I drive an AEV Prospector with a Four Wheel Camper mounted in the bed. My energy system includes two RICH solar 250 watt MEGA panels wired in series, feeding a MPPT 100/30 and two LiTime 100Ah lithium batteries wired in parallel. A BMV-712 with temperature sensor provides information and VE.Smart networking is utilized.
Over the past two months, I have operated my Modular Energy System (MES-K470) solely on solar power, without relying on a DC-DC converter or shore power. This experience has confirmed that the system I designed, built, and installed effectively meets most of my requirements. Although my research indicated that typical solar installations on Four Wheel Campers range from 160 to 300 watts, my calculations suggested that a 500-watt system would be optimal for my application, even given my relatively low power consumption. After reviewing my research and calculations multiple times, I proceeded with the 500-watt installation as planned. I am glad I did, as reflections on discussions with other Four Wheel Camper owners over the past several years reveal a common dissatisfaction: their systems consistently deplete faster than anticipated.
The system has successfully cleared the first of three major operational hurdles - performance during extended adventures in forested and mountainous terrain under tree canopy. Two hurdles remain: operation during winter months and extended operations at a fixed campsite.
(1) Forests and mountains under tree canopy during extended trail navigation: This scenario proved challenging, as I often drove at 10–20 mph through dense tree tunnels, where the solar panels received a dynamic mix of shadows and intermittent sunlight. It served as an excellent test of the MPPT controller’s ability to handle rapidly fluctuating light conditions. I gained valuable insights and continue to fine-tune the system for such environments.
(2) Operation during winter months: Short daylight hours and low sun angles pose significant challenges here. Based on my recent experiences, I am confident the system will perform well in the open deserts of the Southwest. However, areas like Florida and other southern states with dense evergreen foliage may present difficulties. The ultimate test could be along the Canadian border in January or February - perhaps a trial to schedule for 2027.
(3) Extended operations at a fixed campsite: This will be particularly intriguing, as campground stays often involve parking under tree cover. I suspect this is due to the preference during peak summer camping seasons to avoid direct sun exposure, which can make open areas uncomfortably hot.
Returning to recent lessons learned: I began noticing a gradual downward drift in the State of Charge (SoC) several weeks ago. The battery would no longer reach 100% before transitioning from bulk to absorption mode - initially stalling at 99%, then 98% - even on bright, sunny days. Reviewing the Victron Energy BMV-712 manual, one section piqued my interest.
The following three screenshots from the Victron Energy BMV-712 battery monitor app on my phone provide further insight (Alpha, Bravo, and Charlie from left to right for reference). In Alpha and Bravo, the voltage rises quickly to 14.39 V during the transition from bulk to absorption. Notably, Alpha reaches only 96% SoC (abnormal), while Bravo achieves 100% SoC (normal). After one hour in absorption at approximately 14.4 V, the system shifts to float mode, with voltage dropping accordingly.
I attribute these variations to an adjustment shown in Charlie: increasing the Charge Detection Time from 3 minutes to 10 minutes. This requires the system to meet three criteria for 100% SoC recognition: (1) voltage above the Charged Voltage threshold of 14.2 V, (2) tail current below 5% (10 A in my setup), and (3) sustained conditions for at least 10 minutes. When I initially designed the MES-K470, I anticipated that the bulk of the effort would involve design, construction, and initial testing. As a newcomer to this field, however, I am discovering that substantial work remains in the system optimization phase. It will be fascinating to determine, over the next several years, whether diverse applications (e.g., forests, deserts, summer, winter, southern vs. northern latitudes) necessitate tailored settings or if a single general configuration suffices for all.
I am considering reducing Tail Current to 3 or 4%.
I would appreciate any constructive feedback to help me resolve this issue - my goal is to reach 100% SoC on sunny days. Maybe I misunderstand the capabilities of the system but it seems that once I am in float the system begins to utilize battery power despite it being mid-afternoon on a sunny day. Thank you in advance.