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Author Topic: Big re-work at Nowty Towers.  (Read 6823 times)
Nickel2
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« Reply #45 on: July 19, 2020, 09:07:22 AM »

Hi Nowty, Can you give more info on the balancer please.
Cheers, N.
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EpEver 4210A at 24v
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kdmnx
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« Reply #46 on: July 19, 2020, 12:15:27 PM »

Iíve not seen a balancer used in a Lead-acid application before. Mostly the cells are ďbalancedĒ by overcharging. Obviously balancing is a big deal for lithium batteries because overcharging can be disastrous.
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nowty
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« Reply #47 on: July 19, 2020, 12:21:39 PM »

Iíve not seen a balancer used in a Lead-acid application before. Mostly the cells are ďbalancedĒ by overcharging. Obviously balancing is a big deal for lithium batteries because overcharging can be disastrous.

They are lithium, I sold off the forklift LA pack a year ago.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
pantsmachine
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« Reply #48 on: July 19, 2020, 12:37:58 PM »

Nowty, that is a mightily impressive set up. I am chuffed to emulate a small part of it.
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8.045kWh PV system with Solar edge
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Solar I boost charging 12kWh 210 ltr OSO system tank
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nowty
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« Reply #49 on: July 19, 2020, 12:53:47 PM »

Hi Nowty, Can you give more info on the balancer please.
Cheers, N.

Patience Nickel2, they only arrived yesterday ! fight

But already, I've been busy, Grin

I threw away the crappy ultrathin connection cables and upgraded them to a set of fused links. I never connect anything to my battery bank without a fuse, I want no drama.



So there are no instructions, only a spec and a picture that suggest you can cascade them to match a battery bank of any size.

And the youtube video I already referenced (remember to remove the space after the https:),     https: //www.youtube.com/watch?v=-RfMKpyHkm4

SPEC
Operating voltage: 3.0V - 4.2V
Working power drain 15mA
Termination voltage: 2.9V (into undervoltage sleep state <1mA)
Maximum Balance current: The Cell difference V / Balance current    0.1V / 1A     0.5V / 3.5A     1.0V / 5.5A
Balance accuracy: < 5mv
No external power supply is required, internal energy in each high cell is transferred to the lower adjacent cell in the pack to balance the entire battery pack.



So for my Growatt packs of 14 cells, they don't make one for that size but I can use two 7/8 S boards with one of the mid cells overlapped across both boards.

I have now isolated one of my Growatt battery banks, which is now 5 growatt units in parallel. I plan to install this on the middle unit (3 of 5), with the idea being that the balanced cells will cascade to the other 4 units. But initially, I am going to disconnect it from the string so I am just dealing with a single pack to experiment with.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
Nickel2
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« Reply #50 on: July 19, 2020, 03:40:42 PM »

Nag registered!  Smiley
(24 hrs is long enough to have them installed, working, documented, etc...   stir  )
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1.140kW mono south-facing at 49*
EpEver 4210A at 24v
New (Old) 8S7P LiFe battery, 105Ah @ 26.4V
EpEver STI1000-24-230 pure sine inverter
Of course it'll work. (It hasn't caught fire yet).
nowty
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« Reply #51 on: July 20, 2020, 12:11:39 PM »

Well I got some initial drama yesterday, I blew one up. fume sh*tfan

However it was all my own fault. I didnít bother putting some tape over each connector in case I accidently touched an incorrect cell. Inevitably, one connector brushed a cell further up the bank, big spark, followed by the release of magic smoke, followed by a very large bang with my head right next to it. One of the solid state capacitors blew up having way in excess of the rated 6.3v across them. facepalm




Lesson learnt as it takes about 3 weeks to get another delivered from China. So I changed to plan B, which was to use my remote test point which I reconfigured to connect to each of the cells in half a unit. As I only have one board left, I can now only test half the cells but, its easier doing it this way. ballspin




Despite my initial setback, I am glad to say it seems to work as in the youtube video. I recorded each cell voltage before and after connecting, straight away there was some slight differences showing that the high cells were bleeding current and the low ones were having current added. The currents were too small to measure accurately with a clamp meter as my cell differences are quite small, typically 20mV to 30mV for adjacent cells.

But then I shorted each cell in turn with a 0.5 ohm resistor. This had the effect of dropping each cells voltage by about 0.5V which raised the charging current by about 3.5A which was very measurable with my clamp meter and It also matches the spec.

Pic - Before shorting the cell, voltage is 3.873v, current says -0.58A (which in reality is close to zero because the clamp meter does not zero very well).


Pic - After shorting the cell, voltage is 3.426V (drops by 0.45V), current says +3.02A (so its increased by about 3.6A)



I repeated this on every cell and I get a similar result. This resistor test really sells it for me, that's a reasonable amount of current to shift and the board does not even get warm. extrahappy

I left the balancer on all night, at the start there was a difference of 62mV between the highest and lowest cell. By the morning that max difference had dropped to 13mV at the test point and 20mv directly measured at the battery. The difference is due to the voltage drop in the 6 metre long cables from the test point. Some of these differences were positive and some were negative. This was consistent with the current flow direction with an outflow from the higher voltage cells and an inflow to the lower voltage ones. By using the theoretical resistance in the cables, I calculated that the charge / discharge rates this morning were only around 50mA to 100mA, so any further balancing is going to be very slow, but thatís close enough for me. signofcross

In fact at the start most adjacent cells were about 20mV or 30mV difference, but by morning almost all were less than 5mV, which again is within the stated spec.

I have now connected back up the other 4 Growatt units in the bank so I will see over the next day or so how the balancing spreads outwards to the other parallel connected batteries. tumble
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
pantsmachine
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« Reply #52 on: July 20, 2020, 05:50:20 PM »

Does this mean you have auto balancing on your battery system? Is that one more step towards fitted and forgot? Sorry to hear one went bang, I still trust you.  tumble
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8.045kWh PV system with Solar edge
7.2kWh Pylon tech battery storage
18kWh Heater Storage
Solar I boost charging 12kWh 210 ltr OSO system tank
Deep insulation, air leak controlled home
Zoned & Balanced CH wet system
Hive 2
Low energy bulbs
24 kW Leaf
Masanobu Fukuoka garden & wooden hot tu
nowty
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« Reply #53 on: July 23, 2020, 10:20:01 PM »

My active balancer experiment has been running for a few days now and it seems to work nicely.

To recap, I am testing a Chinese cell balancer on a bank of five cannibalised Growatt 4.8kWh packs in parallel. I am only using one balancer on the centre pack and relying on parallel cell links every two cells to ripple out the balancing to the rest of the pack. I needed two balancer boards to cover all 14 cells, but due to a mishap I only have one, so until I get a replacement I can only run the balancer on cells 1 to 8. However that lets me easily compare the difference between the balanced cells 1 to 8 vs the unbalanced cells 9 to 14.

Below is a diagram of the cell layout and only yellow cells have the active balancer attached.



The voltage on cells 1 to 14 on Bat 3 are as follows,

1  - 3.766V
2  - 3.767V
3  - 3.771V
4  - 3.770V
5  - 3.771V
6  - 3.771V
7  - 3.771V
8  - 3.764V

9  - 3.784V
10 - 3.757V
11 - 3.792V
12 - 3.709V
13 - 3.766V
14 - 3.757V

The max difference in voltage in the first 8 cells which have the balancer connected is now only 7mV after starting a few days ago with a max difference of 62mV. The last unbalanced 6 cells have a max difference of 83mV.

Also I note that the max difference in cell voltage on cells 1 to 8 on the other battery packs Bat 1, Bat 2, Bat 4 and Bat 5 have also narrowed to around 10mV - 20mV.

I have now moved the balancer from cells 1 - 8 to cells 7 - 14 to see what effect that has over the next couple of days.
« Last Edit: July 24, 2020, 02:01:05 PM by nowty » Logged

12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
biff
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« Reply #54 on: July 24, 2020, 09:22:14 AM »

Good stuff Nowty,
      I have Question..
 One of my projects is putting 3 strings of 10  x 12v  Yousa
 NPL65- 12i together.
 I intend it to be a compact set up with 2 rows  end to end in series. Previous attempts at this many years ago were doomed to failure  because either  No 3s or 7s failed in the 110ah yellow powersafe or the  Yousa 100ah  were so good that they shut down the W/t the moment they hit 138 Vs.  These  NPL65s are content at 12.60 but it is written on them that they are happy to discharge to 10.5 wackoold,
My intention is to group 30 of these into 3 strings as above but in order to keep an eye on their individual  12v progress I need to run a short wire from each connector to the front of each layer of 10 batteries, This way I will be able to shelve them closer together and not need to access them,
 So I intend to use 9 short cables to  sit out on the front of each layer, the wires will be coloured black for the inside 5and white for the outside  row 9 wires in all, per layer, with insulated  bullnozed crimped ends.
 So when I want to check the voltage of each pack, I start with the charge disconnected,  with the volt meter from left to right and  working with the negative  pushing the probes into the insulated bullnosed wire end connectors, I move along from left to right  each connector serving as positive and negative in turn.
  Long story short,  would it be possible for me to balance these small batts with a similar idea as yours?
       Sincerely  Biff
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nowty
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« Reply #55 on: July 24, 2020, 10:57:57 AM »

  Long story short,  would it be possible for me to balance these small batts with a similar idea as yours?

Biff, in my search for this product I came across a HA02 device specifically for (4 x 12v) batteries and it can be cascaded to 120v if you buy 3 units. Looks like they were thinking of you. Shocked

They seem to be for sale in the usual places, ebay, aliexpress, banggood, amazon.

https://www.aliexpress.com/item/32889102321.html?spm=2114.12057483.0.0.4ae2785458DiVm




PS - My overnight run with my balancer on the cells 7 to 14 which last night had a max voltage difference of 83mV is now down to 26mV. Grin
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
biff
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« Reply #56 on: July 24, 2020, 11:48:00 AM »

 Thanks for that link Nowty,
         I will read up on them. From the diagram, it looks like the 10 batts all have to be disconnected. Maybe not.  I will investigate.
 Excellent  result with your own equalizing,
       Cheers,   Biff
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nowty
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« Reply #57 on: July 25, 2020, 09:11:41 PM »

Update on the cell balancing, 2 days after changing the cells the balancer is on. Now they are on cells, 7 to 14 (in yellow below).




The voltage on cells 1 to 14 on Bat 3 are as follows,

1  - 3.684V
2  - 3.683V
3  - 3.689V
4  - 3.687V
5  - 3.688V
6  - 3.690V

7  - 3.676V
8  - 3.670V
9  - 3.668V
10 - 3.671V
11 - 3.676V
12 - 3.670V
13 - 3.675V
14 - 3.674V

The max difference in voltage on the first 6 cells which no longer have the balancer connected is now 6mV so they have hardly drifted at all.

The max difference in voltage on the cells 7 to 14 which started out with a max difference of 83mV, then down to 26mV after 12 hours, is now only 8mV after two days.

So still looks good, but now need to wait a few weeks before I receive my second board so I can cascade the two together to see if the voltage difference of the two battery halves can be narrowed.
« Last Edit: July 25, 2020, 09:19:23 PM by nowty » Logged

12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 50+ kWh's.
Hot water storage of 15+ kWh's.
Storage heaters of 15+ kWh's.
EV BMW i3 (another 30+ kWh's of storage).
6kW+ Ground source heatpump.
310,000+ litres of water harvested from underground river.
pantsmachine
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« Reply #58 on: July 25, 2020, 10:18:38 PM »

What is the positive effect of balancing? I can see pulling one unit too low in discharge if it's out of whack low already but don't know the ins and outs of this.

P.s if the reason was just so all the numbers match, that would be reason enough for me. I am interested if batteries will continue to go out of balance and if unremedied the difference becomes vast? Never thought of this before.
« Last Edit: July 26, 2020, 08:10:04 AM by pantsmachine » Logged

8.045kWh PV system with Solar edge
7.2kWh Pylon tech battery storage
18kWh Heater Storage
Solar I boost charging 12kWh 210 ltr OSO system tank
Deep insulation, air leak controlled home
Zoned & Balanced CH wet system
Hive 2
Low energy bulbs
24 kW Leaf
Masanobu Fukuoka garden & wooden hot tu
oliver90owner
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« Reply #59 on: July 26, 2020, 08:32:26 AM »

The outcome could be dead cells if allowed to completely discharge and/or a fire if a cell, or the rest of the cells, are over-charged.  The Growatt cells when fully charged would be at 4.2V, but the Pylontech only go to about 3.7V(?). 

Iím not sure if Nowty only runs his Growatt cells to about 3.7V, or if his Victron charge controller can be profiled to achieve 4.2V per cell.  Seems a mis-match running two different Lithium chemistries together?

Looking forward to comments and/or explanation of how he does it (Iím Ďin that boatí at present - 10kWh of Growatt batteries and no BMS/cell balancing/solar charge regulation).
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