Montana Motor Stables: Radio Friendly MPPT charge controller for Off-Grid Radio Comms by Julian OH8STN

Friday, December 1, 2023

Radio Friendly MPPT charge controller for Off-Grid Radio Comms by Julian OH8STN

Radio friendly solar charge controllers for off-grid ham radio.

There’s a video which goes along with this blog post. Which one you watch first is completely up to you, but please do take time to go through them both.

Ok Let’s get started.

Hello Operators. Very often I am asked for my recommendations o Radio Friendly solar charge controllers. So far there really is only one brand I’ve contrinously come back to throughout the blogs and channels journey. I’ll explain why.

There are three criteria by which I choose a solar charge controller specifically for radio communications work.

How portable it is
How RF quiet it is
If it is truly MPPT (Maximum Power Point Tracking).

Lets go over each of my criteria.

Lightweight and Portable

Man-portable refers to equipment or devices that are designed to be easily transported and operated by a single individual. This term typically applies to military or tactical gear that can be carried, deployed, and operated by one person without the need for additional support or heavy machinery. Man-portable equipment includes items such as antenna, radios, power supplies, solar panels, surveillance equipment that are specifically designed to be lightweight, compact, and easy to handle by an individual Operator in the field.

MPPT Maximum Power Point Tracking

Maximum Power Point Tracking (MPPT) is a technique used in renewable energy gear, such as solar photovoltaic (PV) systems, to maximize the power output from the solar panels. The primary function of an MPPT is to continuously adjust the operating voltage and current of the PV system to match the optimal point where the panels generate their maximum power.

Solar panels have a non-linear relationship between their voltage and current outputs, meaning the maximum power point varies depending on factors such as temperature and irradiance. By utilizing MPPT, the solar system can dynamically track and adjust to this maximum power point, extracting maximum available power from our solar panels.

MPPT algorithms typically employ a control mechanism that continuously measures the voltage and current of the PV system and adjusts the operating point accordingly. This enables the system to efficiently convert the harvested solar energy into usable electricity, resulting in improved overall system performance and higher energy yields.

RF Quiet

RF Quiet refers to a state or condition in which a device or system operates without interfering with radio frequency (RF) signals. In practical terms, it means that the device or system produces minimal or no electromagnetic interference that can disrupt or degrade radio communication.

When a device is RF Quiet, it does not emit unwanted RF signals that could interfere with the operation of our nearby ham radio gear. This is particularly important in environments in weak signal work, where very weak signals can be washed out, by the noise generated from our charge controllers.

In order to achieve RF Quietness, devices are designed and engineered to minimize electromagnetic emissions and adhere to specific RF regulations. These regulations (should) ensure that devices meet certain standards and do not cause harmful interference with other RF systems.

By being RF Quiet, devices can coexist and operate without causing disruptions or performance issues for other wireless systems, allowing for efficient and reliable wireless communication.

Choosing a charge controller

If you’ve already watched the associated video published with this blog post, you already know Genasun charge controllers are my recommendation. I have tried other charge controllers like the Victron, which generally speaking works extremely well for generic applications. Sadly, the Victron created too much RF noise on 30-160 meters HF, for radio communications work. You can watch more Victron test video here. Genasun has continuously ticked all the boxes needed for an off-grid ham radio power supply, over the past 6 year I’ve been using them. There are some annoying restrictions, but we’ll discuss those later.

Choosing the correct Genasun charge controller is perhaps the most confusing part of this topic. As long as we keep our off-grid ham radio gear DC and 12V (11-15V), without inverters, choosing an MPPT charge controller is very simple. Let’s create a few constants which any new station operating off-grid should follow anyway.

The battery is LiFePO4 at 12.8 volts nominal voltage. This usually means a voltage operating range range of ~11 volts to 14.2-14.6 voltage depending on your battery.
We are using DC to power our ham radio gear
Our solar panels output DC between 15-32 volts
There are no inverters used in our system.

We need to know a few things about our system before choosing.

Battery chemistry eg lead-acid or LiFePO4
Battery chemistry tells us which type of charge controller we will need for our chosen battery.
Operating voltage of our battery
Operating voltage tells us the voltage our charge controller should support.
Maximum voltage of our solar panels
Maximum voltage of our solar panels tells us the max input voltage our charge controller should support.
Maximum current of our solar panels
This will tell us the maximum input current our charge controller can handle from our solar panel.
Maximum charge rate of our battery
This number (usually in C-Rating) tells us the maximum charge current for our battery

This is the Power Queen battery used as primary storage for the Off-Grid Ham Shack

Battery specs

12.8 volts nominal
14.4 volts fully charged
100 amp hours
100 amp maximum load
100 amp max charge current

This is a Genasun GV-10L charge controller. It is set up in its default configuration:

14.2 volts (12.8 nominal)
4S (4 in series) LiFePO4 cells
Has a maximum input voltage of 32 volts
Maximum current of 10.5 amps

Compare the specs of the Power Queen battery, with the specs of this charge controller.

The capacity of our chosen battery has nothing to do with which charge controller we use! If the correct voltage is selected, if input current is not exceeded, and if the correct charging profile is supported by the charge controller, it should be able to charge our chosen battery. The only difference between a charge controller supporting 5 amp or a charge controller supporting 10 amps, is how fast they charge the battery. Two more important metrics of our charge controller are the max output current and max output voltage of our solar panel!

Where to buy?

Genasun

Remember Genasun offers a 5% discount for Genasun North American and Genasun EU for viewers and readers or the OH8STN blog and YouTube channel. Just use the coupon code “5foroh8stn” on Genasun North America ( https://sunforgellc.com/genasun/ ) and Genasun EU ( https://genasun.eu/ ).

Power Queen LiFePO4 batteries (affiliate links)

Remember to use my 5% discount: JULIANOH8STN on the Power Queen (Official USA website) https://ipowerqueen.com/?ref=0q1c0pan

Remember to always use my 5% discount: JULIANOH8STN on the European Power Queen Website https://www.ipowerqueen.de/?ref=732d60hj
Remember to always use my 5% discount: JULIANOH8STN on the United Kingdom Power Queen Website: https://uk.ipowerqueen.com/?ref=k0j3c653

K-Tor Powerbox 50 Hand crank generator

The handcrank generator in the video is from K-Tor. It is called the Power Box 50. It’s a 50 watt hand crank generator with 12-volt cigarette lighter output. That 12-volt output connects to the solar panel input on a Genasun GV8 Boost controller for 12.8-volt LiFePO4 batteries. Here’s the purchase link: https://www.k-tor.com/shop/generators/power-box-50/

Genasun Overdrive

The video mentioned the Genasun Overdrive functionality.

The new Genasun Overdrive (GO) feature is available for all GV-5, GV-5-MOD, GV-10, and GVB-8 controllers. This feature can be included in the firmware with the Custom Voltage (CV) version for lead acid and lithium versions. This feature is in addition to all the other Genasun capabilities that make Genasun unique in the off-grid market.

The GV-5 and GV-5-MOD are still rated with a max output current of 5A, but GO allows the charge controllers to be paired safely with panels/arrays providing up to 15 A of current without reducing the charge controller’s efficiency or performance.

The GVB-8 charge controller with GO has a reduced input current limiting threshold, averaging an approximate maximum of 8.3A so that it can be utilized with input sources that can potentially exceed 9.0A. The GV-10 operates similarly to the GVB-8 with reduced current limiting, though instead of limiting its input current to ~8.3A on average, it limits its output power to ~132W on average.
Read more at https://sunforgellc.com/genasun-overdrive-go-for-gv-5-and-gv-5-mod/

Handcrank Generator from the video

The handcrank generator in the video is from K-Tor. It is called the Power Box 50. It’s a 50 watt hand crank generator with 12-volt cigarette lighter output. That 12-volt output connects to the solar panel input on a Genasun GV8 Boost controller for 12.8-volt LiFePO4 batteries. You’ll find it here: https://www.k-tor.com/shop/generators/power-box-50/