Beginners Guide to Processing 18650 Cells | Cell Database


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Herebus Hell Build
#41
(07-20-2017, 08:48 PM)daromer Wrote: The discharge curve itself was not from the Opus in my case but iCharger when i did test fake cells. Here you can see curves from the Opus itself: http://lygte-info.dk/review/Review%20Cha...%20UK.html
Opus cut directly as above shows. It thats true or not im not sure. it doesnt feel like it cut directly.. But I havent tested it.

(Sorry if that wasnt clear j-man) I have changed my text above so its clearer.

The top voltage is as you say! I have seen 4.3V as well.... Always check all slots on the cheap units Smile

Ah right ok Smile

hahaha yeah always check them. And if you need higher voltage change the internal slider Big Grin
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#42
(07-20-2017, 06:33 PM)The-J-Man Wrote: looking real good!

just wanted to add in that the OPUS capacity test is not accurate. It shows anywhere between 8-15% more discharged energy then it actually was. OPUS gives you a reference but no exact number you can trust. I have purchased and returned these charges until I had 3 similar ones. They are now about 9% wrong. Several threads out there about the inaccuracy of these chargers, its a shame as in general they are awesome.
In your case the 2700mAh is most likely about 15% higher. 2700-405 = 2295mAh real capacity. Think of it this way as well, if someone is selling cells that are 2700 they wont sell them as 2400 Wink
You will never get the rated capacity at a 1A discharge. Calculate your total capacity either with 2400mAh per cell as you purchased or about 2300 which is more likely, and possibly even 2250 at a 1A discharge.

all the best with your project!

Good points, however the batteries that I purchased were straight from the manufacture, and advertised as 2400mah.  So from what you are saying, what I got was spot on what I paid for.


Cheers

Battery Management.

I'm current building the battery pack, and soon will be done and ready to hook the batteries up to the Goodwe BP Changer.

I am running with s14p52 @ 2400mah

My proposed settings for the charger:

Charge to voltage 57.4V (Max@S4.1V)
Charge Current 40A

Battery Capacity 100 Ah to be safe?
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#43
Set the capacity to what it is. I would set it to 125Ah or so. Then i would adjust it when you run your first full cycle to what you did get out of it. Cut of is generally done via voltage any way. Unless you going to have cut off via capacity?
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#44
Photo 
An update:

1. GoodWe battery Inverter is installed, save the mains current sensor. 
2. Battery packs half done.

I have had some issues with the GoodWe BP software.  It seems the templates for the battery setup requires a cold reboot.  With the best option to select Lead-Acid, as the Lithium and defined settings don't allow for bottom voltage cut-off and does not require a BMS.  The app is  being updated, and with luck will improve over time.  You can configure the unit through the display.....but that's so yesterday.  Self power consumption for the GoodWe seems very small (seat of your pants assessment), which is definitely a plus.

Ill see if I can get BMS information from GoodWe, reverse engineer and put together a BMS using an ESP8226 per cell.

ETC maybe two weeks Smile with an expected saving of at least a $1.25 a day. 




Thanks for your support.
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#45
I have been working on a ESP based BMS circuit.  Essentially each battery pack will have an ESP such as a ESP8266 connected to the dump board.

The board provided a dump circuit, voltage sampling and LED when dumping.  It is designed to be off when ESP shutdown/sleeping due to low voltage.

Ill use off-the shelf power supply (switching) and off-the shelf ESP module and hot glue them together.

Circuit designed was done in EasyDA...a very nice and quick browser based application that will allow you to go from design, PCB routing and fabrication.

Next step is to get the parts and bread board them.

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#46
Photo 
Where are on track and almost done.

The GoodWe inverter is now connected to the mains power to measure import and export power.

The last of the battery packs have been soldered.  Now waiting on some heat shrink and eye lugs from China...next week as a guess, then its go live Smile

Was going to balance before connecting, but all the batteries are sitting on the same value (4v)...so no need.

As background, I'm going to be running S14P52 (6-7Kwh).  I have done the maths and the inverter is happy to run on S14, with a voltage of around 57.5v.  Would have have liked to go S15, however the cut off voltage was too low.


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#47
Those packs look so nice! Great job! Can't wait to see them plugged in and functioning!
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#48
Thanks guys for the info on the Opus charger. And the issue with the methods of testing charge capacity and the potential for error.

As an update, I had some issues with the Goodwe BP charger, where the unit would keep resetting every few minutes, interrupting the charge and discharge operation.  I have been discussing the issue directly with the manufacture Goodwe, rather than through the local vendor.  Goodwe have agreed to replace the unit. Props to them.

In the down time waiting for the issue with the BP charger to be problem solved, I noticed one of the battery packs self discharging.  Faced with removing all the solder joints to determine which battery was faulting, I decided to run an infrared temperature sensor over the unit.  I picked up the issue in a snap, as one of the wires to one of the cells was around 4 degrees above the other cells.  I cut away the plastic and replaced the battery, quick as.

Cheers
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#49
(08-08-2017, 04:01 AM)Herebus Wrote: I have been working on a ESP based BMS circuit.  Essentially each battery pack will have an ESP such as a ESP8266 connected to the dump board.

The board provided a dump circuit, voltage sampling and LED when dumping.  It is designed to be off when ESP shutdown/sleeping due to low voltage.

Ill use off-the shelf power supply (switching) and off-the shelf ESP module and hot glue them together.

Circuit designed was done in EasyDA...a very nice and quick browser based application that will allow you to go from design, PCB routing and fabrication.

Next step is to get the parts and bread board them.



Really interested in this, i've been doing a similar setup with ATTiny's and powering it directly from the pack it's monitoring and then this is reported back to an ESP8266 management board but i've introduced some inaccuracies by having to do it over an optoisolator so needs a redesign.  I had thought after i'd done it that an ESP8266 per pack might have just been easier and as cost effective.

Col
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#50
(09-05-2017, 01:46 PM)Chickey Wrote: Really interested in this, i've been doing a similar setup with ATTiny's and powering it directly from the pack it's monitoring and then this is reported back to an ESP8266 management board but i've introduced some inaccuracies by having to do it over an optoisolator so needs a redesign.  I had thought after i'd done it that an ESP8266 per pack might have just been easier and as cost effective.

Col


Good work Chickey (Col),

I have refined the design, as I found an internal divider already designed into the ESP, so just needed to work with it it rather than recreate it.

The new circuit is simpler:

   

You can check the rest of the design from here:
https://easyeda.com/Herebus/New_Project-...1ec827693f

I still need to get the stuff.

Cheers
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