Engine driven generators

[Robbo]

If I understand the question correctly then yes I'd choose a Combi first (or separate inverter and charger) with the TravelPower being a "nice to have" addition, although that presumes the engine had a decent 12v alternator, not some ancient 35A job!

 

I'm presuming most will have to add a high amp alternator to take advantage.

[by'eck]

 

Even if you start from scratch, a seperate system makes more sense. A high amp alternator with decent inverter costs roughly the same, but gives you more options, you don't even have too have one alternator, as 2 smaller units can provide the power if you really need a high continuous power without using the batteries.

 

Basically what I was saying but with the caveat that its far from the most efficient, just practical if you have the hardware already and spare engine power.

[Felshampo]

Thanks for that. I think I understand it all a lot better now.

One more question. If you had a seperate generater would this have any advantage over the TravelPower? Does it come down to having a backup for the engine as it seems having alternatives is good.

[Robbo]

Thanks for that. I think I understand it all a lot better now.

One more question. If you had a seperate generater would this have any advantage over the TravelPower? Does it come down to having a backup for the engine as it seems having alternatives is good.

 

Has the advantage of a seperate engine that's matched for the power so will use less fuel. I have a Kolher 4Kw, which I think has around a 10hp engine in it.

[dmr]

Thanks for that. I think I understand it all a lot better now.

One more question. If you had a seperate generater would this have any advantage over the TravelPower? Does it come down to having a backup for the engine as it seems having alternatives is good.

 

Swings and roundabouts and much debated on this forum with some people having very strong opinions.

A separate generator will give redundancy if the main engine fails, but correctly maintained boat engines are very reliable.

Some people believe running the main engine to generate electricity will damage the engine (bore glazing) and wear it out more quickly.

A petrol generator is cheap but getting petrol can be a drag and storing it on a boat is dangerous.

Running a generator half in and half out of the boat can kill you (CO fumes).

Diesel generators are big and loud and will upset those around you if you run them outside, and you need big generator to charge batteries quickly or run washing machines and power tools etc..

A proper built in generator in a sound proof box is good but very costly and takes up boat space.

 

................Dave

[by'eck]

Thanks for that. I think I understand it all a lot better now.

One more question. If you had a seperate generater would this have any advantage over the TravelPower? Does it come down to having a backup for the engine as it seems having alternatives is good.

 

Yes agree with Robbo. A separate generator will offer redundancy as well as saving wear and tear on main engine if you are not moving. Ironically most suitcase generators use the same technology (inverter/generator) as the main engine driven TravelPower/Dynawatt anyway.

[dmr]

Wot Dave said!

 

Our 175A alternator can give about 2kw via the inverter, whereas the near-identical sized TravelPower can give 3.5 kw and runs much cooler than the 175A alternator at the same power, due to its high voltage. Higher voltage to give the same power needs lower current, and it is the current that causes heating in windings and wiring.

 

But in fact we got ours mostly to introduce some redundancy. It gives us an alternative source of mains power should the inverter fail, and an alternative way to charge the batteries (via the Combi) should the 12v alternator fail. Redundancy is good!

 

Yes, travelpower runs cooler so is more efficient, but WHY???

Copper loss is "i squared R" but for ten times the voltage we need ten times more turns and as space is limited would have to use thinner wire so with a higher resistance. Ive been worrying about this (my present pre-occupation with alternator operating temperature)

 

.............Dave

[by'eck]

 

Yes, travelpower runs cooler so is more efficient, but WHY???

Copper loss is "i squared R" but for ten times the voltage we need ten times more turns and as space is limited would have to use thinner wire so with a higher resistance. Ive been worrying about this (my present pre-occupation with alternator operating temperature)

 

.............Dave

 

Well I think you have answered that point already.

 

Major alternator loss is the ohmic I²R loss in the stator windings, so current is the dominant component. Higher voltage means lower current to produce the same power output.

Edited October 7, 2014 by by'eck