Is Li-ion now viable for off-grid?

[sensij]

Here's another graph where cells look as 'balanced' as on your graph but since the charge current continued to flow you can see it took stronger cells 8 min 20 s to 'catch up' to the same voltage as weaker ones (part between Battery Full and 2h30min point). At charging current 0.4C it corresponds to imbalance of 0.4 x 500 / 3600 = 5.5%. This graph also illustrates the problem bypass board is supposed to solve- during that 8 min 20 s interval bypass boards on the weaker cells are supposed to bypass full charging current of 40A in this case. The graph is for a battery made from Winston 100Ah cells. This also shows the precision demands on voltmeter used- the tick marks on the right scale are in 2.5 mV increments.

That chart is a very different charge cycle than what anyone suggesting top balance here would use, and some of the risks you are hitting on come from those differences. In addition to the relatively high rate of charge (@pnjunction recommends no more than 0.33C here), there is zero absorb time in that chart. In a top balanced system, with absorb set at a pack voltage equal to or below the cell voltage at which bypassing would begin, the current that those boards need to pass will be much more limited than your chart suggests.

I'm having some trouble following your string of objections to @karrak's experience. If your goal is to understand a grid tie peak shaving application, that is really different than off-grid, and it might be worth starting a new thread so that the different design and operating guidelines for the two applications don't get mixed in a confusing way.

[max2k]

That chart is a very different charge cycle than what anyone suggesting top balance here would use, and some of the risks you are hitting on come from those differences. In addition to the relatively high rate of charge (@pnjunction recommends no more than 0.33C here), there is zero absorb time in that chart. In a top balanced system, with absorb set at a pack voltage equal to or below the cell voltage at which bypassing would begin, the current that those boards need to pass will be much more limited than your chart suggests.

I'm having some trouble following your string of objections to @karrak's experience. If your goal is to understand a grid tie peak shaving application, that is really different than off-grid, and it might be worth starting a new thread so that the different design and operating guidelines for the two applications don't get mixed in a confusing way.

I guess, you're right it's a different application altogether.