Libre Solar Community Forum

MPPT-1210-HUS Self Start Capability


I am wondering if it is possible to modify the MPPT 1210 to provide self start. That means it starts charging if there is solar energy available but the BMS has shut off the battery back (which cuts the power supply for the 3.3V microcontroller). The MPPT 2420 has the ability to power itself from solar power only, MPPT 1210 in its official form not.


Hi Werner,

unfortunately, the internal 3V3 power supply LDO (U5, AP2210-3.3) has a maximum input voltage of 15V, so I don’t see an easy hack to make this work in the MPPT 1210 HUS.

The MPPT 2420 HC has a new circuit that selects the solar side (up to 80V for that charge controller) only if no voltage is “seen” at the battery terminal and it uses the more efficient (lower voltage) supply rail from the battery if available under normal operation conditions. I just tested this circuit before Christmas and it got a small update to make it work properly (PCB v0.2 in the develop branch). However, the feature is currently not implemented in software, so it would not yet start up if the battery voltage is below the absolute minimum. Shouldn’t be a too big change, though.


Hi Martin,

thank you for the quick answer. Yes, I saw that only 15V are permitted for the SMPS controller ic, so I would have to clamp the “solar” voltage below that level. I think, a small additional SMPS (“China-Module”) with an enable/disable control and a diode to prevent backflow could do the trick here. Do you have any idea of the peak current required to boot the 1210?


Yeah, that could do the trick. As long as you don’t have any additional equipment powered via the UEXT connector, the power consumption on the 3V3 rail should be really low, I guess it’s less than 50 mA peak. The average self-consumption of the charge controller is <10 mA @ 12V.