RV Solar: The 5 Mistakes I Made on My First Build
I built my first RV solar system in 2022. It cost about $2,400 and worked, sort of, for the first six months before I had to redo half of it. Here are the mistakes — in order of expense — that I'd skip if I were doing it again.
Mistake 1: Underspec'ing the panels
I started with 200W of solar (two 100W panels) on the Sprinter roof. The reasoning was 'we'll mostly be plugged in or driving, so we don't need much.' That was wrong. We boondocked far more than expected, and 200W could not keep the fridge running on cloudy days.
Fix: I upgraded to 600W (three 200W panels). That's the right number for a two-person rig with a fridge, laptops, and lights. If you're spec'ing solar from scratch, 600W is the floor for serious off-grid use, not 200W.
Cost of the redo: $480 panels + $80 mounting + 6 hours of labor.
Mistake 2: PWM controller instead of MPPT
I bought a Renogy 30A PWM (pulse-width modulation) charge controller because it was cheaper. PWM controllers are 70-75% efficient. MPPT (maximum power point tracking) controllers are 90-95% efficient, which means a $30-50 upgrade pays for itself within a few months in usable power.
Fix: replaced with a Victron 100/50 MPPT. The difference in real-world charging — especially in cold or partial-shade conditions — was huge. Should have done it from day one.
Cost of the redo: $180 (controller) + 1 hour rewiring.
Mistake 3: Wrong fuse sizes between battery and inverter
This one was scary. I fused the inverter run with a 200A fuse on a 2,000W inverter. That sounds reasonable until you realize 2,000W ÷ 12V = 166A continuous, with surge currents up to 300A. The 200A fuse blew on inverter startup with a microwave (3 seconds of high surge) and the wires got warm enough to soften the insulation slightly.
Fix: 300A fuse, 4/0 wire, both upgraded. Don't undersize fuses on inverter runs. Look up the inverter's surge spec, not the continuous spec, and size to that.
Cost of the redo: $90 in proper wire + $25 fuse + 3 hours rewiring.
Mistake 4: Bad battery temperature management
I installed three Battle Born 100Ah lithium batteries under the dinette. They have a low-temperature charging cutoff (32°F / 0°C) — below that they refuse to accept charge to protect the cells. We hit that cutoff multiple times in mountain camping below freezing, and it kept us from charging despite full sun on the roof.
Fix: I added a heating mat (Battle Born sells one for $80) and insulated the battery box with closed-cell foam. The mat draws ~30W from the bank itself when active and is thermostatically controlled. Charging works at any temperature now.
Cost of the redo: $80 + 2 hours.
Mistake 5: Cheap inverter
Bought a no-name 2,000W inverter for $180. It worked, but the AC output was a 'modified sine wave' that made our laptop chargers buzz, our fridge run hot, and our coffee grinder sound like it was dying. Modified sine wave inverters are fine for resistive loads (lights, heaters) but bad for anything with a motor or electronics.
Fix: replaced with a Victron MultiPlus 12/2000 (pure sine wave, doubles as a charger when on shore power). Everything works correctly now.
Cost of the redo: $1,100. By far the biggest single line item.
What this would have cost done correctly
The right system from day one would have been: 600W panels ($720), MPPT controller ($180), 3x100Ah lithium ($2,700), heating pad ($80), 2,000W pure sine inverter ($1,100), proper wire and fusing ($300). Total: ~$5,080.
What I actually spent: $4,800 on the wrong stuff first, then $1,955 on fixes. Total: $6,755.
I paid $1,675 to learn this lesson. You can pay $0 by reading this post.
What I got right
Two things, in fairness. (1) Battle Born lithium was the correct chemistry — they're holding up perfectly two years in. (2) The Victron Cerbo GX I added later for monitoring is excellent and I'd buy it again.
The shortcut
If you don't want to design your own: the Victron-based 'expedition' kit from any reputable installer (Battle Born partner shops, for example) gets you 90% of what I built for ~$5,500 fully installed. That's not cheap but it's also not the $10k some shops charge.
Membership Harvest Hosts — Free overnight RV stays at 4,000+ wineries, farms, and breweries — pays for itself in ~4 nights. Build power EcoFlow Delta Pro — The 3.6kWh power station that's replacing inverters and battery banks in modern van builds.