Homebuilt 12 Volt Generator Part I

My soon to be home and for that matter all of Great Barrier Island doesn’t have any reticulated electricity or water supply. So basically, individual households are living off the grid and utilize a combination of alternative energy systems – such as solar, wind, water and fuel-driven generators – to produce power. With this respect, communities like Great Barrier Island should be regarded as a model to strive for.

My property gets all day sun, is classified as a high wind area and has a permanent stream. Clearly, I need to look into methods to generate alternative power out of these three sources. I will blog about my experiences and progress with such projects as I go along, and start here documenting on a  ‘Do It Yourself’  home-made 12 Volt generator that runs on diesel. Obviously, there is nothing green about a diesel generator, but I need a reliable, steady and low-cost electricity source to start with. The plan is to go as green as I can over time and use the generator as a back-up only.

It took some discussions with my ‘Main Energy Man’ (MEM) Gary until he convinced me to buy a diesel engine and to convert it into a generator rather than buying a completed one. Essentially, he said: “Ideally, you want to have tools that can be used for multiple purposes.” A generator is build in such a way that its engine is permanently linked to an alternator, thus it can only be used to produce power. Therefore, it makes more sense to having a sole diesel engine that can be hooked up to an alternator (or more) via pulley and belt because the same engine can also be connected by such means to a water pump. For now, I want to link a used car alternator to this diesel engine, build a rack for it and hook this home-made geni to a bank of used car batteries.

I got me a new, Chinese made air-cooled 4-stroke OHV double cylinder 211cc diesel engine, that produces a maximum of 3.8 hp at 3000 rpm. It has an overall size of (430 x 345 x 470) mm and a gross weight of 32 kg. I obtained it through an auction on Trademe (New Zealand’s answer to Ebay) for 640 $NZ. Yesterday, I drove downtown to a warehouse in Howick to pick it up.

New Zealand is an island far way from the ‘rest of the world’ and sometimes you experience this fact in day to day life. For example, if you want to purchase something or are seeking specific information on a product, like on interest rates on bank accounts, there is a good chance you will end up dealing with 3 types of people: the teenager, the elderly and the unqualified sales person. Now these categories can be quite interdependent. If you ever inquired in a bank about opening a foreign currency account and about its interest rates, you probably know what I mean. 15 minutes later, you will probably still hear something like: “Yes, we do exchange Euros into $NZ.”

So what happened to me in the warehouse, you ask. I ended up talking to a very friendly lady who gladly took the 640$ from me, gave me a receipt and pointed me towards a plain box that apparently contained my newly acquired engine. While she started wandering off, I called her back and said, that I have a couple of questions and would like to inspect the engine. What I wanted to know was for how long this company has been selling these engines, whether they have a track record of things that might go wrong with it over time and if I could buy such spare parts right now to prepare myself in case something goes wrong. After talking to the friendly lady for about 10 minutes and a further 10 minutes with her colleagues, which were 2 not so friendly ladies and a man that looked like 14 years to me, I only gathered that they have been selling these units for a ‘long time’, that ‘they never had any complaints’ , that ‘these engines will run forever’, that ‘we are of course no engine experts’ and that ‘I’ve got 1 month of warranty in case there were any issues’.

What to do? I’ve been in this situation many times and well, I was happy with the price for the engine and loaded it into my car. This is when I noticed that no manual was provided. So I go back inside and inquire about the manual. Long story short: ‘these engines are so basic, they don’t come with a manual’, ‘we never had any complaints’ and ‘is there anything else we can help you with?’. I responded that it would be good to know which type of oil the engine uses. I got: ‘Well, it is a diesel engine. It hardly uses any oil and it is probably of generic type’. Again, very helpful! I decided to leave it at that and figure it out myself, as clearly I was just wasting time.

At this stage Gary and myself have tested the engine, it runs smoothly and uses around half a liter of diesel per hour on idle. I will report on the assembly of the generator in ‘Homebuilt 12 Volt Generator Part II’, once I have organized a second hand alternator, 6-8 used car batteries and the belt for the pulley. For now, I’ve uploaded pictures of the little, beautiful diesel engine, the pulley I got and provide a useful link for such a project.

A sleek 211cc diesel engine, 3.8 hp at 3000 rpm
Air-cooled 4-stroke OHV double cylinder, 2.5 l diesel and 0.75 oil tank
Side view with recoil starting system
Pulley and bush were around 100$ and are directly connected to cank shaft
Another perspective

One thought on “Homebuilt 12 Volt Generator Part I”

  1. One correction, the diesel engine is single pot, so only one cylinder. This is not a problem as it accounts for the low fuel usage and being much simpler will result in considerably less maintenance in the long run. One thing to remember of any diesel engine is that it essentially burns oil as well as diesel, so it’s important to check the oil before every run.

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