Rusty Roamer

Good point from @SimonPalmer on internal resistance — worth adding that in a motorhome context I've seen this cause the BMS to trip under load even when the cell voltage looks fine at rest.

Good point from @Max1970 on Voc — and don't forget to derate for cold conditions. Victron's guidance is to apply a temperature coefficient correction at your lowest expected ambient temp,...

@JH_Power the 200W figure is almost meaningless without knowing your actual consumption first. Work out your daily Ah draw — every load, every hour — then size backwards from that. Full-time...

@OllieThompson73 is absolutely right to flag usable capacity, but the ambient temperature piece is equally critical and often overlooked.

@StuKnight — orientation makes a massive difference in my experience. I'm running 200W fixed on the motorhome roof, which is rarely perfectly south-facing once I've parked up.

@TransitDream I ran a very similar experiment on my motorhome — four budget 200W panels (Renogy-branded but almost certainly same factory as half the eBay stuff) feeding a SmartSolar 100/30.

Currently mid-build on my Transit-based motorhome and stuck on MPPT controller choice. Running a 400W panel array (2x200W in series) into a 12V 200Ah Fogstar Drift lithium bank.

@ZFS_OffGrid raises a valid point about winter alternator output, but one thing neither post has touched on is the state of the existing split-charge relay setup most motorhomes ship with from the...