A Super Simple AWESOME Off Grid 12V System... Step By Step With Diagrams PART 2

Updated: Jun 16





Hi everybody and welcome to PART 2 of our awesome set up, if you are just joining us at PART 2 and have not seen PART 1 of our post please follow the link below to so you can see how we got to this point.





If you have read PART 1 already We are just going to jump straight into this by adding the solar.


At the moment you should have something that looks like this...



At the end of PART 1 I left you with these two paragraphs...


You might have noticed that I just wrote all summer long and that was on purpose as solar is pretty useless in the winter with the long nights and bad weather so to be off grid all year round we are going to need something to be able to efficiently charge your batteries in the winter too.


So the next thing we are going to add to this set up is a B2B charger..


So lets move on to PART 2...


In the summer when the days are long and the sun is high in the sky solar is amazing and you won't need anything else, each 100w of solar will top your batteries up by about 55ah on a sunny day in summer however on a sunny day in the winter 100w of solar will only top your batteries up by about 8.5ah and this is nowhere near enough.


So for winter we have to add another charging option and the best thing for this job is a B2B charger (DC-DC, battery to battery).


For this set up I recommend this one


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Sterling Power 12v 60amp Battery to Battery Charger BB1260



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As you have a large battery bank and you want to be off grid all year round then a 60 amp B2B charger is perfect for this set up, the lower the amps of the charger = more hours driving to top up your batteries.


Our battery has a maximum charging rate of 92amps and we have 30.5amps of that coming from our solar set up (365w panel ÷ 12v battery = 30.416) so that gives us 61.5 amps left over. 60 amps is the closest we can get to that and in the winter every amp counts.


B2B chargers are quite new technology and are now pretty much taking over from split charge relays/vsr/split chargers. They are wired up pretty much exactly the same as a split charge relay but work completely differently, with split charge relays your alternator charges your vans starter battery until it is sufficiently charged then the relay senses that it if charged and then diverts the power from your alternator to charge your leisure batteries.


The problem with this is when your split charger thinks that your battery is charged it stops putting charge into either of your batteries but when batteries have been off of charge for a couple of hours they settle so what a split charge relay thinks is fully charged is actually only about 80% charged.


B2B Chargers are much more intelligent, they alternator keeps charging your starter battery and then your starter battery powers your smart charging unit to charge your batteries and can charge them up to 99% of capacity.


So to wire your B2B charger to your starter battery, van and leisure batteries you are going to need some more cables and inline fuses.


Red Battery Starter/Welding Flexible PVC Cable Wire 110 Amp 16mm MKGT® (16mm² Red, 10 Meters)



YOU WILL NEED UPTO 10 X METERS OF THIS

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Black Battery Starter/Welding Flexible PVC Cable Wire 110 Amp 16mm MKGT® (16mm² Black, 1 Meter)



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All Trade Direct 2 X Strip Link & Midi Fuse Holder For Striplink & Midi Fuses Fuseholder Fits All



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Once you have all of the bits above then we can start to wire the B2B charger to your starter and leisure batteries, first we have to make some more cables up.


So find the positive (red) 16mm2 cable and off of one end cut yourself 3 short lengths


2 x 20cm lengths

1 x 30cm length


First take your 30 cm length and on one end attach a 16mm2 M6 (6m) lug and on the other end

attach a 16mm2 M8 (8mm) lug and crimp both securely into place.


Next take 1 x 20 cm lengths and attach a 16mm2 M6 (6mm) on to one end of it..


With the last 1 x 20 cm length and on one end attach a 16mm2 M6 (6m) lug and on the other end attach a 16mm2 M8 (8mm) lug and crimp both securely into place.


Please see picture below...




Next find your negative (black) 16mm2 cable and cut yourself a 50cm length.


On one end attach a 16mm2 M8 (8mm) lug and crimp securely into place, please see picture below...


First put one of you 100 amp midi fuses into one of your midi fuse holders.


Then take your 20 cm length of positive (red) 16mm2 cable with a M6 (6mm) lug on one end and nothing on the other end and bolt the lug on to either side on the midi fuse holder.


Next take your 30 cm length of positive (red) 16mm2 cable with a M6 (6mm) lug on one end and an M8 (8mm) lug on the other end and bolt the M6 (6mm) lug to to other side of the fuse midi fuse holder.


Please see picture below...

Next take the end of the 20 cm length without a lug on the end strip enough insulation off of the end and wire it directly to the + out terminal on the bottom of your B2B charger. (number 3 in the picture below)...





Now bolt the end of the 30 length with the M8 (8mm) log on it to any spare terminal on the same bus bar as your solar MPPT controller.


Please see picture below...






Next take your 50 cm length of negative (black) 16mm2 cable with a M8 (8mm) lug on one end of it.


Strip some insulation from the end without a lug attached and wire it directly to the negative terminal on your B2B charger (number 4 on the picture below)...




You should now have something that looks like this...






Next you need to find your long length of 16mm2 positive (red) cable. You should have had 10 x meters to start with but you cut 2 x 20 cm pieces and 1 x 30cm piece off so it should be just over 9 meters long.


Again as with everything in this post it is best to keep all cables as short as possible for safety and to minimise volt drop.


Hopefully you will only need a few meters of this cable but depending on the route you take to your battery and the length of your vehicle you might need more.


First take your long length of 16mm2 positive (red) cable and strip some insulation off of one end


Next wire that end directly to the + in terminal on your B2B charger (number 5 in the picture below)...



Next neatly run your long length of positive (red)16mm2 from your B2B charger through your van to your starter battery. This will depend on your van some are under the bonnet, some are under seats some are in footwells so you will need to find yours and a decent route to it.


Remember this cable carries a lot of AMPS it needs to be protected from the body work and getting damaged, it is best to run it through conduit and also rubber grommets wherever it passes through any sharp body work as the last thing you want is the bare insides of the positive cable touching anything metal whilst it is a live circuit.


When you have run your cable from your B2B charger to within a few inches of your vans starter battery cut any extra cable off (we will use this later) and crimp a 16mm2 M6 (6mm) lug on to the end


Next find your last remaining 20 cm length of 16mm2 positive (red) cable with a M8 (8mm) lug on one end and a M6 (6mm) lug on the other end, a midi fuse holder and a 100 amp midi fuse.


Put your 100 amp midi fuse into the midi fuse holder


Take the cable that comes from your B2B charger and bolt the lug to any side of the midi fuse holder


Then take your 20 cm length and bolt the M6 (6mm) lug to any side of the midi fuse holder...

And finally to finish the install of your B2B charger connect the M6 6mm lug from the 20 cm cable to the positive terminal of your starter battery.


Please see picture below...


Congratulations 🥳🥳🥳🥳


You now have an awesome off grid self charging set up that can keep you powered all year round, no matter how many daylight hours you have or how bad the weather gets and that is pretty awesome.


We have left a spare terminal on the bus bars that your MPPT & B2B chargers are connected to, this is so you can add a 240v onboard charger if you wish to do so. we have not chosen to add one to this set up as it is an off grid set up however if you're planning on staying in lots of campsites with hook up points and want extra power capacity an onboard battery charger with a hook up point kit is what you need. We will be making a video on this very soon so don't forget to subscribe to our youtube channel to see it when it is ready, LINKS AT THE BOTTOM ON THE PAGE


Now it is time to add everything that will run off of our system.


As you might have noticed from your vans built in fuse box and from our set up so far that every single circuit need to be fused for safety.


So to keep things neat and tidy and easy to keep track of the best option is to add a blade fuse box and then run all of your little bits and pieces to and from the fuse box.



So for this we recommend one of these...




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You should have 50 cm of positive (red) & 50 cm of negative (black) 16mm2 cable and some 16mm2 M6 (6mm) cable lugs left over from your MPPT & B2B install but just incase you don't...





Red Battery/Starter/ Flexible PVC Cable Wire 110 Amp 16mm by MKGT® (16mm² Red, 1 Meter)



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Black Battery/Starter/ Flexible PVC Cable Wire 110 Amp 16mm by MKGT® (16mm² black, 1 Meter)



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Cable Lug 16mm2 M6 20x Cable Shoe






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First take your 1 x meter of positive (red)16mm2 cable and cut yourself 2 x 20 lengths.


On the fist length attach a 16mm2 M8 (8mm) lug on to one end and a 16mm2 M6 (6mm) lug on to the other end the securely crimp into both place


On the second length attach a 16mm2 M6 (6mm) lug on to one end and a 16mm2 M10 (10mm) lug on to the other end and securely crimp both into place.


Please see picture below...






Next put a 100 amp midi fuse into a midi fuse holder and attach the M6 (6mm) lug from each cable to either end on the midi fuse holder.


Please see picture below... (pay no attention to the cable lengths in the picture below they should be equal 20cm lengths)



Now take the end with the M8 (8mm) lug on the end of it and bolt it directly to any spare terminal on your empty positive bus bar.



Please see picture below...