But over the several year expected life of the battery, the cumulative effect is probably quite significant.
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 435
Joined: Fri Jan 03, 2014 3:18 pm

Re: Green New Energy Active Balancers-do they do anything?

Postby Gordon-Loomberah » Mon Apr 24, 2017 12:08 pm

After over 4 years observing my cells, and logging the system at 1sec interval, I'm not really concerned about 10mV balancing, only that they are reasonably close most of the time and that there are no high or low voltage excursions.

One thing I have noticed is that the cells will not accept as high a charge as when they were new, meaning I need to keep them at Vabsorb for longer to reach "full charge", although having Vabsorb at under 55V means longer absorb times anyway. However, that's a topic for another thread.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5762
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Green New Energy Active Balancers-do they do anything?

Postby NealinPerth » Mon Apr 24, 2017 1:12 pm

Gordon-Loomberah wrote:We don't know how old Neal's cells are, but the online blurb does say the balancers work best with new cells, and as you mention, you will never get perfect balance with cells of differing capacity.

However, that doesn't explain the divergence at the top of charging when net current is well under the claimed current transfer ability of the balancers. A high cell's voltage should not continue to increase when the net current flow into that cell is negative, ie it should be discharging, making the voltage fall, if the specs are to be believed.


My cells are 3 years old. They came out of the same crate with consecutive serial numbers and terminal volts within 1mv of each other. The most recent pack discharge test (@C/10) showed that there was still 200 Ah capacity available down to cell volts of 3.0 volts. I'm fairly confident that they are still in reasonable nick.

I agree with Gordon that the at the low net charge current the high volt cell should have stopped diverging.

By doing this testing I mainly wanted to confirm that the device was working out of the box and not faulty. If the balance currents are so low that it takes 6-12 months to notice any difference I'm not sure theyre worth bothering with.

A good manual pack balance can be done within a week and will last a couple of years with low C setup such as in caravans and RVs.

I'll email the electric car parts company I purchased these things through.

Works as designed or faulty out of the box? It would be interesting to find out if ( and how ) they evaluated the effectiveness these devices before offering them for sale.

Neal
NealinPerth
Solar Supporter
Solar Supporter
 
Posts: 7
Joined: Fri Apr 21, 2017 11:19 am

Re: Green New Energy Active Balancers-do they do anything?

Postby Warpspeed » Tue Apr 25, 2017 1:08 pm

One further thought I had on all this...

The amount of current diverted may (?) depend on the voltage differential between cells.
If the differential is ridiculously high it could very well transfer several amps, but if its only millivolts of difference, you may only see a very small rate of current transfer.

It may not be possible to transfer six or ten amps if the cell difference is already quite low.
Warpspeed
Solar Crusader
Solar Crusader
 
Posts: 435
Joined: Fri Jan 03, 2014 3:18 pm

Next

Return to Components, Installation And Performance

Who is online

Users browsing this forum: No registered users and 7 guests

new solar power specials