Integrating solar and / or wind generators.

Blocking Diodes.

There is often some confusion about this, even in the chandlers shop.

Firstly, do not confuse diodes included within a solar array that isolates the separate elements with the diodes required to stop the solar panel discharging the battery when there is no sun. The later is unlikely to be built into a panel, the former usually are.

Some controllers include blocking diodes to prevent discharge, some do not, and further confusion can arise because a controller that supports a wind generator and Solar may have blocking diodes to isolate the two from each other and the alternator but does not have diodes to prevent discharge through the solar panel, this is the case with my Marlec HDRi controller and the fact that the product description on the box mentioned the former caused confusion at the chandlers where the sales person assumed the diodes were to prevent discharge, they are not! Fortunately I had already read the manual and knew differently, from the manual:

"Note : Solar panels must be fitted with appropriate blocking diodes."

Blocking diodes are cheap and should be well over-specified for the current to be carried, if not they will get very hot and you are loosing power. Multiple diodes can be put in parallel to increase current handling capacity (2 approximately doubles the rating, three trebles it etc.) but the better option is find a seriously big one.

My blocking diodes (under the acrylic sheet there to guard against short circuits)
This unit has two diodes combined with a large heat sink that doubles as the
common output terminal, one diode is used for the main array, the other for the
small panel on the cabin roof. Each element can carry 110 amps which is way
over the top for my system so should remain cool with minimal losses.


Very small trickle charging panels are sometimes connected directly to the battery, perhaps plugged in through a 12 volt power point so they can be removed. Whilst you can get away with this for very small units you can't for a panel of any size as the continuous charge will gas the battery (see battery types by technology) so you need a controller to manage the process. 

Generally it is worth paying more for a good controller which should do a better job and will also give you some information about the system such as battery voltage, instantaneous current or power being supplied, power supplied since reset etc. Some, like the Marlec HDRi, have dual outputs so that charging the starter and service batteries can be controlled independently, a major benefit in my view although it would be nice if the starter battery was given priority. 

Some will support just solar, others Wind Generators and Solar, the latter are specific to a model or make (or makes) of wind generator but OK with generic solar panels up to a certain power.

The picture above shows my HDRi hybrid wind and solar controller (centre, silver coloured) mounted in a dry spot, well ventilated, close to the batteries and with the display panel easily to see. The switch on it shuts down the system and limits the speed and noise of the wind generator, unfortunately you can't turn the wind off and leave the solar running. 

Also shown is the shore power consumer unit (lower left), battery management displays (top left) and the external regulator for the alternator (bottom right).

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