Tiny Powered Alternators & DC Generators

[skenn_ie]

Permanent-magnet brushless motors work quite well. The Kv number is the RPM per volt, whether you drive it electrically or mechanically to produce electricity.

[newhaul]

Originally Posted by skenn_ie

Permanent-magnet brushless motors work quite well. The Kv number is the RPM per volt, whether you drive it electrically or mechanically to produce electricity.

you mean like my wind generator 400 watts in 15 knots wind.

[Joe Okros]

Well, I have had a little Honda 1000W generator for about 14 years, I bought it second hand in St Maarten for I think $50 when the original owners upgraded to a 2000W unit. On my boat I also have an ancient 2500W Freedom (Now Xantrex) Charger/Inverter. The little Honda outputs about 8Amps at 110 V which translates to about 60A at 14V charging my batteries when plugged into the Freedom. This has saved my ass a few times when various issues have compromised my battery capability. I'm a big believer in redundancy and while cruising we had a combination of Balmar 140A Alternator, Solar Panel, KISS wind generator and the little Honda as options and I have never run out of options. So there is definitely a place for a small gas powered 4-stroke genny, but I would advise to also have a decent capacity Charger/Inverter to go with it.

Its also been a lifesaver for using power tools all over the boat

[skenn_ie]

Originally Posted by rgleason

1.5-2 hp that could output 10-30a (150watts-450 watts at 14.8v) or maybe water/wind generator but that does not work at anchor and is much less power for water generator (3-6amps I guess) at our low speeds .

EngineHP/2 is about what you can expect from the alternator, be it 110, 220, 14 or 28V. Rectified 3-phase is best for DC as the load on the engine and output voltage stay far smoother.
Permanent magnet alternators and PM brushless motors are pretty much the same thing. Motor POWER ratings tend to be for short duration. If it says 2.5kW, the chances are that it would burn up if you ran it at that for more than 15s or so, either as a motor or alternator. I would estimate 30% max, for continuous operation.

[skenn_ie]

I am wary of using fancy chargers with small generators. The chargers can overload the genny and kill it. With the old transformer types, if the AC drops, so does the charging voltage/current

[john61ct]

Originally Posted by skenn_ie

EngineHP/2 is about what you can expect from the alternator, be it 110, 220, 14 or 28V.

What does that mean please?

With examples may help

>If it says 2.5kW, the chances are that it would burn up if you ran it at that for more than 15s or so, either as a motor or alternator. I would estimate 30% max, for continuous operation

There are dozens of large-frame alts on the market designed to output close to or at their rated output 24x7.

Obviously a good VR is needed to derate current output if environmental conditions allow things to get too hot.

[skenn_ie]

Originally Posted by john61ct

What does that mean please?

With examples may help

>If it says 2.5kW, the chances are that it would burn up if you ran it at that for more than 15s or so, either as a motor or alternator. I would estimate 30% max, for continuous operation

There are dozens of large-frame alts on the market designed to output close to or at their rated output 24x7.

Obviously a good VR is needed to derate current output if environmental conditions allow things to get too hot.

Sorry, I meant 30% rated power if using a brushless motor.
a 5HP engine driving an alternator will produce about 2.5HP of electricity
(750W = 1HP)

[john61ct]

So 134A per 5HP.

Seems a bit higher than IRL, but in the ballpark.

And again, a diesel engine vs a gas one will be a different ratio IRL.

[skenn_ie]

Originally Posted by john61ct

So 134A per 5HP.

And again, a diesel engine vs a gas one will be a different ratio IRL.

How ?

[john61ct]

Take an Atomic gasser, rated at what 30HP ?

What's the biggest alt Actual amps output you could run off it, prop removed, serpentine (polyvee) belt?

Now do the same with a Beta rated 30HP.

You really think alt Actual amps output will be similar?

[skenn_ie]

Originally Posted by john61ct

Take an Atomic gasser, rated at what 30HP ?

What's the biggest alt Actual amps output you could run off it, prop removed, serpentine (polyvee) belt?

Now do the same with a Beta rated 30HP.

You really think alt Actual amps output will be similar?

Your polyV couldn't handle that amount of power. Other than that, yes. Engine power, assuming that it is shaft HP, which it should be, will be dissipated in the heat generated in the iron of the generator through eddy currents, bearing losses, air drag, and that fact that the alternator swallows some of it's own power, maybe as much as 30%, electro-magnetically energising the rotor. Fuel is irrelevant.

[Jammer]

I just got a reply from Polar Power.


They have fully marinized permanent magnet generators available beginning at a 3-5kw unit for $14,260. The lower end of the output range applies when the unit is configured to operate at a lower speed for less noise and longer life.


The generators can be set up for any desired voltage between 12 and 550 volts at no extra charge.



All their marine units use Volvo Penta D1 and D2 series engines.

[newhaul]

Originally Posted by Jammer

I just got a reply from Polar Power.


They have fully marinized permanent magnet generators available beginning at a 3-5kw unit for $14,260. The lower end of the output range applies when the unit is configured to operate at a lower speed for less noise and longer life.


The generators can be set up for any desired voltage between 12 and 550 volts at no extra charge.



All their marine units use Volvo Penta D1 and D2 series engines.

would love to find out what pm generator head they put on the d1 .
I have an md1b sitting on a pallet just looking for a job to do.

[Jammer]

They make their own. Unfortunately, they don't sell the heads by themselves.

[Rumpi]

QUOTE=newhaul;2712894]would love to find out what pm generator head they put on the d1 .
I have an md1b sitting on a pallet just looking for a job to do.[/QUOTE]

You actually have some options if you want to diy. I'll list some:

1. Search for a cheap chinese inverter generator with a busted engine. All inverter type generators use PM's. Transplant generator head and electronics. You may need to gear up to get to the gas motor rpm to get full rated power. Simplest option, gives AC power. If you find a generator with busted electronics proceed like option 2 or buy the black box.
2. Get a Honda IMA generator from any wrecked Honda hybrid car. Rewire the stator to lower output voltage, (or completley rewind the stator to your desired specs), rectify and smoothen. Use a solar or wind PWM controller of apropiate input voltage range and amperage to deliver steady DC to batteries. This is a pretty involved option due to the fact that the IMA is an inrunner with no shaft.
3. Get a small chinese PM ev motor. Electronics as above. For small kW there are controllers with regeneration but you will probably need at least a 24V battery bank, this is better suited for higher voltages.

There are other things to consider like load regulation (arduino and stepper motor for the throttle for example), and that's why option 1 might be the best even if you have to buy the electronics as spare parts.