I didn't top balance my packs before installing

[Joeboy]

1500W charger ordered.

[Andy]

Now I've had cell level history graphs for a few days, I have some thoughts. The screen shots below are from one of my earlier packs. There is a misbalance particularly in the mid cells. ie those in the middle of the series. This will have been caused by the extra resistance. The voltage slowly drops as you get further down the packs. I think this has been exacerbated by the balance settings I had. I left the .01V threshold and I think I had 3.35V start balance. The trouble is if you have cells that are lower charge than the rest of the pack they go higher whilst charging. So in normal operations, they get balanced down over a longer period than they get balanced upwards near 100%. (so to speak) . In the second image you can see how the pink yellow cells drop back below the others.

So the settings are very important. On the worst packs, I've now got my balance set to not above .025V ( the green dashed line) to try and bring it back in. I'll tweak it again as they improve. The important bit is to make sure that balance threshold is not exceeded during the charging period. So either have a very high start balance voltage or a high enough delta that exceeds the delta during charge.

There also seems to be a chemistry thing going on around 3.29V where the cells drop off a bit faster. If a cell is lower charge then it dives down at this point much quicker so you can see the cells that need charging. You can also get a rough guess of how much charging is required. I think about 66hours at 2A for this pack. So I'm sat nannying it with my 10A charger. It was an amazon cheapie that has produced lots of magic smoke according to one reviewer so I'm not leaving it on its own This splitting off disappeared after completely balancing one of the better packs.
Hope that makes sense and helps someone.

[Joeboy]

Is there and I mean this with the greatest respect, any chance you are overthinking this? No worries if it's a big thing and what you're into but does it matter that much?

Bear in mind I'm a 10% to 100% soc type and my P-techs are at 87% soh after 8.5 years heavy use. Not making it an abuse competition but that seems fair use for many cycles.

I'm asking where are the gains in worrying? (But nicely).

[Andy]

I hear you. But I think if I'd left it as it was, it was slowly pushing the cells more and more out of balance. Ultimately this would have led to the BMS shutting down the pack well before it should have. The settings are more important than I thought as I was unbalancing my pack rather than balancing.

I've finally set my pack to 10% as well as I can't get through the day otherwise. I'm going to need 4kW of extra charger as well. Good to hear the pylon tech are lasting so well

[Joeboy]

I hear you. But I think if I'd left it as it was, it was slowly pushing the cells more and more out of balance. Ultimately this would have led to the BMS shutting down the pack well before it should have. The settings are more important than I thought as I was unbalancing my pack rather than balancing.

I've finally set my pack to 10% as well as I can't get through the day otherwise. I'm going to need 4kW of extra charger as well.

I'll be honest and say I'm a complete slacker at checking my cell V. Must be 4 to 6 months since I last did it. I'll run across them tomorrow and see where we are. A good reminder to do this, thanks Andy.