I always understood that alternators were 240 volt AC stepped down and rectified to 12 volt DC.
Was I wrong to think that?
Yes ! they are wired and regulated for 12, 24 or 240 volts ....
The 240 volt alternators were fitted to some military vehicles and some of the talbot murvi motorhomes had them, On a previous narrowboat to the one i live on now i had a 240 volt alternator which was part of an electrolux travelpower system, it had its own box of tricks to ensure a smooth output so at above 1200 rpm i could run a washing machine whilst cruising along the cut. I have seen similar things in british gas work vans amongst others where they need mains to use power tools.
My electrical systems are...
Narrowboat .... 2 alternators one 70mp and one 145 amp with a charge controller, i also have a smartguage connected to a smartbank which parallels the outputs to give me around 180 amps of charge as the charge controller is programmable and cons the alternators they are on full load and has temperature sensing on both the alternators and batteries to ensure they dont cook!... i have a 3kw pure sine inverter, a 60 amp charger, a 2kw pure sine inverter generator and 800 watts of tilting solar panels all feeding through 8 6 volt 225amp deep cycle trojan batteries.
Equipment wise i have a full size 12 volt fridge and freezer a washer dryer i only run when either on the genny or with the engine running, a 50" led in the lounge a 32" led in the bedroom a satellite system a microwave a bread maker , berspacher diesel heating running 4 large radiators and a 75 litre calorifier and a few other gadgets ... i cruise march to october without any power issues but i always have a mooring with a hook up through winter as my solar is all but useless for at least 2 - 3 months and running the engine a few hours a day isnt an option as my diesel engine is prone to bore glazing if not worked hard enough.
Motorhome ... Just the standard alternator a 2500/120 pure sine combined inverter charger currently 2 x110 amp leisure batteries but soon going to fit 4 x 6volt 225amp trojans ... the same genny ... motorhome has a microwave sat system, 26" tv and just the standard kit 3 way fridge blown air heating etc currently gas but going to change it or add an eberspacher blown air heater a couple of 275 watt solar panels, also want a gas it or similar as the plan is to use the boat through the summer and disappear abroad for the winter to spain italy or portugal ... also need to change all the light to l.e.d. ... as i said not long bought it so have a long list of mods to work on!
For those who dont understand the way alternators work an alternator will only output what the battery demands so if you pull up and leave the engine running to charge your leisure batteries you only get a few amps of charge, this is why when you put your heaters, lights, heated rear window etc all on at the same time your engine note changes as your alternator is running to near its full output.... so if you are running your engine for a hour on not much more than tickover to charge your leisure battery you will be lucky to get more than a few amps going into it , certainly a fraction of the rated output of your alternator.
For those building a van and designing an electrical system from scratch particularly for wild camping you need to do a power audit and have at least twice as much as you will ever use between battery charges plus a little extra .... for example if you are using 100 amps in an evening then running the next day to replace that charge your battery bank should be at least 220 amps (because of the peukert effect the 220 rated amps is nearer 200) and you should never allow your batteries below 50% s.o.c. (state of charge) most leisure batteries are between 150 and 300 cycles @ 50% which means everytime you run them below this thats one cycle used up ... get to 150 and they are as dead as the parrot in the monty python sketch! i never let my batteries go below 60% min and the 6 volt ones on my boat although expensive last between 8 and 15 years as they start at 1250 cycles ... also be aware batteries sulphate and need a charger which has a desulphation stage where it ramps the charge up to over 14.5 volts for a couple of hours to shed the plates of the sulpher that builds up on them .... this is why your standard 110 amp leisure batteries are probably down to around 85 amps of capacity within 12 months ... even more so if your motorhome sits for long periods without regular battery charging and maintenance.
Sorry if i have rattled on, i am certainly not trying to teach anyone to suck eggs, so if you know all the above please forgive me but hopefully there will be a few out there i have imparted a little knowledge or awareness to and should anyone require any help wiring sizes fuse ratings or anything else i am more than happy to help
Rick
