Your MX60 works with the Lithium batteries? I was told I had to upgrade to get lithium….
Nope. You were lied to.
When "Lithium" refers to "LiFePO4," "LFP," "Lithium-Iron," etc., they are effectively drop-in replacements for lead acid in almost all cases.
Any assertion that a charger "won't work" with LFP is almost always driven by sales motivation, i.e., someone is trying to sell you something, or they are just ignorant.
Often, many "Lithium" chargers actually have undesirable features based on misconceptions by charger manufacturers or for reasons that don't apply to one's situation.
It is stated repeatedly, "LFP doesn't need a float charge." That is very true if you are placing the battery in storage. If you're using it in a cyclic power system, it IS necessary because the float voltage is what tells the solar to power the loads by ensuring the battery doesn't drop below the float voltage.
For a 12V system, if a charger:
1) Charges to 13.8-14.6V.
2) Floats at 13.6V (can go as high as 13.8V if cycling regularly).
3) Doesn't equalize above 14.6V.
4) Doesn't use temperature compensation.
(Multiply voltages by 2 for 24V and 4 for 48V)
It will work fine in the vast majority of cases.
Concerning #3, even if a charger does force an equalization cycle, the battery BMS will cut off charging to protect the cells.
For something like the MX60, FM60 or FM80, they will all work fine with lithium as their charge parameters can be customized. The key issue is that the temp probe must not be installed to ensure temperature compensation is not active, or it needs to be disabled in the configuration.