Generating power after engine failure.

[Pretty Funked Up]

I would have thought that running the rad. fan constantly would be a must if running a vehicle in this manner?

 

not really its no worse than a traffic jam on a hot sunny day. It should cut in and out as needed. I would start to worry if it stayed on permanently though.

If its a works van then what the hey

Edited November 22, 2011 by Pretty Funked Up

[Guest]

not really its no worse than a traffic jam on a hot sunny day. It should cut in and out as needed. I would start to worry if it stayed on permanently though.

If its a works van then what the hey

Well yes,I was assuming it was a private vehicle . I would have thought overheating might be a worry though if fast idling for say two hours without movement? Maybe not.

[bizzard]

Whats wrong with that old SR2,they don't usually pack up just like that.

[Higgs]

Go into camping mode, reduce your power consumption, stick with the genny. If possible.

[ditchcrawler]

Given the distance between the Daihastu and the boat you are looking at a 70ft round trip - call it 25metres by the time you've got a bit of dangle in there.

You also need to consider that the alternator puts out 70A.

So with these as the assumptions the Antares cable voltage drop calculator says you are going to need a pretty serious cable, for example 25sqmm will have a voltage drop of about 1.3v, which is about as high as you should go on a charging circuit from a vehicle alternator. Ideally you want the voltage drop to be at the most half of that, and that means 50sqmm cable or more - and that gets "pigging" on the expensive scale.

 

An alternative (and admittedly not a nice one) is to move the batteries to the car on rotation and use a "more normal" set of jump leads.

Well after all the threads there have been on battery charging and the danger of volt drop, thank goodness for a sensible reply.

[GUMPY]

Why the stupid sarcasm? My battery charger has leads that are less than 3mm thick. They are capable of charging at 20 amps. OK they are shorter but losses due to cable length are not that great.

Its not stupid sarcasm I just cant belive that after all the threads on here about voltage drop it hasn't sunk in to some peoples brain cell.

 

Bob18 has it about right, although for me more then 0.1v drop is too much hence the reason I have 50sqmm cable on my 24volt alternator and its about 1.5m to the batteries.

 

For the OP I would stay with the generator and the charger it will save you ruining your truck as they dont like running at tick-over or just above for long periods. The same reason that I always use a genset to charge my batteries when the boat is not moving never the main engine.

[AlanH]

I just cant belive that after all the threads on here about voltage drop it hasn't sunk in to some peoples brain cell.

 

More stupid sarcasm! Why do you have to be insulting?

[Grace and Favour]

Is running the Daihatsu 2.8 Diesel (at 2,000 rpm) going to be that much cheaper than running your nondescript petrol genny ? (and that's not taking into account any security / safety issues you may have with the car )

[AlanH]

Given the distance between the Daihastu and the boat you are looking at a 70ft round trip - call it 25metres by the time you've got a bit of dangle in there.

You also need to consider that the alternator puts out 70A.

So with these as the assumptions the Antares cable voltage drop calculator says you are going to need a pretty serious cable, for example 25sqmm will have a voltage drop of about 1.3v, which is about as high as you should go on a charging circuit from a vehicle alternator. Ideally you want the voltage drop to be at the most half of that, and that means 50sqmm cable or more - and that gets "pigging" on the expensive scale.

 

An alternative (and admittedly not a nice one) is to move the batteries to the car on rotation and use a "more normal" set of jump leads.

I haven't read the previous threads on this subject so perhaps you could help me.

 

What effect would a voltage drop of 1.5v have on the actual charging of the battery? Would it not charge at all? Would it take longer? Would it only partly charge it? Would it damage the battery?

 

I genuinely don't know and as you seem to have the knowledge and are capable of posting without insults I'd be grateful for the help.

[blodger]

I have found unregulated dynamos driven by a lawnmower engine ideal as the volts drop in the cabling makes the voltage useable on a sufficient size battery bank.

 

The orginal OP might find it cheaper & more efficient to use his alternator of the SR2 with a lawnmower engine in the interim, depending on the alternator, as with them you often have to up the charging volts with diodes to achieve the amps, etc.

 

ETA you can get a lawnmower engine for free on Freecycle or intercepting at the tip. All you need is a board some bolts, a belt & a switch or two, etc

Edited November 23, 2011 by blodger

[Bob18]

Answering your questions:

Yes.

Yes, lot longer.

But not fully.

Yes, long term the battery life would be reduced.

 

At 1.5v below normal charging voltage you will only get about 65-75% of the maximum charge into the battery. Keeping a battery in this state will reduce its life. It is difficult to predict by how much without knowing a lot about the battery concerned, but a first estimate would be a 10-25% reduction in remaining battery life for every month that this low charging voltage was used.

 

It is not an easy subject, but without knowing a lot about the charging capabilities of your truck, the battery type, and the battery history I can only talk in generalities.

 

Looking at the other replies I think the best one is to get small, cheap inverter - something around the 500-750w will be adequate - put this on your vehicle somewhere and use this to power your mains charger on the boat. (Taking note of the comments about vehicle security and so on). We are of course assuming you are nowhere near a suitable shore supply.

[AlanH]

Answering your questions:

Yes.

Yes, lot longer.

But not fully.

Yes, long term the battery life would be reduced.

 

At 1.5v below normal charging voltage you will only get about 65-75% of the maximum charge into the battery. Keeping a battery in this state will reduce its life. It is difficult to predict by how much without knowing a lot about the battery concerned, but a first estimate would be a 10-25% reduction in remaining battery life for every month that this low charging voltage was used.

 

It is not an easy subject, but without knowing a lot about the charging capabilities of your truck, the battery type, and the battery history I can only talk in generalities.

 

Looking at the other replies I think the best one is to get small, cheap inverter - something around the 500-750w will be adequate - put this on your vehicle somewhere and use this to power your mains charger on the boat. (Taking note of the comments about vehicle security and so on). We are of course assuming you are nowhere near a suitable shore supply.

Thanks.

[Guest]

Its not stupid sarcasm I just cant belive that after all the threads on here about voltage drop it hasn't sunk in to some peoples brain cell.

 

Bob18 has it about right, although for me more then 0.1v drop is too much hence the reason I have 50sqmm cable on my 24volt alternator and its about 1.5m to the batteries.

 

For the OP I would stay with the generator and the charger it will save you ruining your truck as they dont like running at tick-over or just above for long periods. The same reason that I always use a genset to charge my batteries when the boat is not moving never the main engine.

I agree with your paragraphs two and three. I am no expert, but I too can't see the truck taking kindly to running at fast idle for what might be several hours.

 

I am a bit surprised at your first paragraph though. Maybe the person who didn't quite understand the volt drop issue hadn't read other threads on the subject?

Edited November 23, 2011 by Guest

[alan_fincher]

Answering your questions:

Yes.

Yes, lot longer.

But not fully.

Yes, long term the battery life would be reduced.

 

At 1.5v below normal charging voltage you will only get about 65-75% of the maximum charge into the battery. Keeping a battery in this state will reduce its life. It is difficult to predict by how much without knowing a lot about the battery concerned, but a first estimate would be a 10-25% reduction in remaining battery life for every month that this low charging voltage was used.

Thank goodness someone who clearly understands the topic is prepared to type a sensible and well thought out answer!

 

(Well done!)

[Bob18]

(in response to Catweasel's recent post - and to try and help the OP understand)

 

Or the OP just doesn't have the knowledge to understand "voltage drop".

Its a bit of a daunting subject if one has not lived in the hard world of big currents, small voltages and long cables.

When taught at school we are taught "electricity" in a very controlled environment, one which is as near ideal as possible. If your education about electricity stops there then you have only a corner of the picture. What you don't learn are the real "fun" things that happen when you scale up.

 

A few simple things to understand:

Every cable has a resistance, not a lot, but it is measurable.

The longer a cable is the higher the resistance.

The fatter the cable is, the lower the resistance.

 

The result of this is that when you try to draw current through a cable you have a voltage drop. Obviously the longer the cable is, the greater the drop, and the fatter the cable is the lower the drop.

What is less obvious is that the more current you try to draw through a cable the harder it gets, so the higher the voltage drop.

 

The resistance for a given cable type is (more or less) linear with both length and cross section (thickness), so that is easy to calculate - sometimes you will see a cable resistance quoted as so many Ohms per metre (or kilometre). This means you can quite rapidly work out the relative voltage loss for a given bit of wire -twice as long gives twice as much loss.

But for the current things get more complicated - I'm not going to go into the maths just now - its what is called a "square law", which means that if you double the current you multiply the loss by four (the square of two).

 

 

 

 

(This is how fuses work - they are short and thin in comparison to the rest of the wiring, so heat up quickest until they melt, hopefully before the rest of the wiring has got too hot for safety.)

Edited November 23, 2011 by Bob18

[jonathanA]

Do you use the car every day - say for going to/from work ?

 

if so I'd think about taking one battery with you and rigging it up to charge on a 'split charge' basis in the back whilst you drive about. cost a few quid for some reasonable cable say 6MM and a cheap relay (for this purpose). my mitsubishi has a cigar lighter in the boot space which is only live when the ignition is on and I've used this to charge a leisure battey before (cigar lighter to croc clip leads all thats needed). in my case the battery was not heavily discharged so the 10Amp (120W) cigar lighter fuse didn't blow, guess a heavily discharged battery might draw enough current for long enough to blow the fuse (remember the current drops off very quickly)

 

just a thought might save a bit of money on genny petrol - the other obvious thing is to get a diesel genny and run it on red diesel.

[Guest]

(in response to Catweasel's recent post - and to try and help the OP understand)

 

Or the OP just doesn't have the knowledge to understand "voltage drop".

Its a bit of a daunting subject if one has not lived in the hard world of big currents, small voltages and long cables.

When taught at school we are taught "electricity" in a very controlled environment, one which is as near ideal as possible. If your education about electricity stops there then you have only a corner of the picture. What you don't learn are the real "fun" things that happen when you scale up.

 

A few simple things to understand:

Every cable has a resistance, not a lot, but it is measurable.

The longer a cable is the higher the resistance.

The fatter the cable is, the lower the resistance.

 

The result of this is that when you try to draw current through a cable you have a voltage drop. Obviously the longer the cable is, the greater the drop, and the fatter the cable is the lower the drop.

What is less obvious is that the more current you try to draw through a cable the harder it gets, so the higher the voltage drop.

 

The resistance for a given cable type is (more or less) linear with both length and cross section (thickness), so that is easy to calculate - sometimes you will see a cable resistance quoted as so many Ohms per metre (or kilometre). This means you can quite rapidly work out the relative voltage loss for a given bit of wire -twice as long gives twice as much loss.

But for the current things get more complicated - I'm not going to go into the maths just now - its what is called a "square law", which means that if you double the current you multiply the loss by four (the square of two).

 

 

 

 

(This is how fuses work - they are short and thin in comparison to the rest of the wiring, so heat up quickest until they melt, hopefully before the rest of the wiring has got too hot for safety.)

A very useful explanation for people who need information about this important subject. Perhaps the mods. could pin this?

[Amwris]

I hope your car is parked somewhere very secure, if you're planning to leave the engine running whilst unattended.

 

How about fitting a cheap inverter to your car and running a 240v extention lead to your charger?

 

Keith

 

Wow what a lot of input! Thanks.

 

I did think about running an extension from the 240v inverter on the daihatsu (its a camper van) but thought the distance would be more of a problem with ac current rather than dc?

 

incidentaly the vehicle is on private land and very secure.

Cheers

 

Phil

[Bob18]

Phil, a sensible question.

 

To supply your 30A charger you need something like 450watts, which is about 2amps at 230V.

Assuming you use a fairly ordinary "13Amp" extension lead, which is about 1.5sqmm and 10metres long.

The voltage drop is about 0.65V - which is about a quarter of a percent of 230V, not a lot.

 

So, as I said, a sensible question, and I hope you find the answer to be a comfort.

[Amwris]

Phil, a sensible question.

 

To supply your 30A charger you need something like 450watts, which is about 2amps at 230V.

Assuming you use a fairly ordinary "13Amp" extension lead, which is about 1.5sqmm and 10metres long.

The voltage drop is about 0.65V - which is about a quarter of a percent of 230V, not a lot.

 

So, as I said, a sensible question, and I hope you find the answer to be a comfort.

 

 

Cheers for that Bob. I have just tried a small inverter plugged into the fag lighter. It wouldn't have anything to do with feeding the 30 amp charger (small squark followed by the light going out) but is currently running my 240v system and charging my laptop. I will keep popping out and checking engine temp but with the cool weather and a fan kicking in surely that would be ok?

 

Hopefully I'll buy a bigger inverter tomorrow and it should run the 30amp charger (hopefully?)

 

I am currently looking for a replacement engine as the SR2 is very underpowered for a 56ft all steel and the head gasket has gone on it.

 

Cheers Phil

[David Mack]

Given the distance between the Daihastu and the boat you are looking at a 70ft round trip - call it 25metres by the time you've got a bit of dangle in there.

You also need to consider that the alternator puts out 70A.

So with these as the assumptions the Antares cable voltage drop calculator says you are going to need a pretty serious cable, for example 25sqmm will have a voltage drop of about 1.3v, which is about as high as you should go on a charging circuit from a vehicle alternator. Ideally you want the voltage drop to be at the most half of that, and that means 50sqmm cable or more - and that gets "pigging" on the expensive scale.

 

Or to put it another way, Gibbo recomends that to balance the charging and discharge loads on a bank of batteries you should do this:

 

 

rather than this:

 

 

As far as the charging is concerned, using a set of 'jump leads' between the car battery and the boat batteries would be akin to doing this:

 

 

David

[Guest]

Thanks David for posting the first diagram - I now understand what Gibbo has being banging on about...re battery connection.

Edited November 23, 2011 by MJG

[Amwris]

Or to put it another way, Gibbo recomends that to balance the charging and discharge loads on a bank of batteries you should do this:

 

 

rather than this:

 

 

As far as the charging is concerned, using a set of 'jump leads' between the car battery and the boat batteries would be akin to doing this:

 

 

David

 

 

lol thanks!