Caravan off grid system upgrade . still not sure i understand the what a mppt c/c can and cant do 24 v or 12 ?


New Member
Jun 18, 2020
Hi there ! im struggling to get my head around understanding the can and cannot do with a mppt charge control i have a 17 foot caravan with a basic single panel 30 amp PWM and a 120 amp hr battery Agm type all installed by the previous owner/s of the van lighting circut is hooked up to the load output and theres a 12 volt w/ pump .diesel air heater, shower exhaust fan and 12v light in shower area as well as 2 ciggy outlets one for Engel 40 litre fridge and the other is general use i plug my 12 volt alpine cd player and speakers into anyhow i want to upgrade to a 400 - 600 watt system i have 220 cm x 200 cm roof space easy to access and is flat metal cladding here in Australia ebay is drowning in cheap over rated no name panels but also some good quality ie Victron . renolgy etc and it would seem mono crystaline panels seem a good bet havent totally dissmissed poly as yet anyhow at first i thought keep it simple go 12 volt panels in parallel get a 40 amp mppt epever or a renolgy Li pretty simple for me to install but the panels to charger cable distance will be 4 - 5 meters so voltage drop will be a factor etc as i have learnt this will mean 6awg or 4awg cable then i watch dozens of u tube videos a lot of variable info untill i hit Will.s utube channel and finally some well explained teaching . very much appreciated i might add. now from there i found my way here and am learning even more ... the renolgy 400 watt kit set up is aval here as shown on this site, from ebay au 4x 100 watt panel cable fuses mppt mounting brackets and branch connectors so in parallel it would be 5.25 amps x 4 = 21 amp optimum at 12 volt i liked the next option shown here that is series / parallel so if i understand correctly thats 18 volts x 4 =72 volt x 5.25 amps that goes to the charge controller ? and then is it correct that the mppt controller will convert & charge my 12 volt battery bank via it processor ? if so then it would be possible to run 6mm square 10 Awg cable instead of heavier gauge because the voltage is higher the amps are lower ?and if i can fit more panels provided i have 150v /40amp c/control eg the nice all aluminium Epever i can run up to 520 watts of panels if total voc is under 150 in series parallel or no ?? Help !! im feel stupid asze asking these basic questions ... But i really have one shot to get this right and a maxium $3000 au for the set up including battery which im going lithium as there benefits have me sold 100 amp hr 13kg ( $800 each owch } vz agm 32kg weight is important to keep as low as possible so i can have 2 lithium batterys and drop 6kgs . i also need to stay 12 volt on the batteries because all the van accessories are 12 volt if i want to run x 3 200 watt renogly panels they would just fit in the space avaliable there 1680 x 657 x35 mm 9.52 amp x 24.1 Voc 12 volt =28.5 amp 72.3 voc ? but i will need a 60 amp c/control as the watts exceed 520 watt no problem bit more cost than 40 amp but with 3 panels instead of 4/5 save on mounting brackets so kind of balances out. how would you best wire 3 panels ? anyhow im now going in circles !!!! so hopefully some of what i ask makes sense ? i forgot to say i would like to run a small victron 12/500 or 12/800 inverter the battery allows max 100 amp continuous hence the wish to try to have a 600 watt panel system and add batteries in parallel as i can afford too over 6/12 months i will be off grid altho a back up honda io or yamaha 1000 watt inverter generator will be purchased later there around $1299 new here but plenty of low hour second hand units aval around $700 wealthy retirees buy them new do the big trip around Oz over 6 months +/- and sell them when back home with 100hrs use or less so that.s the plan choosing the best method to wire the panels and understanding the prameters of the mppt and required fusing either in 12 volt or series for efficiency is what i need to get right and maximise the area i can use with the best possible watt output thanks in advance Rick :unsure: