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Another DIY Powerwall in Germany (15 kWh)
#11
Did you check the internal resistance at all and include this in how the the packs were built?
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#12
Hi!

No, I did not check the internal resistance. I was trying this first, but I think the Opus charger is not very accurate at this. If you measure 4 times, you get 4 different readings depending on how good the contact is on the sliders.
As my load per cell is very low, way below 0.5 A / cell even at full load and below 0.1 A under normal conditions, I guess the impact of internal resistance is minor.

best regards,
Alex
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#13
(07-03-2017, 03:32 PM)Chicken Wrote: Hi!

Thank you for the nice welcome Smile
I'm located in the south of Germany near Munich.
The passive balancers are from http://shop.lipopower.de/ they basically can be set at any voltage and as I don't want mine to fully charge up to 4.2 V, I have them set to 4.1 V.

Was trying to attach the software here, but it didn't accept the file format Huh . It's a simple java app and cell data can be imported from .txt


Check the screenshot how this looks like. I have a text file with cell number and cell capacity. Using the java app I have made the excel sheet which tells mit which cell goes into which cell block Smile

best regards,
Alex

Hi Alex,

very interesting, I'll check out the specs of the balancers later. I'm using these balancers and have a max. voltage difference of about 30mV in my 200p7s powerwall.

The software also looks interesting, too bad I already wrote my own Cool . It's based on Access and I made a table to enter capacity, voltage after a full charge and voltage after 2-3 weeks. This way, I can sort out cells with a high voltage drop due to self-discharge without meassuring the internal resistance. Then I can enter the number of cells per pack, the number of packs I want and the desired capacity per pack including some parameters like minimal capacity per cell, minimum cell voltage and maximum voltage drop between the two meassures.
Already made 70 packs of 20 cells (420Ah@24V overall) this way and it's working great. Here're two screenshots:


How long is your powerwall in production? And how do you feed your battery power back into your house?

Have sun!
Oliver

Cells tested: 6.234 (overall: 12.414 Ah, average: 1.991 mAh)
Cells in production: 3.360 (overall: 7.056 Ah, average: 2.100 mAh)
Powerwall setup: 7s480p, 1.008 Ah, 26 kWh
Project page
Live solar/powerwall values
Daily graph
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#14
Hi!

My powerwall is just finished and running only one week now. This is still basically test running to see how things are going.
As inverter I use the new MPP Solar PIP 5048MS with Power factor 1.0. http://www.mppsolar.com/v3/pip-hsms-pf1-series/

best regards,
Alex
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#15
Any particular reason you chose the PF1 version?
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#16
yes, 5000 W continious and 10000 W surge power. The PF 0.8 versions only have 4000/8000. The price difference was minor. So it was an easy choice Smile
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#17
For me the PIP is not an option because of the no load consumption of 50Watt, which means if during the night I have something around 100-200watt, the efficiency is horrible and for powerwall of for example 5kwh it will consume a bit chuck of energy....
I'm considering a small efficent victron, maybe 1000watt for constant small loads(fridge, router, water pump, lights etc), AND a cheap 3000watt (maybe SHI-3000w) for loads which can be turn on explicitly, like the laundry, dish washer, oven etc.
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#18
Hi!

got some more cells (~ 500), mostly samsung and panasonic.

thinking about building the same layout again and upgrade to a total of 3920 cells (~ 30 kWh)
So I'm starting to measure cells again Smile

best regards,
Alex
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#19
(07-07-2017, 04:22 PM)Chicken Wrote: Hi!

got some more cells (~ 500), mostly samsung and panasonic.

thinking about building the same layout again and upgrade to a total of 3920 cells (~ 30 kWh)
So I'm starting to measure cells again Smile

best regards,
Alex

Some of those packs look like they would be a pain in the butt to disassemble.
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#20
Yes, indeed. Especially those stuck together with glue Sad
But if the glue is too sticky, I usually just cut the heat shrink wrapping and afterwards just rewrap them. This is faster than removing all the glue.
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