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Author Topic: Big re-work at Nowty Towers.  (Read 6591 times)
kdmnx
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« Reply #60 on: July 26, 2020, 09:55:26 AM »

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.

If the cells become unbalanced (because they self-discharge at different rates) then you are over-discharging / damaging the lowest cells, and over-charging / damaging the highest cells.
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12x JA Solar 340Wp panels (total 4080Wp)
Lux Power inverter charger
5x PylonTech 2000 2.4kWh batteries (total 12kWh (11kWh usable))
TheMaster
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« Reply #61 on: July 26, 2020, 06:09:47 PM »

Bloody impressive setup Nowty
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Roof mount 9 x QCells Q.PEAK DUO panels 340w (3.06kW) South/South West
Solaredge Inv 3kW
Ground mount 18 x Canadian Solar 365w panels (6.5kW) South
Solaredge Inv 6kW
27 Power optimisers
Total solar 9.56kW
LuxPower inv
6 x PylonTech 2.4kWh batteries Total 14.4kWh (12.96kWh usable)
Ecodan ASHP
nowty
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« Reply #62 on: July 26, 2020, 09:33:09 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.

If you read back towards the bottom of page 3 you will see I suffered an unexpected dramatic drop in voltage on two cells as the battery units were running very low. They had been that low before and been ok so some voltage drift or some loss of capacity must have occurred over the past year. Having such a large bank also makes it a pain to keep periodically checking. Any voltage drift is very slow and small so I only need a small balancer to keep the whole system in check.

I don’t need the cells to be exactly matched but I am trying to illustrate that the active balancer board is indeed working and not just a dummy board with an LED that lights up. There have been reviews of similar products which don’t seem to work but this one has worked exactly to the published spec.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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.
nowty
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« Reply #63 on: July 26, 2020, 10:47:08 PM »

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(?). 

I’m 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 (I’m ‘in that boat’ at present - 10kWh of Growatt batteries and no BMS/cell balancing/solar charge regulation).

That is a very good observation. If I was doing this all again I would not have bought the Pylontechs due to their expense. But I bought them for my Sofar ME3000SP which was grid connected and the Growatts for my Offgrid system. Once I combined the two with my G100 compliant SMA Sunny Island setup I decided to combine the two battery banks.

First, I limited the charging voltage to 53v but this was not optimum, especially as I was still adding more Growatt capacity. So I reused the same system I used when I mixed lithium and lead acid batteries a while back.

I use a voltage level activated relay to control a heavy duty DC disconnection relay to isolate the Pylontechs when the voltage rises above 52v and reconnects below 51v. In that way I can increase my Growatt charging to 54v or 55v and keep the Pylontechs happy at their lower voltage.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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.
nowty
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« Reply #64 on: August 02, 2020, 11:11:06 PM »

My replacement board arrived from China in less than 8 days which I find incredible, so I now have all cells on Bat 3 connected to the active balancer with cell 7 connected to both boards as per the (implied) instructions.



Balancer now on cells 1 to 14 on Bat 3 (shown in yellow)



Its been running with the second board for a couple of days now and the voltage on cells 1 to 14 on Bat 3 are as follows,

1  -  3.721V
2   - 3.720V
3  -  3.722V
4  -  3.722V
5  -  3.722V
6  -  3.723V

7  -  3.712V

8  -  3.706V
9  -  3.704V
10 - 3.706V
11 - 3.707V
12 - 3.706V
13 - 3.707V
14 - 3.707V

Cells 1 to 6 (all on board 1) are now within 2mV down from 6mV from my last report and down from 62mV at the starting point.
Cells 8 to 14 (all on board 2) are now within 3mV, down from 8mV from my last report and down from 83mV at the starting point.
Cell 7 (connected to both boards) is at a voltage between the two sets of cells. So cell 7 is being charged by cell 6 but is also being discharged to charge cell 8 so the cascading of the two boards appears to work, albeit very slowly.

All cells now have a max difference of 19mV which is down from 22mV from my last report and down from at least 100mV at the starting point. I suspect its going to take a long time to bring the two halves closer together but even the current 19mV is better than acceptable.

« Last Edit: August 02, 2020, 11:18:09 PM by nowty » Logged

12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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.
kdmnx
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« Reply #65 on: August 03, 2020, 07:33:59 AM »

How accurate is your multimeter? My (cheapo) one claims to be accurate to +/-0.009V.
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12x JA Solar 340Wp panels (total 4080Wp)
Lux Power inverter charger
5x PylonTech 2000 2.4kWh batteries (total 12kWh (11kWh usable))
knighty
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« Reply #66 on: August 03, 2020, 10:29:57 AM »

nowty, thanks for the posts etc..

ordered some for my electric bike and my nephews


a few years back when I was more into electric bikes BMS options were a bit slim... I posted on the electric bike forum thinking about building my own using capacitors.... the same as these boards.... and I was ridiculed :-o

glad to see they work  :-)
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nowty
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« Reply #67 on: August 03, 2020, 12:45:37 PM »

How accurate is your multimeter? My (cheapo) one claims to be accurate to +/-0.009V.

Even though its a cheapo Chinese jobby, its pretty darn accurate.

I was so paranoid about accuracy a while back that I bought a voltage reference source to check it, in fact I was so paranoid about the reference sources that I bought two of them from different suppliers to see how close they were. The datasheet on the chips say they use laser wafer trimming to give a maximum error of +/- 2.5mV at 2.5V output so thats a maximum error of 0.1%. Typically its much better than that, in fact the two reference sources gave exactly the same reading.

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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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.
kdmnx
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« Reply #68 on: August 03, 2020, 12:50:06 PM »

Cool! Should have known you’d be on it!

Is there a calibration screw you could use to dial that last mV?
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12x JA Solar 340Wp panels (total 4080Wp)
Lux Power inverter charger
5x PylonTech 2000 2.4kWh batteries (total 12kWh (11kWh usable))
oliver90owner
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« Reply #69 on: August 03, 2020, 02:42:27 PM »

How accurate is your multimeter? My (cheapo) one claims to be accurate to +/-0.009V.

Who actually cares about ‘accuracy’ for a test such as this?  Nowty is only comparing readings from each of the cells.  Precision/repeatability is far more important for this duty.
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kdmnx
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« Reply #70 on: August 03, 2020, 02:50:51 PM »

How accurate is your multimeter? My (cheapo) one claims to be accurate to +/-0.009V.

Who actually cares about ‘accuracy’ for a test such as this?  Nowty is only comparing readings from each of the cells.  Precision/repeatability is far more important for this duty.

If you’re going to the trouble of measuring something you should always be aware of the accuracy of the tool you’re using. Seems like nowty is on the same page.
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12x JA Solar 340Wp panels (total 4080Wp)
Lux Power inverter charger
5x PylonTech 2000 2.4kWh batteries (total 12kWh (11kWh usable))
nowty
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« Reply #71 on: August 03, 2020, 03:12:14 PM »

Oliver90owner's right that I don't care about the accuracy for this balancing testing, but I do need something accurate when you have a lithium cell nearing the 4.2V thermal runaway point. Shocked

0.1V accuracy is just not good enough. sh*tfan

I prefer at least 0.01V for that. fingers crossed!
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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.
nowty
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« Reply #72 on: August 05, 2020, 04:18:16 PM »

I have added another cell link between cells 7 and 8 so each half battery is now linked so I can more easily balance each half battery manually with my power supply if needed. Balancer as before, now on cells 1 to 14 on Bat 3 (shown in yellow)



I gave the half battery bank (with lower voltage) a quick overcharge to help equalise up the two halves.
Then left a couple more days and now the cells are even closer together.

1  -  3.859V
2   - 3.859V
3  -  3.857V
4  -  3.860V
5  -  3.860V
6  -  3.861V
7  -  3.856V
TOTAL – 27.012v

8  -  3.855V
9  -  3.855V
10 - 3.855V
11 - 3.859V
12 - 3.858V
13 - 3.859V
14 - 3.859V
TOTAL – 27.000

Both half batteries are now practically equal, battery bank currently set to full charge at 54V.

All cells now have a max difference of 6mV which is down from 19mV from my last report and down from at least 100mV at the starting point.
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12kW+ of PV installed and 65+ MWh's generated.
Useable home battery storage of 45+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage 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 #73 on: August 05, 2020, 06:21:33 PM »

Impressive Nowty,
       👍
       Biff.
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
todthedog
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« Reply #74 on: August 06, 2020, 05:56:35 AM »

Nice Nowty   Cheesy
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Kidwelly South Wales
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