The intertec 3500 is not able to fully charge lithium batteries, which only at 14.7 volts.
Here's the specs I found on it:
DC Output Voltage: 13.2 to 14.0 Volts DC (nominal ~13.85V max at no load)
Even though lithium batteries voltage peak at 13.6V, they need 14.6 (or 14.7 according to some sources) to finish charging the top 15%. It also needs higher (than lead acid or SLA) voltage and amperage to charge in general. Since lithium will absorb current at a high rate, it is likely to over load the intertec.
Larry
