There are benefits from using higher voltage panels that can be realized when a system is designed for an MPPT controller. An MPPT controller can also be the centerpiece of a DIY converter.

MPPT manufacturers always specify a maximum voltage coming into the panels; some also specify a minimum or optimium voltage.

• Victron: Vpanel >= Vbatt + 5v to start MPPT, Vbatt + 1v thereafter.¹⁾
• Genasun (nominal 12 systems): 15-18v for constant power supplies²⁾, ⇐ 27v for PV.³⁾
• generic rule of thumb: Vpanel >= maxiumum Vbatt + 30%
• generic rule of thumb: Vpanel = maximum Vbat *

MPPT controllers are most efficient when input voltage (Vpanel) is about 2x nominal battery voltage (Vbatt). When Vpanel rises above 2x Vbatt more heat is generated when downconverting.⁴⁾ At less than 2x the controller may not have enough “headroom” to work efficiently.