Electrical Generators

This group of pages are intended for local residents in the jungles of Hawaii and other islands that use their power generators every day for charging batteries and running the household. I have been a mechanic for years and never had to experience small generators producing AC voltages. In the mainland these generators are a luxury and a regular mechanic rarely sees one to work on. Here in a jungle on a sub tropical island is different than people living on the mainland's that have access to power grids, people are off grid and power outages are common in a jungle so backup systems are a must have.



I went out on a worksite where a generator was required and a family was involved. Their generator was an (11kW) and one power cord was going from one outlet to the Outback charge controller. I could not imagine why one outlet was used rated at 30 Amps AC which calculated to 3600 watts or 3.6 kW fuel was being burned at a rate that a 15 horsepower engine requires and that only 4.83 horsepower is required to generate 3.6 kW.



This made me stop and realize how many people around the area are actually using their generator and storage systems properly or at their optimum performance levels? You are paying for every watt you use as well the storage capacity in Amp hours in the field of power generation and storage systems . The engines on generators need to run at their specific rated speeds in any AC situation, so the longer the generator runs without producing maximum potential in kW the  fuel consumed, maintenance and wear will occur as if the generator was producing it's optimum watts. The information on the pages in this set will provide you with the correct way to set up your generator charging systems. 






Most everyone using an electrical generator needs to know some very important facts regarding maintenance. One of the most important issues is changing engine oil. The less expensive generators are usually all air cooled meaning no radiator to add water. An air cooled engine runs at higher temperatures than the water cooled ones and this requires an oil that has certain advantages over the conventional automobile oils.



Since 2010 the auto manufacturers required oil manufacturing companies to change formulation for additives. This was done primarily to help the catalytic converter live longer. Most all automotive engines are water cooled meaning they have a radiator and a water pumping system. Automotive oils are designed for this and come in various weights or viscosities. A straight weight engine oil is better for this area than a multi viscosity oil for any type of engine. Your oil will work better for your engine if it is a straight weight. This means instead of 10W40 you  simply purchase straight 40W (Weight), the multi viscosity oils are made for areas that the temperature changes dramatically from day to day or night to night or month to month. In Hana we are dealing with very little temperature change so the multi weight oils are not as good to use as the straight weight oils.



NOTE that the weight of the oil is not a physical weight measurement in numbers that are relevant, one quart of 40W oil actually weighs in pounds exactly the same as one quart of 10W40 in a mechanical aspect. The viscosity is referred to as the weight although specific gravity changes slightly as the oil thickens or coagulates like blood from a cut. The viscosity is a resistance to going into a small hole and like you syrup for pancakes. Syrup has multiple viscosities and dependent on temperature just like the oil but inversely. Heating the syrup will cause it to flow quickly and the colder it gets it will flow slower and multi viscosity oil works opposite or inverse, when you heat oil up it goes to 40W at a specific engine temperature which is thicker than when it gets cold and ends up as 10W very runny and little lubrication properties compared to the 40W.


Todays engine oils are not designed for the needs of an air cooled generator or mower engine. Manufacturers recommend additives that cost more to add them or just simply buy the oil that is designed for air cooled engines.


The air cooled engine oil of preference is the Aeroshell 100 + or the 150+. You can purchase that by the quart Michelle @248-7379 or by the case over at Maui Oil Company in Kahului, Hawaii. The oil is more expensive than regular engine oil, Michelle pays 98 to 99 dollars for 12 bottles and has to drive to the other side to pick it up so expect to pay 12 dollars a quart at the least or go buy 12 @ Maui Oil.



Do this test for oil lubricity in your oil and I guarantee without doubt when you do the same test to the Aeroshell you will be convinced and feel the difference.


OIL LUBRICITY TEST- Dip your finger into a cap of your engine oil and press two fingers together and rub until your fingers under pressure stop sliding apart. Now take and dip your finger into the Aeroshell Oil and do the same thing. You will feel that the pressure applied to stick your oil will not stick the Aeroshell.



Secondly to the lubricity is the ability of your oil to transfer heat from the air cooled components of the engine. Heat transfer ability is double or better with the air cooled piston aircraft oils. Chevron has one also which is as high as the Aeroshell but need to special order and price not available until ordered.






Charging Batteries


Charging the battery is a primary function of a generator that produces AC voltages. Most batteries in use today in mobile or DC storage systems use lead and liquid electrolyte (acid) to store electrons. Use this link to go to the BATTERIES page which will give more information, also go to this page DC STORAGE for a detailed description of what to expect in a Generated DC system and in particular the photovoltaic or PV systems using an Outback charge controller or similar.  

Size your generator for your specific needs, every size up means you will burn more fuel. Add up all the items you will possibly use at the same time. Example; a fridge (800 W), 2 lights (150 W), computer-laptop (50), and the possible intermittent load like small appliance or power tool. The total continuous load would be 800+150+50=1000W generator required so the generator in the far left picture would be the one to chose over the far right generator @11,000 Watts. One horsepower will generate 746 Watts of electrical power so total watts divided by 746 will tell you what the horsepower needs to be at minimum to produce electrical current for your specific loads.

Each horsepower costs a specific amount in fuel and for example a one horsepower engine producing 746 Watts could possibly use 1/2 gallon of fuel per hour, a 2 horsepower engine 1 gallon per hour, a 3 horsepower 1.5 gallons per hour and so on. All generators producing useable AC electrical current have to run at a set RPM at all times, so not using the electricity is like throwing money out the window.



The picture on the far left is a 1500 Watt generator so we know it has to have at least 1500W / 746 = 2.02 horsepower, the horsepower engine in that generator on the far left is most likely a 2.5 HP engine. Important to view is the number of electrical outlet plugs on the panel of the generator. This generator has one so that means all 1500 Watts will go through one plug in or we can calculate amperes by 1500 divided by 120 volts or 12.5 amps.



Now we look carefully at the middle generator @3500 Watts continuous (3500 / 746 = 4.7 Hp) and using a 5 Hp (horsepower) engine. There are 4 plug in receptacles on that generator panel so the total wattage is divided up 4 ways, the smaller ones are less current rating than the larger receptacles.



Looking now at the far right generator of 11,000 watts and using at minimum a 15 Hp engine dividing into 6 individual receptacles you can now understand why a larger generator gives you no more than a smaller one, it just costs proportionally more. Rule of thumb is one dollar per watt or a 1500 watt generator will end up costing $1500 USD (dollars). You can get the generators slightly less expensive but your electricity will end up costing a dollar a watt on average.



When using one of these inexpensive generators for your AC needs and using an Outback type charge controller keep in mind you only have one cable going into the charge controller. So even if your generator is 11000 Watts one plug can only produce a certain amount and whatever the breaker is rated at. In addition you are paying over 5 times more than is necessary for the electrical energy you are generating.