Originally Posted by Sailing Ozzie
New to the forum but have been reading it on n off for years.
I've just bought a Roberts 45 with a Hyper 9 120HP Electric Motor.
It has a battery bank but it's currently not being charged by solar or wind, it will be eventually, but for now I just need to get it moving.
I am looking to buy a generator to charge the batteries... It'd be great to run the motor straight off the generator but therein lies my dilema.
Is it too hard? Should I just buy a small petrol generator to charge the batteries - petrol being dangerous onboard, but there will be some anyway for the tender- and save my money for boat renovation, or is it possible to run off a geni.
I spoke to Tim at EVWorks Western Oz (who was really helpful) who supplied the motor and he suggested I just buy a cheap generator and cheap battery chargers for now and he'll supply a quality charger once I have it moved and can tell him what batteries I have on board. He also said peak power of the motor is 80000watts. But the guy I bought the boat from says it's detuned via the operating software and only draws a max of 70amps and normal running is at only 30amps (120vdc) and suggests I could buy a diesel generator and use a bridge rectifier to change the 240v to 120vdc.... But that sounds dangerous on board a boat.
Buying a generator upfront without knowing how I intend to use it could be a waste of time, so I am seeking advice on what way I should go.
Another issue, I've read that 2 stroke engines can handle bad fuel that's sold in remote locations- I intend to cruise- so if I buy a 4 stroke petrol geni, I may run into reliability problems?
Does anyone have any use full opinion on what I should do?
<EDIT> OOPS, I should have read the next page before replying! Looks like you went for it and got screwed. Condolences. Better luck next time. There will be other boats. A good survey
can cost many hundreds of dollars but also save you many thousands. </EDIT>
If the seller doesn't know anything about his batteries, then I can almost tell you as a fact that the batteries are toast, and need replacement, due to absolute utter lack of monitoring and maintenance
. So there is that. Find out what sort of batteries are aboard, first of all. Figure on spending several days charging
them from shore power
. If they are FLA batteries, very likely you will need to equalize. See the Trojan site for general information if you don't know how to do this or when or why to do it. The bank may be 144v, 120, 96, or not a multiple of 12v at all. If they are 6v or 12v batteries, then you can isolate them appropriately and charge with a heavy duty automotive charger
for cheap. You should be able to run a couple of them from a typical shore power
circuit with no problem. Charge, reconnect, let them sit overnight, and check the voltage and specific gravity the next day. Extra credit for doing a load test but this will add a lot of time to your sched.
A bridge rectifier does not change 240vac to 120vdc. You will need an appropriate transformer or better yet a large Variac to control the voltage. The rectifier simply changes AC to a very ripply DC. Are you talking US 240vac? With two hots and a neutral? In that case you use just one hot leg and neutral, and case ground, to get 120vac. Consult an electrician if you are in the slightest doubt about what you are doing, so you don't kill yourself or innocent bystanders or divers. If you are talking about 240v as supplied in most of the world, you need a transformer. Some isolation transformers have this capability, with a simple jumper change at the output terminals. Again, if you are not very comfortable and knowledgeable messing about with electricity, and I suspect maybe you are not, have an electrician pay you a visit and help you get things sorted out.
BTW, not only does a rectifier not turn 240vac into 120vdc, it doesn't even turn it into 240vdc. The problem is that AC voltages are measured in volts RMS. Root Mean Square. 120VAC actually rectifies into 170VDC. So your transformer will not be the 2:1 ratio you would expect. This is why I recommend a large Variac. You adjust the primary to secondary ratio by turning a big knob on top until you get the output voltage that you want.
Additionally, a 120VDC battery bank is generally not actually 120VDC. With common types of Lead/Acid batteries, the voltage will be significantly higher. A 12v FLA battery fully charged should read about 12.6v. So actual voltage of a 120v bank of FLA batts will actually be about 126vdc. However, when charging
, you need to be able to apply voltages of 14v to 15v, and even for trickle charging you will want at least 12.8v applied to each 12v battery, minimum. Consult the website of the manufacturer for specific setpoints. Add the voltages for a series bank. So you can see that you may need an output that goes as high as 150vdc, but NOT 170vdc. With a Variac, you can charge according to an accepted charge algorithm for your battery, as long as current
stays below rated max for your variac, wires, and rectifier. A fuse or breaker should be considered absolutely required. Note that this all manual charging method requires constant monitoring, and guarding against looky-loos getting zapped.
The simple way to charge your batteries is to simply use a mains charger that is designed for your type of battery. If shore power is 240vac and 50hz, make sure that the charger will accept that as an input.
You may well find that your batteries are useless, or nearly so. Be sure you have a plan for dealing with that. You could probably, if there is a lot of golfing or a lot of retirement
communities nearby, pick up 20 6v golf cart batteries, rebuild
the battery box
if necessary, wire them, charge them, test them, and go. Or you could just blow the whole thing off. I really have a bad feeling about this project
. In general, I think it is a terrible mistake for someone not very familiar with e-boats to buy an e-boat from someone who likewise is unfamiliar with them. But who knows?
boat for cruising really needs a diesel
genset, even if you have a good solar
power setup. Just sayin. If the batteries are good, then a 5kw or so genset is something good to buy and install before you try to bring the boat home. You COULD go as small as 3kw maybe. Or up to say 10kw.
Does the boat have a good dinghy
, with a gasoline powered outboard
? If conditions are amenable, you could keep the dink made up on the hip for exiting the harbor, sail out and homeward, set up the dink again as your mini tugboat for entering harbor, and once you can get a line or two on the dock
, muscle the boat into your slip. A crew person in the dink would be almost essential, of course. At this point you have no idea whether or not your propulsion
system is dependable, or even at all usable.
All these doubts I and others are raising ought to have the price
of the boat at a VERY distressed level. So, you could actually be getting a pretty good deal simply because nobody with any sense will touch it. If it is not going very very cheap, I wouldn't take it. Nope. And I AM an electric
boat guy. There will be other boats.
outboards are no more able to burn bad fuel
than 4 strokes, IYAM. The moral of that story is do not run it on bad fuel. Change the filter regularly. Change the FUEL regularly. Don't let it sit all year in the tank. Best to not mix it until you need it, so if the gas is getting old, you can burn it a little at a time in your car. Else, run your outboard
enough to use up the mixed fuel in a timely manner.
The main advantage to 2 strokes is that for the same power, they are significantly lighter. OTOH, 4 strokes don't need lube mixed into the fuel. Speaking of, try to get ethanol free gasoline for your outboard.