Marine Solar Planning Guide
Typical marine solar panels are comprised of a number of silicon cells (normally 32+) connected together electrically in a series string. Individual silicon cells produce only around 0.6v to 0.7v, and so enough of them have to be connected together in series to produce a voltage high enough to be able to charge a 12v battery.
A Charge Controller must be connected between the panel and the battery to reduce the panel output to a safe charging voltage. Some panels have less than the normal number of cells and produce less voltage than is required to charge a 12v battery, and these will require either a special boost controller, or for a number of them to be connected in series to produce a higher voltage.
Will a Battery Monitor properly show Solar, Wind, or Hydro Output?
Many boats these days have a battery or systems monitor permanently installed. Popular models include: E-Meter, Link 10, Victron BMV, Philippi BCM, etc.
With these meters, DC current is measured in and out of the battery by a device called a Shunt that is installed in the negative lead to the battery. A Shunt is simply a bar of metal with a known resistance between the two ends.
The resulting drop in current is then measured by the monitor and multiplied to give the correct current reading. The Shunt is the very last item connected to the battery negative post, and no other negative leads must be allowed to by-pass it. This is to ensure that it measures every amp of current going both in and out of the battery.
As you can see from the example below, it is possible for solar panels or a wind/hydro generator to supply power for DC loads directly, via bus bars or other connection points, without their current flowing into the battery or through the battery monitor Shunt.
Firefly AGM Battery Testimonial - Nigel Calder
We now offer Firefly Oasis Group 31 battery with award-winning Firefly Microcell™ Technology with Carbon Foam plates to ensure longer battery life in deep discharge PSOC applications.
Nigel Calder tested this battery in real-world conditions. Here is what he thinks:
"In preliminary testing I worked the Firefly batteries hard in a real-world (onboard, while cruising off the west coast of Scotland) partial state of charge operation. The goal was to minimize engine run times and optimize electrical system performance in an 'off-the-grid' situation with limited recharging opportunities. The kind of operating regime I followed spells death for most lead-acid batteries. In contrast, after two months of intensive cycling, the Firefly batteries tested out with 100% of the capacity with which they started. These are encouraging results which, if substantiated over longer periods of time, represent a 'game changer' in terms of lead-acid technology and boat electrical systems design. I look forward to collecting more data."