Campervan plan schematic and questions

[TenagaSurya]

This pair of diagrams shows my plan for a solar panel and inverter upgrade to an existing simple 12v alternator-powered lead acid battery setup in an old Volkswagen T4 campervan. Main loads are a small fridge (nonstop) and a 600w inverter for charging three laptops and occasionally running a tiny kettle.

The first image is stage one of the plan, mainly adding fuses, a shunt & monitor, battery cutoff, inverter and portable solar panels. The second image is the same but with the addition of a DIY lithium battery (size to be determined after trialling the new setup) and a DC to DC charger to avoid trouble with the stock 90A alternator. Sorry for hurting people’s eyes, my awful schematic looks like a birds nest - let’s hope it doesn’t end up that way for real..

I am hoping for comments/criticism from any of you kind forum folks before I begin (re)wiring the van. I also have the following questions I am hoping for some advice about:

1. Do I need to fuse all the inputs from low wattage solar panels? If so, at 12v and currents under 20A are inline (small) blade fuses good enough for that?

2. I already bought a single-pole breaker to disconnect portable solar panels and avoid any arcing. But now from reading the forum now I see people usually disconnect both pos and neg - why is this?

3. Is it safe to use this charger that came with the 200w solar blanket or is it likely to overcharge batteries? I am assuming it is not genuinely MPPT as it claims but rather PWM. The manual claims “Voltage of stop charging 14.7V”. It is not manually adjustable nor even selectable for battery chemistry. [https://cdn.soselectronic.com/productdata/d2/9a/7866275a/mpl15.pdf ]

4. In the future upgrade where I add a LiFePo4 battery, is it possible to use my existing mains-powered lead acid charger as the input to a Victron Orion Xs DC to DC charger, rather than throwing it out? In which case I could wire it in on the DC to DC charger side of the voltage sensitive relay.

5. What to use for strain relief / to restrain cables in general? I have a roll of wide double sided velcro I am thinking of stapling to the wiring backboard and using for tidying cables. But it won’t provide substantial strain relief.

Stage one:


Stage two:

 

[Rocketman]

A couple of points…

The charging is different on the gel vs the lithium battery- so each time you change over you need to reprogram all your chargers. Pull out the gel battery and replace it with a lithium- so both lithium’s are in parallel.

You need a much bigger bus bar than 4 lugs! Or it will be a rat’s nest of wires.

Also look at combining a few items (saves space and wires). Look at the smaller Victron Multiplus inverter/charger - I believe they make a 800w &1200w units. Plus it can be reprogrammed for both gel and lithium.

Also fuses protect wires - not equipment- so you size the fuses for the wire size. For example on the battery you have awg6 wire on a 100a fuse - that should be a 50a fuse or probably a larger awg1 wire (if I remember my wire size correctly).

You also have 8awg on the solar - 8 will handle 40amps - your mppt is only 20amps and your panels will produce less than 8 amps - 10awg is fine or even 12awg.

Size the wire for the load.

Good Luck

 

[TenagaSurya]

Thanks Rocketman for your reply! I was initially keen to combinine the two battery chemistries because the gel battery is still ok but I am impatient to add more capacity, and the only sensible new battery choice is Lithium. I was thinking I could swap back and forth with the switch and charging profiles but I guess it’d be too easy to forget or muddle it up.

I’m sure you’re right about the bus bar being too short, the picture already looks like a rat’s nest in fact. It seemed like an upgrade because right now there’s a pancake stack of lugs with everything on the battery terminals - this is from a professional campervan conversion company (conversion done many years ago).

I’ll look at the fusing & wire sizes again. I had been relying on the midi fuse column of this table from bluesea. Actually midi fuse holders themselves with their 6M terminals look a little undersized for 6AWG cable. Maybe I should go maxi.

I can't afford one of the Victron all-in one inverters though. Maybe it's better to spend the money on a Victron Orion XS DC to DC converter? I can't be monitoring battery voltage while I drive so it seems more critical to get quality there.