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JAP (Just Another Powerwall or Jesus Angel's Powerwall)
#1
I do not want to bore everyone with stories of what happened after I decided to build my powerwall so far, I may from now on when I do some updating I will be more detailed but summarizing everything is not fun and I feel a bit lazy today. So let's get down to the facts:

Cells, + - 100 collected here and there and + -700 bought to sabado through this forum (120 Dell laptop batteries).

   
   
   

Test equipment 8 tp4056 and 2 Opus BT-C3100.

   

Cell holders, I liked the idea of Average Joe, pvc pipe since I work in a company in the sector and had easy access to these materials but it is difficult to find pipe by its interior measurement so I discarded it and bought the holders we all have at aliexpress, but the seller had problems and after 12 days since he placed the order as shipped without being I had to cancel it. Finally a friend is making me the holders with his 3d printer, he says he does not care and it's cheap, we'll see what he thinks after have done the 42 I need initially.

   

About the fuses I also liked the choice of Average Joe, so I bought them. I've made my first test with cells with less than 1000mAh.

   

Yes I know, the same problem of cold joins, tomorrow I will receive a 100w soldering Iron.


I plan to use the owitte's system because I like it, I have easy access to copper pipes and a free wall Big Grin.

I will try to make some kind of BMS with an ESP32, have enough analog inputs for 14S, at least will monitor it, to balance is another problem...

It took me a month to process the cells, now I only have to give a second pass and see if any lose the charge after a month to discard it.

On panels and inverter I'm still thinking.
JustMeTMC, hbpowerwall, owitte And 1 others like this post
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#2
Looking good Smile I like the custom cell holder. Nice and clean. You must like teal a lot for your colors Tongue

What kind of solder are you using? I notice there is brownish residue left on some of the cells in that last picture. Sometimes the flux residue can actually rust the ends of the cells; so you might wanna take a brass brush and wipe it off to be safe.
JustMeTMC likes this post
Proceed with caution. Knowledge is Power! Literally! Cool 
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#3
yep, gota wash the flux off !!
If you'd like to support the forum please feel free to use my affiliate links to purchase all kinds of stuff for your projects 
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#4
Yes too much flux, I added flux moreover my tin has flux core
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#5
(07-30-2017, 07:36 PM)jesusangel Wrote: I do not want to bore everyone with stories of what happened after I decided to build my powerwall so far, I may from now on when I do some updating I will be more detailed but summarizing everything is not fun and I feel a bit lazy today. So let's get down to the facts:

Cells, + - 100 collected here and there and + -700 bought to sabado through this forum (120 Dell laptop batteries).





Test equipment 8 tp4056 and 2 Opus BT-C3100.



Cell holders, I liked the idea of Average Joe, pvc pipe since I work in a company in the sector and had easy access to these materials but it is difficult to find pipe by its interior measurement so I discarded it and bought the holders we all have at aliexpress, but the seller had problems and after 12 days since he placed the order as shipped without being I had to cancel it. Finally a friend is making me the holders with his 3d printer, he says he does not care and it's cheap, we'll see what he thinks after have done the 42 I need initially.



About the fuses I also liked the choice of Average Joe, so I bought them. I've made my first test with cells with less than 1000mAh.



Yes I know, the same problem of cold joins, tomorrow I will receive a 100w soldering Iron.


I plan to use the owitte's system because I like it, I have easy access to copper pipes and a free wall Big Grin.

I will try to make some kind of BMS with an ESP32, have enough analog inputs for 14S, at least will monitor it, to balance is another problem...

It took me a month to process the cells, now I only have to give a second pass and see if any lose the charge after a month to discard it.

On panels and inverter I'm still thinking.


Hi, looking at your idea on ESP32 as a BMS.  Looking at doing the same, not started, just kicking around some numbers.  Would be great to collaborate.  Was looking at using python and clustering them...all independent.

I was going to use a mosfet which would dump around ~<400ma for balance, a voltage divider on a analogue pin to measure voltage, and a temperature monitor 1-wire/i2c.?

Software could determine:
rate of charge
discharge time 
compensate for temperature

Get back if you are interested.
cmg_george and JustMeTMC like this post
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#6
My idea was make something like that.

https://www.youtube.com/watch?v=OBlmPQVaO4E

But as many cells as posible with that ESP32,

https://www.banggood.com/ESP32-Developme...ds=myorder

it has 14 analog inputs but not 14 additional pins to activate the mosfet, so maybe must use a couple and control 7 banks with each one.

Maybe will add some lcd/tft to show the values, but the main reason to chose esp is to send data to a grafana server, so maybe on site screen is secondary.

I will post when I have the ESP32 and made some test.
Korishan, BlueSwordM, cmg_george like this post
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#7
(08-01-2017, 12:13 PM)jesusangel Wrote: My idea was make something like that.

https://www.youtube.com/watch?v=OBlmPQVaO4E

But as many cells as posible with that ESP32,

https://www.banggood.com/ESP32-Developme...ds=myorder

it has 14 analog inputs but not 14 additional pins to activate the mosfet, so maybe must use a couple and control 7 banks with each one.

Maybe will add some lcd/tft to show the values, but the main reason to chose esp is to send data to a grafana server, so maybe on site screen is secondary.

I will post when I have the ESP32 and made some test.



Yeah, for each battery pack you could have a 1-wire 2405, (opto isolated) Mosfet and temp probe (DS18B20), with another wire to measure voltage.  It would be nice to have an isolated voltage sensor  on a 1-wire....so only a single pair string across all cells expandable.

With the ESP32 proving the smarts and a web interface to manage the environment.

Voltage measurement would be problematic when measuring multiple  voltages across a string of cells, so need to think about this more on the easiest and most accurate solution.

Like the YouTube that you provided, I was thinking on similar lines however with a ESP8266, it would handle temp 1-wire/i2c with no additional parts, analogue input for voltage measurement, plus the driver pins for the mosfet.  Isolation is not needed as each unit would be stand alone, plus the ESP8266 is super cheap. Power would come from the lipo pack.
shrinkable / expandable and cheap per unit.

Both approaches have there advantages and disadvantages.  The biggest issue for me is voltage measurement for each cell if done centrally, and how this can be done...easily.
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#8
Yesterday I made a test with single cells pack and some components I already have, Arduino Uno, 2x 4WR82J resistors in series and a 75N75 mosfet.
This mosfet has a Drain voltage 40A at 10V, as the arduino only can feed 5v that is too low so I only discharge a current of 0.25A from battery.

Maybe a mosfet like IRL640 that drain 10A at 5v is more appropriate for us, moreover ESP32 have 3.3v logic.

About analog readings with only the ESP32 you have to make voltage dividers and make some test and calibrate it.

I do not think we need isolation while we feed the whole system with 7s so the negative of the first series is the negative for all, use a step down convert to power the ESP32 and voltage dividers so the last series that may have 29.4V can be measured with ESP32 in a range of 3.3V.

After all test I do not rule out that the best solution is an ESP8266 per series. Maybe converting that high voltages to 3.3V range will lose accuracy.

Next I have to make an order of components I will buy mosfet and resistors more appropriate to test a 7s bank.

Regards
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#9
(08-02-2017, 03:27 PM)jesusangel Wrote: Yesterday I made a test with single cells pack and some components I already have, Arduino Uno, 2x 4WR82J resistors in series and a 75N75 mosfet.
This mosfet has a Drain voltage 40A at 10V, as the arduino only can feed 5v that is too low so I only discharge a current of 0.25A from battery.

Maybe a mosfet like IRL640 that drain 10A at 5v is more appropriate for us, moreover ESP32 have 3.3v logic.

About analog readings with only the ESP32 you have to make voltage dividers and make some test and calibrate it.

I do not think we need isolation while we feed the whole system with 7s so the negative of the first series is the negative for all, use a step down convert to power the ESP32 and voltage dividers so the last series that may have 29.4V can be measured with ESP32 in a range of 3.3V.

After all test I do not rule out that the best solution is an ESP8266 per series. Maybe converting that high voltages to 3.3V range will lose accuracy.

Next I have to make an order of components I will buy mosfet and resistors more appropriate to test a 7s bank.

Regards

With a mosfet you need the gate voltage to be 1-2v +/- difference from the source depending on the depletion type to turn the FET on.  So unless you switching batteries in and out of circuit, the ground with respect to your driving circuit becomes an issue.

So say a 4 battery pack will have a source voltage of say 12V to ground, so to switch this on you will need a difference of 1-2 volts.  You could do this with say an opt isolated version of the FET...BUT as the voltage dynamic changes the current (power) across the load resistor will also change.  So at 60v the power dissipated will be larger than when its 4V.

So if you are intending to go down your suggested path, each cell will have a floating earth, with its own discharge circuit, opt-o isolated with a n-channel mosfet (depletion mode / drive the gate voltage -2V to drain to get the GS negative.).

I have been kicking around the idea of a capacitor based switch load, which will switch between cells to lift or discharge cells, more energy efficient with less issues of heat dissipation.  Still playing with the idea.
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#10
So, if we need the same GND to Gate (esp32) and Drain, we need at least all outputs to be pwm so we can send less voltage to mosfet connected to high series, there are bigger resistors too so can manage more watts, but at these point I wonder if wouldn't be easiest use relay boards, they are optoisolated and only have to worry about the resistor connected to NO and send a high or low to port and you get a fix current drain.
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