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PHOTOVOLTAIC STORAGE WITH TESLA S MODULE
#1
sorry for my english, this is my first post
I suppose may be interesting for someone to realize a project like mine: to use a pair (or more but even number) Tesla S module for energy storage from photovoltaic plant.
After some monts of experiments I realized the project, now I have a 10 kWh battery at low cost with an Goodwe EM serie hybrid inverter
The job was no easy, first no one inverter house helped me to modify only one parameter or to know some serial protocol to external bms battery, second: Tesla module has  6s (12s if two in serie) when the almost all hybrid inverters need a 14s external battery to work properly and for that serie has some voltage limits.
For solving these problems I realized a gateway, with this device I send to inverter the BMS data from modules traslated by one of admitted battery (BYD, PYLONTECH...)
So I have a board for digital signals and another one for relays
A power relay is used for cut power connection in case of faults, a precharge relay is controlled by timing circuit, another relay is used to control an external load  when SOC is 100% from more than one minute.
For solve the problem of internal voltage limits of battery use of the inverter it was necessary to open inverter and analyze circuit, furtunally I found the network who read battery voltage and I modified a resistor value withan external circuit
I thik to add two more modules in the future, these first two is enough for one night on summer but I suppose not when daylight become less



Patalhetas likes this post
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#2
Welcome.  Sounds like you're well on the way to a BMS solution - congratulations on this.
As far as inverters for 12s (instead of 14s) - there are a few such as Magnum that have a compatible low-voltage cut-off range.  Lithium-ion (Tesla packs included) have a sharp discharge curve that starts at around 3.4-3.5v/cell.   There just isn't much power below 3.4v and doesn't help the life span to discharge lower on a regular basis.

3.4v * 12 = 40.8v.  3.5v * 12 = 42v.   If you can find a low cutoff inverter down to 41v or 42v - I think you'll be in good shape to use 12s battery bank.
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#3
ops...
I posted in wrong place

(08-14-2020, 06:21 PM)OffGridInTheCity Wrote: Benvenuto. Sembra che tu sia sulla buona strada per una soluzione BMS - congratulazioni per questo.
Per quanto riguarda gli inverter per 12s (invece di 14s), ce ne sono alcuni come Magnum che hanno un intervallo di interruzione di bassa tensione compatibile. Gli ioni di litio (pacchetti Tesla inclusi) hanno una curva di scarica netta che inizia a circa 3,4-3,5 v / cella. Semplicemente non c'è molta potenza al di sotto di 3,4 V e non aiuta la durata della vita a scaricarsi regolarmente.

3,4 v * 12 = 40,8 v. 3,5 v * 12 = 42 v. Se riesci a trovare un inverter a taglio basso fino a 41v o 42v, penso che sarai in buona forma per utilizzare un banco di batterie da 12 secondi.
thanks

now I have solved:  simply modyfing a smd resistor value inside the inverter I have a correct behaviour
4,15 and 3,3 are now the work tension limits for each cell
The inverter can work at battery voltages lower than the nominal ones, but it is limited by the hardware settings, I have identified the circuit that reads the battery voltage and that controls the charge and discharge limits, with a modification of the voltage divider I took the inverter to work on the voltage thresholds of a Li-Ion 12s
The beginning and end of charge-discharge cycle now is controlled at two near thresholds by my gateway and by the circuit I built to show to inverter the reference voltage level I whant, then also if my gateway faults, is the inverter who limit operating voltage at a little widest band
madmike, Patalhetas, bart.cerneels like this post
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#4
Alcuni screenshot di PVmaster, l'app per il monitoraggio remoto degli inverter Goodwe.
Va notato che la lettura della tensione della batteria è quella reale. 

Patalhetas likes this post
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#5
Welcome to SLS, franco. I know english isn't your primary language, but please try to use English to the best as you can. Google translate does a fairly decent job for most translations if you need help. SLS is a world-wide forum, so we need to have the common ground of communication, which happens to be English, unfortunately. I'm not a particular fan of English, too nasty of a language, imho. Wish I was raised speaking french or spanish at least.
Proceed with caution. Knowledge is Power! Literally! Cool 
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#6
(08-14-2020, 06:22 PM)franco Wrote: ops...
I posted in wrong place

(08-14-2020, 06:21 PM)OffGridInTheCity Wrote: Benvenuto. Sembra che tu sia sulla buona strada per una soluzione BMS - congratulazioni per questo.
Per quanto riguarda gli inverter per 12s (invece di 14s), ce ne sono alcuni come Magnum che hanno un intervallo di interruzione di bassa tensione compatibile. Gli ioni di litio (pacchetti Tesla inclusi) hanno una curva di scarica netta che inizia a circa 3,4-3,5 v / cella. Semplicemente non c'è molta potenza al di sotto di 3,4 V e non aiuta la durata della vita a scaricarsi regolarmente.

3,4 v * 12 = 40,8 v. 3,5 v * 12 = 42 v. Se riesci a trovare un inverter a taglio basso fino a 41v o 42v, penso che sarai in buona forma per utilizzare un banco di batterie da 12 secondi.
thanks

now I have solved:  simply modyfing a smd resistor value inside the inverter I have a correct behaviour
4,15 and 3,3 are now the work tension limits for each cell
The inverter can work at battery voltages lower than the nominal ones, but it is limited by the hardware settings, I have identified the circuit that reads the battery voltage and that controls the charge and discharge limits, with a modification of the voltage divider I took the inverter to work on the voltage thresholds of a Li-Ion 12s
The beginning and end of charge-discharge cycle now is controlled at two near thresholds by my gateway and by the circuit I built to show to inverter the reference voltage level I whant, then also if my gateway faults, is the inverter who limit operating voltage at a  little widest band

Franco, I for one would love to know how your bridge works! I have 2 goodwe inverters 3kw and 5kw and would like to have them speak to my DIY 18650 battery packs.Great work getting your installation this far.
Regards Madmike
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