By Boat Battery editorial team · 2 minute read · Editorial policy
Photograph the array through the day and compare controller energy readings under similar conditions. Rigging, aerials and the boom can make nominal panel capacity a poor guide to daily yield.
Map shade through the day
A boat moves relative to the sun even while anchored. Record where the boom, mast, radar and aerial shadows fall in the morning, around midday and later in the afternoon. Repeat with the normal sail cover and tender position. A clean photograph taken only at noon can conceal the conditions that dominate the rest of the day.
Record controller energy and conditions
Use daily controller energy readings where available, noting cloud, location and whether the bank was already full. A full bank may cause a controller to reduce output even in strong sun, so a low harvest figure does not automatically mean poor panels. Likewise, a single peak-watt reading says little about total useful energy across a day.
Review panel strings and controller limits
Discuss the observations with the installer before changing series or parallel wiring. Array voltage, cold-weather open-circuit voltage, controller input limits and protective devices all constrain the options. Different electrical layouts respond differently to shade, but no generic wiring rule replaces checking the actual panel and controller specifications.
Compare placement and access
Compare alternatives using usable deck space and service access as well as watts. Moving an obstruction, splitting independently controlled arrays or changing panel placement may help in different circumstances. Keep walkways, handholds and emergency equipment accessible. After any change, repeat the same observation process so the improvement is supported by measurements rather than an impressive label.
Bring this to the solar discussion
- Morning, midday and afternoon shade photos
- Panel and controller model numbers
- Daily yield with weather and battery state
- Usable mounting area and access requirements
Frequently asked questions
Does low solar output always mean a faulty panel?
No. Shade, weather, a full battery, controller limits and wiring issues can all reduce output. Compare conditions and check equipment diagnostics before replacing parts.
Related installation planning resources
Use these notes to prepare your own measurements and questions. Check the exact equipment manuals and have the proposed system assessed for your vessel before buying or changing electrical components.
Calculate your boat battery capacity
The house bank calculator takes your loads, your nights on the hook, your solar and your alternator, and returns the bank, the DC-DC charger, the AGM equivalent and the weight you take off the boat.
Open the calculator