Plan to do a balance charge before capacity check

F

floydR

Moderator
Joined
Aug 23, 2017
Messages
1,648
I am trying to figure out where to hook the balance leads to A BYD 24 volt battery. Theses are the voltages I measured yesterday. All the bms wiring diagrams I have seen start with 1 and go up in voltage as the numbers increase.
trying to use the icharger x8 first to charge and balance the battery to full then discharge each cell individually. Am i correct in where I have each wire connected?
The VT# are on the circuit board on either side of the battery
+ 8Th cell voltage wire 9
vt0=26v
+ 7th cell voltage wire 8
vt1=22.6v
+6th cell voltage wire 7
vt2=19.4v
+ 5th cell voltage wire 6
vt3=16.1v
+ 4th cell voltage wire 5
vt4=12.9v
+ 3 cell voltage wire 4
vt5=9.6v
+ 2nd cell voltage wire 3
vt6=6.5v
+ 1st cell voltage wire 2
vt7=3.2v
connection to negative side of 1st cell
vt8=0v wire 1
Or am I making things harder then they need to be?

later floyd
 
How the voltages "stack up" like that is correct but which order ie 0V on vt0 or 0V on vt8, not sure - doesn't that manual have a diagram?
You might be able to check for continuity with main -ve or main +ve & pin vt0 or vt8?
 
No manuals with theses batteries. You lost me when you said -ve :s floyd gets lost a lot on here. The battery has one positive terminal and one negative terminal and 9 voltage sense terminals least I think that is what vt means. Could you explain what -VE means?

Maybe circuit board was the wrong name, it carrys the balance lead traces and temperature lead traces to an onboard bms which a few people have managed to pull data from but from what I read none have managed to get it to work as a bms. Most people just Wire in there own bms and completely take the bms out.

Guess I need to watch more videos and read some more.

Later Floyd
 
No worries :)
positive terminal = +ve eg "posi" = plus or +, "tive" shortened to "ve"
negative terminal = -ve = OV eg neg or - & ve again!
Most systems use "negative ground" method, so usually negative battery connects to earth/ground & battery positive terminals are positive (relative to ground or 0V).
So battery negative (-ve) = 0V

Temp probes are more of a lead acid thing, ignore them.
The balance leads connect to the junction between cells like you listed.
So usually its like in this pic:
https://imgur.com/bEJcV
or here:
https://www.electriccarpartscompany.com/24V-8S-EV-BMS-Battery-Management-System

That model icharger doesn't seem to have a good wiring diagram!
Maybe do some testing with a single cell?
 
Its correct but as said crosscheck so the order on the charger is correct. Ie lowest or highest.
 
I will recheck the order prior to connecting the balance charger and am going to do a capacity test on each cell.

Thank you
later Floyd
 
Note that you cannot do a capacity check on the balance leads unless you want to wait forever. You need to hook up each cell to be able to properly cap test.

You can of course test the whole pack and when first cell reached its bottom you can let it rest for 5 minutes and estimate capacity left in the other cells by reading voltage
 
Thanks Daromer
I was Thinking about disconnecting each cell and testing that way, But when I take something apart and put it back together there is often n extra part.
I hadn't planned that far ahead. It was extremely windy yesterday so didn't work on the battery. I will test the whole pack soon. I believe that the icharger x8 has to have the balance leads hooked up to do a regen discharge, but could be mistaken need to read the manual again.

later floyd
 
The balance need is not needed but IF you run without it you just Lost 98% of the information doing the test :)
 
I think daromer means you could choose to do a discharge test without the balance leads connected but you'd get less info.
Still a very good idea to charge the pack & allow it to top balance for a while until all the cells equal before a pack discharge test.
 
I wasn't very clear on what I was gonna do. :(

First check the cells with multimeter (done)--> Next wire up the balance leads--> Normal Charge to 3.6v per cell(28.8v battery)---> balance the battery---->next do a normal discharge with balance leads in place.
Took out the BYD bms, rechecked voltages, going to have to make a waist high work bench. Too hard on the hands , knees and back sitting on the ground.

Later floyd
 
Managed to get the Icharger X8 hookd up without letting any magic smoke out.:)
found out that the x8 screen is not visible in sunlight. had to moved behind a door to really see it.
image_ylinwd.jpg

don't have a big enough battery to do a regen discharge. Used a hoverboard battery to check this much. it is more out of balance than I thought.

Just glad it works

Later floyd
 
Thats why the DUO generally is better :) If you dont have a regen battery you can just dump it into heat easily on the 2nd channel :)
 
Slowly charging the battery at 2A (I need to get a real power supply) I will be old and grey or bald by the time it finishes. let see 2A Starting at 11%(the x8 read 11 % at start of charging) = 195.8 AH 97.9 hours to charge probably longer.

later floyd
 
Managed to change the amps to 6amps, tried 12 amps but the power supply shut off.

image_krtvsy.jpg
72mv out of balance
Starting to get in balance the more it is charged.

image_banrjz.jpg
61mv out of balance
Oh and I found a battery to do a regen discharge to to. The other BYD battery duh
later
Floyd
 
The battery has entered CV part of the charge. At last 2 and a half days off off and on charging. Probably 30-40 hours on the charger.
when I wasn't here or was asleep the charger wasn't on.


image_qcpjnr.jpg



image_gtrfmq.jpg

at 2amp charge the voltage difference was down to 3mv then I upped the amps to 4 then the voltage difference grew untill it was 199mv now the current has dropped the difference is going back down.

image_vyargs.jpg

I don't know what to make of these readings.

Later floyd
 
feeling better about the battery

image_rihvop.jpg

The cells are balancing out shouldn't be long before it is done charging

Later floyd
 
I finally went ahead and did a capacity test the results were underwhelming 2.5 kwh 106 AH

image_klmiih.jpg

Need to test the other battery, connect them in parallel after the test.
Install the bms(ANT) on The battery.
Decipher the instrutions there are 3 sets of bms on the instruction page. The old (mine), the new (upated screen?), the newest (connections all in front?)
https://www.aliexpress.com/item/32710469857.html?spm=a2g0s.9042311.0.0.70b94c4dtnZjcr
 
I think I will just parallel my 2 BYD batteries, Maybe each cell connected in parallel maybe just the positive and negative posts. Togather they have 218 AH 5 .8 kwh Still more than I had before.
since the batteries have only been cycled once I am hoping that it will wake up if that is even possible. Some say it isn't possible some say that it works

image_vymmyt.jpg

I am not sure this makes sense .:)t is well past my bed time.

later floyd
 
You must log in or register to reply here.
Back
Top