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I am not anti-generator but just questioning why you feel the need for one. You have two substantial leisure batteries. If these do all you need then it is just a matter of re-charging them. You have a large and efficient generator in your engine.  Just run your engine for a short while each day and your batteries are topped up again. 

You should not need an external generator unless you have a requirement for  large amounts of current at 240 volts. Carrying around a lump of a generator plus a can of petrol  is something best avoided if you can.

Saxo, I am sure you are technically right. However, in the real world we do not all live at the technical extremes.

When charging on tick over it is unlikely the op will have the main beams on, windscreen wipers, air conditioning, blower at max and windscreen defrost operating. Therefore, there will be more current available for charging. Unless he is extremely wasteful he is also unlikely to completely flatten 2 x 110 amp/hour batteries in 24 hours.

Whilst it is true a leisure battery needs external charging to keep it at 100%, how many of us actually do this and yet our batteries carry on from year to year without trouble. A week on a rally field is unlikely to make any difference.

I am not saying that he should not buy a generator, just that he should consider whether he actually needs one. With a bit of careful electrical resource management he may well find he can manage quite happily with what he already has. As to weight, he already has the batteries installed, the Honda will be additional.

Still if the op feels the need for a big boy's toy I guess he will get one !

I brought a genny 8 years ago for our first motorhome, 4 motorhomes down the line I've used the genny once.

John.

Another problem with charging a battery from a car, specific to a diesel engine, is that diesel engines are not designed to run for extended periods at idle speed and it is recommended that if it is running for longer than 5 mins to switch it off.

Saxo1

Well I have to agree with apple tree here.

Ive read many threads on what generator to buy and have often thought why not let the engine run for half an hour to top the batteries up? I dont understand the need for one.

Sometimes we well drive to a supermarket/beach to kill two birds with one stone. When we get back the battery meter says full. Okay, technically it may not be full, but all I know is I can put the lights on and watch TV that night.

I also agree that Saxo may be technicaly right on some points, but would add that the alternator on my Ducato is 110amps.

The thing about an alternator is that most produce very little till they reach 1200 rpm and then it's normally very low, as little as 10 amps,so allowing for the amount drawn to keep the fuel pump, electronics etc active, to keep the engine running, even if the output is 10A, a half hour  will only put in app 5A at a fast idle speed.

It is OK to use the car to charge the battery but you need to be driving it to increase the revs for it to be of any real use.

Your 110A alternator is more than adequate to charge a battery if driven, but at idle speeds they are designed to produce just enough to keep things going to improve economy and reduce emissions,,in the worst case scenario it is possible to flatten s battery if left at idle for a long period.

The other factor is the increased engine wear,carbon build up and degradation of the oil when a diesel engine is idling, they are most efficient when working hard.I have seen studies that indicate that 1/2 an hour at idle speed causes twice as much wear as 1 hour at 60 MPH on the motorway.

I'm not dismissing the concept but just trying to highlight the pitfalls of just doing it at idle speed.

Saxo1

Quote: Originally posted by saxo1 on 09/3/2012

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The thing about an alternator is that most produce very little till they reach 1200 rpm and then it's normally very low, as little as 10 amps,so allowing for the amount drawn to keep the fuel pump, electronics etc active, to keep the engine running, even if the output is 10A, a half hour  will only put in app 5A at a fast idle speed.

It is OK to use the car to charge the battery but you need to be driving it to increase the revs for it to be of any real use.

Your 110A alternator is more than adequate to charge a battery if driven, but at idle speeds they are designed to produce just enough to keep things going to improve economy and reduce emissions,,in the worst case scenario it is possible to flatten s battery if left at idle for a long period.

The other factor is the increased engine wear,carbon build up and degradation of the oil when a diesel engine is idling, they are most efficient when working hard.I have seen studies that indicate that 1/2 an hour at idle speed causes twice as much wear as 1 hour at 60 MPH on the motorway.

I'm not dismissing the concept but just trying to highlight the pitfalls of just doing it at idle speed.

Saxo1

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