Bump. I have a similar (or same???) question as Short Shot, and maybe I need the answer to be more blunt ?. I have a single 160w panel on roof of van. Vmmp is ~18.4, and Voc is 22.7. I just bought a 100ah battleborn to replace a 105ah AGM. My “older” Morningstar Prostar PWM does not have a Li profile (only Gel, Sealed, and flooded). Battleborn says Morningstar will work, but I’m thinking about ”upgrading” to victron smart MPPT 100/20, to get a Li profile, plus to get at least the minimal voltage/amperage status/logging/history info it provides. The concern (or maybe it’s an “imagined“ concern) is, will the victron kick in early morning, or in filtered (forest) light, or will I need to be in full sun to kickstart the charge on the LiFePO battery? @RCinFL insinuated some MPPT controllers might have a PWM mode that would kick in, even if the MPPT mode didn’t; would this apply to the Victron? If not, whose MPPT’s have the “backup” PWM mode? 160w definitely isn’t overkill for my needs (fridge, fan, lights, maybe even heater blower…no inverter, though that would be nice), but adding solar capacity runs into “real estate” limitations on the roof. Ideally I would like to be able to stay out in the woods for a couple days/nights with only minimal charging, and not worry about the batteries being spent before the second day.
***If the 5v plus rule for MPPT is based on Voc, am I correct that I should not have any concerns? If based on Vmp, it sounds pretty iffy, unless there is the PWM fallback mode.***
OKAY, that’s enough…or maybe TMI for my main question, I think, …but here’s the rest of the story…for anyone wanting to go down the same rabbit hole I’m stuck in, and provide addnl advice
I have a 2nd string of batteries (nominally 186ah, AGM…not true deep cycle, more “UPS” type batteries…they were free, and are high quality, but are now 5+yrs old, so don’t know SOH, but they fit in a space under the van…a space many 100ah batteries won’t, or certainly not 2 of them. I can split the loads somewhat between the 2 strings with switches. My usual mode of operation was to use the 105ah battery during the evening, but switch the fridge load over to the 186ah string overnight; in addition to this, I had to be a bit tactical during the day while charging. And I spent too much time trying to time the charging such that both strings were as full as possible before sunset. The 186 usually made it thru the night running fridge & fan without drama, but the 105 would not, especially once the days got shorter…dropping below 11.9v under fridge load (which cycles…maybe 4.5a max, running 25-35% of the time), and whatever else I ran (fan, lights…both very minimal loads); battery would end up at maybe 12.1v resting at dawn. The Morningstar began flagging it (yellow light meaning 1/2 empty, and even red, meaning low), except in the best of circumstances. I’ve checked for phantom drains, and haven’t found any, though maybe they are just more illusive. Last piece of info: I also have a CTEK d250s (older, also no Li profile), which provides alternator charging while driving, and a claimed MPPT solar capability. But it is limited to 23v solar input, so a bit of an anomaly in the MPPT world; this is one additional reason I can’t just add a 2nd panel in series…that and the real estate issue. Nonetheless, the CTEK does help if I’m driving. in fact, if driving during the day, I can have CTEK charging one battery string from alternator, and the solar charge the other string thru Morningstar. On such days, or if driving into the late evening, I do not have battery issues, assuming I have everything switched appropriately, to direct the alternator to the greatest need, charging and loads.
Adding solar capacity is a real estate challenge, replacing the 186ah string will be an expensive challenge, with physical size and temperature control constraints, and replacing the CTEK another expensive proposition. But, if I win the lottery, it would be great to have some sort of 150-200ah string of LiFePO in place of the current 186ah AGM string (hence still 2 strings: 100 + 150+ ah, 2 controllers…and maybe more solar, with a higher voltage if advantageous...in case the answer to the original question is that the Victron will need full sun to do any good whatsoever. Regarding roof space, I could possibly add a small 55w flex panel, which could do some good given 2 controllers, 2 battery strings, but not useful to bump voltage in series, nor really run in true parallel.
