Professional BoatBuilder - December-January 2018

46 PROFESSIONAL BOATBUILDER

We are entering a new era of energy

systems on boats, with extraordinarily

high-rate charging devices and batter-

ies that can absorb pretty much any-

thing we can throw at them. Together,

these will give us greatly improved

e ciencies and onboard lifestyles, but

with these gains come new installa-

tion and service challenges as boat

builders and re t yards make the con-

version. Fortunately, we also have the

tools to help us through these chal-

lenges and ensure safe and reliable

installations.

About the Author: A contributing edi-

tor of Professional BoatBuilder, Nigel

Calder is the author of B o a t o w n e r ’s

Mechanical and Electrical Manual and

other marine titles (including, earlier

in his career, Marine Diesel Engines),

and is a member of the American Boat

& Yacht Council’s Electrical Project

Committee.

fully loaded charging circuits should

not exceed 3% of the rated voltage (i.e.,

0.36V on a 12V circuit), but in any

event should never exceed 10%, or

1.2V on a 12V circuit.

Let’s say the voltage drop is too high.

It may be caused by cumulative resis-

tance in undersized cables but is

frequently the result of resistive con-

nections. In high-current circuits,

these will form hot spots. We have

some particularly useful new tools

for detecting these hot spots. One is

an infrared-laser heat gun, which will

give precise temperature readings

from very speci c locations, and the

other is a thermal-imaging camera,

which will show temperature gradi-

ents within a larger area. Simple ver-

sions of these cameras can be bought

for less than $200 to plug into any

smartphone.

____)____

On circuits carrying continuous high

currents, all connections must be elec-

trically perfect and extremely tight.

Useful Tools

An e ective means to check for

potential heat problems in high-cur-

rent DC circuits is to switch a multi-

meter into its DC volts mode, place

one probe at one end of the circuit

(e.g., the positive output terminal in

the back of an alternator) and the

other at the other end of the circuit

(e.g., the positive terminal on the bat-

tery being charged) using extension

leads if necessary, and to fully load the

circuit (i.e., run charging devices  at

out). Note that the meter leads are

both on the positive side of the circuit

(i.e., the same side) and are not mea-

suring from positive to negative. Any

voltage registered represents voltage

drop caused by resistance in the cir-

cuit. In principle, the voltage drop on

SYSTEMS: Battery Technology

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