Installation manual

hence the cost of the cable). Changing the "design load voltage" will also have a dramatic

effect, which may lead you to choose an MPPT controller for sites with long cables.

Try to keep losses as low as possible, particularly if you have limited hydro generation and

need all the power you can get. A loss of 5% in cables is normal. Cables with losses greater

than 10% should only be used in cases where the cable cost is very significant in the total

equipment cost and/or where you can generate plenty of power (more than needed).

Be warned that high cable losses may cause nuisance triggering of any Klampits fitted in

your turbine.

5.5. Charge controller choice

A vital part of battery systems is the charge controller. This device protects the battery by

regulating the current fed into it, so as to limit the rising battery voltage to a particular

maximum limit. This "set-point" is automatically chosen for the battery type and temperature

and its state of charge. There are two types of controller to choose from:

5.5.1. Diversion load controllers

PWM (Pulse Width Modulation) diversion load controllers are needed when the turbine is

connected directly to the battery. They work by diverting excess current into a heating load

known as a "diversion load" or "dump load". More details follow in the next section.

Pros and cons of diversion load controllers versus MPPT controllers:

Pros:

 Lower cost

 Simpler wiring at safer voltages with fewer things to go wrong

 Provides useful heating output for hot water etc.

 Internal losses are low <1%

 Displays how much energy it has dumped on a screen in some cases

Cons:

 Turbine runs at battery voltage, so manual turbine rpm optimisation is often needed

 Hydro rpm can never be perfectly optimised as it varies with the battery voltage

 Direct connection of turbine to battery does not fail safe; failure of the PWM controller or

attached element can result in severe overcharging of your battery bank or complete

flattening and damage (resistive element locks on). MPPT regulation generally fails safe

but costs a little more. As the battery bank is often the most expensive part of the

system, you need to carefully consider if the small saving is worth the risk.

 PWM type diversion controllers and their heating loads can make a significant buzzing

noise that might be unwelcome in a living space.