Chuck's 18650 14S120P+1 UK Powerwall.

chuckp

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Jul 29, 2018
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Packs mounted and operational for 24hrs +.

28 X 40P packs configured as 14S80P at a little over 170 Ah, so not quite the 14S120P I wanted but still looking for cells. I have enough space on my main busbars for another 28 packs and room below to fit another set of busbars for 56 more packs if needed.


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Now i wish I'd wrapped the first 11 packs when I made them, it's playing havoc with my OCD all these different colours but there's no way I'm stripping packs to wrap them.

24 hrs in since battery went online. This morning the battery capacity was down to 32%, sun up and solar supplied the house and charged battery up to 92%, battery started to supply house at around 1700hrs at about 3hrs in i had 78% capacity left, another 1 1/2hrs and I'm now down to 61%. So won't see me through the night without a little top off from the off peak supply,


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Pack voltages are staying fairly balanced could be a little better though, swings back and forth between 0.041V and 0.076V. Pack 9 seams to be the culprit, I'm guessing that maybe a high resistance cell may have slipped through testing.

I have limited the charge and discharge current for the moment to see how it runs. Charge current limited to 30A/375mA per cell and discharge limited to 20A/250mA per cell.

Peak loads are only supplement by the battery at the moment, but since my typical demand is between 0.450Kw and 0.980Kw battery is meeting our requirements without any grid supply.
 

chuckp

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Wall has been up and running for a week now.

Packs have now settled down and staying balanced to between 0.034V and 0.038V


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chuckp

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ajw22 said:
I've set my BMS to start balancing at 3.8+V and 15mV delta. With only 50mA bypass, having it start as early as possible helps a lot.

Do you have yours set to Balance only when charging or do you leave it on all the time?
 

ajw22

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The BMS balances only when it's being charged. So on the android app, my settings are :
"Open balance: open" (not sure that it does... Chinglish for "enabled"?)
"Balance Mode: [when] charging"
"Balanced turn on: 3.8V"
"Balancing precision: 0.015V"

So as soon as the voltage of one cell increases to above 3.8V, and there is at least one other cell at 3.785V or lower, the high cell starts to be drained at 50mA... or rather charged 50mA less than the other cells.
 

chuckp

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I'm using the version on iphone.

Very similar I just prefer the home screen with the bars showing the cell voltages.

I have a "Balancer Enabled" button and a "Bal. Only When Charging" button.
If I disable the Only When Charging but leave the Balancer Enabled, I would have expected the balance function to be on all the time a cell is above my start voltage and there's a difference greater than my delta to balance setting.

This is not the case it's only when charging with the Balance Only When Charging is enabled that it operates. I'm unsure if it's supposed to work like that of not
 

ajw22

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Not 100% sure, but unless you have a battery that is both capacity and IR balanced, you may want to stick with just balancing when charging.
Say you have pack#1 that has a somewhat higher IR. That pack will show a relatively high voltage when charging, and show a relatively low voltage when discharging, even though the SoC is perfectly in sync with all other packs. Depending on thebalancing tolerance, you could have the absurd situation of the balancer draining #1 when charging, and draining #2~#14 when discharging. ...In theory... a long working day, and quite drunk, so take it with a bucket of salt.

Also, wanted to commend the beautiful layout. Though a little space inefficient, I believe it's the most maintenance friendly design I've seen so far. You can easily see both sides of all cells, and you can just take out a pack without much consequence by just disconnecting 2 connectors.


[see pic] Is there a reason why some are red and some black? Are they just heat shrinks? And I don't think I've seen those mid-section terminals. Are they crimped? Soldered?

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jdeadman

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Sean said:
Earth rod clamps, so screw thread compression.


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OOOOOHHHHH those are nice

And I do love the look and layout of your System Chuck
 

chuckp

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ajw22 said:
Not 100% sure, but unless you have a battery that is both capacity and IR balanced, you may want to stick with just balancing when charging.
Say you have pack#1 that has a somewhat higher IR. That pack will show a relatively high voltage when charging, and show a relatively low voltage when discharging, even though the SoC is perfectly in sync with all other packs. Depending on thebalancing tolerance, you could have the absurd situation of the balancer draining #1 when charging, and draining #2~#14 when discharging. ...In theory... a long working day, and quite drunk, so take it with a bucket of salt.

Yes they stay in balance very well, since I've change it to start balance at 3800mV with a delta of 15mV they are sitting better at between 26mV and 30mV


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ajw22 said:
Also, wanted to commend the beautiful layout. Though a little space inefficient, I believe it's the most maintenance friendly design I've seen so far. You can easily see both sides of all cells, and you can just take out a pack without much consequence by just disconnecting 2 connectors.

Thank you for your comment.
Yes the idea was to make it as user/maintenance friendly as possible, I could have condensed it down a lot more but the pathway I've built along never gets used for access and space wasn't a constraint. i have space for another 6 rows that's another 84 packs at the moment. Also should the need ever arise I have enough wall expanse to repeat the same set up another two times, not that I think I'll ever need that amount of storage capacity.

ajw22 said:
[see pic] Is there a reason why some are red and some black? Are they just heat shrinks? And I don't think I've seen those mid-section terminals. Are they crimped? Soldered?

image_pzdkkg.jpg

Just heat shrink, I only had around half of what I needed in red or black to do them all the same. Since the middle 13 bars are both pos and neg i thought that mixed on those bars, with all red for pos and all black for neg would look ok.

The bars are standard 3/8" or 9.5mm earth rods with extra terminal clamps spaced evenly at a little over pack and mount length.

The terminal connections are 10mm2 X 8mm hole terminal lugs crimped.


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I may crimp and solder on the next rows though but it would be only for belts and braces, not really required to do both.


Sean said:
Earth rod clamps, so screw thread compression.


image_ttcrob.jpg

Yep that's exactly what I've used.


jdeadman said:
OOOOOHHHHH those are nice

And I do love the look and layout of your System Chuck

Thank you jdeadman, yeah I'm pleased with the way it's shaping up. Thinking about doing something with a RasPi and a display screen now. But I'll have to beg borrow and steal the programming, its something I've never been involved with.
 

chuckp

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384
Powerwall has been up and running for a couple of weeks now, so far all good.
Packs are staying fairly balanced with a difference of less than 0.030V at the highest, typically around 0.022 to 0.025, .

I've had to do a few charges from the off peak grid supply to keep them online due a lack of Sun at the moment.
However we are pretty much covering our peak consumption, obviously a bit of an increase in the off peak due to charging but since it's half the cost of the peak rate still works out for the better.
On the odd days I'm getting a fair solar gain I'm still exporting a little but nowhere near as much as I was. Daily self use rate on the solar is now closer to 70% rather than the 20% before the wall went live. The last few days due to the low gain i have seen a 100% self use rate. Even on a bad day before I would still export 60% or more.

I'm not sure just how accurate the Solaman App data is, although they say it is real time monitoring i notice sometimes it can be a good 20 mins or more between data from the inverter refreshing with the app.

Need to pull my finger out now, source some more cells and get some more storage capacity.
 

Earlonics

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Love the look and journey you've been on chuck, going back to the start of your build where did you source the fuses from? Are the plans for your battery bracket freely available? Is your battery wall covered in?
So many questions.
Thanks in advance
 

chuckp

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Been busy processing more cells, got a good batch this time.
463 cells after charging, weeding out heaters and self dischargers.
Currently carrying out capacity testing, so far approx 90% are testing between 2100 mAh and 2500 mAh and at between 70-90% of original capacity, a few have even been slightly over specified.
IR's between 45 and 120 mohm but this is only Opus testing so not really a good example.
 

chuckp

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Little update, two weeks ago I completed my latest batch of 14 40P packs/modules and got them mounted on the powerwall, now putting my storage capacity up to 13+ kWh.


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They have been running for a little over a week now and everything is looking good.

Getting a full solar charge into the battery and suppling the daily consumption for the house, still exporting more than Id like to, but that will get better once I have another row or two of modules installed.

At the moment the battery is lasting all evening and most of the night. I have a period of a few hours in the morning when the system is in standby and Im using the grid before the sunrises enough to meet the house demands and have a sufficient surplus to start charging the battery.

Generally very pleased with how its going.

Ive given up on the idea of try to read the Xiaoxing BMS on a Raspberry Pi. I did find a few sources for code online but I just cant get my head around it all.
 

chuckp

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Phase two begins, adding wind turbine to system.
 

chuckp

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Please excuse the mess in the yard we had a severe wind storm and lost a couple of sheds so we now have crap all over the place waiting to be cleared up once the weather improves.

I cleared a space amongst all the crap everywhere at the bottom of the yard and built some shuttering around reinforcing mesh. Set a template to hold the 25mm stainless steel column mounting bolts and spent a day mixing up concrete.

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After 4 weeks or so I stuck the shuttering to reveal my support base, a little over one cubic meter of concrete, approx 2.5 ton of concrete. I don’t think it will be going anywhere in a hurry.

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I have a little grinding back to do on the top to neaten up the concrete between the bolts and make the top of the base flat. But it has gone in level. Set a 1 1/2” pvc pipe down through the base and out through the side for the turbine cable to enter a control box mounted on the side of the support base.

I have 10M column to mount on top of the base. At the moment it’s in the workshop I’ve welded some brackets to the base flange, Fabricated a second flange plate that will be bolted down directly to the concrete base and be secured by the four outer bolts. This will make a hinge plate that the column base flange will be hinged off of and this will bolt down on the four center bolts once raised, Aim is that this will allow me to lower and raise the column for maintenance.

I have a 48V 1000W turbine, Aliexpress special to mount on the column for evaluation purposes, plan is to run a big enough supply cable from the turbine into the house that will eventually take a 4-5Kw turbine.

More to follow in due course.
 
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floydR

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Looks Good. Better job than my last concrete work. Did the 11/2" pvc pipe get moved while pouring the concrete? It is plumb with the base plate in the second pic and looks like it is on an angle to the base of the concrete in the last pic. Does the base extend below ground level?
Later floyd
 

ajw22

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I always thought that wind turbines need either a deep/wide foundation, or 3+ anchors with tension wires to prevent them from tipping over? I guess it depends on a number of factors... Is there a guideline for surface-block setup like yours?

Looking forward to reading your Aliexpress 48V/1000W turbine experience.
 

OffGridInTheCity

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I have the impression, that like batteries, the advertised 'rated' power of wind turbines can be overblown in comparison with actual results. Looking forward to a report on how much it actually produces. Totally jealous (in a positive way) :)
 

ajw22

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the advertised 'rated' power of wind turbines can be overblown in comparison with actual results.
I'm on the fence about this, because many leaving poor reviews totally overestimate their wind resource and/or clearly have no clue what they're doing. And then there are plenty of seemingly not-fake, good reviews.
So maybe there are Chinese wind turbines that offer adequate quality/performance for very cheap prices?
Of course there are many makes and models, some with obviously impossible claims.

Totally jealous (in a positive way) :)
Me, too. Wind would complement my solar nicely in the winter, but I have too many neighbors and trees nearby.
 
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