Solar panel costs versus running the engine

[trevskoda]

Engine

1) Lets assume that your engine will consume 5 litres of fuel ticking over for one hour, so approx £5.50 per hour.
2) Also assuming you are using a normal split charge relay fused at 20 amps, so approx 19 amps per hour of charge.
3) I am not adding costs for wear on the engine.

The cost is about 29 pence per amp hour of charge.

Solar

1) Lets assume you are using a 150w mono panel with an MPPT charge controller.
2) You fit the Solar kit yourself so the cost is approx £160.

After you have consumed 550 amp hours of charge you will have broke even.

How long will it take in the UK to get 550Ah of charge from a 150W panel?

This really is a "how long is a piece of string" question.

Here is an approximate calculation

Over a lovely sunny summers day, your panel could easily be expected provide 40Ah of charge to your batteries (if your batteries needed that much charging)

150w panel / charge voltage of 14.4v = 10.41A Max
Take 75% of this to allow for loss = @ 7.5A
1 hour at 80% = 6Ah
2 hours at 70% = 10.5Ah
2 hours at 60% = 9Ah
2 hours at 50% = 7.5Ah
2 hours at 40% = 6Ah
Other daylight = 1Ah
(I know these numbers are guess work for our pedantic members)

So 14 good summer days of charge would produce 550Ah of charge.

Some folk know there stuff and heres the proof,o ye of little faith ehu for you.:bow:

 

[maingate]

Batt to batt charger is infintely better than any generator, and takes up no space, and MOST IMPORTANTLY is completely silent!!!!

They are not suitable for some motorhome charging systems and can cause problems.

 

[channa]

I would also suggest that the point about running a Diesel engine on Tick over for an hour or even two while it say charges any batteries & puts a bit of warmth in the cab on an occasional basis between periods of Decent Road work and it causing Engine Damage is Arguable.
I have done it on The Nest for about 40 min on the some cold mornings with the heater on while I square away, I use to do it ALMOST DAILY on my Boat engine of 20 years. Taxi Drivers, Ice cream vans at Events, AA/RAC/GREEN FLAG type Recovery vehicles, Crain's, Police Vehicles, Road Repair Crews, Motorway Safety Cushion Trucks, ALL run there vehicles for absolutely HOURS on absolute minimal loads on a REGULAR basis.
Maybe there is a case on the more Modern Performance Diesel engines.

Just because these people do it does not make it the correct thing to do. Sometimes the job necessitates bad practise

Have a read.

Diesel Engine Myths

Channa

 

[2cv]

Can you enlighten me on your quick charge system please,i am very disappointed with my lb charging as my van has Euro 5 engine with smart alternator. bazz

"Bentley use an EOS control panel made by EMP of Totton Southampton, they also supplied Auto cruise vehicles with control panels.
This unit has the features of charging the leisure battery once full it will divert charge to the vehicle battery.
self setting fuses
solar Ready will regulate a solar panel up to 100watts. current charging reading.
A management button which will inform you of the hours available for a given power drain.
Water levels fresh and waste
reverse polarity warning
shuts down water pump when tank at minimum
and of course the emergency start procedure as soon as the engine starts it reverts back to normal.
quite a clever piece of kit."
When the battery failed I almost went for the solar panel, the control being already part of the EOS, but decided to try first with the new battery. I have found no problem with the system since, and always have the engine as a back up should a problem ever arise.

 

[chrismilo]

Batt to batt charger is infintely better than any generator, and takes up no space, and MOST IMPORTANTLY is completely silent!!!!

Yes would second that cheaper than a Genny that's my next plan a 60 batt to batt charger probably a 60amp sterling as alternator is only 75amp could change alternator for stronger an get 120 amp or even 180amp batt to batt charger still cheaper than a genny and silent they charge 5 to 20 times quicker than running engine so if stuck 10 mins of idle engine would give the batteries a good enough boost.

 

[trevskoda]

Yes would second that cheaper than a Genny that's my next plan a 60 batt to batt charger probably a 60amp sterling as alternator is only 75amp could change alternator for stronger an get 120 amp or even 180amp batt to batt charger still cheaper than a genny and silent they charge 5 to 20 times quicker than running engine so if stuck 10 mins of idle engine would give the batteries a good enough boost.

Problem here is the starter will pull so much load you will have to drive 20miles to recover,where as solar is a win win .

 

[Admin1]

They are not suitable for some motorhome charging systems and can cause problems.

All motorhome charging systems generally need to be adapted to fit B2B chargers. The last one I fitted required modification to the PCB in the habitation control unit.

 

[Deleted member 36]

Depends!
Just after we purchased our present M/H, the Stirling Battery to Battery charger went belly up
It ruined the two new leisure batteries
I removed it ,and it sits in my garage. It cost two new batteries!
Luckily, the previous owner coughed up!:dance:

 

[Nesting Zombie]

Engine

1) Lets assume that your engine will consume 5 litres of fuel ticking over for one hour, so approx £5.50 per hour.
2) Also assuming you are using a normal split charge relay fused at 20 amps, so approx 19 amps per hour of charge.
3) I am not adding costs for wear on the engine.

The cost is about 29 pence per amp hour of charge.

Solar

1) Lets assume you are using a 150w mono panel with an MPPT charge controller.
2) You fit the Solar kit yourself so the cost is approx £160.

After you have consumed 550 amp hours of charge you will have broke even.

How long will it take in the UK to get 550Ah of charge from a 150W panel?

This really is a "how long is a piece of string" question.

Here is an approximate calculation

Over a lovely sunny summers day, your panel could easily be expected provide 40Ah of charge to your batteries (if your batteries needed that much charging)

150w panel / charge voltage of 14.4v = 10.41A Max
Take 75% of this to allow for loss = @ 7.5A
1 hour at 80% = 6Ah
2 hours at 70% = 10.5Ah
2 hours at 60% = 9Ah
2 hours at 50% = 7.5Ah
2 hours at 40% = 6Ah
Other daylight = 1Ah
(I know these numbers are guess work for our pedantic members)

So 14 good summer days of charge would produce 550Ah of charge.

Hi ya,
With respect, & as I tried outlining in I think it was one of the first reply's, There just isn't enough information in the op to make a fair comparison to the question. Even you had to make Several assumption's in your post. We don't even know the size or fuel type of the engine to make a comparison too !
change the figures above to the data for say a 120/150 amp Balmar Alternator that gives out some 90/110 amp output at tick over, (as I had on my Boat), Lets assume we only have to put some 30 amp BACK into the used leisure battery & the Fuel used by the engine at idel down to approx. 2.5Lt per hr, (as mine does), and compare that with the panel & the return it yields in the 8 months from say October to May very different results. we can all make the figures say completely different things depending on the variables used !.

Of course I agree & have suggested that a Well Matched solar installation can be BRILLIANT. BUT SO many variables come into play to give a usefull & Fair answer on such a sparse & brief OP for comparison of Solar vs Engine charge time
Kinda Thing. Just sayin !

 

[Admin1]

I have now installed more than 20 Ctek D250S units, 7 of these where installed with the optional Smart Pass unit. The only issues I have had are with solar panels that output more than 23 volts, voltage drops due to motorhome manufactures installing under size cables (for length of cable) and finding the original dual charge relay to disable it.

 

[Admin1]

Hi ya,
With respect, & as I tried outlining in I think it was one of the first reply's, There just isn't enough information in the op to make a fair comparison to the question. Even you had to make Several assumption's in your post. We don't even know the size or fuel type of the engine to make a comparison too !

Yes they are based on figures researched from the internet.

change the figures above to the data for say a 120/150 amp Balmar Alternator that gives out some 90/110 amp output at tick over, (as I had on my Boat)

This is not really relevant as nearly all motorhome dual charging systems are fused at 20 amps.

Lets assume we only have to put some 30 amp BACK into the used leisure battery & the Fuel used by the engine at idel down to approx. 2.5Lt per hr, (as mine does), and compare that with a 10 watt poly panel & the return it yields in the 8 months from say October to May very different results. we can all make the figures say completely different things depending on the variables used !.

I looked on the internet for idle fuel usage for 2 litre diesel engines fitted in vans. There is quite a bit of information based on real world usage. For instance, there are people reporting the fuel usage for motorway maintenance vehicles that idle for 12 hours to keep the safety lights running. The reported usage was between 3 and 8 litres per hour.

I use my engine to charge my batteries as I have an 80 amp B2B setup. I would guess that I have run it about 10 times for about 1 hour on idle over 18 months. I am about to fit my third replacement EGR valve. I did not factor in the damage cause to modern diesel engine caused by idling.

 

[Byronic]

An IC engine diesel or petrol of about 2.5L capacity will produce more than 5kW of power at idle speed. Does using this amount of power to turn over an alternator putting out less than 0.5kW of electrical energy to charge a battery make sense. I will say no more and flounce off stage right.

 

[rockape]

We were parked up in one place in Scotland for 4 days last month (a campsite), by the last day the batteries were getting a little low, and we don't do ehu, so I had the engine idling for 20 mins. We were about 50yds from the nearest other van, but it's a little like walking around the house when you've got in late, everything seems very loud.

I was very self conscious doing it and wouldn't have done it normally.

I'd definitely get solar panels, even if they are fairly useless in winter.


Going off topic, but same site a few days earlier, and on a site with about 100 pitches, all with ehu, and about 4 vans present, some guy parks about 3ft from us, totally obscuring our view out of the see window, cos he had a short hook-up lead. Grrrrrrrr!!

And I guess you had a short fuse??

 

[Nesting Zombie]

Yep don't doubt most of what you have said, in fact nice post & a Really good system your on about.

But What makes you think its a Motorhome the OP is on about ?, Why Base it on a 2.0 ltr engine ?, Does it run on Cooking Oil at 40p a ltr ?. Why base HIS charging system on a 20amp, When you have got a 80amp ?.

He just gave vary sparse & random parameter's using loose words like 'Engine Hrs' 'Solar' & 'OFF GRID' & I'm simply trying to point out that in my view its not enough information to base a fair comparison on.

it seems I cant get the point I'm trying to make over on the Key Board. So I will Bow out & hang what's left of my Head in shame. Certainly Not meant to be an argumentative post.

 

[hextal]

And I guess you had a short fuse??

Just moved the van several pitches further along.

 

[Nesting Zombie]

An IC engine diesel or petrol of about 2.5L capacity will produce more than 5kW of power at idle speed. Does using this amount of power to turn over an alternator putting out less than 0.5kW of electrical energy to charge a battery make sense. I will say no more and flounce off stage right.

Nope, Of course it doesn't. It just might be more convenient at times. Like using a 230v inverter of a 12v supply, Really in officiant but can be useful and convenient at times. The Mad things some people do.

 

[Admin1]

Yep don't doubt most of what you have said, in fact nice post & a Really good system your on about.

But What makes you think its a Motorhome the OP is on about ?, Why Base it on a 2.0 ltr engine ?, Does it run on Cooking Oil at 40p a ltr ?. Why base HIS charging system on a 20amp, When you have got a 80amp ?.

He just gave vary sparse & random parameter's using loose words like 'Engine Hrs' 'Solar' & 'OFF GRID' & I'm simply trying to point out that in my view its not enough information to base a fair comparison on.

it seems I cant get the point I'm trying to make over on the Key Board. So I will Bow out & hang what's left of my Head in shame. Certainly Not meant to be an argumentative post.

It is unfortunately a question that is almost impossible to answer, even with all the information.

I did not think that you were being argumentative and you should never bow out in shame. The points that you put are correct.

What if it was a really fuel efficient engine that only used 1 litre pre hour?
What if he is running on a cheaper fuel?
What if the weather was awful every time he goes camping?
What if he only have one 80Ah battery?
What if he only uses 5Ah per day?

Etc

I like debate, it helps us all learn and evolve.

 

[hairydog]

2) Also assuming you are using a normal split charge relay fused at 20 amps, so approx 19 amps per hour of charge.

That assumption is very wide of the mark. The reason that a lot of split charge relays have 20A fuses is that that is far more than you can expect to see.

The alternator adjusts its output to match the starter battery'd needs. What goes down the split charge wire is very much an also-ran. If you put an ammeter into the circuit, I would excet you would see significantly less than 10A after the first few minutes. Possibly little more than 5A.

I can't test this for myself to give real-world figures because I use a battery to battery charger, which charges the aux batteries at far higher rates, depending on their state of charge.

Perhaps someone with a split charge relay and a suitable ammeter could do a real world test? The easiest way is with a clamp ammeter, but ones that measure DC are not all that common or cheap - but a normal multimeter will probably do for the job if the current is as low as I suspect.

 

[Admin1]

That assumption is very wide of the mark. The reason that a lot of split charge relays have 20A fuses is that that is far more than you can expect to see.

The alternator adjusts its output to match the starter battery'd needs. What goes down the split charge wire is very much an also-ran. If you put an ammeter into the circuit, I would excet you would see significantly less than 10A after the first few minutes. Possibly little more than 5A.

I can't test this for myself to give real-world figures because I use a battery to battery charger, which charges the aux batteries at far higher rates, depending on their state of charge.

Perhaps someone with a split charge relay and a suitable ammeter could do a real world test? The easiest way is with a clamp ammeter, but ones that measure DC are not all that common or cheap - but a normal multimeter will probably do for the job if the current is as low as I suspect.

I agree, it is unlikely that you will get a 19A charge, however I was working on the theoretical maximum of the circuit.

You would need to have a Aux battery at under 50% charge to get the full current flow.

 

[Nesting Zombie]

I think that its a case of ' GIVE MORE INFORMATION or parameter's in a question' even if its for the purposes of debate.

I will say though, A LOT of GREAT ideas & in fact Major Breakthrough's have happened in the 'Brain Storming' & Mad idea Moments & Debate we use to have from my years in Research & Development aimed at the marine environment.