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Top Balancing...Do I need to go to 3.650V?

MisterSandals said:
Did you arrange the cells into batteries as i suggested based on settle volts? Or just random cells into 8S groups?
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This initial set up and charge were just random cells as they came out of the boxes. I was going to use your suggestion of arrangement once I had both sets top balanced.
 
LivingTheDream said:
Ok, I had them in parallel at 3.615 and all settled overnight disconnected and are reading in the 3.440 range. This was on the first batch, so the second one I'll stop at 3.550. I understand that this is only for the initial top balance. Once I start hooking everything up, then I'll start diving into the settings that they should run at.
Click to expand...
You misunderstand me.

Top balance is different than your in service charge profile.
The in service charge profile should be 3.55 volts per cell.
For the provisioning you want to take the pack until the first cell hits 3.65 volts.
That way you can see how far it shot up from the rest of the pack.
 
Ahhh, ok. So I'm good taking it to the first cell hitting 3.650 and then switching to parallel and taking the pack to 3.615?
 
Initial charging in series will most likely produce one cell that runs to 3.6 well before the others. The spike does not indicate anything initially except that it was at a slightly higher state of charge from the get go. At the top end there is very little extra charge that creates the spike as the voltage rises exponentially at the end. This is the very reason for the parallel top balance.
 
LivingTheDream said:
Ahhh, ok. So I'm good taking it to the first cell hitting 3.650 and then switching to parallel and taking the pack to 3.615?
Click to expand...
If the delta between the high cell and the low cell is .150 when the first cell hits 3.65 I think you should skip putting them in parallel.
Declare it a provisioned battery and let the BMS fine tune the balance going forward.
What BMS are you using?
 
time2roll said:
Initial charging in series will most likely produce one cell that runs to 3.6 well before the others.
Click to expand...
Make note of this cell and any cells that start to diverge before the rest. These are good candidates for being the lower capacity cells.

Good notes and observations will be key to forming the best possible batteries.
LivingTheDream said:
This initial set up and charge were just random cells as they came out of the boxes. I was going to use your suggestion of arrangement once I had both sets top balanced.
Click to expand...
Once you start messing with the cells like this diminishes the top balance.
 
smoothJoey said:
Declare it a provisioned battery and let the BMS fine tune the balance going forward.
Click to expand...
I think that any effort he makes in grouping the 16 cells into 2 groups of 8 similar cells will be highly beneficial. His initial responses indicate he has significantly varying cells. Now is the time, with a little patience and methodology to match the cells as much as possible.
 
smoothJoey said:
If the delta between the high cell and the low cell is .150 when the first cell hits 3.65 I think you should skip putting them in parallel.
Declare it a provisioned battery and let the BMS fine tune the balance going forward.
What BMS are you using?
Click to expand...
I'm using an Overkill.
 
MisterSandals said:
I think that any effort he makes in grouping the 16 cells into 2 groups of 8 similar cells will be highly beneficial. His initial responses indicate he has significantly varying cells. Now is the time, with a little patience and methodology to match the cells as much as possible.
Click to expand...
Missed or forgot that bit.
If they are poor quality mis-matched cells then they should be individually charged/discharged for capacity.
I guess we are trying to save the OP some time?
 
I re-read the thread, now I remember that OP is using a generator to do the top balance/provisioning.
 
smoothJoey said:
Good, glad its not a Daly.
At least you have a fighting chance.
If the cells drift too much you may need an active balancer.
Click to expand...
Good to know! LOL! I did something right.

I'll take the readings off my first set and post them here in a minute.
 
smoothJoey said:
@LivingTheDream where did you get these cells?
I think that will give us an idea of what quality they are.
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I got them from Amy Zheng at their Houston warehouse. I was in TX and had such a bad experience here in the group buy, that I drove to their facility so I could inspect them with my own eyes. They look great, no dents, QR intact, etc.
 
LivingTheDream said:
I got them from Amy Zheng at their Houston warehouse. I was in TX and had such a bad experience here in the group buy, that I drove to their facility so I could inspect them with my own eyes. They look great, no dents, QR intact, etc.
Click to expand...
Those cells should be fine.
 
Put another way, there are 2 vendors the provide the best quality cells that we have access to.
Docan is one of them.
 
smoothJoey said:
Good, glad its not a Daly.
At least you have a fighting chance.
If the cells drift too much you may need an active balancer.
Click to expand...
Just found this on a search. My 280ah 4s battery has a Daly 200 amp BMS.
My trailer has been sitting over winter, but I just plugged it in, and it has now been floating at 13.64 volts for a few weeks. I took a meter to the cells, and find a variation of .15 volts.
Should I be concerned?
 
Electric Personality said:
Just found this on a search. My 280ah 4s battery has a Daly 200 amp BMS.
My trailer has been sitting over winter, but I just plugged it in, and it has now been floating at 13.64 volts for a few weeks. I took a meter to the cells, and find a variation of .15 volts.
Should I be concerned?
Click to expand...
I would add an active balancer for $20

Although 13.64 is on the high side for float service. I would be looking to change the converter.
 
Electric Personality said:
Just found this on a search. My 280ah 4s battery has a Daly 200 amp BMS.
My trailer has been sitting over winter, but I just plugged it in, and it has now been floating at 13.64 volts for a few weeks. I took a meter to the cells, and find a variation of .15 volts.
Should I be concerned?
Click to expand...
What is the highest cell voltage and what is the lowest?
 
I added a 5amp active balancer to my battery, and I like how it keeps all my cells balanced continuously. Maybe not so important if you run your bank at a 90% to 20% charge/ discharge cycles. But if you are needing to run more than that an active balancer will definitely help keep your cells balanced.

Heltec 6S 7S 8S 5A 6A Active Equalizer Balancer/8s Equalizer Lifepo4 Lithium Lipo LTO Energy Transfer Board Fit Capacitor https://smile.amazon.com/dp/B08D9D4NGW/ref=cm_sw_r_apan_i_RFBH0WTR12RYDHAJ3CEH
 
Ok, last night I ran to HD and got a DC light bulb. It only pulls 8.8W, which is about the best I could find. I also hooked up my air compressor that barely sputters along at 3.5V, but it's something. I turned on the charger and within a few minutes, here is where I am already. It's as if I didn't even try to bring these voltages together.IMG_95CFCD58D493-1.jpeg
 
Set the charging to stop at 27.60 and put the battery in service. Possibly put an active balancer on.
 
@LivingTheDream how is your balance algorithm configured?
I would set it to balance threshold to 3.45 volts per and the delta trigger to 10mv
Until the cells come with to a delta of less than <50 mv I suggest you have it balance all the time not just during charging.
Also make your normal runtime charge profile...
boost/absorption = 3.55 volts per
float = 3.35 volts per
 
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