Judge my electrical diagram : My broken electrical knowledge

Hi everyone,

First, thanks for your interest and time spend in my topic.
To introduce myself: my electrical knowledge could be resume to god google told me this.

As we all know, internet is a big pot with nice stuff and awful lies, so I am posting here a diagram that we made, we hope that you will have advices, opinions and comments that will allow us to improve seriously our project. Please, be patient, we are learning :wink:

If you have the time, read about our story, if not, jump this quote section :arrow_down:

A bit about the history of caterpillar, our van.

Caterpillar is a T5 - hitop - 2012 - 150k. It has been bought by my gf -J- in 2017.
After buying the van, J and her brother started building the van, making a kitchen side, a bed, and installing

  • 2x100w flexible solar panels made in china + PWM + AGM 150hA + inverter 1000w. And of course some addons - gas cooker for the kitchen, husky fridge etc-

After I arrived in J and caterpillar`s life, the 3 of us started to travel around europe. We made nice trips but systematically we were out of power on a daily basis.
Therefore, we know that our supply of electricity is bad, and that our storage of electricity is also bad. We also had several issues with the flexible solar panels - they burnt.

2023 is the year of the change, and we got both fired from our work, witch clearly is a sign from the divinity of the vans, telling us to restart our caterpillar project, but this time to make it slightly more seriously.

If you dont have the time, move quickly to here :arrow_up_down:

So we restarted our research in the google bible and we found a bit of what we want and also a bit about what we can afford, in terms of time but also in terms of money.

On the short term : buy again 2x100w solar panels rigid, couple them in serie with a MPPT, build on a quick way a safe electrical supply, even if we know that we will be in short. Why quick? Because it is almost summer, so it is easier for us to get each day our battery full.

On the mid term, increase our system with:

  • 2x100 solar flexible, wich will rise our harvest capacities to 4x100w.
  • Add a 2nd victron MPPT -the panels being 2x flexible + x2 rigid they will have different specs-
  • Add a 2nd battery AGM
  • Create a B2B and shore line
  • Add a roof window

Our current consumption is I would say low:

  • 1x water pump,
  • 2x USB lines, computer,
  • 3x strip of leds


  • fridge, computer and drone charging.

*Fridge has 2 modes, the compressor ones needs 220v, the maintaining of the temperature can go on 12v.
Usually we connect it on 220v but don’t keep it on all the time.

:raised_hands:So here is our electrical diagram link::raised_hands:

One important thing is that we plan to make all the connections with ring or blade connectors.
Except if you advice us to make it otherwise :slight_smile:

Also, in the diagram it shows that for the 2xMEGA and 2xMIDI fuses they are mono holders.
We are planning to try to get 1 Holder for all the MEGA fuses and 1 holder for all the MIDI fuses.
Again, except if you advice us to make it otherwise :slight_smile:

A few questions :

  • From the negative bus bar should I link a wire to the chasis of the véhicule ? If yes, what should be the thickness of the wire ?

  • In general terms, are there too much / not enough/ not well calculated fuses/breaker/protections?

  • Do we need a 25mm wire from : A- 150amp to the battery ? B- from battery to bus bar ? C- from positive bus bar to 80amp fuse, inverter and back to negative bus bar ?

  • Is it ok to have 6mm wire that splits into several 1.5mm wire through the wagos on the positive current - fuse box - negative current ? The wagos choosen are the 221 ones.

To finish, for our dear friends non metrics I added the conversion to AWG, the cables proposed by this diagram are:

1.5mm :point_right: 16 AWG
6mm :point_right: 10 AWG
25mm :point_right: 4 AWG

Now it is YOUR turn


And please, dont hesitate to make each single comment that you find useful, we are here to learn and to try to build the best van that we can !

Thank you for your time and patience reading us !

IMO the wire to the battery is too small, 150A breaker on 4 ga.?
Check out BlueSeas Systems they have a chart for Amp/ length/gauge.
Don’t understand a 30A fuse and a 50A breaker on + of the solar panel.
BlueSeas also has a great line of hardware (marine grade) they also have fuses that mount directly to battery posts and stud posts to make your install a lot easier and cleaner install. Good luck with your install!

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Hello and thank you for your answer. I checked at BlueSeasSystem. After checking temperature resistance from the cables that I can get, we modified the cables going from the battery. Instead of using AWG 4 we will use AWG 4/0 (120mm) with a temp resistance of 70`Celsius.

We choose this cable and not something below so if in the future if we need to add batteries in series to the AGM the cables will be able to stand. Is this correct ?

As following your recommendations we proceed with changes into our fuse:

A cable 120mm can hold 292Amp. As the current that passes is 150Amp we apply a +30% in the selection of our fuse. We will therefore put a fuse of 200Amps instead of the initial one.

As also mention, and following our research, we will remove the 30amp fuse from the solar panels as we already have a breaker. We also changed the breaker from 50amp to 40amp.
The panels will be on serial, so we will have 24V for 5amp.
The breaker that we will choose is a 30amp. We know that this is oversized -we should need a 15amp right? - but is there any issue to oversize the breaker? If one day we want to add 2 more solar panels at least we have a breaker that we can re use…

We checked BlueSeas system unfortunately as we live in Switzerland it is very hard to get things from outside… Importation of duties makes extremely complicated and expensive to get anything that does not come from here…

Thanks for the advice. Here is the new updated diagram

Thanks for your help, time and support

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Great Job! Looking good. When your pulling your cable you might want to run an extra wires or 2, couple extra feet at each end tucked in the back for any future accessories then you don’t have to tear everything apart to run new wire. A product called split loom will keep all your runs neat and protected. I’m a big fan of overkill in wire size. Plus the bigger the wire and the less voltage drop with long runs.

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Beautiful, thanks for the advices. Do you add extra wire extra feet on each of the connections? Or just you mean for the solar panels.
When you overkill wire size you mean instead of going for for AWG 4 you go for 16 you go for 15? -instead of 1.5mm you go for 2.5mm?-
Noted for the split loom, I guess it makes all the cables tidy.

No, just the extra runs for future projects down the road. Yes, “overkill” is usually next size larger.
You might want to check into an ACR (automatic charging relay) It would connect between your alternator or start battery and your house batteries. When you start you van after a couple seconds it connects you alternator to your house batteries while you van is running, when you turn the van off after a couple of seconds it senses no charge coming from the alternator and automatically disconnects the alt/start batt. from the house batteries, this way you don’t have to worry about a dead start battery. Check to see if your solar controller has a blocking diode or ignition protected it won’t bother your solar system. I put a switch on the output of my controller but I forget to turn it off when the van is running and the ACR is linked with no issues to the solar. It can put a lot of time back in your batts on road trips. DC to DC would basically do the same thing.

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But when you say wire extra, do you mean if I need a 1ft cable from lets say battery to solar panel, to instead of putting 1ft to put 2 ft so keeping an extra just in case? On do this each time, for instance if I have 2 ft between the inverter and the battery to put 3ft?

Sorry, english is not my main language maybe I understood wrong.

For the B2B system it is on our plans but not for this summer as this involves a lot, drilling and wiring from the motor to the 2ndary battery, but thanks a lot for the help and the information !

I hope I understand your question correctly…

Any DC circuits in use should have the shortest length of wire possible to prevent any voltage drop over its length…but also, very simply put, these wires/circuits in use should also be designed in a way that the current can not only be carried safely (minimum wire cross sectional size allowable) but also efficiently (minimum size allowable plus extra cross sectional diameter as cost/weight permits).

I hope this helps.

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If I resume in my words:

Cable must be short as much as possible
Cable diameter can be oversize to reduce voltage drop
Cables are expensive :smiley:

I changed a bit the diagram:

  • added a switch instead of the circuit breaker between panels and MPPT
  • added a fuse 15 amp just after the switch
    (allows to cut current when operating into system, fuse is now at the good ratings?)
  • the cable 120mm (4/0 AWG) has been replaced by 70mm (2/0 AWG) wich makes it connectable with the bus bars (M6 thread)
  • the cable 6mm (AWG 10-11) remains the same, as it is the cable provided by the solar panel and also made for the MPPT it is logical to keep it as it is (?)
  • The cable 25mm (AWG 4-5) has been replaced by cable 35mm (2-3).
  • The fuse between positive bus bar and inverter 1000w, initially drawn at 80amper has been replaced by a 125 amper (to be above the load of the inverter)
  • The fuse between positive bus bar and AGM battery, initially drawn at 200amper has been replaced by a 175 amper (to be above the load of the battery but under the maximum load of the wire)
  • All the cables 1.5mm (AWG 16-17) has been replaced by 2.5mm (AWG 14-15)
  • Of course all the rings and blades has been changed accordingly

I will upload tomorrow the diagram with the changes done.

Edit: :fast_forward: here is the diagram

Thanks for your support and help, I know it is a bit a diary of changing but maybe this could help someone in a similar small configuration that the one that we try to build :slight_smile:

Yes, yes and yes!

And from your earlier post in this thread…assuming B2B is battery to battery…I would advise getting only a DC to DC charger for a T5.

I tried a voltage sensing relay and this didn’t work. This is because the alternators fitted to the T5 are smart alternators, meaning that when they sense a fully charged starting battery, they shut down (to cut down on emissions allegedly). Therefore, once they shut down, they cannot supply any current to the second battery.

The DC to DC charger will in your case be perfect…I have retrofitted a Renogy DC to DC 40A charger in my van and it has saved me a whole lot of heartache!

In respect of wiring the DC to DC charger to the starting battery, the T5 has a hole fitted with a rubber gromet just behind the battery compartment so that you can lead the positive wire from the charger to the battery with out any drilling!

Just a note on your solar panel setup…the output could potentially reach up to 200 watts as they are set up now, but you will only get the rated output current, the same as if it were only one panel in the system. If on the other hand, you connect them in parallel, you would get 100 watts output, but the current would increase to potentially double the rated output.

The important thing to remember is that for battery charging, current flow is more important than watt output (although you do need a reasonable watt output to get the current in the first place). That said, given the latitude of where you say you are in the world…if you can upgrade your panels in the future to around a minimum of 300-400 watts, you will find it helpful.

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Hey guys

Please find the updated diagram with changes made