Advanced Marine Electrics and Electronics Troubleshooting A Manual for Boatowners and Marine Technicians

recharging, but does not add to the engine

starting circuitry.

2 The more common strategy is to have all
the batteries supplying all the boat’s DC
loads, including the electronics package
and the engine starter circuit. However,
this setup requires that all cable runs be
sized to maintain an absolute minimum
voltage drop, and that the battery bank
have sufficient capacity to crank the
engines while maintaining a cranking
voltage of greater than 10.5 V.

3 The third option is to install a DC-
powered UPS device for the electronics
main power supply, such as the
StartGuard DC power conditioner from
Newmar. These boxes, which sell for
about $200, are similar in purpose to

the UPS devices common in computer

installations; they contain a small bat-

tery that “kicks in” to maintain stable

voltage output when there is a drop in

input voltage. The primary difference is

the power source, which is DC, versus

the AC used by land-based computers.

The StartGuard UPS has a maximum

output of 20 amps. If you need addi-

tional current capacity, you can install

multiple units.

I recommend either option 1 or option 3.

If you are interested in option 1—an isolated

and dedicated battery supply for powering

electronic equipment—keep in mind that

space limitations and added cost may rule it

out on your boat. In that case, try option 3, a

DC-powered UPS device.

electronic equipment installation guidelines 137

Typical integration of a DC-powered UPS device with onboard electronics.

UPS

INPUT STARTER OUTPUT

12 VOLT

GPS receiver

loads (20 amps max)

+ 12V

• 12V

** 2

amp fuse

** 2 amp fuse

to 12 V battery to starter #1

key starter

+12 V

+ 12 V from

fused source

(–) common

(wiring option)

OR

push-button

starter switch

to starter #2

switch or solenoid

+

+

*

*

* Refer to manufacturer’s instructions

regarding overcurrent protection.

† Terminal block not provided. Multiple wires may be attached directly to UPS

if preferred.

†

** Recommended; must be supplied by installer.

VHF radio

starter solenoid