12V - 120V -24V Electric system for campervan

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polonus asked Feb 18, '21

12V - 120V -24V Electric system for campervan

I am building a campervan and try to figure out the best solutions. I have dual alternator Ford Transit with 175Amp output and my "pre-plan" is to use it to connect to 3000W inverter and run 120V to Victron Multiplus 3000W to 24V battery banks. (3 LiFePo4 batteries 170Ah 24V connected in parallel). For solar power I am thinking of Victron Solar Charger Controller 250V/100Amps.

I am not an electrician and my questions may be naïve, but I still need the answers:

1. Can the outputs of Victron Multiplus and the Solar Charger Controller be connected to the same Busbar?

2. What kind of solar panels are best for that setup?

3. Where do I need to connect circuit brakers?

MPPT SmartSolar Lithium Battery campervan

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Answer 1 · 2021-02-18T18:18:34Z

Kevin Windrem answered · Feb 18, 2021 at 06:18 PM

If the first inverter is there only to feed 120 volts into the Multiplus AC input, you may be better off using a DC to DC converter to bridge the 12 volt starter battery and alternator to the 24 volt DC bus.

You may also need to convert the 24 volt DC house battery system to 12 volts to feed lights and other DC loads in your RV (refrigerator, etc.).

A 12 volt house battery system for DC loads and the Multiplus might be less complicated. I'd still recommend a DC-DC converter between the starter battery/alternator system and the house battery system.

Solar panels: the most you can fit on your roof. Type is mostly a personal choice.

Circuit breakers or fuses should be inserted to protect WIRING from shorts. breaker/fuse goes at the source of the power (e.g., battery bank). Same for the AC paths.

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Answer 2 · 2021-02-18T19:44:36Z

polonus answered · Feb 18, 2021 at 07:44 PM

DC to DC converter forces me to use much thicker wires. If I chose DC to DC converters I'd need 4 or 5 of Orion's Smart 12/24-Volt 15 amp 360-Watt DC-DC Chargers. I'll need 120V inside my van anyway, so going 12V -> 120V -> 24V has its advantages. For instance using roof AC when driving from the vehicle batteries.

As far as the solar panels goes, what should I look for? Voltage? Amperage? Does it matter?

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Kevin Windrem commented · Feb 18, 2021 at 08:00 PM

Power's the thing to consider with solar panels. Consider low temperature open circuit voltage in your design (voltage goes up with lower temperatures) and make sure you don't exceed the voltage limit of your charge controller. Series/parallel (or a combination) depends on how the panels behave with partial shading. I suggest you run some tests after you've chosen the panels. The 250/100 is capable of 2,400 watts into a 24 volt battery bank. That's a lot of solar area for a smallish van. So you can probably save some money and downsize the controller.

The other thing to keep in mind is that the solar panel array needs to output at least 5 volts above the battery voltage to start the controller. I'd consider a solar array that outputs at least 30 volts. Series connecting three "12 volt" panels would get you there.

Victron has a solar estimator that will help you choose the correct solar controller and estimate energy output

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