Battery questions and what do you run?

Cracker This thread is becoming a bit more complicated than it really needs to be. It's not complicated! Watts is a measure of energy used and also of work done. Volts time amps equals watts. Thus a kettle that produces 1200 watts of heat could run at 120 voltrs and draw 10 amps, at 240 volts and draw 5 amps - or 12 volts and draw 100 amps. If run from 12 volts via an inverter it would draw about 115 amps becaue of losses. Where things get a bit complex is that most 240 volt devices are made to run on alternating current, and because of that it is possible to use electric motors that are cheap but extremely inefficient - particularly the so-called induction motors used in most 240 volt fridges, water pumps and fans. As you say many things you might want to use on the road can be obtained in 240 volts versions and run via an inverter (at a loss of 12.5%). But if you try this with a water pump (particularly) you'll find yourself using well over 500 watts to do what you'd achieve with only 100 watts or so at 12 volt/24 volts dc . Fridges intended to run off 240 volts AC use two to three times the energy (watts) of 12/24 volts dc equivalents. By the time you add the 10-15% inverter loss - it's serious amounts of energy - and not practicable in a caravan. One could cewrtainly use 240 volt TV, DVD etc (they use little if any more than 12 volt devices and are much cheaper). Ditto blenders, coffee grinders etc. (Be wary of getting bogged down in the Power Factor thing with AC. Briefly some things like motors and fluros need about 20% more power to be available than they actually use. The extra current sort of rushes back and forward 'filling holes'. Because of this effect you need to use a 20% larger inverter or generator than you might expect - but no extra energy is actually drawn because of it! Best to trust me on this one as you'll otherwise end up knowing more about it than most people have in mind - let alone need to know!) On the whole however I agree with Brian re using 12/24 volts in a caravan or motorhome. Its safe, generally more efficient, and simple. I do however agree with what you (Cracker) say for big domestic solar systems. Our home is totally solar and runs from 28 x 64 watt modules using a 48 volts by 4.5 kW inverter (with 11 kW surge capacity). Where we need extra-low voltage (eg. 12-24 volts) we use switch-mode converters and reduce the 240 volts AC. Why - because its simple, and the inverter etc loss is partially compensated by neglible voltage drop. We do likewise for outside lighting - for safety. Collyn Rivers

Collyn wrote, <start> Our home is totally solar and runs from 28 x 64 watt modules using a 48 volts by 4.5 kW inverter (with 11 kW surge capacity). <end> Wow !! I bet that "hums" at 12 midday in Broome ...in summer, cloud cover 3 oktas or less .... with 50% batteries !!!! [smile] That inverter would not even run our air-con system (draws 5.5 Kw max (Daikin Inverter type) ) kinda puts it in perspective. Anthony Explore this Great Land ... Do it Easy ...Tow a Bushtracker

Helen, If I read Collyn right he does not mean Isolation switches which I think is what you are refering to. He is talking multi stage regulators and some rather intricate solutions which I think are worth looking into. Regards Macka

Hello Anthony, It's slowly sinking in - especially when Collyn mentioned the inefficency of 240v stuff ONTOP of the inverter loss.........THAT GOT ME THINKING ! (and like I really need to think more right now ) I have arrived at the decision to make the primary system 12volt and to make as much use as possible, to justify it's use - having everything 12v. By this I mean that I will install more 12v cig lighter type sockets around the van so that laptop / mobile phone / fans etc can be used with the ( often supplied ) 12v car chargers.(AND INCURR MINIMAL LOSS OF POWER....thanks Collyn) I would like to thank all those who have helped with the callisthenics of my brain. ...... "A good decision is not made , if you chooose from a single item. / point of view, / or go with the masses. P.s I am currently living in Northern Victoria - waiting for the completion of the van, at which time my wife and I will begin a 2, 3 (4 ? ) year trip around Oz. Cracker.

Collyn .....thank you for that input - it's what I was after.... mathamatics. Seeing the losses etc as you explained really helped. I appreciate the frustration of explaining why the sun comes up in the morning. Cracker

Macka, You wont regret the way BTi set up a BT with regards to power especially if you go with 4 x120w panels. I can honestly say that in the 15 trips we've done away from any source of 240v ....I've never started the genny to use the battery charger. One seven day trip had three days of rain and still the 4 panels coped well. Graham with his 4 panels now runs an Engel for drinks as well as the 190L BT fridge. You wont regret purchasing a BT either after 4 years of travelling you'll still have it one piece ..... Birdsville Track and all ....with a great resale value. Trouble is most cant bear to part with them ....[smile] North Vic huh !!! I know the area might be a bit tourist-y now but we intend to one day spend some time in the gold and history rich areas of Ballarat, Bendigo and Sovereign Hill. Regards Anthony Explore this Great Land ...Do it Easy ...Tow a Bushtracker

Cracker,
I used to think like you when looking at solar
electric hybrid houses but the price runs into something like $200,000 and you
would need a bank of panels bigger than a mansion and a room
bigger than my living room for the battery bank. Have a look at a submarines
bank their batteries are huge the size of a room and heavy to boot.
Kindest
Macka/Peter

Sorry Macka, Meant Cracker ... have given myself a big Smacker !! [smile] And any other post where Cracker should be Macka or Macka was referred as Cracker ...the party of the first part "ME" ... apologises ... Regards Anthony Explore this Great Land ...Do it Easy ...Tow a Bushtracker

Well, Cracker, its like this. The Sun doesn't actually "come up" in the morning (or any other time for that matter). In fact, it doesn't 'do' anything, except fart superheated plasma, cosmic rays and particles of various descriptions as it hurtles along at several tens of thousands of kilometers an hour out here in the unfashionable end of a spiral arm of an insignificant little galaxy well out from the Universal Core, towing a bunch of spinning Rocks (we're the third one out); dust; dirty snowballs; and several thousand tonnes of Terrestrial space pollution and so on. Now, if you will just pay attention to the model. See the orange on a string hanging from the coathanger? Well, pretend your fist is the Earth and m,;ljlnzlhgfzdd,................. Griff

Cracker Before you get too far ahead with your plans - be wary of most cigarette lighter plugs and sockets. Almost all lack mechanical locking and tend to arc internally particularly if carrying more than an amp or two. They are a real fire hazard. Hella make good ones - but that's about the only one I'd recommend. Ring Val Rigoli at Fridge and Solar for advice re these (07 5500 5061) - see also his site www.fridge-and-solar.net A friend of mine who lives close to us (at Nungnungurakun) runs a very large air-conditioned house from a big solar system. It uses 88 by 120 watt solar modules set up to run a 21 kW three-phase inverter. Cost was about $140,000 of which the Govt rebated 55%. He also has a big diesel generator but rarely needs it. Our own comparatively modest system produces about 12 kW/day. Collyn Rivers

Griff, ...and on this small 3rd stone from the big fire is a miniscule, exoteric, sentient, fragile being called "Humans" ....who's outer shell (that faces the other beings) becomes hardened and positively crystal delicate with age ...... [smile] Anthony Explore this Great Land ...Do it Easy ...Tow a Bushtracker

Craker, I don't think you will ever regret
it.
Regards
Macka

Anthony, thanks but I never doubted Bti I have the
outmost confidence in them and the vans.
Kindest Regards
Macka ( Yes I love em
too)

Yeah what would we do without you Collyn? You
are a marvel! We should all be buying your books.
Kindest Regards
Macka/peter

Thank you Macka Collyn