C_H_2015_02_

Februar y 2015^29

ideas locker: Petrea McCarthy

Solar? Wind? Engine? A recurring

question in the cruising fleet is how

best to connect a variety of charging

methods to charge the batteries. Here is

what regular CH electrical writer John

Tylor has to say:

"This is an interesting issue with a

variety of compromises and probably as

many opinions too.

I have spent considerable time looking

for a regulator that will take in a number

of power sources and control them to

maximise the charge to the battery. 

Unfortunately, I have not been able to

find any one device that does this and

nor has Kurt Küpper, who owns the

electric supply company Aquavolt. 

It should be possible to connect all

the external sources together (via

individual diodes to isolate them) and

run them through a single regulator, but

I do not have enough devices to test this

theory and check whether this could

cause problems for the wind generator

This leaves us with the problem of

how to best connect these individual

devices.  Many yachties have a solar

panel with a regulator connected to

the house battery and usually a smaller

panel on the start battery; often without

a regulator, an alternator on an engine

and sometimes a wind generator.

Most wind generators have a

regulator (some external but mostly

internal). When the battery reaches

full charge the blades of the generator

will start to feather or be braked. This

is often done by the regulator placing a

load across the output. There is a safety

mechanism when winds exceed the safe

speed too, but from what I can find this

is a mechanical feature.

With each power source individually

regulated, there is always a charge

coming into the battery from

somewhere. For example, during a

bright sunny day the solar panel will

supply a substantial current with

voltage at its maximum. This is not a

problem but if the engine is running,

its alternator sees a high voltage on the

batteries and begins to regulate the

current, which might leave the battery

with less than 100% charge. Similarly,

if it is also windy the solar panel is also

generating and there is the potential for

a similar conflict. 

Some experts suggest a simple

off-switch so only one power source

is connected to the battery at any

time. In this case only one regulator

controls the charge current allowing the

battery to reach a higher state of charge. 

Irrespective of what is connected, the

regulator set to the highest voltage

will dominate. So if the solar panel

regulator is set to the higher voltage

the engine alternator will not supply its

full charging current and similarly if

the wind generator has a higher voltage

it will supply most of the charge to the

battery while the other regulator winds

back its output. I expect one source of

charge current will dominate depending

on the conditions (bright sun and little

wind versus overcast and windy). Of

course at night there is no argument!

I do not see this as a serious problem

as charge will ultimately still flow into

the battery. The individual regulators

should provide sufficient electrical

isolation between each power source;

otherwise you would need a diode

to isolate each device. I have two

solar panels, one unregulated on the

start battery and the big one (with a

regulator) on the house battery. 

We do not run the engine only to

charge the batteries and have not had

a problem getting a full charge into the

battery. The alternator regulator is set

slightly higher than the solar panel so

while the engine is running there is

charge from it going into the batteries.

Charging with multiple inputs

DIDUNO

The expression ‘leading light’, used to

describe a prominent person or dynamic

personality, comes from the name for

navigation markers, placed one behind the

other, which when in line will keep a vessel

in safe water.

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How best to

connect each

charging input to

the batteries?