We have experiment and lighting equipment for outdoor use, using 3S2P Li-Ion battery packs quite similar to these (12,6V max. charge; 11,1V nominal; 9,4V cut-off) that we want to charge from solar modules like those (12V nominal; VMP 17,6V; IMP 1,7A; VOC 20,7V).
The Victron, Renogy, Genasun or EPSolar chargers I found so far all seem to cater to LiFePO4 battery packs, although absorption and float voltages as well as charging current appear to be adjustable for the lower values of Li-Ion chemistry, but the data sheets seem unclear to me.
There are Alibaba or Ebay products, ridiculously cheap in comparison to the above, that claim to be 3S Li-Ion solar chargers (not real MPPT of course), but I am not skilled enough to assess if they are any good.
There are 2S2P Li-Ion battery packs available from various vendors, but there seem to be no solar chargers for these either. What to do? Is Li-Ion battery pack charging a "no-go area" for some reason? Or am I looking in the wrong places? Could one build one's own if one had the EE skills?