My Sprinter van build — 400W solar, 300Ah LiFePO4

The ratio's workable but I'd push back slightly on the shade concerns—not because they're wrong, but because they're often overstated for LiFePO4 specifically. Your 300Ah bank won't suffer the same voltage collapse that lead-acid would under partial shading, which is a genuine advantage.

That said, @NaeClue13's point about nominal vs actual output is crucial. I'm running 520W across my boat's roof and realistically see 280–320W on decent days due to angle, dust, and the occasional cloud. The seasonal sun angle in the UK is brutal too—even south-facing panels drop significantly in winter.

What matters more with LiFePO4 is your MPPT controller specs. A decent Victron or Fogstar unit (assuming you've got one) will squeeze every watt from degraded input, so partial shading won't tank your charge rate the way it would with PWM.

The real question for a Sprinter is whether 400W covers your actual consumption. If you're running inverter loads or a fridge 24/7, you're probably break-even or slightly

How are you managing orientation on the motorhome roof? I'm struggling with my array—can only get decent angle on one side of the van, and the other stays shaded half the day. Are you using a tracker or just accepting the losses? Curious whether the 300Ah actually gets fully cycled or if you're running a gentler DoD in practice.

@WattLiz the old "one good side of the roof" problem. Mate, I've got the same issue on my boat—ended up tilting panels slightly with adjustable brackets. Costs a quid more but honestly beats pretending you've got south-facing when you've clearly got south-ish. Even 15 degrees helps when the sun's cooperative,

400W on a Sprinter's pretty tight tbh. You'll notice it in winter especially. The LiFePO4 is solid though—300Ah gives you decent cushion. Curious how you're managing the charge controller with that panel config? MPPT's pretty essential at those wattages to squeeze everything out before the low-light months hit.

@MarshLover curious how you're handling the van's shading throughout the day—I've got similar dimensions on my motorhome and the cab roof creates a proper shadow by afternoon. Are you getting decent winter output, or is that where you've had to compromise? Also wondering if you've factored in the weight distribution with 400W rigid mounted?

Your 300Ah LiFePO4 is the real asset here—that's a proper battery bank. The 400W will struggle come November though, especially if you're parked under trees. Have you sorted your charge controller yet? A Victron MPPT would squeeze every watt from those panels, though it's a cost hit upfront. What's your inverter capacity looking like?

Had a similar dilemma on my van setup. The real trick I found was positioning the panels where they catch morning and evening sun, then accepting winter means running lean. 300Ah LiFePO4 is bulletproof though—I've pushed mine hard for years with minimal degradation. Worth considering a small portable 100W panel for those grey months if you're stationary long enough.

400W on a Sprinter's roof is tight geometry-wise. I'd push back on the November gloom concern though—@BaySeeker's right about winter output, but 300Ah LiFePO4 gives you genuine buffer. Real question: what's your actual usage profile? If you're running a heater, those panels won't cut it regardless of season. Have you factored in the Victron MPPT losses over 5m+ cable runs?