Battery Capacity testing.

John mac

What's the best and easiest way to test the capacity of a battery .

my 32x200Ah batteries don't seem to be giving me the the expected ~16kWh

(stops discharge at 20%)

Big Lar

How much do you think you are getting ?

Mr Q

https://www.boards.ie/discussion/2058309804/battery-capacity-testing

What type of cells are they?

I assume most people are just using basic capacity testers from Aliexpress or similar. They seem to work fine.

John mac

about 5 or 6 , yea the clab 200

i was hoping not to strip it down again , but if it has to be done then will do it ..

https://www.boards.ie/discussion/comment/120995342#Comment_120995342

10-10-20

You can review the discharge curve for the cell (https://batteryuniversity.com/article/bu-501a-discharge-characteristics-of-li-ion) then you should be able to plot the remaining capacity of the cells as long as the BMS shows each cell voltage individually. If not then you might be able to use a DMM to read the cell voltages off the BMS sense wires.

Also check your discharge rate as you'll see from the graph the higher discharge rates will give less energy due to thermal loss and other factors.

slave1

https://www.boards.ie/discussion/comment/120995474#Comment_120995474

5 or 6kwh is seriously off, did you carry out top balancing, did you carry out initial full charge/force full discharge (some folk skip this crucial step)

John mac

https://www.boards.ie/discussion/comment/120996511#Comment_120996511

yea top balanced , charged fully , cant say I fully discharged though first go ..

slave1

I believe that is an important step and usually plastered on BMS etc for initial setup

John mac

how would i go about resetting it ? . disconnect the bms . ? theres no reset on the software . (REC) any changes i make to the Sofar dont have any effect , except the auto , and timed charge discharge etc..

graememk

No idea on the rec bms and how it works out the SOC

Usually you set the amp hours of the battery (350-400ah)

And then get a known, good 100%, eg all cells at least above 3.4, I personally prefer 3.6.

Do you know why it's stopping?

John mac

amp hrs set at 400 . charge stop at 3.6 balance from 3.4 ish , (dont know exact figs off the top of my head .) when it reaches 100% SOC all the cells are 3.56 ish +- 0.10 . pack is reading 57.6

its the capacity of the pack that dosen't seem correct .

im going to charge it to full in the morning . then let it discharge fully . see what i get ..

slave1

Force discharge, use immersion, charge EV etc

championc

How have you configured it on your inverter ? Is the inverter learning all parameters from the battery pack, or have you set it up like lead-acid's and input all battery voltages ?

John mac

i charged it fully , and did full discharge . showing 5.97 discharge (100% to 20% ) measured using shelly ct clamp direct from sofar . solarman app showing same discharge .

; im charging to full now again ,

Is the inverter learning all parameters from the battery pack, or have you set it up like lead-acid's and input all battery voltages ?

sofar me3000 , battery set as pylon , cant change this .. - could be the bms is setting the battery type .

going to see if disconnecting the bms will reset it . (didnt)

all the cells are evenly charged .

graememk

https://www.boards.ie/discussion/comment/121004687#Comment_121004687

The me3000 tries to pick the best settings when it sees the battery name. The rec must be emulating the pylon completely. I

When you are at 20% what is the voltage of the cells,

Is there any way to set the ah in the rec bms?

slave1

https://www.boards.ie/discussion/comment/121004687#Comment_121004687

IIRC you need to be signed in as Admin to change some settings on BMS software

John mac

yea the rec must be ,,

https://www.boards.ie/discussion/comment/121004940#Comment_121004940

yes amp hrs are set to 400 .

so from the logs ive been keeping , the pack stops discharging at ~51.1 Volts .

cells are (low charge) 3.192, 3.207, 3.195, 3.169, 3.192, 3.190, 3.204, 3.215, 3.205, 3.209, 3.226, 3.198, 3.190, 3.216, 3.205, 3.201.

High charge 100% pack 57.9 3.630, 3.591, 3.636, 3.514, 3.630, 3.628, 3.609, 3.617, 3.625, 3.626, 3.619, 3.630, 3.628, 3.618, 3.613, 3.633

these are the settings on the bms .

they can be changed , if needed .

graememk

https://www.boards.ie/discussion/comment/121009773#Comment_121009773

Start by bumping up the Ah of the battery. but keep an eye on the low end voltages

unkel

@John mac - "so from the logs ive been keeping , the pack stops discharging at ~51.1 Volts .

cells are (low charge) 3.192, 3.207, 3.195, 3.169, 3.192, 3.190, 3.204, 3.215, 3.205, 3.209, 3.226, 3.198, 3.190, 3.216, 3.205, 3.201."

Any reason you only discharge to 51V / 3.2V per cell? There's still 20% in the tank at that voltage and LiFePO4 can be discharged to 2.5V

John mac

i cant get it to go lower . if i change it to 90% discharge on the sofar the settings are not saved , same as i cant change from pylon ..

the bms shows min charge 2.8

graememk

https://www.boards.ie/discussion/comment/121018820#Comment_121018820

Try raising the AH setting in the bms

John mac

upped it to 500 . gonna stick it up to 600 in the morning see what happens /.

championc

https://www.boards.ie/discussion/comment/121018820#Comment_121018820

How are you checking ? You need to check from the Information Menu. If you go back into the setup menu, then it just resets everything each time

John mac

yea checking from the info menu .. no mater what i do in the settings it always reverts to .

PYLON

100Ah

80% (EPS) 80%

think i need to get back on to the REC guy see if theres anything he can tweek in the bms firmware .

unkel

https://www.boards.ie/discussion/comment/121021056#Comment_121021056

You need to save at the end. And then NOT get back into that menu again as, like @championc says, it will reset. Just one of the many quirks of the ME3000SP 😁

John mac

yea , did save . and it gives me

SUCCESS!

just double and triple checked ..

still reverting to above .

unkel

https://www.boards.ie/discussion/comment/121021217#Comment_121021217

How do you check though, by going back into the menu? That's the whole point. Don't do that or it reverts / resets 😂

graememk

You can see battery name from the system information. The ah is meaningless on the sofar btw

The sofar does not like having different battery names and the pylontech can stuff

Eg my zeva had the sma and pylon can running simultaneously. It did not like that at all.

Removed the extra pylon messages from the code and it has worked well since.

The inverter is stopping because the bms is telling it that it is at 20%. That's why suggested increasing the ah on the bms. It isn't counting the ah correctly. Thats the only way it can know the SOC 100ah out, 100ah in and back at square 1

John mac

https://www.boards.ie/discussion/comment/121021237#Comment_121021237

k so to be sure to be sure , , changed properties again . this time i didnt touch anything after the success message .

when the screen reverted to the charging icons i went into the information menu and battery had reset again .

championc

So what happens if you sent the battery type to General Lithium ?

10-10-20

https://www.boards.ie/discussion/comment/121021237#Comment_121021237

It's Schrodinger's Cat of settings then, eh?

John mac

https://www.boards.ie/discussion/comment/121021551#Comment_121021551

same... resets to pylon .