peterriley2
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| posted on 18/6/06 at 08:54 AM |
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working out wattages- need help please
hello!
im in the designing process of making a teardrop caravan for the back of the locost, and in need to fit into the 'eco' theme of the course,
im going to fit solar panels to the top of it. as i will be using power at night when there is no light i plan to store it in a motorbike battery (or
if fund allow an aeroplane battery). this is mainly because it needs to be as light as possible, as im going bec. ive been trawling through ebay for
flexible solar panels, but i cannot work out what kind of wattage i need. as i put it needs to charge the battery, run a small air conditioning
unit/heating unit, run a 15" lcd tv, and charge my laptop, maybe whilst im using it. i shouldnt be using both the tv and laptop at the same time,
so that should cut down the power used at one time. i would only need the tv for at most a few hours each night, and probably a similar time for the
laptop (lets hope i dont get a rainy day when i go away).
id like anyone who knows their electricicals (or solar panels) to tell me how i can work out how to work out if it will work !?! i could also do with
some help on what inverters i need to change the power from 12v motorcycle.
so what do you think- would it work and could i do it without spending crazy amounts of money? any input would be greatly appreciated!!
pic if anyones interested: (hopefully will work)
 
Rescued attachment cravan prnt screen.jpg
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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peterriley2
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| posted on 18/6/06 at 08:58 AM |
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try again:
 
Rescued attachment trailer prnt scrn.jpg
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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DIY Si
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| posted on 18/6/06 at 09:12 AM |
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Whilst I don't know a great deal about solar panels, If you planning on going some distance with it, could you not charge the battery, or a
small bank of batteries from the engine? Would it be poss to fit a bigger (car?) alternator and go this route? This should be enough to last for a day
or two.
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k33ts
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| posted on 18/6/06 at 09:13 AM |
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why dont you upgrade the battery in the tow car and use that and its got a built in charger 
tukcustoms.com
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nitram38
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| posted on 18/6/06 at 09:39 AM |
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On campers you can have a spare battery and a relay that will only charge when your alternator reaches a certain voltage. (go to your local
camping/caravan shop).
You may have to uprate your alternator though.
Solar panels would have to be very large to charge your battery, especially if you are going to drain it daily.
Click here
for 175W panel cost!
Ever thought of wind turbine ?
You could even charge it on the move!
Combined with the alternator method it should be good.
Why do you need inverters?
Most of your kit can be run from 12v (with voltage converters) and again inverters can be expensive and introduce more power losses to your
problem.
[Edited on 18/6/2006 by nitram38]
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RazMan
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| posted on 18/6/06 at 09:55 AM |
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I wouldn't even consider ac invertors as they are usually very inefficient. If you use 12V equipment it will be much easier. You can convert 12V
to higher or lower dc voltages by using dc/dc convertors if required.
As previously mentioned, make max use of your tow car's electrical charging system as it is already available to you.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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joneh
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| posted on 18/6/06 at 10:08 AM |
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You'll need a poo load of panels and a bigger battery to run your TV / Laptop off it for a reasonable time.
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peterriley2
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| posted on 18/6/06 at 10:26 AM |
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i wasnt going to use the car alternator as im using a bike battery in that, and i thought that it has to work pretty hard anyway, without the power
being used elsewhere as well. i was looking at some 80w solar panels, but do you think thats definately not going to cut it? that battery relay
alternator cut off thingy nitram said, where could i get one/how would i make one?
the problem i see with using the car alternator is that i may stay in one place for a few days, and i wouldnt be getting any power in that time. a
turbines a good alternative but i didnt want to compromise the looks, and make it look a little like a hippy wagon(lol).
i didnt really want a bank of batteries as im trying to keep the whole caravan under 100kg's, and batteries would take up quite a portion of
that, not including the space that they would take up......
thanks for the replies, if anyone has any more dont hesitate to put them on, i want to have a lot to consider!!
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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DIY Si
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| posted on 18/6/06 at 10:30 AM |
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I think you'd be better off having a car alternator and a big car battery in the tow car. If/when you take the caravan you could have a
removable boot box with an extra battery set up in it. This could then give you the extra batteries, but keep the weight down in the caravan. Or put a
removable tray in the bottom of the caravan. This could be the same thing so you have a choice of where to put it. Whilst it may add a little weight,
it'll be nice and low, so should aid stability a bit too.
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omega 24 v6
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| posted on 18/6/06 at 10:31 AM |
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For solar panel info and a calculator try HERE
Also as the others said, you could split charge the battery from the tow car using a self switching relay, that does not require connections to the
alternator as it senses the higher voltage when the alternator is charging.
LINKY
The other thing I have used in the past is a battery cut out regulator which allows you to run the battery down to a preset voltage. It then cuts out
and a switch resets it and allows you to start the vehicle. I've only used it on 24volt vehicle but I assume a 12volt version is available.
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nitram38
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| posted on 18/6/06 at 11:33 AM |
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quote:
Originally posted by peterriley2
i wasnt going to use the car alternator as im using a bike battery in that, and i thought that it has to work pretty hard anyway, without the power
being used elsewhere as well. i was looking at some 80w solar panels, but do you think thats definately not going to cut it? that battery relay
alternator cut off thingy nitram said, where could i get one/how would i make one?
the problem i see with using the car alternator is that i may stay in one place for a few days, and i wouldnt be getting any power in that time. a
turbines a good alternative but i didnt want to compromise the looks, and make it look a little like a hippy wagon(lol).
i didnt really want a bank of batteries as im trying to keep the whole caravan under 100kg's, and batteries would take up quite a portion of
that, not including the space that they would take up......
thanks for the replies, if anyone has any more dont hesitate to put them on, i want to have a lot to consider!!
You cannee change the laws of physics Captain!
This is one of the problems that all designers face and one of the reasons we are not yet using battery cars.
Work out the current draw you require and over what time period, then work out what size battery you need.
A 200Ah battery will provide 1A for 200 hrs or 200A for one hour (in reality this is a guide value as batteries have lots of strange properties that
affect these calculations)
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RazMan
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| posted on 18/6/06 at 12:35 PM |
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It might be worth looking at the lighter racing batteries - I was amazed at the small size of my Oddysey battery which is big enough to crank over a 7
litre V8!
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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trogdor
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| posted on 18/6/06 at 02:05 PM |
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solar panels are very inefficent, even the best ones only manage at best 20% efficency. so as people are saying u would need a lot of them to power ur
laptop or tv etc.
Also u have to take into account that it may not be sunny! this is england after all. Solar panels may work, but u will deffo want another option that
provides power, i would imagine its best to have serveral ways of powering ur caravan, maybe even setting it up so u can plug it in, like normal vans
at camping sites. as well as solar panels and wind turbines.
As people have mentioned upgrading ur BEC's charging system is probally the easiest way of doing it.
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peterriley2
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| posted on 18/6/06 at 05:44 PM |
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ive just done the solar calculator, putting in-
19" tv for 2 hours
portable heater for 2 hours
stereofor 2 hours (thought it might be close to the laptop)
and what it advised me was this
im sure this cant be right can it?
anyway thaks for the links and stuff, ill fully investigate when i get the time, hopefully later tonight. where would i find oddysey batteries, and
how much do they cost?
i didnt want to plug it in, as id like to take it off road to places where there are no plugs handy, so want it to be prettymuch self sustaining.
the other option is to have a generator, which could be home made with an alternator. this is not particularly eco, but may solve my problem. i could
do this with a small engine, attaching an alternator. this isnt particularly light however, and i dont like the way that energy could be wasted if the
generator is too big and over powered my appliances. this is also coupled by the cost of petrol.
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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peterriley2
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| posted on 18/6/06 at 05:58 PM |
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ive just been looking at some oddysey batteries like
this, and id just like to know how much better this would be than a normal bike battery, eg r1 or fireblade, how much lighter would it be, and
would it store more or less charge? on its own fully charged, how long would this battery run a tv or laptop for, on average would you guess? its just
that i dont have a clue- i dont know if it would be 5 minutes or 10 hours. cheers,
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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trogdor
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| posted on 18/6/06 at 06:24 PM |
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that can't be right, that solar charger would never be able to power ur electrical items for very long. an electric heater is the main drain, a
laptop wouldn't take much to power it, not sure about the LCD tv tho.
to be honest i was expecting u to need to have pretty much the whole roof in solar panels to charge the battery powering ur caravan.
my housemate is an electrical engineer, or in the process of becoming one! so will ask him when i next see him for u if u like?
a generator would be a waste of time i would think, if u go down that route u may as well set the BEC up to be the generator.
not sure how long a fully charged battery would last, if its just the laptop, it would last for ages, and the tv would prob be ok too, especially if u
got a 12 volt one, i am assuming u can get 12v lcd's? the heater will be the main power eater, if its an average one, say a 2kilowatt heater, it
will exhaust a battery pretty quickly.
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peterriley2
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| posted on 18/6/06 at 06:31 PM |
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that would be great if you could ask your mate, and what do you mean when you say it will drain pretty quickly- around how much time? i wasnt going to
use the car as the generator as i can guess that the petrol would be a great deal more than a small generator unit. as the heater will take the most
power, ill look at different ways to go about it- i know there are diesel units, but dont really fancy carbon dioxide poisoning!
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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DIY Si
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| posted on 18/6/06 at 07:00 PM |
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Would you really need a heater? If you're planning on going off into the wilderness, can't you just take a lighter and find some dead wood
lying about? Or just buy a bigger sleeping bag? Another option could be to have solar water heaters in the roof and use hot water to heat it up. A bit
like central heating. Or if you're feeling really brave, you could use the bike engine to provide hot water heating. Ie pull up some where,
attach some houses to the back of the bec and transfer heat to the caravan. Kind of like using the caravan as a radiator. Might need a fair bit of
water though.
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russbost
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| posted on 18/6/06 at 07:03 PM |
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The laptop is no great problem, the tv is a bigger current draw, but still not impossible - but heating??? No chance, just think about it even a
tiddly 1kw heater (pretty useless given the losses from a caravan) at 12v would be drawing over 80 amps!!!! (W = Volts x Amps)
If you rethink & use portable throw away gaz cylinders - cheap & light then the rest of it could besolar powered without too much problem.
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Peteff
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| posted on 18/6/06 at 07:40 PM |
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Trust me you won't need a heater in a caravan that size, just eat a couple of cans of beans and you'll soon warm it up . Air
conditioning will be an unnecessary luxury as well just put a vent in the door, I thought you were aiming for an all up weight of 100kg? You'll
need a V8 to get it moving with all the stuff you're thinking of taking along there. Get all the stuff you are thinking of taking, put it in a
box and weigh it, bear in mind that you can tow 50% of the vehicles kerbside weight with an unbraked trailer. Unless you are fitting a 1500 Goldwing
engine you are asking for too much from the engine, you will never set off if you stop on a hill. I don't know if you've driven or towed
but you'll realise what you are asking is not feasible when you pull the clutch out of the engine, towing needs torque even for the lightweight
you are aiming for.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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JoelP
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| posted on 18/6/06 at 07:50 PM |
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i burnt my clutch out today, and all i asked of it was to drive onto a transporter last week (you have no idea how much i had to slip to clutch to
make it move up such a steep slope!) and set off in third today, when my gearlever broke. Setting of with a total of about 700kgs (lets say 450 in the
car, 100 in the trailer and 150 in the passangers) would wipe it out within weeks of town driving.
As far as i can tell from the techincal specification on that solar panel, it only provides 2w at 15volts, hence you need 1000 of them to power the
2kw fan heater. A computer is about 400w isnt it? Memory takes a hell of a lot of power to maintain. That too is asking a lot from a battery.
I would strongly recommend using the normal bike generator with a heavy duty car battery, and a small odyssey as a backup, or the other way round. And
dont forget the jump leads! In fact yeah, the other way round. Car has an odyssey, and a removable heavyduty battery in the passanger footwell. 
[Edited on 18/6/06 by JoelP]
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omega 24 v6
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| posted on 18/6/06 at 08:48 PM |
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quote:
As far as i can tell from the techincal specification on that solar panel, it only provides 2w at 15volts
Here here that pissing little thing is the one I use to keep my omega battery topped up.
I have seen 2 off solars on the roof of a commercial vehicle that are about 3 feet by 1 1/2 feet and are used to keep 2 gel batteries fully charged.
The application for the batteries is similar to a tail lift power pack (starter motor turning a hydraulic pump). Said motor probably runs on full load
for 4 mins a day only. I doubt you'd get anywhere near enough panel on the van to be a stand alone power supply.
Buy a small generator (750w output should do you) and use a voltage spike device on the tv and laptop.
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caber
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| posted on 18/6/06 at 10:32 PM |
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I am afraid that solar is not the way to go. Check out yacht chandlers for small wind turbines they are a better bet. While travelling you need to set
up some mechanical charging, if you are not keen to use the engine alternator and a split charge system how about rigging up a drive off the caravan
hub to a car alternator? A good source of compact high power batteries are the carryable boost systems though these are not good for deep
discharge.
Heating is an issue depending on where yo plan to go camping. Insulation is the first starting point 75mm of styrofoam on floors walls and ceilings is
a good start as long as the exterior shell is very waterproof, good windows, not necesarily caravan ones are important. Cheapest heatsource is a gas
cooker and camping gaz bottle stored outside! and as has been said a good sleeping bag is a good thing, though if you are taking a friend get a double
bag
Caber
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caber
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| posted on 18/6/06 at 10:32 PM |
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I am afraid that solar is not the way to go. Check out yacht chandlers for small wind turbines they are a better bet. While travelling you need to set
up some mechanical charging, if you are not keen to use the engine alternator and a split charge system how about rigging up a drive off the caravan
hub to a car alternator? A good source of compact high power batteries are the carryable boost systems though these are not good for deep
discharge.
Heating is an issue depending on where yo plan to go camping. Insulation is the first starting point 75mm of styrofoam on floors walls and ceilings is
a good start as long as the exterior shell is very waterproof, good windows, not necesarily caravan ones are important. Cheapest heatsource is a gas
cooker and camping gaz bottle stored outside! and as has been said a good sleeping bag is a good thing, though if you are taking a friend get a double
bag
Caber
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peterriley2
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| posted on 18/6/06 at 10:32 PM |
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okay, this has all been a great help to get me thinking seriously, ive know realised that with the laptop i can get a tv reciever, and not bother with
a tv at all. the laptop gives out heat which i hadnt thought of, and im now thinking that it would be a good idea to use the excess heat from the hob,
by somehow making a cover for pots that go on it, moving the heat into the main compartment with a small pc fan. this would mean that the wasted heat
from cooking is used, and also i could use it as a simple heater when weather gets cold. so, back to my question, as the laptop is really going to be
the only electrical item (apart from the fan and anything else i think of), how long would i be able to use the laptop for, from a full chatge of a
motorcycle battery,-standard or odyssey? i may still use a small solar panel, just to trickle charge the battery whilst at site. cheers,
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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