Charging Lithium batteries with non lithium charger (my experience)

Hi,

Just want to pass on some info. that may or may not be helpful for those moving over to Lithium batteries and are considering not changing out the non lithium  charger /converter.  I have two  lithium batteries and did not change out the WFCO 8735P (stock for lead acid) in a 2021/320.  I always read that the WFCO will not charge the lithium batteries to 100%.  I have found that my WFCO 8735P does consistantly charge my two x 105 Ah lithium batteries back to 100%, every time although slow.  This is measured with a shunt.  But I have to “fake it” into charge mode by turning off and  on both the battery switch and shore power at the same time.  When that is done, it always starts the charger and takes the batteries to 100%, every time. If only one is turned off, it does not kick on the charger.    Without turning both off/on, the charger will never go into charging mode I think because the voltage of a discharged lithium battery is still higher than a discharged lead acid battery and the WFCO does not detect a low enough voltage to go into charge mode.    Here is the charging data I've seen on a multiple occasions.  This is with the solar charger turned off.  So, after boondocking and back home you may be able to get your lithium batteries back to 100%  and you are not in a hurry.  It maybe worth checking before changing out your equipment and slow charging works for you.  I understand that solar and/or an external charger gets you to the same place…maybe faster.  Just another option that may work for others. And occasionally charging with a lithium designed charger helps to balance the cells.  Below is some data, but I’ve had the same success start at 60% SOC.  The voltage was measured at the converter output on the WFCO (the vcc connection point). The 13.67 is at the resting stage.

Happy charging.... 

Time                    SOC (%)     Current (A)     Voltage (V)
T0                        80            0                     13.27
T  1 hr 15 min.     83            5.85                13.49
T  2 hr                  85            6.26                13.50
T  4 hr  30 min     92             6.00                13.51
T 5 hr   30 min     94             5.82                13.51
T 6 hr   30 min.    97             5.14                13.51
T7 hr    30 min.    99             4.43                13.53
T 7 hr    45 min   100            4.34                13.55
T  8 hr                 100           2.91                 13.58
T 8 hr   15 min     100           0                     13.67