Ideal electrical set up???

[v-lux]

Out of interest, what average amount of hours sunlight are you basing your solar figures upon? And are you taking into account any shadows that may be cast across a panel as this has a drastic effect on the output?

Also, are they assuming that you'll be getting 10A from the panels based on the capability of the charge controller?

[v-lux]

Oh, and re the alternator load. 50A wouldn't be required for very long, the amperage would drop away fairly quickly after the battery has absorbed a chunk. If run quite flat it'll suck it up fast to begin with, but would level off.

Not all too good for a diesel to stand idling either (even though we all do it).

[trentjim]

the panel outputs are based on seasonal efficiency figures so are based on "average" days obviously if its clear blue skies for 16 hours the output will be higher... rainy day and output will be lower.
charge input is nowt to do with the 10Amp rating of the charger controller - thats a maximum, and would allow the system to be expanded by one more panel...the charge input used is based upon expected real world seasonal output of the panels.
James

[trentjim]

Oh, and re the alternator load. 50A wouldn't be required for very long.

i thought the purpose of the stirling charger wwas to keep the alternator current high

[v-lux]

Not necessarily, the current depends on the battery's state of charge.

The more important thing the sterlings do is to amplify the domestic battery circuit. It monitors the voltage at the battery (not the unit output) and makes sure that the voltage is 14.4v (depends on your type of battery as to what the optimum voltage is in fact) which makes sure that it's getting the best charge possible. Amps without voltage isn't going to be much help.

Granted, if the battery is heavily discharged they will whack in as much as the alternator can deliver.

[trentjim]

Trying to figure the cost of charging with an alternator... this is what i've got

Idling consumption of a merc sprinter van
2.2 4 cyl AC on: 0.86 Litres per hour
2.2 4 cyl AC off: 0.49 Litres per hour

i'snt an aircon fuse usually 10A, so lets guess the aircon load at 8A.
8a uses 0.37liters of fuel per hour over idle - assuming a linear ratio - 50A will use 2.31 litres per hour + base idle of .49 litres per hour gives me
2.8 Litres per hour to charge a battery with an idling car @50A

or to look at it another way to put 100Ah back into a battery takes 5.6litres (2 hours)
if we call diesel £1.40 per litre then it costs £7.84 to put 100 Ah into a battery by idling.

from a different perspective..
(via wikipedia) a 200 W electrical load can produce a 0.4 km/L (0.94 mpg) reduction in efficiency on the FTP 75 cycle test... 200w = 16.7A therefore 0.06 loss of MPG per amp or just shy of 3 mpg cost of charging @50A while driving

2 hours at 40mph is 80 miles... at 30mpg this costs £17 -3mpg = £18.66
so using these figures it costs £1.66 to put the 100Ah back when driving

so between £1.66 and £7.84 to restore 100Ah with the alternator

I know in reality the charging ampage will be lower and the charge time longer - which means that thse figures are ballpark minima.

This was the best i could do this evening - very hard to find figures I could use, so if anyone knows a better source of the same kind of info or can pop the fuel line in a pop bottle or something next time they are charging at idle we could tighten these rough figures up

[California Dreamin]

Are you like some time and motion guru....or perhaps a top city analist....one of those financial forecasters?

Wow....just how relivant or 'real world' any of this is.....

Perhaps needs some more figures to quantify?




Martin

[trentjim]

Yeah, it gets worse,
I figured on the way in this morning that I might have the sprinters figures completely wrong, as I dont know for sure if the Air Con compressor is electrical or belt driven (IIRC the Air con on my old MGF was belt driven off the alternator pulley).
if financial forcasters based their maths on "evidence" as shaky as I used above then no wonder they got us into the state we are in!
I'm content with "about £2" to restore 100Ah until I know otherwise

[Cableguy]

Sorry for butting in:-)
I'm looking to upgrade my system having allowed my leisure batt to go to 0 volts!
I'm running a cd,DVD, tv and big amp off mIne. We never hook up.
I've been following some recent threads on sterling chargers.
Whats the advantage of a battery to battery charger, over a more conventional alternator charger?

[trentjim]

dont worry about butting in.... as long as once you decide whats ideal that you post back and let us know....
re stirling battery to battery you might as well start by getting it direct from the horses mouth http://www.sterling-power.com/products-battbatt.htm

[wragster]

Brilliant informative thread guys, but now i've got a headache reading through all those figures!

[ghost123uk]

I like Jim's figures,

I am afraid I too am the kind of person who "likes to know"

[trentjim]

Im now on the gas vs diesel for heating sums...
autogas vs propane and refillable vs exchangable vs fitted bottles.
I thought that a modified autogas tank with an adapted/modified pick up tube would be possible - but the £100 or so it might save aint worth the effort so I think that an 11Kg Gaslow bottle with remote filling kit wins!... just filling time until I actually GET a bloody van and put the plans into action!

[ghost123uk]

just filling time until I actually GET a bloody van and put the plans into action!

~~~~~~~~~~~~~~~~~
The following is non VW =


How about this to while away the hours =

Imagine a stationary petrol engine running on LPG and driving a generator.
The LPG could be from a Propane tank as used in places where there are no gas mains.
Now imagine the same engine but running on gas from the main gas supply.

Which works out cheaper ?

Answers on a postcard...

[trentjim]

Ok,
so the LPG tank is capable of supplying liquid gas (with a little fettling) whereas the mains gas arrives as vapour and would require compressing and cooling to liquefy it before it could be used by the engine....
we therefore need to work out the cheapest way of powering the compression/chiller unit before we can attempt a solution to the initial problem