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Lia Ditton rows solo across Pacific in solar powered boat with Genasun controllers
Photo: Dylan Reeves
Lia Ditton Pushes Onward: Solo Row Across the Pacific
“Usually I stare at the monster waves, to study and anticipate their impact, to try and will them into submission. I run towards fear.”
- WHERE THE WILD THINGS LIVE, Lia Ditton. July 11, 2020.

Lia Ditton is a force of nature. At 40 years old, she’s logged over 150,000 nautical miles—equivalent to 8 laps around the earth—and has competed in some of the world’s most challenging races. A woman of many talents, Lia is also an author, artist, sportswoman, and educator. She’ll soon start her quest to be the first woman to ever row solo across the North Pacific Ocean, from Japan to San Francisco.

On June 17, 2020, Lia set out to solo row on a training trip and record-setting attempt from San Francisco to Hawai’i. In the month she’s been at sea, she’s overcome winds and currents that dragged her off course, a potentially life-threatening capsize, and the heartbreaking loss of a friend and fellow rower, Angela Madsen.

Despite all this, Lia soldiers on. Her 21-foot solar boat is equipped with one Genasun GV-10 and five Genasun GVB-8 MPPT charge controllers. These allow Lia to continue powering her bilge pumps and satellite communications systems, giving her a lifeline back home. After her capsize, Lia worried about losing solar power due to water damage, but thankfully the Genasun controllers kept steady—and so did her spirit. We’re honored to help in powering her journey.

Follow Lia Ditton’s expedition on her website, www.rowliarow.com, Facebook, and Twitter.
Lia Ditton selfie in solar boat on Pacific Ocean
Photo: Lia Ditton
Buck vs. Boost
Solar panels produce their maximum power at a particular voltage, which may vary due to temperature, partial shading, sun angle, and other factors. This optimal voltage at which the most power is extracted from the panel is called the maximum power point. Choosing a solar charge controller with maximum power point tracking (MPPT) ensures that you’re getting this maximum power all the time. All Sunforge MPPT controllers, including Genasuns, maximize photovoltaic power generation by operating the panel at its optimal voltage and delivering the power efficiently to the battery—even when the battery is at a different voltage.

Before choosing the appropriate charge controller, it is important to determine if the panel’s voltage at maximum power (Vmp) needs to be decreased (bucked) or increased (boosted) in comparison to the nominal battery voltage being charged.

All solar charge controllers are power converters: by adjusting the current, they convert the fluctuating voltage produced by your solar panel to the voltage your battery requires as input. Buck converters step the voltage down from high to low while increasing the current. In contrast, boost converters step up your voltage from low to high while decreasing current. Remember, the relationship between power (P), voltage (V), and current (I) is:

P = I • V

By simultaneously increasing the current when decreasing the voltage and vice versa, we’re ensuring that the same amount of power is transmitted in both situations. This means that whether you’re bucking or boosting, all the available power from your solar panels is delivered to your batteries and loads.

How does a buck controller work?

(and when should I use one?)

Use a buck controller when you want to charge a lower-voltage battery with a higher-voltage panel. For example, a 36-cell, “12 V nominal” solar panel has a Vmp around 17-18 V. This is higher than the charging voltage of a 12 V nominal battery (which is typically around 13-14 V). Therefore, if we want to charge a 12 V nominal battery (e.g., a car battery) with solar, we’ll need to use a buck controller.

The Genasun GV-4, GV-5, GV-5-MOD, and GV-10 are buck charge controllers, designed to step down the panel’s Vmp and deliver the max power possible when the battery is at a lower voltage (e.g., 12 V nominal).

Model Max. Output Current Max. Recommended Panel Power
GV-4 4.0 A 50 W
GV-5/GV-5-MOD 5.0 A 65 W*
GV-10 10.5A 140 W
(*) The Genasun GV-5 (or GV-5-MOD) with Genasun Overdrive can be used with oversized arrays to ensure maximum output current in unideal conditions, such as poor irradiance in polar regions, partial shading, exceptionally warm panel temperatures, or overcast days.

Let’s do the math. A 36-cell solar panel producing its rated output of 100 W under Standard Test Conditions (STC) has a Vmp of about 17-18 V, which makes its output current at maximum power (Imp) approximately 5.5 A. This output from the panel becomes the input to the controller. GV-10, after bucking down the Vmp, will deliver about 8 A of output current at 12.5 V, which equals all of the original 100 W from the panel.

I • V= P
Panel output: 5.5 A • 18 V ≈ 100 W
Controller output : 8 A • 12.5 V = 100 W

The Genasun GV-4, GV-5, GV-5-MOD, and GV-10 will charge the battery any time the input voltage (panel Vmp) is greater than the battery voltage and the input power is sufficient to operate the controller. For optimal results, however, the input voltage should be approximately 0.4 V higher than the battery voltage on the GV-4 and GV-5/ GV-5-MOD, and about 1.0 V higher with the GV-10 (somewhat less with lighter loads). This would allow your Genasun controllers to produce their maximum output given the available input.

How does a boost controller work?

(and when should I use one?)

Use a boost controller, like the Genasun GVB-8 or GVB-8-WP, when you want to charge a higher-voltage battery with a lower-voltage panel. For example, if you had a GVB-8, the same 100 W, 36-cell (12 V nominal) panel previously mentioned could be used to charge up to a 48 V nominal battery. The GVB-8 would boost the 5.5 A, 18 V input from the panel to yield an approximate output of 2 A at 50 V (about the right voltage for a 48 V nominal battery).

I • V = P
Panel output: 5.5 A • 18 V ≈ 100 W
Controller output: 2 A • 50 V = 100 W

Here’s another example using a semi-flexible, 20-cell solar panel (9 V nominal with a Vmp around 13 V): the GVB-8 can boost the voltage from the 9 V nominal panel to charge a 12 V nominal (or higher) battery.

The GVB-8 and GVB-8-WP are designed to work with a maximum input current (Imp) of 9A. The maximum panel wattage is dependent upon the battery voltage being charged, as you can see in the following table.

Panel # Cells Panel Vmp Nominal Battery Voltage Max. Recommended Panel Power
20/24 cells 9-13 V 12 V (or higher) 105 W
36/48 cells 18-25 V 24 V (or higher) 210 W
60/72 cells 30-45 V 36 V or 48 V 325-250 W
The minimum panel Vmp (aka, minimum input to the charge controller) is 5V for the GVB-8/GVB-8-WP series. In order to harvest power efficiently, the Vmp needs to be less than or equal to the battery voltage. If the Vmp is higher than the battery voltage, these are no longer ideal conditions for boosting, but the GVB-8/GVB-8-WP will still function by reducing the panel input voltage.

Lastly, it is worth mentioning the nearly non-existent power consumption of the Genasun controllers. We put a lot of care and meticulous engineering into their design, enabling Genasun controllers to have both the lowest operating consumption and lowest night consumption on the market. By comparison, competing controllers tend to draw ten times (or more!) current than our Genasun controllers. This is something we’re really proud of, and we hope you take advantage of it.

Model Night / Standby Consumption
GV-4 0.09 mA (900 uA)
GV-5 / GV-5-MOD 0.125 mA (125 uA)
GV-10 0.9 mA (900 uA)
GVB-8 / GVB-8-WP 5-7 mA
As always, please drop us a line if you have any questions.
Graphic of the Blue Sky Energy SB-RVK(-S) installed in an RV with solar panels on the roof against a green background
Sweet Boondocking!
The SB-RVK(-S) kit is compatible with the majority of 36/60/72-cell solar panels on the market. The included IPN ProRemote Display allows you to program the SB3024iL MPPT solar charge controller with the ideal charge profile for any kind of LEAD ACID or LITHIUM battery. The kit is also available with an external current shunt to monitor the state of charge of your battery pack!

Illustration of PV panel connected to a Blue Sky Energy MPPT charge controller, a current shunt, a battery, and the IPN ProRemote within a solar-powered RV
Stay off-grid as long as you want while the Blue Sky Energy SB-RVK(-S) kit takes care of your power needs. With this all-in-one charging solution, you will be able to maximize the wattage delivered to your batteries by your solar panels!

Choose the solar panel and battery pack that best fits into your RV and the SB-RVK(-S) kit will provide all you need to go solar. Our SB3024iL MPPT solar charge controller has an advanced MPPT tracker to gather all the sunlight available to power your system. The remote display can program and monitor all the settings that you want to keep on eye on, while the external current shunt will report the NET current from your battery bank, including all loads and charge sources.

Need more solar power? No problem! Just add more controllers to your SB-RVK(-S) kit and the network will synchronize them to work as as a single unit—all while keeping the advantages of optimizing independent arrays. Have questions? Give us a call or email techsupport@blueskyenergyinc.com and we can help you to design your solar system with our SB-RVK(-S) off-grid kit.

Have a nice off-grid stay!

Solar-powered golf carts equipped with Genasun GVB-8-WP waterproof boost MPPT controllers lined up on a golf course
Drive 10 more miles per day, for free, with the power of the Sun!
Solar seems like a great option for golf carts, but roof space is limited. This is no problem with the Genasun GVB-8-WP, our waterproof boost charge controller designed specifically for the 36V or 48V system in your golf cart. Just pick the solar panel that fits the roof best and let the our voltage boosting controller do the rest to charge your batteries.

The Genasun GVB-8-WP is a unique MPPT solar controller that boosts the voltage output of your solar panels up to 48V. It has been developed for golf carts, or any other electric vehicles, running on 36V or 48V batteries. It’s waterproof, which means total protection against rain and moisture. No need to worry about washing your golf cart—these controllers can be hosed down!

Thanks to the special Genasun Boost technology, the GVB-8-WP will work power your system from dawn to dusk, even when light isn’t optimal!

Illustration of PV panel on a golf cart connected to a Genasun MPPT charge controller boosting power into 36V or 48V batteries
The benefits of going solar are substantial:
  • • Longer range,
  • • Lower carbon footprint,
  • • Less time plugged into the charger, and
  • • Longer battery life
When batteries are discharged to low levels, it takes a toll on their longevity and health. Deeper discharges mean fewer charging cycles and a shortened battery lifetime.

Installing solar on your golf cart with the Genasun Boost controller solves these problems. Charging while you drive means more daily range and healthier, longer life for your batteries. That’s a win-win!

The Genasun GVB-8-WP is available for 36V and 48V nominal lead acid and lithium battery systems.

Questions or need some help setting up your system? Email us to info@genasun.com.

Graphic of an electric bicycle with a solar panel and lithium iron phosphate battery against a blue background in lesson on battery basics
Battery Basics: LiFePO4 Cells
Chemistry Lithium Iron Phosphate
Nominal Voltage (per cell) 3.2V
Max Charge Voltage 3.65V
Charge Profile 2 Stage (CC/CV)* or Multi-Stage
The main difference between single and multistage charge profiles for LiFePO4 batteries has to do the basic chemistry of the battery. Unlike lead-acid batteries, once a LiFePO4 cell achieves its charge voltage, it is fully charged. Since various cells within the pack can charge at different speeds, a short balancing time is needed at the end of the charge cycle in order to have each cell voltage equate to charge voltage and the series pack voltage. Also since the quality of cells vary greatly, the optimal absorption/ balancing time varies, but 15-30 min daily should suffice.

There is a little debate in the community whether it is harmful to a battery to be maintained at their max voltage (3.55V - 3.65V per cell/ 14.2V - 14.6V for a 4S battery pack) indefinitely. We have had 2-stage controllers that have been successfully operating on original batteries for several years with no ill effect, but the popular opinion is that it is better not to maintain the voltage indefinitely, rather to use a multistage profile which would maintain either no current or minimal current at a voltage which equates closely to the resting voltage of a fully charges battery (once a charge cycle has been completed), extending the life of the cells.

If an application is going to be cycling a cell regularly, then, of course, it will take time daily recharge and the amount of time at the charge voltage will not be the same as an application where a fully charged battery will be maintained indefinitely at its max CV. So the benefits of multistage vs 2-stage charging could also be relevant to your application.

Given the anticipated life cycle of lithium batteries, and its more or less recent emergence into applications such as we are seeing today, it might be several years before we know if 2-stage or multistage make any appreciable difference. Genasun pre-programmed controllers for LiFePO4 have a 2-stage CC/CV charge profile and a per cell charge voltage of ~3.55V in order to minimize stress on the cells without sacrificing significant State of Charge (SOC).

Genasun controllers are also available with custom multistage charge profiles, please contact support@genasun.com for details.

4S LiFePO4 Battery Charge Profile

Graph of stages 1 and 2 of a lithium iron phosphate battery charge profile, where a constant current flows into the battery until the power supply reaches a constant voltage
LiFePo4 (4S) CC/CV*
Constant Current Voltage increases
Constant Voltage 14.2V - 14.6V
Graph of stages 1, 2, and 3 of a lithium iron phosphate battery charge profile, where the battery current drops off as the battery voltage reaches absorption and float stages
LiFePo4 (4S) Multi-Stage
Absorption Voltage 14.2V - 14.6V
Absorption Time 15-30 min.
Float Voltage 13.4V-13.8V
CC: Constant Current allows the full current of the charger to flow into the battery until the power supply reaches its pre-set voltage;
CV: Constant Voltage provides only enough current to maintain a pre-set voltage, The current then reduces as the battery becomes fully charged.
Graphic of plane with solar panels against a grey background in a lesson on lithium ion cells
Battery Basics: Li-ion Cells
Chemistry Lithium-ion
Nominal Voltage (per cell) 3.6-3.7V
Max Charge Voltage 4.2V
Charge Profile 2 Stage (CC/CV)*
Li-ion/LiPO/LiCoO₂ cells generally require a 2-stage, Constant Current (CC) / Constant Voltage (CV), charge profile due to the fact that their saturation time varies.

When choosing your desired charge voltage (for Li-ion/LiPo/LiCoO₂ cells) be aware that the charge voltage (CV) has a direct relationship to the percentage State Of Charge (SOC) and the number of charge cycles you can expect from the battery pack. Read this article.

Li-ion/LiPO/LiCoO₂ cells have a max charge voltage of 4.2V per cell which equates to 100% SOC and ~300-500 charge cycles. If you charge to 4.05V per cell (80-85% SOC), you would expect around 850-1,500 charge cycles. Whichever voltage you choose, multiply it by your number of cells (in series) in your battery pack and you'll get your desired charge voltage. For example, a battery described as "4S2P" has 2 parallel sets of 4x cells combined in series.

Genasun pre-programmed controllers for Li-ion/LiPo/LiCoO₂ have a 2-stage CC/CV charge profile and a per cell charge voltage of ~4.17V in order to minimize stress on the cells without sacrificing significant State of Charge (SOC).

Genasun controllers are also available with custom multistage charge profiles, please contact support@genasun.com for details.

4S Li-ion/LiPO Battery Charge Profile

Graph of constant current in stage 1 and constant voltage in stage 2 of a lithium-ion or lithium-ion polymer battery
Li-ion/LiPO (4S) CC/CV*
Constant Current Voltage increases
Constant Voltage 16.6V - 16.8V
CC: Constant Current allows the full current of the charger to flow into the battery until the power supply reaches its pre-set voltage;
CV: Constant Voltage provides only enough current to maintain a pre-set voltage, The current then reduces as the battery becomes fully charged.

Sailboat with blue sail on water against clouds with caption Never Sail Alone
Solar for your boat: thoughts on efficient system design.
Modern sailboats and pleasurecraft demand a lot of power, both when they are sailing on the wind or underway by motor. The traditional way to generate that power is through the vessel’s engine or generator. But engines depend on fuel and are noisy, dirty, and often unreliable systems. It is better to meet your power needs at sea through on-board solar panels and battery storage.

Unlike most off-grid solar systems, sailboats and other watercraft are unique in the way their solar panels are deployed, which means the wiring and control systems for those panels have to be unique, as well.

In classic off-grid solar applications, such as a rural cabin or an RV, solar panels are installed on a single surface and share a common angle to the sun. This type of installation results in each panel seeing the sun in the same way as the other panels on the system, allowing for a single charge controller to efficiently manage all of the panels at once as they charge the batteries.

Solar systems for watercraft are different, and may look completely different from boat to boat. Given variation in hull design, masts, rigging, cockpit arrangement, deck angles, and aftermarket customizations, there are very few standard surfaces on any boat. Moreover, it is rare that any of these surfaces experiences the sun in precisely the same way as the others at any given moment. Each solar panel deployed across these varied surfaces will have a different angle of incidence, different shading, and even different sizing than each of the other panels in the system. No single charge controller on such a system will deliver the maximum power possible to your batteries at any time–even in the fairest of weather. The constant motion of the boat, passing clouds, and irregular shadows caused by the rigging and structures of the vessel will hamper the system’s ability to reach its potential, every time.

These unique problems require a different approach to solar system design. Since the panels will be operating under different conditions, they will have different optimum operating voltages (the “Maximum Power Point” or “Vmp”). The conventional approach of connecting all panels to the same charge controller would force them to operate at the same voltage, preventing them from reaching their potential. Instead, the optimal solution is to pair each panel with its own smaller and faster maximum power point tracking (MPPT) controller. When managed by its own MPPT controller, each panel will deliver the most power possible at any given moment, even with overcast skies, intermittent partial shading, or low-angle light.

Advanced MPPT controllers like those from Genasun work by tracking the panel operating point up to fifteen times per second. Fast tracking speed allows the panel to run at its most efficient voltage in any given situation and extracts the most power possible to charge your batteries to their necessary voltage, with almost no loss. With a small, fast MPPT controller for every panel, your system will deliver more power than if it utilized a single, large MPPT controller. Against conventional PWM controllers, a well-designed MPPT system can deliver over 30% more power in suboptimal conditions.

Solar power at sea is reliable, clean, silent, and beats relying on your engine when the sails are full. So when you design your marine solar system, be sure to maximize the effectiveness of your panels by giving each of them their own controller. Your overall system size can be smaller, and you will have more efficiency, more reliability, and the freedom to sail anywhere with power at hand.

Diagram of Genasun MPPT solar charge controllers connected to solar panels and battery on sailboats