My 300 watt panels are 12 VDC with maximum 17 VDC output.
The main purpose of an MPPT is:
A. Reduce wiring
and breaker costs when running panels in series
B. Maximize production of solar
output to charge batteries.
C. Control battery charging
Okay!!! Now flip out now and don't read this if you are into solar for houses.
If on the other hand you are a sailor remember:
#1 Simplicity simplicity simplicity!
#2 Redundancy and more redundancy!
With this in mind.
Install one wire to your circuit panel to individual breakers for each panel. It is not like panels will be very far away. With this arrangement you can individually shut off panels, make repairs
, and don't have eggs all in one basket.
NO MPPT and NO SOLAR CONTROLLER
The few batteries on a boat are cheap
compared to a big MPPT. Where is that cool dry place to mount an MPPT or other solar controller?
Further don't you already have two or more other automatic battery chargers? On my boat I have a smart inverter
when running a generator
, a smart alternator
when running the engine
, and the wind generator
is smart too. Why install another smart device when battery charging and equalization
is best done with a dependable supply? Big battery banks take many hours to charge. How are you going to charge batteries and equalize when the sun goes down?
I can hear you all whining all the way out here. "But you will cook your batteries!"
Well perhaps if you are the type to leave your hatch
covers open in the rain or when you leave the boat.
If on the otherhand you know how to close your hatch
covers to prevent water
damage, you are the type that simply can disconnect at the circuit breaker panel most of your solar if leaving the boat.
While on board you can monitor
yourself and can notice when it is bright and sunny.
Further, you may already have an automatic dump mechanism to prevent overcharging. My smart inverter
will turn off the AC when battery voltage is low. I have it set for 13.7 Volts. Huh? If I leave the boat a longer period, I can safely have on more solar power since I know when batteries are nearly charged my AC power goes on. That load includes fan, lights, and stereo.
Important don't shed load by running the blower to your engine
room. That load introduces moisture to a cold engine and increases corrosion
Another really simple thing is an analog thermostat. I have one next to my batteries. When the batteries are charging hard they get hot and a 12 VDC computer fan blows air on them. This keeps them cooler and reminds anyone aboard that hears the fan to check if too many solars are on.
Slightly more complex is my high voltage alarm
and relay. When I am running my fridge and electric watermaker
, they go on at 13.3 VDC. This means they automatically shut off at night and automatically turn on during the day. This device acts like a load shedding device too.
Finally there is the battery selector panel. You do have house and engine battery separate? My solar panels normally only charge house bank. This is a safety
ensuring the engine bank is protected. When voltage is high enough from the solars I manually start charging the engine bank by turning my selector switch to BOTH. Around 4 pm I turn it back. In this manner I have manually charged engine batteries for years. Works fine.
Note: Do not do what I am doing if you have a giant solar array and a tiny battery bank.
In my case I am running 900 watts of solar and 400 AHr house, and 150 AHr engine battery.
That BTW was enough solar that today I ran a large orbital grinder for four hours, and still finished the day with fully charged house and engine bank.
I set the low voltage cutoff on the inverter at 12.3 VDC. This was necessary because of high power draw on startup. All three 300 Watt panels began the day in on position and I didn't have to change them despite bright clear sky since I used the power sanding
. I did change the selector switch manually to charge the engine bank and turned it back in the afternoon.