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

Updated: Jun 16, 2021





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

(please see below)




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



YOU WILL NEED 1 X METER OF THIS




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



YOU WILL NEED 1 X SET OF THESE



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All Trade Direct 2 X 100 Amp Midi Fuse High Current All Midi Amps 40-150Amp & Fuseholder Stocked



YOU WILL NEED 1 X SET OF THESE



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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.