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

I would put the active balancer on it and save all the headaches just make sure you get the 5amp balancer.
 
@LivingTheDream did you scuff the terminals with fine grit sandpaper and clean them with isopropyl before you did the final assembly? Did you use oxguard or noalox? You need good clean terminals to make good connections for maintaining well-balanced batteries. These variances can be indicative of poor connections due to dirty terminals.
 
smoothJoey said:
@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
Click to expand...
I made the changes you mentioned. However, I don't see in the settings on where to change the boost/absorption nor the float. I am using the app on an iPhone if that matters.
 
DerpsyDoodler said:
@LivingTheDream did you scuff the terminals with fine grit sandpaper and clean them with isopropyl before you did the final assembly? Did you use oxguard or noalox? You need good clean terminals to make good connections for maintaining well-balanced batteries. These variances can be indicative of poor connections due to dirty terminals.
Click to expand...
No, I didn't. I'll do that now. Do I need to use oxguard/noalox? If so, is that found on Amazon or...?
 
LivingTheDream said:
I made the changes you mentioned. However, I don't see in the settings on where to change the boost/absorption nor the float. I am using the app on an iPhone if that matters.
Click to expand...
Those are settings for the your charger.
More precisely I mean the charger that you will use to charge the pack during normal operation at pack voltage.
 
To accelerate the balancing of the pack you could float it at 3.5 volts for a couple of days.
It will cause some short term stress on the battery in order to get more capacity over the operational life of the battery.
 
LivingTheDream said:
No, I didn't. I'll do that now. Do I need to use oxguard/noalox? If so, is that found on Amazon or...?
Click to expand...
Are you using tinned lugs? If not, you can probably get by without it. Doesn't hurt to use it, though. Yes you can probably find either on Amazon. I used Oxguard. Apply it after you've cleaned your terminals and bus bars. Some use a lint-free qtip, I put on a nitrile glove (non-powdered), put a dab on my finger, and spread a very thin layer across the terminal and on the busbar where it contacts the terminal. You don't need a lot, and you don't want to "goop" it on.
 
DerpsyDoodler said:
Are you using tinned lugs? If not, you can probably get by without it. Doesn't hurt to use it, though. Yes you can probably find either on Amazon. I used Oxguard. Apply it after you've cleaned your terminals and bus bars. Some use a lint-free qtip, I put on a nitrile glove (non-powdered), put a dab on my finger, and spread a very thin layer across the terminal and on the busbar where it contacts the terminal. You don't need a lot, and you don't want to "goop" it on.
Click to expand...
Ok, I just sanded the terminals and bus bars. Hooked everything back up and I'm still out of whack on three of the cells. I'll work on bringing those down a bit and see what happens. I'll order some oxguard for the final build out. I'm not sure if the lugs are tinned, just what came from Doshan.
 
smoothJoey said:
To accelerate the balancing of the pack you could float it at 3.5 volts for a couple of days.
It will cause some short term stress on the battery in order to get more capacity over the operational life of the battery.
Click to expand...
I'll try to bring the high ones down with a load. In the mean time, I'll be getting the balancer over the weekend. Why does @Will Prowse not care so much for the active balancers? Or did I misunderstand him in his balancing video?
 
LivingTheDream said:
I'll try to bring the high ones down with a load. In the mean time, I'll be getting the balancer over the weekend. Why does @Will Prowse not care so much for the active balancers? Or did I misunderstand him in his balancing video?
Click to expand...
I'm not privy to your thoughts or to Will's.
 
LivingTheDream said:
I guess what I meant was, are there draw backs to using a balancer?
Click to expand...
Yes.
They can undo the top balance of your pack.
I read through some of your old posts and it seems you grossly overcharged these cells at some point.
I think an active balancer is probably the way to go.
 
LivingTheDream said:
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.
Click to expand...
Here you have cells in positions 3,4,8 and possibly 6 that are different (lower capacity). I strongly recommend that you combine them with the 4 or 5 low capacity outliers in your other group.

Just a little effort matching your cells into like 8S sets will reduce what a balancer needs to do. I spent a LOT of time doing this and it works really well.
 
smoothJoey said:
Yes.
They can undo the top balance of your pack.
I read through some of your old posts and it seems you grossly overcharged these cells at some point.
I think an active balancer is probably the way to go.
Click to expand...
Really? I'm not sure when that would've been. I watch them like a hawk. What makes you say that (so I don't do it again)?
 
MisterSandals said:
Here you have cells in positions 3,4,8 and possibly 6 that are different (lower capacity). I strongly recommend that you combine them with the 4 or 5 low capacity outliers in your other group.

Just a little effort matching your cells into like 8S sets will reduce what a balancer needs to do. I spent a LOT of time doing this and it works really well.
Click to expand...
I'll do this tomorrow and see how that evens things out.
 
MisterSandals said:
You labelled your cells and noted all that you’ve done and the voltages and the cell position, right?
Click to expand...
Yes, on this set. I didn't do a very good job on the first set though, but I'll hook them back up and make note of the results in order to match them up.
 
LivingTheDream said:
Ok, I just sanded the terminals and bus bars. Hooked everything back up and I'm still out of whack on three of the cells. I'll work on bringing those down a bit and see what happens. I'll order some oxguard for the final build out. I'm not sure if the lugs are tinned, just what came from Doshan.
Click to expand...
after you sanded them, did you clean them off with isopropyl alcohol?
 
Hello everyone,

Thank you all for your insight and help! I decided to go ahead and charge the pack in series until one of the cells hit 3.650 and then switched over to parallel. I took them up to 3.650 and then cut the power until they dropped down to 3.550 or so. Then I reapplied power to 3.600 and just let it trickle charge from there for about three hours. Took off the PS and let them sit overnight. Now I just disconnected the whole set and took the readings in the photo below. So far so good with a 0.013 differential as noted in green. These cells were I-P. You can also see that cells A-H are still sitting pretty at 0.048 differential which is only slightly higher than the 0.039 from three days ago.

Screen Shot 2022-04-23 at 4.37.15 PM.png
 
MisterSandals said:
Here you have cells in positions 3,4,8 and possibly 6 that are different (lower capacity). I strongly recommend that you combine them with the 4 or 5 low capacity outliers in your other group.

Just a little effort matching your cells into like 8S sets will reduce what a balancer needs to do. I spent a LOT of time doing this and it works really well.
Click to expand...
@MisterSandals do you you think it's worthwhile trying to match these cells? I've been watching them over the last three days taking readings in the morning and evening. They don't seem to be drifting too much. However, there is one cell in each group that is lower that the rest. I've changed the colors to the four highest of each set.
Screen Shot 2022-04-27 at 7.38.52 AM.png
 
Having difference in cell voltages as long as they are all above 3.45v, at more than several hours after absorb charging has completed, does not mean cells are misbalanced.

It more likely means cells have slightly different surface charge dissipation rate. Surface charge voltage bump at end of absorb charge has very insignificant amount (<0.01%) of cell capacity. The rate cells bleed surface charge does not relate to their state of charge.

An LFP cell is fully charged if its no-load/charge rested (>5 mins) OCV terminal voltage is greater than 3.45v.
 
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