Genie Diesel Battery Charger
Cooling Guide

Release 1.0 December 4, 2004
Copyright ©1989 through 2004. All Rights Reserved - Ample Technology


The Genie is a small engine coupled to a large alternator and may run for extended periods at about 80% of its horse power. Though efficient, there is still considerable heat generated which must be removed from the Genie and the surrounding area.

Because of the high load factor, keeping the unit cool is very installation dependent. The purpose of the Guide is to present mandatory and suggested ways to maintain a reasonable engine temperature.

The smaller the area in which a Genie operates, the more stringent are the rules for cooling. The hardest environment is when the Genie is in the sound enclosure mounted in a small lazarette. By following the guidelines in this document, the unit can be successfully operated at rated output. If the guidelines can not be met, then the alternator current limit must be set to prevent overheating.

Combustion Air

It is imperative that the engine be provided with combustion air which is close to ambient air temperature. As combustion air increases in temperature, engine horsepower drops quickly, so a Genie which would be operating at 80% of its capacity will be operating at 100 or 110%. It will overheat. Recirculation of hot air is to be avoided at all costs.

The combustion air intake for the engine can be plumbed with a 1.5 inch diameter hose to a compartment that maintains ambient temperature, or to a dorade vent in the same compartment, say in the lazerette. Use of the air intake silencer will reduce noise. Of course the air filter needs to be attached to the intake hose.

Hot Air Exhaust

The air exiting a sound enclosure may be around 200 $^\circ$ F. While there isn't a lot of air volume, even a large compartment will steadily rise in temperature.

One solution is to mount a blower beneath a dorade vent to blow the hot air out of the compartment. Keeping the compartment air temperature below 140 $^\circ$ F at its hotest point is suggested.

Raw Cooling Water

Hundreds of units are operating with slightly more than one gallon per minute of raw water flow. Units mounted in a sound box are shipped with a raw water pump capable of about 3 gallons per minute. That's close to the limit of temperature exchange on the heat exchanger, so more water doesn't translate linearly to more cooling.

Verifying that there is adequate raw water flow through the heat exchanger is required every time the unit is operated. Water borne obstructions to the intake are an obvious source. One heat exchanger got clogged with the remnants of the internal zinc which had never been changed in six years of operation.

Raw cooling water above 80 $^\circ$ F may require that alternator current limit be reduced. Water at this temperature also means that ambient air is hotter, another reason to reduce alternator current.


Units built in the last couple of years have fiberglass wrapped exhaust systems. Earlier units were not wrapped, but a muffler blanket was an option to keep the exhaust heat in the muffler where it could be cooled with the discharge of raw water from the heat exchanger.

Remote Diodes

When ever a Genie is put inside a sound box, the diodes in the alternator should be removed and replaced with a remote diode assembly. That is, diodes which are mounted outside the sound enclosure. The remote diodes should be mounted so that their waste heat is not sucked back into the sound enclosure.

Sound Enclosures

The Ample Power sound enclosure is the result of considerable engineering and some trial and error. Air is sucked into the enclosure by an electric fan that exhausts that air directly behind the alternator. The fan on the alternator sucks the air through the alternator and spreads it about the box. The box is pressurized by the electric fan and the alternator fan.

Air has to cross from the right front of the box to the left rear to escape. Intake and exhaust air vents have to be baffled, of course, to reduce noise.

Sound enclosures without a good cross flow of air will cause the engine to overheat and alternator current will have to be reduced.


Provide outside ambient air for combustion intake.

Keep the compartment cool.

Verify adequate and expected amount of raw water flow.

Apply insulation around hot exhaust parts.

Use remote diodes with sound enclosures.

Provide good cross flow of air through any sound box.

If necessary, reduce alternator output current to prevent overheating.

Ample Power products are manufactured by Ample Technology, 2442 NW Market St., #43, Seattle, WA 98107 - USA